Index


Lights and electronics

    General info

    The flaming touch and the campfire probably constituted early man's first use of 'artificial' lighting. Prehistoric man, used primitive lamps to illuminate his cave. Nowadays the electrical lighting is the most commonly used form of artificial lighting. The history of electrical lighting is long. In 1809, SIR HUMPHREY DAVY first demonstrated the electric carbon arc at the Royal Institution in London. The electric arc was also used for lighting at the Paris Opera. The principal of the electric arc is still used today by many older followspots and film projectors, used in entertainment facilities around the world. In 1877 Thomas Edison became interested and experimented with electric lighting. On October 15, 1878, the Edison Electric Light Company was incorporated. Edison patented more than 1000 inventions. Besides the incandescent lamp, Edison is given credit for inventing a system of electric generation. Although Edison did not invent the electric filament lamp, he did however turn theory into practicable form and was one of the first to successfully market incandescent lighting. Edison's first successful lamp used carbonized cotton thread as a filament, installed in a glass bulb, with all air evacuated. In 1880 Edison experimented with other materials for filaments, including wood, grasses, hair and bamboo. Of the over 6000 specimens tested by his laboratory, bamboo, became commonly used for filaments. In 1880, on January 17, Patent number 223,898 was issued to Edison for the T.A. Edison Electric Lamp. After the introduction of the tungsten filament, the next highly significant step in the development of the incandescent lamp, came in 1913 when the first gas-filled lamp was produced. Coiled filament gas-filled lamps in 500, 750 and 1000 watt sizes were introduced in 1913. They gave a much better light at higher efficiency with the same life as former lamps. Nitrogen gas was used in the first lamps but argon was substituted in 1914. Nowadays artificial illumination consumes more than 25% of electricity generated over the world. There are several trends in energy saving technologies for lighting industry. The first is implementation new lamps such as fluorescent, mercury, sodium, metal halide, halogen lamps. The second is associated with electronic circuit design for such lamps.

      Outside lighting information

      • Light Pollution Information - Light can pollute the outdoor environment and wash away the view of stars in the sky. This curable problem and can be prevented through the application of well designed and applied outdoor lighting.    Rate this link
      • The Dark Side of Light - Although light pollution?s impact on stargazing is as clear as day, its effects on other environmental elements are just coming into focus. The evidence shows that artificial lighting has dire consequences for animal behavior, particularly on the ability to navigate at night.    Rate this link

      Home and workplace lighting info

      The majority of all indoor and outdoor lighting in the home today is provided by incandescent lamps, commonly referred to as conventional "light bulbs". The light bulb is the most widely used lamp in residential and many commercial and industrial lighting applications for general lighting. Halogen lamps are a type of incandescent lamp that gives "whiter" light, lasts longer, is usually small, is slightly more efficient than normal bulb and costs more.Halogen lamps are best suited for lighting areas where a direct focus of light is required.

      Linear Fluorescent Tubes are the most common source of lighting in commercial facilities and can be found in many homes.Compact Fluorescent Lamps (CFL's) are of the same technology as linear tubes, but much smaller. CFLs operate with a ballast and a screw base adapter to accommodate their use in many indoor and outdoor applications. Typically, a 25 watt fluorescent lamp is supposed to give offas much light as a 100 watt incandescent bulb. Those power rating are about right, if you wait about 1 minute for the fluorescent to comeup to full brightness. When installing compact fluorescent bulbs, be sure that they do not heat too much inside the la,p. It is possible for those to fail due to excessive temperature. They don't need to reach the temperatures produced by incandescent lamps to fail after a month or two. Compact fluorescents are great, get a "name brand" for longer bulb life. Compact florescents should not be used on any circuit which is controlled by scrs or triacs (dimmers, motion detectors, security lights) unless they aredesigned for this purpose.

      Low-voltage halogen lamps are becoming more popular for lighting stores, buildings, hotels, and houses. The lamps come in different configurations and wattages (typically up to 50W). Typical voltages are 6, 12, and 24V, supplied by a safety isolating transformers that are usually connected on their primary side directly to the mains power line (110 VRMS or 220 VRMS). Most typical voltage used for low voltage halogen lighting is 12V. Most of the time the safety isolating transformer feeding the lighting circuit is located in the ceiling of the room near the lights itself. In low voltage halogen lighting the most commonly used lamp types are MR 16 lamps. They are Multiple Reflector 2 inch lamps, seen as shop display lamps absolutely everywhere, available in low voltage flavour 12V (usually 20W or 50W bulbs), needs little transformer beside lamp, and mains voltage 240V flavor usually 50W or 75W and choice of beam angles. The low voltage lamps are typically very bright.

      Lighting for use at a low voltage is to be considered as a power current installation since low voltages, such as 12 V, result in high currents even at moderate outputs which can generate a lot of heat. Installation must therefore be carried out carefully. The cables to the lamps must be fused in order to limit the heat generated, and they must not be twisted around one another as temperatures which are too high may then result. The core area is rough so that voltage drops which are too great do not occur, as this means that the anticipated light yield is then not achieved. Position the transformer close to the load so that the core area can be kept to a reasonable level. The following table provides guidance on the choice of cables for various loads at 12 V:

      Length1 mm21.5 mm22.5 mm24 mm26 mm210 mm2
      1 m120 W120 W200 W*240 W*300 W*420 W*
      2 m 80 W110 W200 W240 W*300 W*420 W*
      4 m 40 W 55 W100 W160 W250 W400 W
      6 m 25 W 35 W 65 W100 W160 W250 W
      8 m 20 W 25 W 50 W 80 W120 W200 W
      10 m 15 W 20 W 40 W 60 W100 W140 W

      * Limited depending on the highest permissible fuse.

      Note on light bubs and fixture power ratings have necessary meaning. You might wonder why should a mostly-metalic goosneck desk lamp say 60W? What if I put a more powerful bulb in it? 100 watt and 150 watt light bulbs radiate more heat than a 60 watt bulbdoes. More heat creates more damage to the light fixture. When the lighting fixture was designed, it was designed to accept a certain amount of heat andstill work properly over the useful lifetime of the fixture. If a fixture is designed to work properly with a 60 watt lamp in it, that means that theheat radiated by a 60 watt lamp will not destroy the fixture and the fixturewill continue to function over its useful lifetime. If a 150 watt lamp isput into a fixture rated for 60 watt lamps, the fixture will soon bedestroyed by the excessive amout of heat radiated by the 150 watt lamp andmay bread down and be the source of a fire. The designers will likely also have in mind a safe working teperature to the user, ie putting a higher wattage bulb in may raise the temperature of any metalwork on the lamp to a dangerous temperature which could cause burns to unsuspecting little fingers. The same principle applies to other lighting fitures as well. So for safety reasons NEVER exceed the wattage rating for the lamps in the fixture that they are going to go in. If you do, there may be damage, and a danger for a fire hazard! If if you need more light (lumens) from an existing fixture, a compact fluorescent rated at anything less than 60 watts of input power wouldbe ok for 60W rated lighting fixture. Typically, a 25 watt fluorescent lamp is supposed to give off as much light as a 100 watt incandescent bulb but the same amount or less heat than 25W normal light bulb. Another tip on some fixtures is to use a small reflector bulb in the lamp. Not only can you get away with a lower wattage for the same amount of lightdirected to a specific area, but for a given wattege, less heat is transferred back into the lamp. When using reflector lamp be sure to check carefully that the reflector bulb fits to it without blocking the air circulation or causing excessive hat to any place (for example getting to near to some heat sensitive part of fixture).

      Suggested lighting levels (Illuminating Engineering Society (IES) Handbook)
      Area: Approximate Light Level (footcandles)
      Offices: 75
      Conference Rooms: 20-50
      Auditoriums: 20-50
      Kitchens: 50 (avg.)
      Cafeterias: 10-20
      Reception Areas: 25-30
      Drafting Rooms: 100-200
      Corridors/Restrooms: 10-20
      Writing Areas: 20-50
      Doctor's Treatment Areas: 200
      Storage Rooms: 5-50
      Stores (general): 30-100
      Stores (sales displays): 50-150

      The foot-candle is equal to one lumen per square foot and "the difference between the lux and the lumen is that the lux takes into account the area over which the luminous flux is spread. 1000 lumens, concentrated into an area of one square meter, lights up that square meter with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square meters, produces a dimmer illuminance of only 100 lux.

      Wall hangings, retail displays, and trade show exhibits of all kinds can be very effectively lit with track lighting. Track light is a light fixture mounted on and movable along an electrified metal track. Lighting tracks are available in a variety of finishes, shapes, sizes and wattages, and with a variety of light sources and design accents. Track lighting is generally used to provide accent lighting, task lighting, and general lighting in that order. Track lighting is a very flexible lighting system. The individual track fixtures can move along the track, be swiveled or rotated while in a given position, and then aimed in any direction giving you excellent versatility to change your lighting scheme whenever the need arises. Track fixtures are available in line voltage and low voltage with a choice of incandescent, halogen, fluorescent, or metal halide light sources. Track lighting fixtures can offer an opportunity to be creative and make an aesthetic statement. Track lighting may use halogen, incandescent, fluorescent, or metal halide light sources. Track lighting can be used very successfully in any number of locations: hallways, museums, art galleries, trade show exhibits, offices, conference rooms, studies, churches, restaurants, taverns, hotel rooms, and libraries.

      Here are few lighting tips for positioning lamps on some lighting applications:

      • Before deciding on a particular form of lighting, check the bulb types - shapes and wattage which can be used with the selected light, as there are many different types available.
      • Traditional wall lighting is often more often decorative rather than practical. The idea is adding soft lighting to the room through candle shaped bulbs concealed behind parchment shades, they are designed as a feature to look at rather than see or read by.
      • Enclosed fittings are useful in a hall, landing, porch or in a bathroom. Many of these designs are weatherproof and therefore are suitable in a damp bathroom area.
      • Spotlights are very fashionable and versatile as they can send beams in any direction when mounted on adjustable arms. They can be used to illuminate cupboards, desks, pictures, mirrors or seating areas. However care must be taken when positioning a spotlight to avoid dazzle when seen from another angle. This problem is easily overcome when the lighting is high up the wall or on the ceiling.
      • Fluorescent tubes can spread light easily over an area. They do have the advantage of bright lights with minimum heat given off. They are more efficient than filament lights at turning electricity into light and cheaper to run.
      • Fluorescent lighting tubes give off different types of light. The cold, whiter lights are particularly useful in a loft, workshop or shed. In the house do not choose a blue or greenish shade, as they are bad for your eyes if used alone and also can make you look ill. It is better to choose a warmer yellow colour for a softer lighting effect.
      • For creating the accent lighting of objects on a wall, the wall itself, or any vertical surface, position the track fixture so that the light coming from the fixture makes a 30-degree angle with the vertical. If you are trying to illuminate a reflective wall hanging that can produce glare (for example, a framed photograph covered with glass), do not place the track lighting more than 2-3 feet from the wall.
      • For wall washing a non-textured vertical surface mount the track parallel to the wall being lit and about 2 feet to 3 feet from that wall on ceilings up to 9 feet. Mount the track 3 feet to 4 feet from the wall on ceilings between 9 feet and 11 feet high.
      • For wall grazing textured vertical surfaces (such as draperies, stone, or brick) mount the track 6 inches to 12 inches from that wall with the fixtures the same distance apart and aimed downward.
      • Both wall washing and wall grazing are generally best accomplished by using recessed lighting rather than track lighting.
      • Some general lighting can be provided by track fixtures aimed at a wall or by spill light from fixtures used for accent lighting.

      There are also special decorative lights that are mostly designed for decorative purposes and the actual light output is secondary need. Examples of such are christmas light sets. They look nice, but do not give much total light output. The world glows with a colorful light at one time of the year - Christmas. Everywhere you look, Christmas lights sparkle and brighten almost every door step, window, and Christmas tree in very manu countries. Since the 17th Century, people have lit their Christmas trees to sit by its' comforting glow. The history of electrical christmas lights starts from year 1882. At year 1882 Edward Johnson, an associate of Edison's, created the first string of Christmas lights by hand wiring 80 red, white, and blue bulbs together in a string. At year 1895 President Grover Cleveland put lights on the White House Christmas tree. In 1903, the first strings of Christmas lights were sold to the masses. Strings of Christmas lights continue to evolve. Filament light bulbs are losing ground to energy-saving light-emitting-diode (LED) Christmas lights. Nowadays it is hard to imagine Christmas without bright, twinkling lights. Christmas lights are available at indoor and outdoor versions. The indoor versions are typically considerable cheaper and are only ment to be used inside. Outdoor Christmas lights are an excellent way to decorate your house and yard during the holidays. Outdoor lights are designed in such way that they are safe to use outside where enviroment can be from wet rain to freezing cold. The outside lights are designed in such way that they are safe to be on those hard environments and will last years in such enviroment (using indoor lights outside would be an electrical hazard and they would propably fail pretty quicly). Most outdoor christmas lights are based on low voltage bulbs and powered through low voltage transformer (typically 24V AC output). The low operation voltage and electrical isolation (provided by transfrer) from mains voltage provide the safety. There are also high power outside lights hat operate at mains voltage directly, those lights are constructed so that they are comptely waterproof and can withstand outside weather (because mains voltage is on this system be careful when using them, do not touch them when power is on in case insulation has failed on some place of the set).

      Usually it is a good idea to select a light that is double-insulated or that has been wired with an earth conductor. Double-insulated lights will show the double box symbol. Check also the lamp rating is suitable for the enviroment they are ment to work at.

      Architectural lighting

      Architectural lighting, the use of light in buildings, is critical to the performance of everyday activities and to the appreciation of the built environment. Using Architectural Lighting Controls, specific architectural details of an area can be enhanced and almost any effect or mood can be created. By controlling the lighting in an area, different moods can be artificially created for the desired effect, whether it be a relaxing atmosphere or to stimulate a lively response. In restaurants, for example, different scenes may be required to create a suitable atmosphere, depending on the time of day, e.g. brighter lights at breakfast time, but more subdued lighting effects at dinner. Many buildings are used for more than one purpose at different times. This creates the need for versatility & flexibility of a system. With lighting control, the mood of the lighting can be altered to reflect the mood of the activity taking place and create a suitable ambience. For example, a church may wish to change the lighting scene depending on the event which is taking place. Different scenes would be suitable for a funeral compared to a wedding. Offices are benefiting from lighting control systems. Gradually altering the levels of light throughout the day working with external lux levels, perhaps by incorporating daylight sensors maintains optimum light levels and can increase productivity in an office. In retail, lighting can be used to encourage people into shops and draw attention. Special effects can be incorporated to create interesting features.

      Disco lighting

      The first effects in dance hall lighting appeared long before disco's started. In the 1940's it was discovered that if you shine a light on a ball covered with mirrors that you get one beam off every mirror (seen for example in 1942 film Casablanca). When disco's came along in the late sixties and early seventies the mirror ball was the first effect to adopted. Other lighting could be provided by red bulbs or other colored light bulbs. First strobo effects were generated by using a powerful spotlight with a spinning wheel in front of it (this wheel has holes in it). Soon "Ultra Violet", which made white things glow in the dark, was adopted to disco lighting (makes white clothers to shine, even underwear through clothing).

      The first real dedicated disco lights were invented in about 1968 when someone decided to control lighting using electronics. The most popular effect from this era wa the light organ, that made lamps to flash to different frequencies, originally three channels (bass, middle, treble).

      In the early seventies light sequencers came to use. The idea was to make the lights only react to the bass beat so that one light channel would turn on at time and the light bulb on would change every time the bass beat hits. This gave an easy and dramatic sound activated effect that the eye could follow easily and the Sound Sequencer or Sound Chaser was born. Over the years various variations of this technology have been used.

      In the later 1970's the smoke machine arrived. Instead of just seeing the lamps flashing, provided you used the right kind of lamp, you could see the whole beam passing through the air. This heralded the reign of the "PIN SPOT" (PAR36) with a narrow concentrated beam. Sound Chasers combined with PAR36 light and smoke could be used to create qutie stunning effects. Ath the same time came motorized effects like helicopter and sweeper that turned the ligth bulb generating the light beam. Next came flower effect, that produces the multiple beams using mirror ball type (possibly colored and spinning) mirror system and force them in one direction through a lens.

      Modern disco lighting nowadays is generally modern technology combined with earlier ideas. Multiple beams of the mirror ball, 3D "in air" beam projection and sound activation are the main components still nowadays. The new component on disco lighting used often nowadays are intelligent lighting instruments. Those intellinget lighing instruments send a light beam through a colour filter and a shape (called a "GOBO") then project it onto a mirror that is aimed to different directions with two electrical motors (usually stepper or servo motors). They allow selection of light color, beam shape, beam brigtness and beam direction. Those intelligent lighting instruments are generally controlled using digital DMX-512 light control interface, and the light operator runs them trough a special light control panel or computer program.

      Stage and show lighting

      Lighting is important in theatre and shows. Lighting allows us to see the performers. Lighting provides a tool for setting moods and tones of scenes on stage. Different type of performanced have different lighting needs. Here are some typical lighting situations:

      • Dance - Back lighting
      • Musical - Beamlighting
      • Theatre plays - a somwhow realistic looking combination of different lights
      • Straight Theatre - Light through a window...
      Stage lighting is achieved by the use of a large number of powerful stage lights, or lanterns (or luminaires). There are a great variety of these, for different applications, or of different make or vintage. So there are many different types of lighting instruments used in any theatre. Each type of instrument plays an important role in the overall lighting scheme. The most common light types used in theatres are plane convex lights, freshnels, profiles, which are the generic classes of spotlights. In addition to this floods are used for various applications. Also used are PAR cans , but these offer little control and are used more in rock lighting than in theatre. Most luminaires use at least one lens, which is a piece of glass with one or both sides curved for concentrating or dispersing the light beam; this produces a variation in the beam angle and the quality of the light produced. Some luminaires utilise an attachment on the front of the unit called a barndoor. This consists of four movable metal flaps which are used to control the spill of light produced.The lamp which generates the light inside light instrument is a glass (or quartz) envelope which contains a filament or electrodes surrounded by a gas. The most common lamp types are:
      • tungsten
      • tungsten halogen
      • HMI (Hydrargyrum Medium arc-length Iodide)
      • CID (Compact Iodide Daylight)
      • SCI (Compact Source Iodide)
      Lanterns are hung (or rigged) in lighting positions and are focused (or angled) onto the stage (or anything else). If coloured or tinted light is required, as is usually the case, sheets of gel (or colour) held in special gel frames are placed in front of the lanterns.

      The light color is controlled by color filters that are placed in front of the light bulb that created the white light. The filter passed through the needed wavelengths to produce the needed light color. In the early days of the electric filament lamp, gelatin color filters were used to color stage lighting fixtures. Gelatin filters dissolved when wet, and could not withstand the high heat from the tungsten halogen lamp. Next filter technology was Cinemoid. Cinemoid used a colored acetate sheeting, with inherent self-extinguishing properties. 'Cinemoid' is no longer produced and has been replaced by polyester based materials, such as 'Roscolux' and 'Lee' filters. All Lee's light control and color effect filters are made from a tough polyester film base, which is impervious to water, is totally transparent and has a high melting point. This base is then coated with specially prepared lacquers. The lacquer coating is applied to both sides of the film, is also tough and flexible and has a high resistance to water and heat. This kind of filters may scratch and the surface color may actually vaporize from the surface, through atmospheric contact. 'Roscolux' filters are designed to withstand the high temperatures of stage and studio lighting fixtures. Roscolux filters are colored when the plastic is in the resin stage before the polymer is cast into film. This results in a tough, resistant and durable filter with the color actually part of the plastic, instead of just applied to it.

      The key to lighting control lies in the dimmer. Light dimmer allows the controlling of the light output (the light intensity) of different lighting instruments. Those dimers used to be resistances, autotransformers, saturable reactors and other specialist components. Nowadays light dimmers use phase control principle and use electronics switching components like thyristors, triacs, GTOs and FETs. Thyristors and triacs being the most commonly used components for dimmers in use nowadays. Dimmers are normally available in channels, which can be thought of as electrical circuits capable of handling a rated load. Standard dimming channels are offered in 600-, 1,200-, and 2,400-watt capacities, which correspond to electrical loads of 5, 10, and 20 amps in 120V AC system. In 230V AC systems most the channels are most often offered with 4A (920W) or 10A (2300W) power. In large dimming setups all the dimmer are usually located in the central dimming room or other central location. The lanterns are usually tailed and plugged up to dimmer outlets via a patch board. Various types of cabling and connectors are used to connect lighting instruments to dimmers. Often times, permanent theatre installations will have special outlet strips along the lighting battens to connect the instruments. In less permanent installations movable breakouts are used. Breakouts connect normal single light connectors to a multi-conductor cable usually terminated with a Socapex connector. Using multi-conductor cables the amount of separate wires coming from dimmers to lights can be reduced (=easier to manage). In small set-ups the lights are just directly wired to the dimmer outlets. In distributed dimming systems the dimmers with few channels of outputs are rigged together with lighting instruments to lighting setup, and then all separate dimmer devices are controlled using one lighting console through DMX-512 bus.

      Typical theatre stage lighting setup has tens of dimmer channels and lots of lights conected to them. A lot of pub venues just use a dimmer pack, small programmable DMX control desk, and a few PAR cans, usually on 4 or 6 channels. This can be a very versatile arrangement for a relatively small investment.

      The light dimmers are most often controlled remotely using light control desk which communicates with the dimmers through control cable, which can carry the control information in either analogue format (usully 0-10V DC) or digital format (most often using DMX-512 protocol). The simplest lighting board one is likely to find today allows the operator to set up two scenes and cross-fade between them. These are commonly referred to as X-Y boards. An X-Y board has a number of channels associated with it, where each channel can control one or more dimmer channels. For example, twelve channels may be controlled with a small board. Levels can be set for each of these individual channels on two scenes and a -fader allows switching between scenes. Advanced lighting boards usually provide all of the same features as an X-Y board, but add the ability to store scenes, record a sequence of scenes in a cue stack, and record light chases. Control desks normally come with provision for controlling 6, 12, 18, 24, 36 or even 48 dimmers (there are also bigger desks in very large systems).

      The followspot is simply a high power spotlight mounted on a stand. An operator (or stagehand) controls the lamp and is able to pan and tilt the spotlight, following an actor anywhere on stage. Today, the followspot fixture is still commonly used, for theatre, dance, opera and other entertainment events.

      In addition to the normal lights controlled by light dimmers, there are a huge variety of units that fall within the general category of 'intelligent'. The most well-known type is probably that of moving lights, where the luminaire is able to control the position of the light beam, together with other aspects of the light quality. Moving lights can be considered as Moving Mirror or Moving Head units. Moving head devices physically point the whole light in different directions by using a motorised yoke. Moving mirror type units (used mostly in nightclubs and rock shows) are best suited for prolonged, fast moving lighting effects. Moving lights are generally controlled using digital DMX-512 interface.In addition to those there are also color scrollers and disco effects. Use of a colour scroller system within a theatrical lighting rig can greatly increase its potential. Instead of fitting one colour filter per luminaire, the scroller allows a row of colours to be stored and wound to the chosen colour. Scrollers are pretty simple to operate. Sending a channel percent value to the scroller will set the position in the string and thus the color. What value you will need to send will depend on how many cells you have in your string, in what oder your colors are there and what color you want. Each scroller takes one light controlling channel. Powering anc controlling color scrollers vary by brand. Scrollers, moving mirrors, and other attachments for light fixturesare typically powered by a special type of external power supply. Thescroller, etc. is connected to the power supply by a special 4-pin XLRcable that provides both the DMX signal and the power (usually 24V) to the unit. You would plug the DMX line from your console into the power supplyand not the scroller. You can buy power supplies capable of poweringmultiple scrollers, so it's the responsibility of the power supply tosplit the signal and deliver it to each of the scrollers. Generally you can think that there is a power supply that takes an AC feed (NOT a dimmed) and a DMX signal from the console and then some number(like up to 16) scrollers daisy chain on 4-pin cable out of the power supply. There are also systems where each scroller takes an AC feed and a DMX signal from the console (many intelligent lighting instruments are built like this). Disco effect are type of intelligent fitting that can be used to create the effects seen in nightclubs and at parties. There is a wide range of equipment available in this category, from simple strobes to multi-colour, multi-beam units. Most disco light effects are either controlled through DMX-512 interface or move automatically semi-randomly based on sound around them (some have built-in microphone or sound input connector for this).

      There are also so called "intelligent lights". Typical intelligent light instrument allows the user to control the light color and direction the light points to, possibly also can change a gobo figure. This kind of intelligent lighting fixtures are generally controlled through DMX-512 interface (idea is that one or more channels in DMX-512 data controls each intelligent light adjustable function). There is wide variety of intelligent lighting fixtures made for different uses, from a small night club to a large rock show stage use. Here are few things to consider when selecting intelligent lighting fixture:

      • 1) Noise from fans... check out everything... Buying sight unseen can lead to disappointing expectations when a unit is either too dim or too noisy. Pan/Tilt limits... Reset options. Some have it others need it programmed in the controller.
      • 2) Stepper motors vs servo.... Just depends on the level of smoothness you're looking for in movement. Some lights are more accurate and move smoother than some other lights.
      • 3) Cycle time... Many of the lower end fixtures run for say 15 mins. and need a cooling down period. Most of the bigger and pricier moving lights have adequate cooling to run continuously.
      • 4) Intensity of candle power &/or lumens output to a defined distance. Compare to a set standard of your application.
      • 5) Check the price and life of the light bulb used in the device. The bulbs can run $140-400 each on some lights.
      Often the Dj lights of 250 watts or less won't have the punch to be really visible when using fresnels, pars, or ERS's of 575/750/1000 wattages forwashes. The Dj gear is OK for smaller events like home parties, small low ceiling clubs, but do not work on large stage applications. SO before getting anything you need to know what purpose do you want them for: club, arena rock, corporatebooths/parties and how much money do you have for units and then buying bulbs. All these factors are issues to add when buying intelligent lighting.

      Typical small "rock and roll" club stage setup few sets of PAR can bars connected to dimmer pack (6 ot 12 channels) and some moving lights.PAR lamps stand for Parabolic Aluminised Reflector. The PARABOLIC ALUMINIZED REFLECTOR (or PAR lamp) is a sealed beam type of lamp, similar to an automotive headlamp. The filament, reflector and lens are all optically aligned at the factory, and sealed into a single lamp - resulting in a highly efficient source. As the PAR lamp is a complete lighting unit, fixtures for them are very simple indeed. The PAR lamp is also sometimes known in Europe as the 'pressed glass reflector lamp'. PAR cans come in many versions (PAR 56, PAR64 etc.). Today, PAR lamps are available in various diameters (4.5" to 8"), and various wattages (75-1000 w.) The highly efficient PAR64 lamp (8' lens) is extensively used by the theatre and entertainment industry and the fixtures are often referred to as 'PAR cans'. The bigger the number with a par can is the bigger its size. Electric lamps used in PAR lamps are sized by multiples of 1/8 inch. Therefor a PAR-8 (if such exists) would have a 1 inch diameter glass envelope.A PAR-64 is 8 inched in diam. To convert PAR number to inches divide lamp number by 8. Some common PAR lamp types:

      • PAR 36: Practically all the PAR 36 fittings are standard disco pinspot type with the very narrow beam 6V 30W bulb. Most typical bulb used is VNSP bulb type 4515, which has 5 degrees beam and uses 6V 30W. The PAR 36 cans almost always have a transformer built in, and the bulb has screw terminals on the back. There are also other more rerely used special PAR 36 lamps used (12V models, up to 100W models etc.). PAR 36 lamp diameter is 4.3 inches (around 110 mm). PAR36 lamps come in a mega range of odd ball voltages and powers for things like marine and aircraft (for example 28V ACL version). Generally PAR36 lamps are a bit shortlived on continuous duty.
      • PAR 38: PAR 38 lamp diameter is around 4.75 inches (around 120 mm). This type of bulbs have typically ES Edison Screw cap. Typical lamp power levels available are 60, 75, 80, 100, 150 and 300 watts. Typical beam spreads are 30 and 60 degrees (special 12 degree bulbs exist also). This type of lamps are common in shop display fittings and security lights, also in outdoor garden lighting (special bulb version for outdoor use).
      • PAR 46: PAR 46 lamp diameter is around 5.75 inches (around 146 mm). Typical lamp power is around 200W. Bulb has blade connectors.
      • PAR 56: PAR 56 lamp diameter is around 7 inches (around 178 mm). Typical lamp power is 300W. Bulb has blade connectors. Typical beam spread is 11x25 degrees. Different beam spreads are available. PAR56 lamps are typically available at 300W and 500W power.
      • PAR 64: PAR 56 lamp diameter is around 8 inches (around 203 mm). Typical lamp power is 500W or 1000W. Bulb has blade connectors. Typical beam spread is 11x25 degrees. Different beam spreads are available.
      Today, the ellipsoidal reflector spotlight is still one of the basic tools of the stage lighting designer for spot-lighting applications. In Britain the 'ER' is referred to as a 'profile spotlight' or a 'mirror spot'. In its simplest form, the ER fixture consists of a housing, a light source, an ellipsoidal reflector and a plano convex lens. The light beam produced by an ER fixture is round (or 'conical') with a sharp defined cut-off edge. The fixture is actually a simple projection device and will optically project the image of anything placed at its focal point. The typical ER fixture has 4 integral framing shutters or an iris - to provided limited beam shaping. In addition, and of particular importance the ER fixture will also accept and project the design of a metal pattern, commonly known as a template or gobo. The typical ER spotlight uses a tungsten halogen type of lamp. Fixtures are available in lens diameters from about 4" to 10" and with wattages from 500 to 2000 watts. The typical stage and studio ER fixture has a lens diameter of 6 inches and a 1000 Watt lamp. The ER spotlight is selected by beam spread. Fixed beam spreads are available as follows: 5, 10, 15, 20, 25, 30, 35, 40, 50 degrees. Formerly in North America (1950's-1980's) beam spread was designated by specifying first the diameter and then the focal length of the lens. Example: a 6x9 (pronounced 6 by 9) was a fixture with a 6" diameter lens and a 9" focal length. In order to determine the spread in degrees of any particular fixture, the designer still needed to consult the manufacturers data sheet as the designation did not accurately identify the beam spread of the fixture. Today spotlights are specified in 'degrees' only. The following table shows approximate beam spread of several common ER spotlight fixtures:
      • 6x9 - 40 degrees
      • 6x12 - 30 degrees
      • 6x16 - 25 degrees
      • 6x22 - 15 degrees
      • 8x9 - 20 degrees
      • 8x13 - 13 degrees
      • 10x20 - 15 degrees
      Profiles are the light instruments that produce the narrowest beam. They operate on a similar principle to a slide or film projector in that they have a focal plane (the "gate") and the image of anything placed in that focal plane will be projected by the lens. The lens can be moved to sharpen or soften the focus. Generally, of course, there is nothing at the focal plane so you get a very sharp edged circular beam of light. These lanterns, however, have beam-shaping shutters (four of them) which can be pushed into the focal plane so that you can change the shape of the beam to square, rectangular or triangular. You can also place a gobo in the focal plane. Incidentally, it is also possible to get an iris diaphragm which can adjust the size of the circle of light projected by the lantern from the full width to a pin-spot. There are two types of profile: fixed beam and zoom. A fixed beam profile produces a beam of fixed spread, whereas you can vary the beam spread of a zoom. The most commonly profile to be found has a beam angle of 23 to 25 degrees. Zoom profiles are described by the extremes of their beam angle: a 16/30 profile, for example, has a beam which is 16 degrees at its narrowest and 30 degrees at its widest.

      Diffrent kind of filters are used to change the color of light that goes out of the lighting instrument. The idea of a color filter is that it is on the way of the lighting beam. The filter only lets the wanted combination of different colors (light wavelengths) through and stops everythign else (absorbs or reflects other color). The most typical way to control the ligth instrument color is to usea normal absorbing filter. It passes through the wanted light and absorbs other lighting.

      • The most often used absorbing filter type is called "gel". "Gels" are made of a special flexible transparent material that feels like plastic, but can withstand more heat than normal plastic. The lighting gels are genrally available as large pieces that are then cut with scissors to size and shape that matched the lighting instrument uses. Gels are generally installed to the color filter holder in the lighting instrument.
      • Other commonly used light color filter type is dichroic filter. Dichroic filters are made of glass covered with a metallic coating (deposited on glass), but they are able to withstand tremendous heat produced by high-powered lights focused in optical paths no larger than a quarter or half dollar. Intelligent lighting uses dichroic filters to change their light colors. Dichroic filter reflects unwanted wavelengths of light instead of absorbing them as normal filters do. Dichroic filters can be used to create saturated colors not capable from the gel filters. Dichroic filters are also available to replace conventional gels, their fragility and high cost estricts their use.
      The gobo has long been the lighting designer's tool to shape the light beam and project light shapes to stage. The gobo is placed to the focal plane of a suitable lighting instrument (typically profile) by the user or a set of gobos can be built into the instuments like intelligent lighting. Gobo is just a shadow mask that lets out the light at right shape and masks out the other light. Gobo is typically made from metal or metal-coated glass, or dichroic coated glass processed to have the wanted shape in it. A standard metal gobo is a piece of sheet metal with cutouts. (You canmake a crude and short-lived version with a Coca-cola can and apocketknife.) Meshed gobos are just like a normal gobo, just with a mesh so they cancarry completely cut out shapes and finer detail. The thing about mesh gobos is that you need to play with the degree of"defocusing" to blur out the mesh but not so out of focus as to make the image too blurry around the edges. A greyscale metal gobo has tiny holes of varying sizes tocreate a mesh and produce the greyscale. By careful juggling with the focus, mesh grayscale goboes will give you a greyscale image, rather than the on-off black and white image that you get fromcut-outs. Glass gobos are etched from metal caoted glass and will carry finest deatal. The gobo itself usually goes into a metal holder that slides into a slot roughly even with the shutters in the lighting instrument. Glass gobos need to be inserted with the shiny (mirrored) side facing the source; metal gobos can go either way. The image on the gobo will generally be projected reversed andupside-down from the way the gobo sits in the unit (trial and error will teach you if you are not sure). Color filter gel can be added as usual to the lighting instument if colors are needed. Taped-together piecesof different colored gels are sometimes used with patterns, but don'texpect to be able to control the color blending.

      Stage lighting systems are generally controllable using some form of lighting control desk that controls the dimmers and moving lights. The simples lighting desk might have just a set of sliders that the operator manually operates. The more complicated lighting desks usually have memory options to store many lighting scenes to the memory and allows the user to recall them as needed. PCs are coming to entertainment lighting quicly with the introduction of suitable control software and DMX-512 interfaces. There has been mixed reviews how well PC performs those tasks. Maybe in simplest systems there might not need to bring in PC, but in complicated systems where the control power of traditional lighting controld desks ends, a PC based system might be a very good choise. One recomendation; do not use the same machine for sound and lighting control; in fact if you are using a PC for any entertainmentapplication; lighting, sound, video, or image playback or showcontrol it isa very good idea to use separate and 'virgin' machines and closed networks. As all of us know Windows based PCs are very prone to crashes and randumerrors; so using separate and virgin machines is always a plus; once you connect a computer to the internet and download files to it or install any applications other than what you need for the show you have comprimised theintegrity of the computer. Always be wary of multi-use computers in show applications; there is nogarauntee that the apps will work well together. Many people have experienced difficulities with standard use machines being utilized for sound playback and show control applications.

      In many show lighting applications you can see two separate lighting controlling systems in use. There can be a traditional lighting desk for controlling the lights that go to the dimmers. Intelligent lights usually use a different console and protocol than the conventionals, and their control cable is run separately. Intelligent lights areoften controller with a special lighting desk optimized for intelligent lights controlling or with a suitable control software running on the PC. The use of PC gets more and more popular because there are many good control software applications that allow the light designer to make vry fancy control sequences that can be played back during the show with few keypresses, and best software even allow visualization that the lighting would look (you can design the effects in advance with just your PC without having the actual instrument or access to show location, and then then just do the fine-tuning at the show place when the instruments are installed).

      The stage lighting is usually handled by a light designer and a master electrician. The responsibilities of the Master Electrician (M.E.) are to hang, patch and focus the lights as per the lighting plot provided by the lighting designer (L.D.). Master Electrician controls the lighting loadin. Master Electrician must make sure all the instruments are hung and cabled correctly. Master Electrician is often called upon to patch the lighting console, focus instruments, manage strike, and so on, depending on the demands of the lighting designer. Master Electrician will get a lighting plot from the lighting designer (LD). If necessary, also find out from the intelligent lighting designer (iLD) where those instruments are going to be hung and how they should be numbered. (Most of the time, this is on the lighting plot.) With the designers, write down which instruments go on the same channel. Often times, especially with the truss, multiple instruments go on the same dimmer, and it is important to know this before figuring out how to cable things. Many times the M.E. or L.D. will also operate the lighting console for the production.

      In theatre environment the safety of foth actors and audience members needs to be considered. For actor safety all the lighting instrument must be securely put to place (so that they cannot fall, and safety cables make sure that if someting goes loose it does not fall to ground), lighting instruments must be in good condition, light away from material that can catch fire (lights can be very hot), light wiring is in good condition and proper fire extiguishers are easily available. Many theatres (most UK theaters for example), with a pros arch, have a fire curtain, also referred to as "the iron". Its mission in life is to give the audience TIME to evacuate in a safe and orderly fashion, and it should keep the smoke from an on-stage fire out of the house. Many theatres also use automatic vents above the stage, which makes sure that the smoke can get out from there easily instead of getting to audience. While these, forming a chimney, ensure that the stage becomes a raging inferno, they give the audience time to get out.

        Wiring

        Building a working stage lighting system involves lots of cabling to feed the power from the power source to the lighting instruments. Different theatres provide different means for connecting equipment to be powered. Some simply provide a large number of standard mains connectors you are used at your home and some provide high-current hookups. Many venues provide some sort of combination of high-current and low-current hookups. Often some medium-capacity feeds are also available.Any venue that has been properly wired by a qualified electrician will have a circuit breaker panel that is used to shut circuits off in the event that they draw too much current. It is the current capacity of circuit breaker (in amperes) that determines how much current a circuit can supply. The breaker size is chosen relative to the type of cabling and connector used for the circuit, as each have different capacities. Stage lighting very often uses a three phase power feed which is wired to the dimmer rack, which distributed the power to different lights. There used to be some specific recommendations on some countries specific to this kind of systems. The requirement/recommendation for phase separation is no longer in the IEE regulations (currently 16th edition). There is no requirement in the 16th Edition (or the 15th) to keep sockets on different phases separate. There is a specific requirement to label 415V potential anywhere where you may not expect to find it.Once upon a time (13th edition of IEE regulations) it used to be a requirement to keep connector connected to different phases on physically separated places (two meters apart..). Many people still think it is. However it hasn't been for the last two editions of the regulations. Stage wiring can use the normal household plugs for lights or some other mains plig types (this depends on regulations and environment used). The following plugs can be seen often in stage lighting systems:

        • Cam-Loc type connector: Cam-Loc is a single conductor mating connection of large brass contacts in a rubber boot that is pretty damp proof. Cam-Lock is standard for feeder-type cable used widely in USA. There are few different sizes that are used to serve everything from a 30 Amp HMI fresnel on a movie set to 600 amps of three phase distribution for a whole rock and roll lighting rig. You need to be careful with camlocks because you need to be very careful that you plug them in right way to the high current three phase feed and a camlock that is not connected to anything has it's power carrying partwith in finger reach on the connector. Camloks are scary things when in the hands of inexperienced crew.
        • Powerlock: Powerlock is a single pole electrical connector that has been specifically designed for use in the entertainment industry. It has large brass contacts in a protective plastic/rubber boot. Powerlock connector is designed to be safer to use replacement for Cam-Loc connectors. Powerlocks are keyed to prevent them being cross-plugged and they are designed in such way that it is hard to touch the mains carruing parts of the connector, no matter if connector is mated or not. Powerlock connector is available in two versions with current rating of 400A and 600A. Powerlock connector can take cables in range 50mm? - 240mm?. In the larger scale rock & roll circuit, Camlocks are rapidly being replaced by Powerlocks as the standard large mains connector. POWERLOCK is available in four standard formats, which allow complete hook up through the standard daisy chain principle. There are two Source connectors (Source connectors are supplied with a male contact incorporating a rigid finger proof nose), one for panel mounting and one for cable attachment. These are identified as Panel Source and Line Source. The two other types are identified as Drain connectors (Drain connectors are supplied with a female contact with an optional spring loaded finger proof nose), one for panel mounting and one for cable attachment. These are identified as Panel Drain and Line Drain. Powerloks are gaining popularity because of added safety compared to Camlocks. Powerloks have a nylon peg up the middle so you can't get your finger in so easily and are also keyed so that you can't plug a phase male into a neutral female, etc. Powelocks seem to be displacing camlocks pretty quickly.
        • CeeForm: CeeForm (CEE 17 7 IEC 309) is the European standard for highish-current connectors, available in 16, 32, 63 and 125A single and three-phase variants. The CeeForm connectors are widely used in Europe for connection of three phase power to theree phase equipment, distribution panels and dimmer racks. Three phase 16A and 32A connectors are often seen in the power input of many dimmer packs and in locations where three phase power is often needed (near stage). You can see 63A connectors on larger dimmer racks. Three phase 125A connectors are seen on many conference halls in the mains ditribution panels to provide power pluggable sub-panels (that provide the needed number of 16A, 32A and 63A outlets for use). Single phase 16A CeeForm connectors are used on some lighting applications to connect power to lighting instruments. Ceeform is water protected, so it will happily sit in the rain without tripping the mains out. Ceeforms are available in splash-proof (IP44) and watertight (IP67) versions. The size of the device is determined by the amperage rating. It is virtually impossible to couple a plug and receptacle of different voltage and/or amperage ratings.
        • Parallel blase (Edison): This is the common plug that you are used to at home in USA as the mains outlet connector. Stage plugs are rated for higher loads (15 or 20 amps) than many home connectors. The main benefit that you get from using this type of plug is that they are readably available at almost any hardware store. The problem with this type of connector is that they are quite easy to unplug accidentally.
        • Stage pin: This is a rectangular connector with 3 cylindrical pins in a row. The ground and neutral are closer together, so they cannot be plugged in backwards. Stage pin plugs come in various sizes for different amperages. In general, the friction between the pins and the sockets is enough to keep them securely seated, and the male pins have a slot where one can insert a knife blade (or pin splitter) to spread the 2 halves and increase the friction. This connector is mainly used in USA. This connector is very much used for lighting instruments because it is mechanically quite good (can stand use, not too big) and using it makes it harder for anyone accidentally connecting something else that dimmable lights to dimmer outlets. Three pin 20A version is commonly used connector version. The normal pinout is that center pin is ground. The pin closest to the ground is the "neutral," and the one furthest away is the "hot." Because of the configuration of the pins, it is pretty easy to plug the plugs together, even in the dark. Spread the male pins gently if the connection seems loose. There are versions of the stage pin plug which are locking.
        • Stage Plug: This is another name for Stage Pin connector. This connector is widely used as lighting wiring connector in USA at Stage and Studio lighting. The three pin version with 20 ampere rating is quite commonly used.
        • Twist-lock: looks much like a household connector used in USA, but bigger, and the 3 pins are all slightly curved. the Ground pin is bent 90 degrees, so when you mate them and twist, they can't be pulled apart (connected and twisted in a clockwise direction locks them to each other). Twist-lock connector is mainly used for USA for currents up to 20A. Twist-Loc is standard in Canadian theatres. The available type of Twist-Loc connectors goes up to 50A 250V. In the modern twist lock this prong turns in towards the center of the plug (pictured top) in the older version the pin turns out. The benefit of this type of plug is that the locking mechanism is quite strong. The problem with this type of plug is that they can be difficult to connect in low light situations. The most commonly used version has NEMA code L5-20 (theree pins, rated for 20 amperes).
        • Round pin UK style sockets: 15A round pin UK mains plugs are UK standard theatre lighting plug and socket. Those plugs were as per pre 70's UK house wiring and are still used to differentiate dimmed from undimmed sockets, that's why you see this kind of connectors in many dimmers. Non fused plugs are generally used in the entertainment industry (as opposed to fused 13A UK plugs with square pin as used in general purpose household mains in UK). This is mainly so that all the fuses are in an easily accessible location, rather than in a plug somewhere up in the roof. The 15 Amp plug/socket combination is the most common in UK although the modern 16A (CEEform) is beginning to take over. Some venues use 5Amp connectors,whic are like the 15A but bit smaller.
        • The CEE 7/7 ("Schuko") grounded plug is used as a standard in Germany, Austria, Norway, Sweden, Finland, the Netherlands, Belgium and France; it is also used in Portugal and Spain. "Schuko" is rated for maximum 16A 250V (used in both 10A and 16A 230V AC circuits). The SCHUKO plug has two pins that carry live and neutral wires, plus two safety ground connetions on the side of plug (they make contact with ground spring on the mains jack). The thing to note on "Schuko" connector is that the connector can plugged to the mains outlet on two ways, interchanging which wire is live and which is neutral. Other note is that you can plug a SCHUKO connector also ot ungrounded power outlet.
        • Many small electronics appliances in Europe use small flat "Europlug" connector. The Europlug originated as CEE 7 and has been around for almost 30years. It is a clever design that fits all the historic national sockets in all European countries, except for the UK. IEC 884 is one spec for the "Europlug" (BS EN 50075). Europlug is used in small electrical and electronic devices that need no protective ground and consume less than 2.5 A. Europlug is found on some small very low power lighting instruments (household lighting instruments, small stroboscopes etc.).

        It is very nice to have different connectors for dimmed power and mains power. Most professional theatres in the USA use either stage pin (a.k.a. 2P&G) or twist lock connected to the dimmers and edison (2 parallelblades with ground) for domestic mains power. You have to actually work atconnecting something which shouldn't be dimmed to a dimmer since it willinvariably have an edison plug. When the power is fed to the dimmer packs and other similar similar system, high power electrical power connectors are used. In Europe CeeForm connectors are often used to connect three phase power to the dimmer racks. In USA cam-lok connectors are the standard for high current three phase power feeds (get a proper electrician to connect this set of five connectors right). In USA also some other connectors are used for high current feeds. NEMA "14-50" ("Harvard Standard") is commonly used connector for high current two phase power for rental dimmer packs (up to 50A per per phase). NEMA "14-60 " is sometimes to feed two phase power (125/250V) up to 60A to dimmer packs.

        In addition to connectors described above there is large number of different multi-pin connectors used to connect a group of mains circuits through one connector. Those multi-pin connectors are generally used to carry the power from light dimming racks to the lighting bars. The most commonly used connectors for this are Socapex and Harting, but there are also many other multi-pin connectors in use.

        • Socapex: Some years ago, the entertainment industry has chosen the Socapex SL61 connectors to become the world wide standard for power distribution interconnection. The Socapex brand is so famous that "Socapex" can be considered has the worldwide generic name for 19, 7 and 37 pins connectors. Some people even call it the "Soca". The 19 pin Socapex is the most commonly used, and the standard wiring for allows running six light channels through it (each up to 20A). 90 pin Socaped is probably the most widely used mains multicore connector, used in both the USA and the UK, used for delivering six 2KW (240V) circuits down a single physical cable. Socapex connector provides three seprate wires (live, neutral and ground) for all six circuits run through it. Pin 19 appears to be unused in most applications, except for Vari*Lite, who use pin 19 for the screen of the multicore. There is a common belief that it is a good idea to common the earth conductors together in each connector; it appears that this is not permitted under the USA NEC.
        • Harting: Harting makes a large selection of industrial connectors. There is a 16-pin Lectriflex/Harting connector that is commonly used for six channel dimmer connections. 16-pin Lectriflex/Harting is commonly used for for aggregating six 2KW (240V) circuits down a single physical cable. The connector is rated at 16A per pin. All six channels have their separate live and heutral pins. There are only four ground pins, that are normally connected togeher and shared by all the circuits on the cable. There is also a 10-pin Harting connector used in some applications, this carries live and neutral through pins on the connector, and ground through the connector metal shell connection. In this way 10-pin Harting connector can carry maximum 5 channels. 10-pin Harting is commonly used to carry four channels of mains power. There is also a 6-pin Harting connector.
        • Bulgin connectors: These 8 pin multipole connectors dominate the low cost and disco marketplace in the UK. They are rated at 5A per pin, with a total plug load of 6A. Those connectors are a bit unusual. The biggest nightmare with Bulgin connectors is that there are a number of different wiring schemes adopted by various manufacturers, making the interconnection of differing equipment problemsome. Fortunately the earth pin is separate from the power pins, and so it is most unlikely that misconnection will cause a shock hazard.

        Multipins connectors are often seen on the back of dimmer equipment and/or dimmer equipment racks. Sometimes separate light circuits are wired to them or out of them using an adapter that adapts the multipin connector to many separate mains single channel mains connectors or output jacks.

        For the multipins connectors descibed above there are widely accepted wiring standard how those connectors should be wired. Please note that just because a connector has a wiring standard, it doesn't mean the cable you're using is following it. Please be very careful, especially with power connectors. Always check when using somebody else's kit. If in any doubt, check!

        When installing lihgt dimmer systems you need to consider the needed power feed for them. When designing system (touring system or permanent installation), to think about is how many dimmers you can drive with the power available. Most dimmers this side of the pond come in multiples of 600 watts (600w 1.2kw 1.8kw or 2.4ks). Usually you don't need the amount of power that is the maximum power of dimmers connected to the mains feed. In general, you can "overload" your incoming power by a decent amount, meaning having more dimmer power and total light load than your feed can handle. You could get away with more since you will never have all channels at full even if all the dimmers are loaded to capacity (which is highly unlikely) unless you are a community theatre were untrained or inexperienced lighting people might have unsupervised access to your equipment. If you have more light instruments than your power input can handle at the same time, you need to make sure that your LDs/and or MEs understand about both the maximum loading capacity of your incoming circuits so they don't plan anything stupid.

        When using three phase power feed with large dimmer packs some things need to be considered in the wiring. First it ia a good idea to distribute the dimmers among phases so that they don't get radically out of phase balance. Phase controlled dimmers are a very highly non-liner loads. Dimmers do generate a large number of odd-order harmonics (worst is third), now unlike the fundamental (50 or 60 Hz line freq.) when 3rdorder harmonics are "added up" in the neutral the magnitude increases.Usual practice is to specify the neutral conductors at 130% of phaseconductors (rated for 130% of nominal phase current).

        Modern dimming systems are larger in dimmer quantity, more heavilyloaded with fixtures and more accurately fired than ever before. Electronic dimming can present many stresses on the electrical transformer that feeds thedimming system, which will make this switch gear chatter and potentiallyover-heat the wiring and the transformer. In general terms, the SCR switching distortsthe normally smooth AC waveform. This distortion is the worst in the dimming range of 35% to 70% and travels through all of the wiring involved in the system. A typical power feed to a dimmer rack would have three hot legs, one neutral anda ground wire (three-phase four wire + ground 120/208 volt servicein USA, 230V/400 volt service in Europe).In worst case (all of the dimmers are set for a 35% dimming range) more current can be carried on neutral wire than what it is rated for (unless oversized neutral is used). This can cause overheating the wire covering, wire connectionsand the transformer without main circuit breaker tripping(because the draw on the hot legs is still below their capacity).The chatter of the switch gear is an audible warning of a potentially critical problem. The chatter can also be very irritating, especially during quiet moments. This problem can then be magnified by the layout of the power feed and load wiring.

        There are also considerations of the cable types to use. The wires used in stge work need to be able to take hard use, sometimes hard climate environment (in outside shows for example) and sometines need to withstand very hot conditions. The "pig tail" is a term that refers to the cord on stage instruments. Modern pig tails are made with fiberglass and other composite, heat resistant substances. In the old days these cords were coated with asbestos as a heat insulation. Unfortunately, asbestos has a nasty habit of causing cancer, so they are not allowed anymore. This by no means implies that you will never see stage instruments with asbestos (those can be found on old istruments).

        You should, if buying second-hand, check that the lantern is safe and that check should include earth continuity between the plug and the case. You will presumambly be in possession of some test equipment so identifying which wire goes where shouldn't be too difficult. The simplest test is to measure the quality of the connection with a multimeter (you should get very low ohms reading between connector ground and equipment metal case). On some countries (for example in UK) you need to do PAT test that makes sure that groudn id connected and there is no breaks in insulation. Generally as long as you get the earth right, in normal lamp wiring it shouldn't really matter which of the other two is live or neutral. An incandescent lamp is passive device, it just conducts, so as long as it is between the hot and neutral, it doesn't care what color the wires are and which one is live/neutral. An exception to this is if the lamp socket is an edision screw (or equivalent) the neutral should go to the outer (neutral is less likely to cause danger if you accidentally touch it). If the lamp or wiring has a power switch that switches only one wire, then that wire should cut the live wire.

        Don't rely on other people's advice blindly. Check it youself. Someone's life might depend on it.

      Rigging

      Rigging involves hanging things over other people. Attention to SAFETY is important. If something goes wrong, somebody can get hurt.Riggers need to know the proper methods of securing items like cable, also called as wire rope, to other objects without the possibility of slipping. Most common way to rig lights in theatrical environment is toright the lights to scaff using some suitable lighting clamp. Scaff is a 48mm steel tubing used for temporary constructions and lighting bars. Overloading a line poses a serious threat to the safety of personnel, not to mention the heavy losses likely to result through damage to material. To avoid overloading, you must know the strength of the rigging system and components used in it.This involves three factors: breaking strength, safe working load, and safety factor. Breaking strength refers to the tension at which the line will part when a load is applied. Breaking strength has been determined through tests made by rope manufacturers, and tables have been set up to provide this information. The "safe working load" (SWL) of a line is the load that can be applied without causing any kind of damage to the line. Note that the safe working load is considerably less than the breaking strength. A wide margin of difference between breaking strength and safe working load is necessary to allow for such factors as additional strain imposed on the line by jerky movements in hoisting or bending over sheaves in a pulley block. The SAFETY FACTOR of a line is the ratio between the breaking strength and the safe working load. Safety factor will vary, depending on such things as the condition of the line and circumstances under which it is to be used (safety factor is usually 4-10) .

      Foggers and smoke machines

      Many productions can benefit from the use of artificially generated smoke.

      • Dry Ice is probably the most atmospheric fog effect, as it hangs low on the stage and gives a "walking on clouds" effect.
      • Smoke (sometimes called Glycol smoke, Glycol fog or chemical smoke) is the easiest and cheapest effect to produce. It tends to rise into the air and obscure the action. The basic principle is that a mineral oil or glycol based substance is heated, atomising the substance. This is then forced out of the machine under pressure.
      • Haze is widely used to show up the light beams of intelligent lighting units, allowing an attractive pattern of beams in the air to be produced. Haze is only visible when a light beam is shone through it towards the audience.
      • Oil mist Oil mists are used for lighting effects, accentuating the effect of spotlights. They are produced by passing compressed air through a reservoir of highly refined mineral oil.
      • Occasionally pyrotechnic smoke effects are used. They give off a range of by-products which are harmful. The storage and use of pyrotechnics is specialised and may be subject to specific legislation concerning explosives. Pyrotechnic smoke effects are generally useable only at outside performances.

      Commercially available machines are available that use a chemical fluid to generate smoke. The fog fluid is generally made out of glycol and water, making it relatively non-irritating and safe for use in a theatre setting. For low-lying fog effect, fog machines are often used. These machines use dry ice.

      There are several types of smoke effect available, each of which will produce a slightly different result. Smoke is particularly effective at bringing the beams produced from moving lights and lasers to life, and has become an essential part of some lighting displays.

      Low hanging fog on the floor consist of mist droplets. These fogs hug the floor because the air in which the mist droplets aresuspended is colder and denser than the original room air. WWater and very cold substances such as dry ice or liquid nitrogen are most often used to create the fog. However, any liquid inert gas can be used.Some of the low-lying fogs also employ chemical fog fluids in theirsystems.The low hanging fog is usually generated just by dropping "dry ice" to hot water. Low hanging fog can also be generated using a 'standard' smoke machine and coolingit's output (run through icd or use special chiller/cooler).There are also "ultrasonic mist OR fog" device which brings out fog using just normal water. There are also devices called "oil crackers", which break oil to very small droplets. This fog does not usually does notsow much, but makes the lights and lasers clearly visible.

      There are three main types of smoke/fog machines widely used:

      • Dry ice - these machines produce a low lying, rolling fog effect by dropping solid carbon dioxide ("dry ice") into boiling water. Dry is very cold (-70 degrees centigrade) and will lose about 30% of its volume every day as the carbon dioxide sublimes back to a gas. The solid carbon dioxide is available in pellet or block form from industrial gas suppliers and can be stored in an insulated polystyrene container. The visible "fog" effect is actually water vapour. The carbon dioxide gas is invisible.
      • Smoke - a glycol/water mixture is vapourised by heating under compression. Nearly all smoke machines work this way. Glycol or mineral oil smoke 'Smoke guns' all work on the same principles although their size, precise method of operation and the chemical used do vary. The basic principle is that a mineral oil or glycol based substance is heated, atomising the substance. This is then forced out of the machine under pressure.
      • Haze - a very fine mist is produced which is used for enhancing light beams in the air. This is either produced by vapourising oil (an "oil cracker") or by dispersing a glycol fog using a fan. Cheaper haze machines are a low-output glycol fog machine with a fan to disperse the output. More expensive machines use different vapourisation techniques to produce a very fine and regular haze output. Safety hazards: On glycol based machines the nozzle of the machine may be hot. The haze may condense in and on nearby equipment.

      There are also smoke effects that use liquid carbon dioxide (CO2) or liquid nitrogen to generate smoke effects. When those devices spray out liquid cardbon diodide or nitrogen, the coolign effect of it causes the water in the air to turn to visible moke together with the CO2. Liquid CO2 or liquid nitrogen used for example for generating "fog burst" effects. I have also heard that CO2 fire extinguishers are used on some places to generate fog effect (those needs to be separate for ones recerved for real firefighting purposes).

      When using fog effects be warned of some potential healt effects. Smoke and vapour effects can give rise to a variety of hazards depending on the substances used. Manufacturers and suppliers must provide information about the hazards which may arise from their products. This information should be obtained and used when carrying out risk assessments. The following general hazards may need to be considered:

      • Freeze burns or frostbite caused by skin contact with liquid nitrogen or blocks of dry ice
      • Skin irritation from mineral oils or glycols
      • Asphyxiation due to high concentrations of carbon dioxide or nitrogen gases
      • The presence of toxic substances in the smoke or vapour
      • Smoke or vapour may obscure visibility and so increase the possibility of slips, trips or falls.
      • Slips due to spilt oil
      • Heat generated by the devices (for example the fogger nozzle can be dangerously hot and cause burns if touched)

      Dry ice generated fog, is almost all water vapor, but also does have anappreciable quantity of CO2 in it. Used in areas with adequate ventilation/airflow is perfectly safe. If you put too much thistype of fog to a closed room it can get very hard to breathe (toomuch CO2 in air and too little oxygen). Carbon dioxide is toxic and can causeunconsciousness in a few minutes at levels above 7 percent.

      Water Base Fog technology is achived by pumping Glycol/Water mixture through a heat exhanger (simeitmes called heat chamber). The heat exhanger has been heated to the point where at the fog fluid mixture will vaporize. The fluids own vaporization forces the hot mixture through the output nozzle where, when mixed with the ambient ear, it form an opaque aerosol (fog). The fog is made up of tiny droplets of glycol that form around the small particles in the air. The suspended droplets reflect the light, thus make the illumination visible. The normal components used in this type of fogger are a solenoid pump to push the liquid in, and a fibreglass lagged heater block based on a sandwich of aluminium plates, a heating element and a long piece of copper capillery tubing snaked around between the heater plates. In some units the heater is tubular with the capillery tubing wound round it, but the effect is the same. At switch on the unit will not pump liquid until the heating block has come up to the correct temperature, whereupon the pump can run and squirt the fluid into the block. When it does, the fluid evaporates very quickly and the resultant increase in pressure not only causes it to form a dense superheated vapour, but forces it out of the front of the machine via the exit port, which can be as simple as the end of the capillery tubing being poked out, or in some cases a small pinhole orifice to make sure that the internal pressure is kept high. The resultant dense vapour exits the front of the machine and upon contact with the cool air it forms a dense cloud that is a very close relation to real fog.

      In relative terms the ingredients used in smoke fluid are pretty safe, but there is always an ongoing debate in the entertainment industry about whether the output of a smoke machine is safe or not. When exposed to strong concentrations of the fog many people tend to get watery eyes and dry throats and noses. Persons suffering from asthma or allergic sensitivity may experience irration, discomfort or allergic symptoms when exposed to heated fog effects. It's a good policy to ensure that where smoke is being used in the vicinity of performers it is kept to the minimum required to achieve the desired effect. When using fogger machinces (glycol fog) it s a good idea to worry about the asthmatics. Some asthmatics can get a a dangerous reaction out of the fogger fog. Most (90% ?) of 'asthmatics' as we all know cough & splutter in stage smoke because of the psychological effect, not the actual effect. So most of the people are fine with stage smoke, but there will always be some who do genuinely not get on with the stuff. When using fogger on show it could be a good idea to put a warning that fog is used. Safety hazards: Smoke can condense back to fluid near the nozzle of the machine. This can cause a slipping hazard. The nozzle of the machine is very hot and can cause burns. Large amounts of smoke can cause panic and disorientation in an audience.

      Fogger is not the only type of smoke/fog effect that has been used. There has been also some checmical fog techniques used in some applications. One is called Sal ammoniac. Sal ammoniac is ammonium chloride. When heated it decomposes into ammoniaand HCl both of which are vapours. These recombine at lower temperaturesto form a fine dispersion of ammonium chloride particles in the atmosphere,with the appearance of a dense white fog. You get the same effect if youopen bottles of ammonia solution and hydrochloric acid and bring themtogether - where the fumes mix a white cloud of ammonium chloride is formed. According to the data sheet those chemicals are harmful by inhalation and irritating to eyes. Another common chemical fog used in the film industry was titaniumtetrachloride. This fumes strongly in air by reaction with atmosphericmoisture to form titanium dioxide and HCl. Not very pleasant stuff: Causes burns to skin and eyes. If ingested causes internal irritation and damage. Vapour is irritating to eyes an respiratory system.'This kind checmical fog is not according today's safety standards and should not be used nowadays. When making smoke / fog, stick to modern smoke fluids and dry ice (and similar safe technologies)!

      You should test any smoke machine(s) and hazer(s) in the venues you plan to use it in. If the locations have smoke detectors then there is a very distinct possibility that a smokemachine could set them off. This should be checked before the show. There are many places where smoke machine / fogger can't be used because of the fire alarm systems those places have. This kind of devices are now banned in many venues (or you have to pay a fortune per performance to have fire dept. standing by on site). So check the venue before using this kind of devices in them. Beware of smoke detectors in the venue; if possible disable them during the effect, if this is not possible a test run is advisable. If in doubt, don't use the smoke, evacuation of the venue during the show is not the effect you are after.

      General safety notes: Smoke can cause psychosomatic effects in certain members of the audience; some people may believe the smoke causes them difficulty in breathing or makes them cough, so they have these symptoms. There is no evidence that smoke actually causes these problems but you would be wise to use the minimum smoke required and get rid of it by ventilation as soon as the effect is complete.

      Discussion forums for lighting designers

      • LightNetwork at Delphi - The LightNetwork is an online stop for the theatrical lighting professional, teacher or student.    Rate this link
      • rec.arts.theatre.stagecraft newsgroup - discussion on theatrical lighting    Rate this link
      • Show-Control Talklist - The show-control mailing list is for the discussion of all aspects of show control, including (but not limited to) design, construction, operation and maintenance of computers, lighting, rigging, networks, sound and special effects, as well as projection, video control, stage management, electronic design, and show production as it specifically relates to show control. Subscribers include theatre and show professionals and vendors, teachers and students, community theatre volunteers and others who are interested in the subject.    Rate this link

      Black Light

      A UV / Black Light effect is where certain dyes and pigments fluoress in the visible spectrum when illuminated by light out of the visible spectrum. This enables for example floating scenes whereby animators, puppeteers dressed in black can be completely invisible.You can also use black light effect to haveconcealed text or other figures revealed when the black light is applied. Black light is also used in some application just to get nice shining text, by painting the text with fluorencing paint and shining black light to it. Black light fittings produce light that is just beyond the blue end of the colour spectrum. The light is most often put to use by using fluorescent fabrics and paints, which respond to the light to give vibrant colours. Non-fluorescent materials do not respond to this wavelength of light, and so remain dark (or invisible). Simply, fluorescence is due to the absorptionof light at one wavelength, relaxation of the absorbing material to a lowerenergy (the energy difference normally being converted to heat) and thenre-emission of light with this lower energy and hence a longer wavelength.The process is not limited to UV excitation, but this is the waveleght that is most often used (invisible light source, visible light out).The useable wavelenght range depends upon the absorption and emission processes of a material.Blacklight is an ultra-violet light from which the most harmful part of UVradiation (shortest wavelengths) have been filtered. The UV light used in black light effects is not in normal use a danger to eyes. But do not look directly at the black light tube very nearly and avoid very much exposure to strong black light, because very strong black light can still be dangerous to eyes and skin. There are actually two different commonly used types of black light, but they work in basically the same way: A tube black light and incandescent black light bulb. The conventional black light design is just a fluorescent lamp with a couple of important modifications. A tube black light is a basically a fluorescent lamp with a different sort of phosphor coating. This coating absorbs harmful shortwave UV-B and UV-C light and emits UV-A light. UVA light has wavelength of 320-400 nanometers (typically around 360 nanometers). Typically about 2% of the total input power of fluorescent black light lamps can be emitted in the visible 380 - 760 nm band.The only way to create a real blacklight effect is with realUV sources. UV tubes, UV cannons, whatever. An incandescent black light bulb is similar to a normal household light bulb, but it uses light filters to absorb the light from the heated filament. It absorbs everything except the infrared and UV-A light (and a little bit of visible light). In practice this kind of black light bulb does not work well, because they usually put out much more visible light than useable UV. Some people have used some stage lights with suitable color filters to get effect which resembles somewhat black light effect. Some people have used dark blue color filters (like Lee 181 Congo Blue) to emit dark blue light, which is not well visible, but can cause some flurescense on some materials. All trials with normal bulbs and filter emit some light in the visible spectrum and practically no UV. The reason for this is that standard theatre lamps cannot produce light in the non-visible UVspectrum therefore cannot produce a good UV / Black light effect. The reson for no UV on theatre lamps is a result that normal incandescent bulbs do not practically give out any UV and the some amout of UV produced by some halogen bulbs is filtered out by the lenses in the lamp. By using gels like Congo Blue (L181) or Tokyo Blue (L071) one cansimulate a UV sequence but there will be visible dark blue light inthe scene therefore you cannot have invisible puppeteers or operatorsbut you can have concealed text revealed. Most UV stimulated pigments will fluoresce brightly well into the blueregion of the spectrum. It's a common trick to get a quick UV styleeffect by using a deep blue gel.Using gel is not the same effect nor is it as effective as using black light tubes. That's a "UV style effect" not actual UV wavelengths. Nowadays there are also UV LEDs which can emit suitable wavelength for black light applications. Safety notice: Longwave UV and the shorter visible violet wavelengths are not completely safe to the human eye. If the lens of the eye is subjected to ultraviolet exposure comparable to that of bright daylight, it is possible for "nuclear cataracts" to form or get worse. This is a dull brown tint in the lens, and is permanent.

      • Black Light Basics - The many styles and sizes of black lights that are available often make people confused. Hopefully the text on these pages, which was compiled from a number of sources, will answer many of the most common questions regarding Black Light.    Rate this link
      • Blacklight LEDs!    Rate this link
      • Fluorescent Blacklights - There are fluorescent tubes that emit UV. The phosphor coating on the inner surface of the tube absorbs the UVC emitted by the low pressure mercury arc, and emits longer UV wavelengths. There are at least six different UV-emitting phosphors used in fluorescent lamps. One common lamp is the ""BLB" fluorescent lamp. The tubing is made from a very deep violet-blue glass known as "Wood's glass". The "BLB" lamps are used for special effects due to their ability to make fluorescent objects glow very brightly.    Rate this link
      • Hacking a Fluorescent Style Blacklight Tube into a Blacklight Filter for Use with Other Light Sources    Rate this link
      • How Black Lights Work - The conventional black light design is just a fluorescent lamp with a couple of important modifications. A tube black light is a basically a fluorescent lamp with a different sort of phosphor coating. This coating absorbs harmful shortwave UV-B and UV-C light and emits UV-A light. UVA light has wavelength of 320-400 nanometers (typically around 360 nanometers). Typically about 2% of the total input power of fluorescent black light lamps can be emitted in the visible 380 - 760 nm band.    Rate this link

        Build your own lights

        Its really hard (i.e. expensive) to create really convincing lightning, but its easy to build some basic lighting devices. There is no reason to put together a concert lighting system, since those sorts of places tend to have a very good lighting system already in place and crew to work them for you. If you need is something that allows you to play anywhere, any time and have your own lights, then constructing your light system can be an useful idea. When building your own lighting systems, it is nowadays a good idea to shop around, because nowadays there are lots of cheap lighting equipment available, and building your own does not make sense in most cases. In most cases combining cheap readily available parts in a creative way and maybe adding some homebuild extra features is the most sensible solution instead of trying to build every lighting device in your system from ground up. You can buy for example get cheap flood lights for less than 10 US dollars per lamp, connectors and switches cost only few dollars cheapest, house light dimmers less than 20 US dollars per channel and wire is quite cheap. Hardware stores and electronics parts shops are places where you can easily find the most parts. By the time you have built the controller, light poles and made the cables, you will probably have spent $200.00 for a basic system.

        If you want a dimmer system with several dimmers cheaply, then using a few wall plug light dimmers to control your lights (remeber to use dimmers that are designed to handle the light load you plan to control). There are also cheap dimmers that can ble instelled "in-line" on the lamp cable (designed to replace switches on lamp cables). One idea to build a simple lightboard is to use dimmer switches designed to replace normal wall light switches. Using several such dimmer switches you can quite cheaply control several light channels. In this system want to put a dimmer switch inline between a plug and an outlet. The whole board is then plugged into the outlet for the power. Each outlet is similar to normal wall outlets (you control you lamps here). When building the device get some electrical boxes where you install those components. One wire (live wire, usually white in USA or brown in Europe) goes straight from the plug to one side of the outlet. The neutral wire (usually black in USA or blue in Europe) goes from the plug, through the dimmer, to the outlet. The easiest kind of box to use are regular plastic or metal switch boxes. Plastic is a little nicer and safer. Ground all your outlet boxes (if they're metal) and dimmers and outlets properly. You can put multiple dimmers and outlets on one plug, so long as you don't pull more than a total power alloved (1800-2400W in USA, typically 2300-3600W in European countries). If you don't know how to wire a household dimmer, you could be asking for trouble in taking this on yourself. For many applications it is a good idea to build dimmer boxes that contain four dimmers each. If you need 8 dimmers, build two identical units. Probably you don't want your fire marshall see it.

        When building or using your homemade lights, be very careful that nothing goes wrong as a result of faulty wiring or other mistakes. Please note that the use of home made gear in public venues can be a liability nightmare. When you use commercial purpose made kit which has been properly maintained you are in a more legally defensible position if something goes wrong. Faulty lighting equipment can start a fire or damage to the venue's electrics.

        Photographing stage lighting

        Photographics stage performances well is a hard taks. Photographs of stage scenes seldom do justice to thelighting or the set in many cases. It's an age-old tussle, especially atamateur shows between the lighting designer and a photographer, because what's likely to be great for the audience is seldom half right for the snapper. Genrally it is pretty dark on stage. To ger good results on low ligt condition you'll need a fast lens (f2.8 - any faster then depth of field becomes an issue) and a fast film (at least 400, if not 800 or 1600). You also need to take into consideration that the stage lighting colour temperature is much lower than daylight. You will either need a tungsten-balanced film (seriously limiting your choices)or an 80 series blue correction filter. The specs say you want to beusing 80A for tungsten to daylight, but 80B or 80C is a bettercompromise between getting something that can be printed neutrally, andnot losing too much light. If you tell them to correct it in theprinting, you can shoot unfiltered on daylight film, but the results arepretty hit-and-miss.Theatre photography is a bit of an art, and one that few can say reflectsthe 'real' live viewpoint. A good quality SLR with tungsten balanceslide film usually gives the best results. If it is not staged forphotography in a special photo call(when you can freeze the actors inplace) then you need a reasonably brisk film, a 200-800 ASA. The fasteryou go, the grainier the image. Slide film is often used because its colour saturation is far beyond that ofprint film (for example Fuji 640 tungsten balanced slide film). Slide film is very fine for slides. Yf you want prints consider a print film. The reason for this is that what you gain in glowing saturation on illuminatedtransparencies is mostly lost when you print them. Also, slide film ismuch less forgiving of exposure errors. Ideally you'll be spot meteringso this won't be a problem, but most metering systems get confused bylarge areas of black onstage. Slide film will probably also cost youmore to develop and print, and comes in a much narrower selection,especially of fast speeds. Looking lighting photographs can be positively depressing, as the contrast range is very sensitive to uniformity. A photo can show up dark spots andpatchiness that you never noticed in the live performance. If you just look at the photographs of the performance, then you may get a totally wrong impression of the quality of thelighting. Digital cameras, if you play with the settings, can give nice results on lighting photographing. Color correcting on the computer can help a lot but can be pretty tricky. his is especially true if you have have a stage split into areaswith strongly different color highlights or you are going to print the photographs.

      Special place lighting

      • Museum And Gallery Lighting - Lighting for Museums and Art Galleries has a unique set of priorities, those of conservation and effective display. In many ways these two requirements conflict as there is a necessity to restrain lighting levels to promote the former whilst the latter requires sufficient light of a high quality to provide optimum viewing conditions.    Rate this link

    Light bulbs

    A "normal light bulb" is also known as an incandescent light bulb. These bulbs have a very thin tungsten filament that is housed inside a glass sphere. They typically come in sizes like "60 watt," "75 watt," "100 watt" and so on. The basic idea behind these bulbs is simple. Electricity runs through the filament. Because the filament is so thin, it offers a good bit of resistance to the electricity, and this resistance turns electrical energy into heat. The heat is enough to make the filament white hot, and the "white" part is light. The filament glows because of the heat -- it incandesces.

    The incandescent light source was introduced in 1879. It is fairly well known that Thomas Alva Edison invented the first reasonably practical incandescent lamp, using a carbon filament in a bulb containing a vacuum. Since that time, the incandescent lamp has been improved by using tantalum and later tungsten filaments, which evaporate more slowly than carbon. Nowadays, incandescent lamps are still made with tungsten filaments.In an incandescent bulb, current heats the tungsten filament, which glows white hot. To prevent the filament from rapidly oxidizing, the bulb is filled with an inert gas, mainly argon at low pressure. Much of the energy dissipated by the filament is heat; only a little is light. The filament of an incandescent lamp is simply a resistor. Inside that fragile glass envelope is a coil of wire that's as much as a metre long and less than 50 microns thick. Shrouded in an atmosphere of inert and sometimes expensive gases, this tungsten wire literally burns away the whole time it's turned on. If electrical power is applied, it is converted to heat in the filament. The filament's temperature rises until it gets rid of heat at the same rate that heat is being generated in the filament. Ideally, the filament gets rid of heat only by radiating it away, although a small amount of heat energy is also removed from the filament by thermal conduction. The filament's temperature is very high, generally over 2000 degrees Celsius, or generally over 3600 degrees Fahrenheit. In a "standard" 75 or 100 watt 120 volt bulb, the filament temperature is roughly 2550 degrees Celsius, or roughly 4600 degrees Fahrenheit. At high temperatures like this, the thermal radiation from the filament includes a significant amount of visible light. Because the filament emits only about 12% of the energy input as visible light, while converting the entire energy input into heat, conventional bulbs are roughly 10% efficient.

    The color of the light coming from light bulb is typically measured with color temperature numbers. A typical 100W domestic light bulb is color temperature 2850 Kelvins (nominal daylight direct sun can vary between 5400-6000 Kelvins). The color temperature of halogen bulbs is typically soewhat higher, because their filaments run hotter. When the a light bult is run at lower than rated voltage or they are dimmed with dimmer, the temperature of the light bulb filament drops, this the color temperature. Very rough data extracted from the colour temperature conversion nomogram in the back of the Strand booklet "The Art of Light" gives esimates for a tungsten lamp:

        100%:    3200K
         80%:    2900K
         65%:    2700K
         50%:    2500K
    
    This is just as an example to give general idea how the light bulb colro temperature varies. Don't rely on these figures as a reference.

    Filament lamps have a positive temperature coefficient meaning that the resistance of the filament goes up with temperature. The resistance at the normal operating temperature is such that it would make the bulb to take the nominal power from the voltage what the bulb is designed to work at. If the temperature is less, the resistance is lower. Typically the the normal light bulb resistance when the bulb is cold is around one tenth of the resistance that it has when it is turned on. This causes that when you turn on the light bulb, it take a quie high current peak until it heats to working temperature quicly. The inrush current as the filament heats to working temperature is some seven to 15 times the steady-state current, creating circuit-protection issues. Every time you turn a lamp on, the filament rises from ambient temperature to more than 2500 degrees Celsius in a few milliseconds (or to as much as 3300 degrees Celsius for halogen types in almost same time). This temperature boost inevitably creates a thermal shock that's often sufficient to rupture depleted wire. Another favourite failure mode occurs as the element cools and passes from a semifluid state back to solid form. In either case, when you reapply power, the weakened element sometimes snaps or molten metal flows, creating a short circuit that blows fuses or trips circuit breakers.

    An incandescent lamp can be easily dimmed by changing the voltage that is bed to the bulb. An incandescent lamp responds to the average (RMS) value on the input. As long as the thermal interia of the filament is greater than 1/2 the cycle time, the lamp will act as if it had a lower voltage when fed with a chopped waveform. Light dimmers use typically this kind of chopped waveform.

    The fact that a bulb uses 100 watts of energy doesn't mean it gives 100 watts of light (typically only 10% or less of the energy consumed by incandescent lamps is actually used to produce light, the rest ends up as heat). The problem with incandescent light bulbs is that the heat wastes a lot of electricity. Heat is not light, and the purpose of the light bulb is light, so all of the energy spent creating heat is a waste. Incandescent bulbs are therefore very inefficient. In a 120 volt, 100 watt "standard" bulb with a rated light output of 1750 lumens, the efficiency is 17.5 lumens per watt. Some lower power bulbs produce perhaps 15 lumens per watt of input power. This compares poorly to an "ideal" of 242.5 lumens per watt for one idealized type of white light, or 681 lumens per watt ideally for the yellowish-green wavelength of light that the human eye is most sensitive to.To get most light buy the bulbs that give the highest number of lumens for every 100 watts of energy used. Most light bulbs average around 500 lumens per 60 W.A lumen is the unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source having an intensity of one candela. There is no direct correlation between lumens and watts because other variables may affect the relationship, such as lamp design life and fill pressure. Tungsten halogen lamps try to reduce filament evaporation by including small amounts of bromine in the bulb atmosphere. The bromine forces the tungsten to redeposit on the filament. Halogen lamp life is about twice that of conventional incandescent lamps.

    Incandescent lamps are available in wattage ranging from 2 to 1500 watts and above. In many cases, the light level generated by a particular luminaire can be increased or decreased simple by switching to a different lamp wattage (do not exceed the maximum lamp power allowed in the luminaire). Incandescent lamps are "resistance smart." The lamp's filament is designed and sized to offer a preset amount of resistance to current flow. This controls the amount of current passing through the lamp. As long as the bulb voltage is right for applied mains voltage, it will work well. Light bulbs have changed very little over the years. They are the cheapest form of lighting product, but they are also the most expensive and inefficient light source in the long run.The bulb type has effect on the bulb live and light it gives out.Incandescent bulbs bring out warm yellow tones and are recommended for living rooms and dens. Halogen bulbs are the brightest, whitest and more expensive. They cost twice as much as incandescent bulbs but also last twice as long. Halogen bulbs give out more light per watt than "normal" incandescent bulbs (up to almost 2 times more in best cases). Typical halogen light bulbs offer a life span of 1,500 to 2,000 hours. Incandescent light bulbs are voltage-driven devices. Operating the bulb at even a few volts above test conditions quickly shortens the life of the bulb compared with its stated specification. The resistance of a tungsten filament is lower when it is cold than when it is hot so if you measure its resistance with a multimeter the result obtained is a little misleading. Once you apply voltage across it so that current flows it heats up and its resistance increases. This means that the initial current is typically few times greater than the normal running current. The high current surge and the effects of very fast filament heating are reason why light bulbs usually fail at switch-on. Dichroic lamps are special reflector floods incorporate a dichroic reflector. In a lamp with a conventional reflector, much of the infrared energy (heat) from the source is reflected into the beam. In a lamp using a dichroic reflector, some infrared energy is dissipated out through the reflector, and not into the beam, resulting in a cooler beam. Those 'cool beam' lamps are particularly useful for museum or gallery lighting applications where excess heat could damage precious artwork or artifacts. Dichroic lamps are manufactured in MR11, MR16 and in various PAR sizes to PAR38.

    Here is a comparision of lumen/watt figure of some different commonly used light technologues:
    Lumens/WattLight Source
    100-190 low pressure Sodium (HID) (150 for 90W low pressure sodium lamp, clear)
    50-150 High pressure Sodium (HID) (115 for 1000W dual arc-tube high pressure sodium lamp, clear)
    100 Sylvania 18 watt low pressure sodium
    84 32W, 48" MOL, T8 OCTRON fluorescent lamp
    75 Best white LEDs announced 2004 (not available in volume)
    60-65 standard F40T12 cool white fluorescent
    64 250W mogul based metal halide lamp, clear
    60 150W single ended compact metal halide lamp
    48-60 compact fluorescents
    45-55 Super bright Red/Orange LED
    35-45 Super bright Green LED
    17.5 Tungsten Halogen Single-End SUPER-Q Frosted Finish D.C. Bay 100Watt
    17.5 100W Incandescent A19 Bulb, softwhite
    14.5 60W Incandescent A19 Bulb, softwhite (standard bulb)
    6 incandescent night light bulb (7w)
    6 6w incandescent flashlight bulbs

    The history of incandescent lamp technology is long. In 1877 Thomas Edison became interested and experimented with electric lighting. On October 15, 1878, the Edison Electric Light Company was incorporated. Edison patented more than 1000 inventions. Besides the incandescent lamp, Edison is given credit for inventing a system of electric generation. Although Edison did not invent the electric filament lamp, he did however turn theory into practicable form and was one of the first to successfully market incandescent lighting. Edison's first successful lamp used carbonized cotton thread as a filament, installed in a glass bulb, with all air evacuated. In 1880 Edison experimented with other materials for filaments, including wood, grasses, hair and bamboo. Of the over 6000 specimens tested by his laboratory, bamboo, became commonly used for filaments. In 1880, on January 17, Patent number 223,898 was issued to Edison for the T.A. Edison Electric Lamp. After the introduction of the tungsten filament, the next highly significant step in the development of the incandescent lamp, came in 1913 when the first gas-filled lamp was produced. Coiled filament gas-filled lamps in 500, 750 and 1000 watt sizes were introduced in 1913. They gave a much better light at higher efficiency with the same life as former lamps. Nitrogen gas was used in the first lamps but argon was substituted in 1914.

    Most light bulbs are designed for the mains voltage operation directly. In addition there are light bulbs that are designed to operate at low voltage sources, for example 3V bulbs on some flash lights and 12V bulbs used in car lighting and low low voltage halogen lights. There are also some special applications where several low voltage bulbs are wired in series to make them all operate together directly from mains voltage. For example there are fairylights where there are tens of low voltage light bulbs wired in series. This works well when all the lamps are same type (same voltage, same power rating), their norminal operating voltage makes together the mains voltage and the whole system is built so that insulation is rated for mains voltage. The downside of this arrangement is that when one bulb goes out, the whole light system goes out. Thanks to the wonders of modern technology, a little shunt wire hasbeen added to modern fairylights. This can be seen just above theglass bead that supports the filament, and is in the form of a fewturns of wire with a low dielectric strength coating which remainsintact at low voltage, but which shunts when the lamp goes opencircuit and 110/240V is present.Modern sets are also available with electronic shunts that maintain circuitcontinuity without increasing the current through the rest of the lamps like a shunted lamp (the electronic component is in the holder which gets warm when no lamp is present).

    Gas discharge lamps

      Fluorescent lights

        General information

        Fluorescent lamps are low pressure or low intensity discharge lamps. The lamp consists of a closed tube that contains two cathodes, an inert gas such as argon, and a small amount of mercury. Typically the glass tube is filled with a mixture of argon and mercury vapor. The metal electrodes are coated with an alkaline-earth oxide. When voltage is supplied to the lamp in the correct amount, an electrical arc strikes between the two cathodes. This arc emits energy that the phosphor coating on the lamp tube converts into usable light. Commonly used phosphor coatings are zinc silicate and magnesium tungstate.

        The fluorescent lamp was first introduced to the public at the New York World's Fair in the late thirties (1937). The lamps were introduced commercially in about 1938. The fluorescent lamp is a low pressure gas discharge source, in which the light is produced predominantly by fluorescent powders activated by ultraviolet energy generated by a mercury arc. Typically, a fluorescent lamp must efficiently generate 253.7 millimicron ultraviolet radiation to excite the phosphors coating the inside of the tubular glass bulb. The lamp is usually in the form of a long tubular bulb with an electrode sealed at each end.

        The modern fluorescent lamp has an efficacy of approximately 65-80 lumens per watt. Today fluorescent lamps are also available in circular and 'folded' shapes. Lamps with various different color temperatures and color rendering properties are commonly available. The most common fluorescent lamp is the CW or cool white version, although new 'warmer' versions are now gaining popularity, worldwide. All fluorescent lamps require a ballast, for operation. A fluorescent lamp tube has argon combined with a minuscule amount of mercury. At the low pressure within the lamp, becomes mercury vapor, even at temperatures only slightly above room ambient. An electrical discharge ionizes the mercury vapor, which emits UV radiation. The UV radiation stimulates phosphors that coat the interior of the lamp's glass envelope, and the phosphors convert essentially all of the UV radiation to visible light.

        The conversion of electrical energy to light is much more efficient than in an incandescent lamp, and a considerably smaller fraction of the input energy is converted to heat. Generally fluorescent fixings give out ~ 3 times as much light/watt as a halogen. The color of the light that a fluorescent lamp produces depends on the composition of the lamp's phosphors. Fluorescents used for general lighting purposes are nearly enoughentirely of "hot cathode" type. The mechanism for conducting electronsfrom the negative electrode to gas/vapor is "thermionic arc". The negative end of the arc, even though it is much more distended than awelding arc due to the low gas/vapor pressure, heats the electrode to atemperature such that molecules in a coating on the electrode lose theirgrip on some of their electrons. Hot cathode fluorescents are generally near or a bit over 100 mA in their smallest sizes (one popular one may oftenwork reasonably at 60 mA) and the usual sizes take generally around 220-450 mA and a few take more.

        The most typical fluorecent lamp type seen in Europe is offices and homes is lamp where there is is one fluorescent bulb (or sometimes two in series) wired in series with a magnetic ballast that limit the current though the lamp to the needed range. In addition to this there is also the starter (passes power for some time though tube heaters when bulb is turned on) and usually some kind of filter capacitor (for RFI filtering and/or power phase compensation). This construction is simple and works well with mains voltages used in 220-240V countries. There the voltage is well enough for the tube to start conducting reliably and there is enough voltage range for the simple magnetic ballast work well (the tube voltage is something in 60-100V when it is on). The simplest sort of ballast, generally referred to as a magnetic ballast, works something like an inductor. It is sufficient for fluorescent lamps operating at around 230V AC or higher voltage. Different lamps require specialized ballasts designed to maintain the specific voltage and current levels needed for varying tube designs. Magnetic ballasts modulate electrical current at a relatively low cycle rate, which can cause a noticeable flicker. Magnetic ballasts may also vibrate at a low frequency. This is the source of the audible humming sound people associate with fluorescent lamps.

        At countries that use 110V mains voltage this simple approach does not work, because that voltage is too low for reliably opeating a fluorescent lamp directly with simple ballast. In 110V world the fluorescent lamps need to use a more complex ballast that steps-up the voltage for the bulb to initially reliably start. This kind of ballast is much more complicated, more expensive and less energy efficient than the simple "just coil" ballast. Many fluorescent lamps operating at 110V AC nowadays use electronic ballasts that can properly power the lamp from 110V power supply with better efficiency than magnetic ballast and are not too much more expensive than those complicated magnetic ballasts. Modern ballast designs use advanced electronics to more precisely regulate the current flowing through the electrical circuit. Since they use a higher cycle rate, you don't generally notice a flicker or humming noise coming from an electronic ballast.

        In many office building and similar places there are also fluorescent lamps that operate at higher voltages than 110V in USA and Canada. In those buildings there are usually higher voltage three-phase power in use within the ouse for power distribution. In many places the fluorescent lamps are powered with 277V AC or 347V AC that is derived from higher voltage three-phase power system (between phase wires or between phase and neutral). At those higher voltages the simple magnetic ballast lamps work well. In such building using higher voltage for lighting saves money.

        In a cold cathode fluorescent lamp as well as neon glow lamps, the cathode mechanism is "glow discharge". This is a multilayer processbut in this process positive ions of the active gas/vapor ingredient(s)accelerate towards the electrode and knock electrons from atoms of theelectrode material to permit conduction from the electrode material to thegas/vapor. This is more practical and has longer life than hot cathode with lowercurrents. Miniature cold cathode fluorescent lamps have typical operatingcurrent often around 5 mA. "Neon signs" are cold cathode and frequentlyfluorescent and usually operate at 20 mA. There is a large style of coldcathode fluorescent (rare) with operating current somewhere around ormaybe a little over 100 mA. One advantage of cold cathode fluorescent is a lack of extra wear from starting. The disadvantage of glow discharge over thermionic arc is that glowdischarge has a much higher voltage drop in the cathode process (typically 55-80 volts) compared to usually 8-12 volts for thermionic arc. Cold cathode fluorescent lamps can be for example seen in applications like neon lights as used for advertisements and for example as miniature back-lights as used in laptop computer LCD screend.

        Cold-cathode fluorescent tube (CCFT) / Cold-cathode fluorescent lamp (CCFL) is a special form of fluorescent tube without heaters on the cathodes. CCFL is often used as a backlight in LCD flat panel displays and also in some decorative lighting applications (for example decorating PC cases). CCFL bulbs are typically small (typical diameter 3-10 mm, lenght 10-30 cm). CCFT requires an adjustable, current-limited, high-voltage, ac-power source. Generally the tube needs quite high voltage to start operate and then operates at lower voltage (up to several hundred volts). EMI and tube-lifetime considerations practically dictate a sinusoidal waveform to be used for powering CCFT. There are also some large cold-cathode fluorescent tube systems that use high voltage mains powered transformer capable of putting out high voltage at current of around 100 mA.

        Note on installing fluoresent light fixtures: Many mains powered florescent fixtures need to be grounded to work properly. Two wire fixtures might need the correct wire connected to the neutral and hot. If they are reversed, they will be hard to start. That you can touch yours andhave them start indicates you may indeed have a reversed hot andneutral.

        Developed in the late 1980's the compact fluorescent lamp revolutionized the lighting industry. This lamp (also referred to as the PL lamp), is simply a folded fluorescent tube, sometimes no larger than a standard 'light bulb'. The ballast is usually mounted in the base pf the lamp. This new lamp allows most household incandescent lamps to be replaced with these new energy saving fluorescent lamps. PL lamps are available in various wattages from approximately 9 - 50 watts, and are available from all major lamp manufacturers. Compact fluorescent light bulbs, or CFLs, use fluorescent light technology in a compact size that can be used in place of standard light bulbs. Compact fluorescent light bulbs use 70 percent less energy than standard incandescent light bulbs. Roughly, roughly, a compact fluorescent lamp produces as much light as an incandescent lamp of 3-4 times as much wattage. Good compact fluorescents normally produce 4 times as much light as good incandescents, except compact fluorescents can be dimmed by non-ideal temperatures, heat buildup in fixtures, etc. CFLs come in a variety of sizes, depending on wattage and manufacturer, and will fit most standard lighting fixtures. CFLs last an average of 10,000 hours, compared to only 850 hours for a standard incandescent light bulb. Generally you can replace a norma light bulb in the fixture with a compact fluorescent lamp that mechanicaly fits to the lamp in most cases. Be prepared though that if you put a compact fluorescent in a fixture designed for an incandescent, the light may not be distributed in a less favorable manner than that of the incandescent. Some lamp fixture work better than other with compact fluorescent bulbs.

        Fluorescent lamps and incandescent lamps can vary significantly in efficiency with manufacturer and model due to various issues of design and quality. "Standard" fluorescents of the more usual "shades of white", especially the 4 foot T8 (1 inch diameter) ones, are a little more efficient than compact fluorescents. Compact fluorescents with magnetic ballasts are usually less efficient than ones with electronic ballasts and they also have quality issues. Non-compact fluorescents also suffer from ballast issues. Generally fluorescent lamps with color rendering index higher than 86 or so have less photometric output than most usual ones with rated color rendering index in the range of 53 to 86.

        Fluorescent lamps are not the optimum lamp types for outside lighting in freezing cold enviroment. Any fluorescent lamp will have an issue with temperature being way off it's optimum operating temperature. This creates two problems:

        • The lamp will be very dim when it is cold. It's possible to use fluorescent lamps in insulating sleeves that are designed for cold ambient temperatures. These are designed for outdoor applications in locations where winter temperatures are cold. If you fit a thermal sleeve to the tube, it will eventually warm up, but this can take half an hour, so it's not suitable for occasional use.
        • The tube starting voltage will be much higher than usual, which can make the lamp much harder to start. If the lamp will start at all depends heavily on the control gear and the length of the tube. 5' tubes on SRS (Semi-resonant start) control gear used to be the norm for very low temperature on 240V mains as it generates 500V across the tube for starting, but this has vanished from the scene with the advent of electronic control gear.

        Compact fluorescent lamps have also the same problems as listed with normal fluorescent tubes. For outside operation in cold environment select lamps that are rated for this.

      Neon lights

      The colorful neon lights used ad company logos and other advertising purposes are an another story. The history of neon lights is long. The initial color source is the inert gas which emits a characteristic color when electricity is applied. The two most common gases are neon which emits a fiery red, and a mixture of argon and minute particles of mercury which emits a subdued blue. Clear glass allows you to see the characteristic colors emitted by the gas. Fluorescent powders may be painted or baked to the inside walls of the glass tubing and the source light is then converted into a multitude of shades such as pink, turquoise, and green.

      Neon lamps are typically is powered by voltages in the 2,000 to 15,000 volt range from a current limited source. The needed voltage depends on the used gas mixture and the length of the tube. Even though the current is in the milliamp range (or few tens of milliamps). If a neon piece is not properly mounted, wired, and insulated this voltage poses both a shock and fire hazard. Well made neon lights can last decades. In practical terms the expected life span is between 8 to 15 years. Neon light system components can be repaired and recharged.

      The neon transformer can supply different current, voltage and frequency as needed. The voltage is typically in 4-15 kV range and the current limit is typically around 30 mA. The traditional ferrous core neon transformers work at mains frequency (50 Hz or 60Hz) and supply AC output. As a rule of thumb you can say that you need 1000 VAC per meter (about 3ft) of standard diameter tube (13 mm diameter) to make it work and for normal brightness you need 20-30mA of current. Neon sign transformers are distinguished from traditional transformers by being current limited and center grounded. Center grounded simply means that the center of the transformers output winding is electrically connected to ground. This results in both output terminals being hot with respect to ground (quite typical value is around 4 kV per output, total 8 kV per output pins). Current limited means that when the transformer's output is shorted, only a limited amount of current will flow. Current limiting is achieved by the use of a tightly coupled, magnetically saturable (usually iron) core. The iron core provides resistance to the fluctuating magnetic field which, in turn, impedes the current flow.

      Many modern electronic neon power supplies supply either DC or high frequency AC (usually 20-30 kHz). The high frequency neon tranformers are quite often used nowadays. The limit on high frequency AC output models is that the output wires cannot be long (usually maximum of around 2 meters). The transformers with DC output allow longer cable runs (around 100 meters or so).

      Neon transformers are failsafe, at least in most civilized countries (legal requirement). Usually this is done with ferroresonant cores. It means that the current output is constant, regardless of the load (more or less), and they can sustain this indefinetly. If you have only one meter of tube, and connect it to the 5000 VAC transformer, the output voltage of the transformer will be about 1000V and 30mA of current will flow. Since those transformers are not perfect, the current will be a bit higher with shorter tubes, and they will get hotter too. The transformer's life will be a bit shorter and also the tube's electrodes will wear out (and blacken) a bit faster. So for best performance you should be have the transformer output voltage that matches the needs of the tube. Electrical transformer have typically built-in open circuit protection and thermal protection.

      There are also other kinds of neon lights in use. Special little bulb neons /neon glow lamps) are very commonly used as indicators that the mains electricity supply is on.The typical current for a baseless type such as the NE-2 is about 0.3 mA (for some other bulb types it is in 0.5-1 mA range). This kind of neon lamps typically fire at about 90volts and then sustain a voltage of around 60 once fired. Around 330 Kohm resistor is a common with the NE-2 as a 220V AC line indicator(lower resistance values like 47-100 kohms are used for 120V AC). The exact resistor size is usually not critical as long as the current is not mode than the bulb can handle. This kind of little neon bulbs are also used in "phase testers" which are used to test if some wire has mains voltage on it when you touch thewire with this instrument (sometimes this feature is built into a screwdriver).Those phase testers generally use a very high resistance (few megaohms) resistance to limit the current to a very low safe value (safe enough to touch).

      Metal halide lamps

      Metal Halide lamps are essentially mercury high pressure discharge lamps that have additional metal halides in their arc tubes. Metal Halide lamps provide improved efficiency and improved color rendering qualities over mercury lamps. The modern metal halide lamp has a luminous efficiency of 85-115 lumens per watt. The first metal halide lamp was developed about 1960.

      • Metal halide lamp    Rate this link
      • The Metal Halide Story - Metal halide lamps are one of the fastest growing light sources in the United States today. Metal Halide lamps have gone through a revolution of change and improvement over the last several years. New technology, particularly pulse start technology, now allows users to select among a broad variety of lamp types to suit a wide range of applications.    Rate this link

      HID lamps

      HID lighting stands for High Intensity Discharge Lighting. Modern followspots and projectors now tend to rely on a High Intensity Discharge, (Xenon, CSI, HTI, etc.) lamps. The HID lamp group is one of the three major lamp groups used in modern lighting (other two are incandescent and fluorescent). The HID lamp group includes mercury vapor and metal halide lighting systems. The HID lamp group is by far the most important lamp group used in modern exterior and industrial lighting. HID light sources are highly regarded for their long life and high efficacy. The compactness of HID lamps also increases optical control and allows for a great deal of flexibility in the area of luminaire design. The first HID lamp introduced was the mercury lamp in 1901. Later, low pressure sodium, high pressure sodium and metal halide lamps, were developed. All of these sources consist of electric arcs, operating in a gaseous environment, sealed within a glass tube or bulb. HID light sources are all more efficient than the electric filament lamp, however they also have limited color rendering abilities, due to their 'line' spectrum (not continuous spectrum). Many HID lamps are now also provided with a phosphor coating on the inside of the bulb. This coating causes additional secondary emissions of visual radiation, providing a wider 'spectrum' of light and color. Typical applications include industrial, commercial and architectural lighting. HID lamps are "amps dumb." You can't connect them to mains directly.HID lamps do not have a built-in resistance to current flow, and must rely on an external ballast to set and limit current flow to the lamp. The wattage and voltage ratings of the HID lamp and its ballast must match exactly.

      Sodium lamp

      The high pressure sodium (HPS) lamp has steadily developed and gained in popularity, since its introduction 1966. It provides a more economical source of illumination than mercury, fluorescent, or incandescent and has a more natural color than low pressure sodium. The HPS sodium lamp has a luminous efficacy of approximately 80-140 lumens per watt.

      HMI lamp

      The HMI lamp (mercury medium arc iodides) lamps were developed by OSRAM GmbH to meet a need established by the German Federal Television System in 1969, and their use quickly spread throughout Europe and to the rest of the world. Although originally designed for television lighting, they are now used for location film lighting and as a source for many common followspot spotlights. The modern HMI lamp is highly efficient (100-110 lumens per watt), and produces a daylight type spectrum with a color temperature of 5600 degrees K. Lamp wattages currently range from 200 to more than 12,000 watts. Although not widely know in the name HMI, the H stands for mercury (Hg), M indicates presence of Metals and the I refers to the addition of halogen components (iodide, bromide). HMI is the registered trademark of Osram Lighting. The HTI lamp is a more recent version of the HMI. They area available with an integral reflector and are often used in followspots, fiber optic illuminators and in slide projectors.

      Sulfur Lamp

      Sulphur lamp was developed in 1994 by Fusion Lighting (USA). About the size of a golf ball, the sulfur lamp consists of a quartz bulb containing non-toxic sulfur and inert argon gas at the end of a thin glass stick. A microwave energy source of 2.45 Ghz. (magnetron) bombards the lamp while a fan cooled motor spins the lamp at 3400 rpm. The microwave energy excites the gas, which heats the sulfur, forming a brightly glowing plasma that can illuminate a very large area. The first early prototype lamps were 5.9 Kw. units with a system efficacy of 80 lumens per watt. Correlated color temperature was about 6000K with a color rendering index of 79 CRI. The sulfur lamp starts within seconds even at low ambient temperatures and can be dimmed. The surfer lamp emits no electric or magnetic fields and the light output remains constant over its life. The energy output is continuous throughout the visual spectrum (much like sunlight) however the source is low in both the ultraviolet and infrared energy. Several companies are working with Fusion lighting to develop new fixtures and equipment for the sulfur lamp.

      Circuits

    LEDs in lighting applications

    The light emitting diode (LED) is p-n junction semiconductor lamp which emits radiation then biased in a forward direction. The emitted radiation may be either invisible (infrared) or in the visible spectrum. Invented in 1967, the LED had been traditionally used strictly as an indicator device. LED's are commonly used in indicator lighting applications. Due to their very long life and low operating current, they are ideal replacements for incandescent indicator lights. LEDs have come a long way from their humble beginnings as simple on-off indicators on panels and displays. Early LED's came in red only. Traditionally LED palette used to be only mostly red, followed by green and then yellow and orange, and their brightness was still only enough for indoor applications. By the mid 1990's blue and white LED's had been developed. Many of the older limitations associated with LEDs have changed dramatically in the past few years. New high-efficiency LEDs boast brightness that makes them usable in daylight and provides colors that include long-sought blue and even white.

    Traditionally LEDs have only been available on different colors and the LEDs that give out white light have just became widely available just quite recently. There are different technologies to get white light out of LEDs. The very first white light LEDs used three different color LEDs inon one package to generate white light. Many so-called white LEDs actually use three color light sources, a blue LED that stimulates red and green phosphors, to simulate a white emitter. But because the blue LED is highly directional and the phosphors are omnidirectional, the effect is dependent on the viewing angle and thus is uneven. There are also LEDs that give "nearly white" light by using just one phosphor. Those LEDs use blue light generating LED and phosphor that generates yellow light (blue generated the blue, yellow color activates gree and red on eye).

    Leds have already replaced light bulbs in virtually all indication applications. Now with the advent of super bright leds, many illumination applications are being taken over by leds also. Until recently, though, the price of an LED lighting system was too high for most residential use. The versatile LED is now bright and colorful enough to use in applications beyond simple indicators and readouts. The virtues of LEDs, compared with incandescent sources, are clear: long life plus power efficiency. LED (light emitting diode) lamps consume less than a quarter of the electricity that fluorescent lighting does, and the lamps last about ten times as long. A 1.2 watt white LED light cluster is as bright as a 20-watt incandescent lamp (bright enough to read by). The lighting quality can be comparable to that of cool white compact fluorescent lamps, with color rendering indices near 85. LED lights powered from DC source don't flicker. The light is very directional in small arrays. Most LED vendors cite an operating LED life of 100,000 hours under nominal operating conditions. LEDs maintain colour consistency when dimmed, and integrate efficiently into advanced optical systems with high illumination efficiencies.

    The power savings potential with LEDs are dramatic, but you still need to understand the vendor's intentions and what you need. The common signal-integrity unit for defining the amount of light emitted compared with energy input is lumens per watt may be misleading. An incandescent bulb distributes its photons relatively evenly around its source in a non-directional, spherical mode, whereas an LED is inherently a directional source. In addition, the output of the incandescent lamp covers most of the visible spectrum, whereas LEDs are wavelength-specific. As a rule, an incandescent source is 10 to 20% efficient, but an LED is 80 to 90% efficient. Individual LEDs are designed to be driven from low voltage current limited sources. The typical operation voltage per LED is only few volts. When you have to run LEDs from higher voltages, you need to use various techniques to make it work well. Here are few circuit ideas used to drive LEDs from various power sources.

    • For low power indication applications from low voltage DC source (5V to 24V) a simple series resistor is typically used to limit current to typically to 10-20 mA current range
    • DC powered LED clusters typically use many LEDs in series so that the LED votlages together are quite near to the intended power source voltage (usually few volts less) and the rest is then consumed with current limiting resistor
    • Switched mode power supply constant current source drives various number of LEDs nicely from large input voltage range efficiently
    • Mains powered (120V or 230V AC) indicator lights use typically use a series capacitor and a series resistor to limit the power going to LED without too much power loss. A rectivifier brige (and sometimes a filter capacitor) or a reverse-connected diode in parallel are used to protect the LED against wrong AC voltage polarity.

    A standard LED lens without any diffusion produces a relatively narrow viewing angle of about 12? on either side of the LED center. With special techniques vendors can make the LED viewing angle spread to as much as ?35?. To get broad-area illumination using LEDs, you need an optical diffusing lens or an LED array. Many illumination systems use an array of LEDs to develop the desired overall intensity. Current LEDs are generally not a lot more efficient than light bulbs. You can generally expect light output of around 15-50 Lumens per watt. LEDs are current-driven devices. Usually, a voltage source provides this current through a current-limiting resistor at a low cost. Most LEDs, regardless of efficiency, have a nominal current drive of 20 mA; some units can use a maximum drive of 70 mA. Regardless of current level, you need to maintain the drive current within specification in all operating conditions. With LED technology you still need to grapple with issues of source drive, brightness, derating, spectral output, and viewing angle. To use LEDs in more than simple indicator applications, you need to understand LED-drive models, compensation for temperature increases, the legitimate ways of assessing brightness, and viewability factors.

    When you need to drive many LEDs from higher voltage than typical LED operating voltage, it may seem simplest to just connect all your LEDs in series, which ensures that each LED has the same forward current. This topology works, but you have to make sure that your current source has enough compliance for the sum of the forward-voltage drops of the LEDs, nominally 1.4 to 3V for each LED. At the other extreme, you could run each LED from its own parallel branch for maximum redundancy and lowest compliance voltage at the source. Between these two extremes, you can use a combination of series and parallel strings to manage the trade-offs. In practice, most LED arrays use a 12 to 24V-dc source and three to six LEDs per series string to achieve a satisfactory trade-off.

    White LED lamps are now available with standard screw-in bases to fit incandescent fixtures. They are much smaller than compact fluorescent and even incandescent, because instead of a bulb, there is an array of tiny diodes lining the rim of the base. The biggest limitation to LED for common residential use is the cost of manufacturing due to still-limited production runs. There is still a limited number of manufacturers, but this is changing.

    Sometimes there has been discussion if pulsing a LED will help to make it to appear brighter that applying continuous power of same amount. In some special cases human eye can detect a blinking light better than steady light, but generally pulsing does not help. The human eye response peaks at about 10Hz, then begins to decline,getting pretty weak by 40Hz or so. Above 70Hz the lightappears to be continuous, with an apparent brightnessthat's equal to the average light power level, so there'sno benefit to pulsing the light. In the 5 to 15Hz regionwhere there is a benefit, you'll realize that the lightappears to be strongly flickering, which is an attention getter, especially in the peripheral vision. So pulsingat 10Hz would be a good idea for an alarm signal. A blinking LED will certainly get extra attention, but if it continues to blink without stopping, it may alsocreate some irritation. As faras our visual system is concerned, there's no advantage toshort powerful pulses vs longer ones with the same number of photons.

    Dimmers

    In many situations, luminiares are not used constantly at full power. They are generally required to fade in and out, and to be used at different brightnesses, or intensities, at different times. A device is required to regulate the amount of electrical voltage sent to each luminaire, thereby allowing the intensity of the light to be varied: this is a dimmer. A light dimmer allows controlling of light bulb brightness. The basic idea of dimmer operation is that it limit the electrical power that gets to the light bulb. Dimmers today come in many styles to control different types of loads. In some old mains powered lighting systems variable transformer is used as light dimmers, but nowadays they are largely replaced by electronic light dimmers with operate using phase control principle (first this kind of SCR based system was publicly demonstrated in 1962 in London). There are also some other dimmer types used in some special applications (variable transformers, simple resistors for very low power bulbs and PWM controllers for DC lights).

    Proper matching of control system types to the load is very important. Not all dimmers work properly with all types of loads. Using wrong type of dimmer causes that the dimming does not work well, and in worst case can damage the light dimmer and/or the lamp connected to dimmer. Normal incandescent bulbs can be dimmed with very many dimmer types, but some other light types are harder to dim. Be warned not to dim lights which have motors or control electronics in them (unless they are specifically designed to be dimmed). For example if you dim a typical disco light (one with electronics and motors) it will probably damage the electronics.

    One light dimmer regulates one lighting circuit, or channel, allowing the electrical supply sent to the attached lumainire to vary between 0 and the mains voltage (230V or 110V). Each dimmer is designed to work up to a maximum electrical load, called its capacity. Any number of luminaires can be connected to a dimmer, until the capacity is reached. In stage lighting applications the dimmer systems are generally built from many dimmer packs. A dimmer pack comprises a number of individual dimmer modules, housed together for convenience.

    The first dimmers used in theatrical applications used to be quite simple resistive current regulators. Tens of year ago devices like slider resistance that housed in a sheet metal casing and which is used mounted on the front of the switchboard, was used to control the ligth brightness (used to waste lots of power and heated considerably). Some very old systems even used a bucket with metal bottom and a spade with salt water in the bucket, just dip the spade further in to pass more current (wouldn't like to operate it personally). Those "water dimmers" using glass cylinders with a metal plate at the bottom were real in the theatres in the earily 1900s. In some applications those resistive dimmers were replaced with adjustable autotransformers. Those early methods worked, but the downside of them was that they are big and hard to make remotely controllable.

    An effective and widely used modern method of controlling the average power to a load through a triac is by phase control. This means that a typical light dimmer circuits use a form of Pulse Width Modulation (PWM) to control the brightness of the bulb. It controls the brightness of the bulb by turning the bulb ON for part of time and then OFF for part of time. An incandescent lamp responds to the average (RMS) value on the input. As long as the thermal interia of the filament is greater than 1/2 the cycle time, the lamp will act as if it had a lower voltage when fed with a chopped waveform. Phase control is a method of using the triac to apply the ac supply to the load for a controlled fraction of each cycle. In this mode of operation the triac is held in an off, or open, condition at a time in the half-cycle determined by the control circuitry. The brightness of the bulb is a function of the ON time to the OFF time. In the on condition the circuit current is limited only by the load, i.e. the entire line voltage (less the forward drop of the triac) is applied to the load. Modern mains light dimmers use TRIACs to control the flow to the light bulbs so that only needed part of mains pulse wave enters the light bulb (the PWM operation is syncronous to mains power). This basic principle of operation of a dimmer, has remained unchanged for forty years. SCR dimmers chop the sine wave on the front end, IGBT dimmers chop it on the back end. Many times users of dimmers have noticed buzzing sound that dimmed lighting systems make. The "Buzz" is due to inadequate chokes. The choke controls the rise time when the SCR "turns on". Any resistive load, such as an incandescent filament type of lamp, simply "sees" the chopping as equal or the same as a voltage drop. Because a filament takes a measurable amount of time to "heat up" or "cool down". The on and off cycles blend into a steady degree of incandescence that we see as a "level".

    Many modern dimming systems that allow curves to be set usually have a program that allows the dimmer output to be set by the "apparent" voltage level. Inductive loads are another issue entirely. In the early days of SCR dimming, motors and transformers such as those used in many slide projectors and such, either destroyed the dimmer, were destroyed BY the dimmer or both. Most, but not all, dimmers on the market today have electronic circuits to deal with the problem.

    Electronic dimming using triacs or thyristors use a technique which switches on the device at certain point after the AC power has crossed the zero reference line. By nature of it's construction , the device turns off the passage of current thru it when the current is zero (at the zero crossing point). very convenient, since we can switch it on every cycle at a point very near the zero crossing or far from it. If we switch it on near the zero crosssing we get a brighter lamp since the device remains on longer before turning off t the next zero crossing. This sudden turning on of the triac or thyristor creates transients which buzz very nicely on the audio line at 50 or 60 Hz and the harmonics of those. This noise problem can be reduced by putting large inductors on the output of the triac this sudden rise can be smoothened to a certain extent, but not perfectly. Since the largest current rise is at the centre of the AC waveform (there the voltage is highest so current is highest with resistive load), you will typically find the largest amount of noise when the dimmers are at around 50%. Modern high-specification dimmers have a choke which increases the switch-on rise time from an uncontrolled 2?S to typically about 350?S, and they generally comply with standard EN55014 (representing the levels for residential electrical emission).

    Besides the noise coupled to electronic circuits you can sometiems hear acoustic noise from the dimmer itself. The fast current rises on the dimmer electronics can make some components inside dimmer to make noise. Most typically this noise comes from the filtering coil, but in some cases the noise can coem from filtering capacitors, wires, circuit overload protectors and such parts. Sometimes the lamps connected to dimemr output can make noise. However, even with good quality filtering, you can in many cases clearly hear a lamp filament resonate as the intensity is altered or set to a static dimmed level. Audible noise is also often present at the dimmer device itself, caused by some choke vibrating/resonating (there are chokes inside dimmer in power input and output filters, and also on some circuit breakers that project dimmer channels against overload). Resonance in the lamp filament, colloquially called "lamp sing" is caused by the high frequency switching of power to the lamp. There are several factors which affect lamp sing, main things being the type of light bulb and the risetime of the choke. The longer the rise time, less singing. Improvements can be made using higher inductance chokes. It is now common for choke risetimes of up to 600?S to be specified for TV and concert hall installations. Although technically possible, the higher inductance adds significant weight, volume and cost to each dimmer channel in the installation. With an increased inductance in the dimmer circuit, there is a proportional loss of efficiency due to an increase in lost power which is dissipated as heat from the choke, and often causes an increase in audible .hum. from the choke windings. Singing can also be reduced with careful design of the choke and snubber capacitor combination in dimmer circuit (success is often variable with mass-produced, budget-priced dimming).

    Light dimmers are quite energy efficient, although they are not ideal.As one might expect, in spite of its usefulness, phase control has some disadvantages. The main disadvantage is the generation of electromagnetic interference (EMI) in triac applications. Each time the triac is triggered the load current rises from zero to the load-limited current value in a very short time. The resulting di/dt change generates a wide spectrum of noise that may interfere with the operation of nearby electronic equipment unless proper filtering is used. For mains operated light dimmers the efficiency is usually in the rangeof 90-97% depending on dimmer load and design for a normal triac basedlight dimmer (phase control). The efficiency of a dimmer module can be determined by loading it to full capacity and then measuring the voltage drop across the dimmer module (you need at True RMS voltmeter between the Line and neutral wires to do the measurement). The SCRs (Silicon Control Rectifiers) or triac that provide current control in the power device, part of the dimmer module, drop about .75 Volt across each junction (there are two). The choke is responsible for the remainder of the voltage drop. The amount of voltage drop across the choke varies proportionally to the connected load. This means that there will always be a dimmer insertion loss of at least 1.5 volts + the voltage drop across the choke. This is true for all SCR / Choke based dimming regardless of manufacturer. This power loss in dimmer needs to be taken into consideration when calculating the amount of Heating Ventilating and Air Conditioning (HVAC) required in a dimmer room of large dimming systems.

    Dimming can be used to extend lamp life in some applications where long lamp life is more important than maximum amount of light. Turn to the tungsten halogen section of most lamp manufacturers catalogues and you will find a small graph which correlates things like % of rated lamp voltage against % rated lamp life and color temperature. If you study these graphs they will show that 5% under voltage (i.e. dimming) will produce a much longer average life without significantly affecting the light output or the colour temperature. Dimming more than that usually reduces light output considerably and changes the color temperature quite much. When lamp is dimmed a lot, the light output drops very much faster than consumed power (so the efficiency of lamp drops considerably when normal lamp is dimmed). One inherent drawback of the ubiquitous thyristor dimmer is that when it is switched on, noise and harmonic disturbances are caused due to the rate of change of current. High peak currents are also generated. Resonance in the lamp filament, colloquially called "lamp sing", is generated by the abrupt, high frequency switching of power to the lamp. The solution has traditionally been to fit a large inductor (choke) to the dimmer circuit to reduce lamp sing and radiated emissions. Filter chokes used in dimmers are typically measured in micro second rise time. The usual 'conducted emissions'filter uses the rise-time inductor with a capacitor across the mains input. The cap value depends on the choke and the dimmer power rating.You can't practicably filter out the low-order mains harmonics.The most basic choke used in thratrical dimmers is typically rated at at around 350 microseconds with 500and 800 micro second rise time chokes also available.

    Here is some data of dimmer choke values and rise time relationship (data is collected and adapted from document found at http://www.almag.co.uk/new22.htm (not available anymore on web). The rise time is for 10% to 90% rise time.

    coil     230V AC       110V AC
    mH risetime risetime
    microseconds microseconds
    0.9 50 100
    1.6 100 210
    4.3 200 420
    5.7 300 640
    7.9 420 870
    Generally, the longer the rise time of the choke, the less filamentnoise it will produce. Unfortunately to achieve higher rise time,the choke requires more wire to be wound around the core.This increases the production costs; hence the dimmer will cost more.Aside from the filament hum, dimming induced noise in sound systems is alwaysa concern. Through the operation of the dimmers RFI or Radio FrequencyInterference can be produced. For example sensitive sound equipment shouldhave an isolated power feed to avoid the potential RFI produced by the dimmers. Using dimmers with higher micro second rise time filter chokes will reduce audile noise and RFI. In Europe standard EN55015 defines the noise suppression for light dimmers.

    Dimmers are typically designed for resistive loads in mind. With resistive loads, such as incandescent lamps, the current and voltagecurves match. This will keep every light dimmer happy.Once you start trying to work with reactive loads, such astransformers, motors, or fluorescent lamps, you may get unhappy dimmersunless you use spacial dimmer designed to handle inductive loads.When faced with an inductive load the pulse driven triac circuits oftenturn off with the back EMF from the load. Unfortunately most seem to be quite happy to conduct on one half of the phase but not the other which causes the load to be run on half wave AC (pulsed DC component).This kind of DC balance problem will saturate transformers and damagethen quickly (they overheat).With many normal dimmers and a small inductive load, a resistive ballast in parallel will usually keep the dimmer happy. But be warned that therecan still be some small DC balance problems left which can causeproblems (this varies depending on the dimmer design).For a dimmer to generate nice AC output without DC, the controllingelectronics has to have the firing pulses symmetrical. They don't have to be far out to generate a few volts DC that'll cook a transformer.

    Dimmers are available in many forms. For household use dimmer switches come in four popular styles: dial, slide, touch pad, and combination light switch/dimmer slide. Since dimmer switches come in different shapes and each operates a little differently, you should always follow the instructions included with the switch for installation and operation. Theatrical applications and rock shows generally use remotely controlled dimmer packs. Each dimmer pack contains many individual remote controlled (usually 0-10V DC or DMX-512 controlled) light dimmer circuits in one case.

    Typical light dimmers as discussed earlier work using forward phase control. Forward phase control is when there is a "wait" time after zerocrossing, then you fire the thyristor and it conducts current for theremainder of the half cycle (until the next zero crossing when the PNjunction that is conducting becomes reversed biased). Forward phase control turns on under load and has a choke to limitrate of current rise ("rise time") but turns off along the same slopeas a sine wave.This is not the only way you can make a mains light dimmer. Reverse phase control is when current switching component begins to conduct right at zerocrossing, and conducts through the half cycle until "some point" whenthe transistor (IGBT in the IPS case) is biased off. Reverse phase control turns on at zero crossing andhas a rate of rise that is the same as the slope of a sine wave, butturns off under load and has a "fall time". The IGBTs in the IPS stuffdissipate heat during the "fall time". There are several advantages that can be used: no flter choke needed (size, weight, cost), ability to sense current and shut down if needed (can shut down power in the middle of phase if overcurrent is detected) and this design gives you bility to change "fall time" via software (though the longer the fall time the more heat the IGBT has to dissipate). Reverse phase dimmer works also better with some electronic loads that do no work well with normal dimmer (for example electronic lamp transformers that power low voltage halogen bulbs etc.). The main disadvantage of reverse phase dimming high component count (the current stuff is better than before but there still are a bunch of parts on one of those boards) which leads to higher cost. Reverse phase control still generates harmonics like normal dimmers. Since reverse phase control is cutting off the "back end" of a sine wave at some point, right thereyou have a waveform that is something other that a sine wave and wefind ourselves back in harmonic land. The harmonic reduction in some special stuff (IPS dimmers) is achieved by firing one half ofthe dimmers in forward phase control and the other half in reversephase control. Literally (well almost anyway) half the harmonics are coming and the other half are going and now we actually do have summing that is trending towards zero.

    In addition to the systems described above there are sinewave dimmers on the market. Dimmers with a sine wave output are hardly a new phenomenon. The resistance dimmer in its many forms, whether a pair of electrodes in a container of salt water, a rheostat-like slider, or a mechanically operated "grand master" system, always produced a nice clean sine wave output which varied only in amplitude. It was only the fact that these dimmers were heavy, expensive, load-dependent, produced vast amounts of waste heat, and required some form of direct mechanical operation that caused them to be bypassed for other technologies. There has been some low power home light dimmers that have used variable autotransformers (variacs) to control the voltage to the light bulb. Some high-end dimmer switches, such as the ones once commonly used in stage lighting, are built around an autotransformer instead of a triac. The autotransformer dims the lights by stepping down the voltage flowing to the light circuit. A movable tap on the autotransformer adjusts the step-down action to dim the lights to different levels. Since it doesn't chop up the AC current, this method doesn't cause the same buzzing as a triac switch. This approach works, but is expensive and bulky on large power systems.

    There are a lot of other dimmer switch varieties out there, including touchpad dimmers and photoelectric dimmers, which monitor the total light level in a room and adjust the dimmer accordingly. Most of these are built around the same simple idea, chopping up AC current to reduce the total energy powering a light bulb, as the dimmers described above. Attempts have been made in the past to produce a sine wave output dimmer by using various semiconductor devices as the variable resistance, but each of these has run up against the difficulty of the available semiconductor technology not being able to handle the currents, voltages, and heat dissipation required for a robust, reliable production dimmer. The new wave of sine wave output dimmers has taken a different approach, using the switch-mode technology widely used in devices as diverse as the ballasts of many discharge luminaires and the power supplies of virtually all computers and lighting consoles. There are few companies which work on sinewave dimming field.Dynalite has been shipping the SVC (Sinewave Voltage Converter) dimmer since 1998. Bytecraft VST (Variable Sinewave Technology) won an award at PLASA 98. Jands Electronics has announced the development of a prototype of its SWDim sine wave dimmer. The principle behind all of these sine wave dimmers is very simple: The incoming mains is switched on and off between 600 and 1,000 times per mains cycle (30-50kHz) with the on time (width) of each pulse being proportional to the required output power from the load, a method known as Pulse Width Modulation (PWM). The very finely chopped output is then filtered back into a continuous waveform through an inductor similar to the choke on a phase control dimmer, but very much smaller, as the pulse frequency is higher. The shape of the filtered output waveform is almost identical to the input waveform, only its amplitude is different, precisely what happens in a resistance dimmer. Sinewave dimmer is very complicated electronic device. Only with a large number of sensors to gather data, a fast processor, and some clever software is it possible to maintain the complex dynamic equilibrium necessary for a sine wave dimmer to function. But when those are implemented properly, lot of extra function and protection technologies can be added to the dimmer. There are some dimmer technologies that has been earlier in large use but later not used anymore. One early means of lamp 'dimming' was through the use of the salt water dimmer. The dimmer consisted of a tank (or barrel) of salt water brine with a permanent electrode submerged. As a second electrode was slowly raised (or lowered) into the brine, the conductivity between the two electrodes would increase (or decrease) respectively. Lamps connected in series to the dimmer, would be dimmed accordingly. It was not uncommon for a theatre to have a large number of these dimmers and it is said that the heat from the boiling brine would often help to heat the backstage areas. Undoubtedly messy and difficult to operate and maintain, the electric salt water dimmer was soon to be replaced by the somewhat more efficient (and dryer) electrical resistance dimmer. The resistance dimmer was simply a long length of wire, usually wound in the form of a coil. A 'wiper' contact would move along the coil, usually controlled by a manual leaver (or motor control). As the contact moved along the coil, the coil resistance would decreasing or increase accordingly. This coil resistance was placed in series with one or more electrical filament lamps to provide a relatively efficient means of dimming. This type stage lighting switchboards were large and heavy. The first autotransformer was developed and patented about 1933 by General Radio Company (USA). This device was a continuously variable transformer with the trade name of "Variac". The Variac provided a much more efficient means of dimming electric lighting fixtures in theatres, than did the existing resistance and saltwater dimmers of the time. In the 1960's, the American Superior Electric Company, produced a number of autotransformer dimming systems for theatre and television applications. Autotransformers can also be motorized for remote operation. The autotransformer dimmer is still used today in some applications (recording studios & hospitals) as they do not generate radio frequency interference (RFI) as does a modern SCR type dimmer.

    Domestic light dimmers usually incorporate a mechanical switch for isolation (and a minimum dim level) to ensure that an OFF light really is OFF. A typical wall switch dimmer has a clearly defined 'off' click' which corresponds to a mechanical switch. There are some remote control wall dimmers ( touch dimmers ) which perhaps dont have the physical isolation when set to off. In home dimmers some dimmer units intentional go from 'off' to directly say 20 percent to avoid any uncertainty as to whether the power was really off or not. Providing an air gap isolation when a system is aparently 'off' is a good idea in domestic systems. In a domestic or similar situation, who would be liable if someone got a shock from a light fittting, if the 'off' setting was actually causing some leakage. Where dimming is done by chopping the waveform, which is generally the case in any efficient dimmer, it is possible, with more cost, to ensure that the waveform has no time of passing current. The control circuits in cheap dimmers can't quite do that. In addition to the control accuracy problems, there can be leakage cause byl filtering components near triac (for example through "subber circuit" that is in parallel with triac). Once you are getting into scene control systems, then the cost isn't so much to get a real "off". Still, if you really want a true disconnecting off, add a switch ahead of the controller.

    Theatrical dimmers use a number of different technologies to reduce the current. They also very often have an intentional feature what is called a pre-heat setting, that leaves a couple percent of the current flow even when at nominal 0% which keeps the lamp filaments warm. This reduces the warm-up time to get to the desired light level when it does come up, and is supposed to reduce thermal stress in the lamp, extending it's lifespan. So pretty much any recent manufacture theatrical dimmer system will be constantly bleeding a little power to the loads. Certainly many larger dimmer units only have isolation at the wiring hub via a circuit breaker - and not at the local control position.

    Dimmers are designed to drive light bulbs and similar loads. Driving other types of loads with dimmers is not generally a good idea unless you know absolutely that this is ok. If the dimmers aren't rated for light inductive loads (which they probably weren't) then they could have fed the lights with a slight DC component due to non symmetrical triac latching on the two halves of the sine wave. This would pop the fuses. In some cases it can smoke the transformers too. Inductive loads are a nightmare to SCR or Triac dimmers. Even something a small as fan motors. A substantial resistive load (in parallel with inductive load) will often solve the problem.

    Driving devices and switch mode power supplies with power from dimmer is generally not a good idea. Most poeple at one point or another have tried this, some with limited success and others with unpleasant results. For example plugging a moving light into a dimmer is bad news. Even when leaving the dimmer at FULL and turning it OFF when light needs to be powered down. The problem here is that FULL ON and FULL OFF might not be what you expect them to be, and the output between those extremes is genrally anything but sinewave. Many theatrical dimmer systems feed a low voltage through at off to keep the bulbs warm. Some theatrical dimmers are "regulated" to give the show the same look even under slight variations in supply voltage. This can mean that even when you think it's 100% on, it's not. Another danger to plugging different electronics devices into dimmers is that the DMX signal has absolutely no fault tolerance or error correction/detection. Dimmers can end up at odd levels even if the console never sent a level other than full or zero to that channel. One thing to point out too, on most dimming systems you can change the scale type on a dimmer to a non-dim or switched mode. Be careful though, this is often NOT the same as a module performing the relay function. Usually it is only changing the behavior of how the dimmer is reacting to data. If you switch a standard dimmer to non-dim in the software, you could be still clipping the waveform, which can still smoke your electronics device. The dirty secret of most digital dimmers designed before about 1995 is that they are analogue dimmers in digital clothing. In a true non-dim module, there is nothing clipping the wave at any point in the electrical path. Its just a glorified DMX switch.

    When installing light dimmer systems you need to consider the needed power feed for them. When designing system (touring system or permanent installation), to think about is how many dimmers you can drive with the power available. Most dimmers this side of the pond come in multiples of 600 watts (600w 1.2kw 1.8kw or 2.4ks). Usually you don't need the amount of power that is the maximum power of dimmers connected to the mains feed. In general, you can "overload" your incoming power by a decent amount, meaning having more dimmer power and total light load than your feed can handle. You could get away with more since you will never have all channels at full even if all the dimmers are loaded to capacity (which is highly unlikely) unless you are a community theatre were untrained or inexperienced lighting people might have unsupervised access to your equipment. If you have more light instruments than your power input can handle at the same time, you need to make sure that your LDs/and or MEs understand about both the maximum loading capacity of your incoming circuits so they don't plan anything stupid.

    SCR dimmers are a nightmare from a power quality perspective. At the output end the dimmer waveform is very distorted. Running at 50%, the triac or SCR pair will turn on when the voltage is at its peak, with a huge hard edge. The 'clean up' inductors slow this down a bit, but it's still largely there, and will to some extent reflect back into the incoming supply. The load the dimmer puts on the mains supply may possibly distort the supply waveform. There are cases where the supply impedance is low enough that it will just absorb the harmonics without much harm, and there are cases where sypply impedance is higher an unfortunate sound man can bear witness. The problem can be severe if the supply comes from a small generator or some sort of electronic inverter. For the usual public supply there is no real problem but the supply company may want to know if we are talking about a load of tens of kilowatts or more. Generally it is a good idea to have separate power feed directly from the transformer or house main distribution panel for audio and lights, so the place where the distortion from dimmers meet the power going to the audio dystem there is the lowerst possible network impedance (least amount of distortion gets through).

    When using three phase power feed with large dimmer packs some things need to be considered in the wiring. First it ia a good idea to distribute the dimmers among phases so that they don't get radically out of phase balance. Phase controlled dimmers are a very highly non-liner loads. Dimmers do generate a large number of odd-order harmonics (worst is third), now unlike the fundamental (50 or 60 Hz line freq.) when 3rdorder harmonics are "added up" in the neutral the magnitude increases .Usual practice is to specify the neutral conductors at 130% of phase conductors (rated for 130% of nominal phase current).

      Basic dimmer circuits

      A basic light dimmer is a mains voltage controlling device which controls which amount of each mains halw wave gets to lamp and which does not. This is done by controlling the conduction angle (time after zero cross) in which the mains switching element (usually TRIAC) starts to conduct. When TRIAC starts to conduct, it will conduct up to the next zero crossing of mains voltage (time when current decreases zero). An RC network delays the trigger pulses on the gate of the TRIAC. The longer the RG time constant is, the longer it takes for the TRIAC to trigger which causes less time of conduction. Less time of conduction means less power to lamp which means less light output.

      This kind of simple triac based light dimmers (e.g., replacements for standard wall switches) widely available at hardware stores and home centers. While designed for incandescent or heating loads only, these will generally work to some extent with universal motors as well as fluorescent lamps down to about 30 to 50 percent brightness. Long term reliability is unknown for these non-supported applications.

      Remember, that most mains powered dimmer circuits are "hot" and dangerous! Line power circuitry should be constructed only by qualified persons and enclosed into a suitable protective case before using it. A circuit that is not properly built can be a safety hazard, because baddly designed or wrongly built circuit can electrocute you, cause lots of noise to mains power and can even start a fire in your house.

      • Basic Light Dimmer Circuits - The circuits presented in this document are the type of common triac based light dimmers (e.g., replacements for standard wall switches) widely available at hardware stores and home centers. While designed for incandescent or heating loads only, these will generally work to some extent with universal motors as well as fluorescent lamps down to about 30 to 50 percent brightness. Long term reliability is unknown for these non-supported applications.    Rate this link
      • 1200 Watt Lamp Dimmer Circuit - This circuit is a lamp dimmer circuit that is capable of controlling up to 1200 Watts of load powered from 220VAC source.    Rate this link
      • 230V DIMMER - A reliable and efficient all-around performer. This is a tried-and-true diac & triac combination that offers both simplicity and high performance. With a load up to 3.5A, the power rating is 750W at 230V. Original source Velleman kit (K5001). There are plans to modify this for 110V operation.    Rate this link
      • A High-Resolution Digital Dimmer - This is a basic 555 timer based mains dimmer. The operational amplifier (LM339) is performing a zero-crossing function and, due to this, the integrated circuit (555) is being activated each time a zero-crossing condition occurs. Once activated the 555 will wait a short time before it triggers the transistor and, in turn, the triac. In conclusion, the Digital Dimmer described here offers a very reliable control phase (from 10% to 95% of the ac sine wave). It can be used for lighting applications, or single-phase motor speed controls, or any other kind of application circuit where a reliable control phase is needed.    Rate this link
      • Basic Incandescent Light Dimmer Circuits - circuit diagrams of common light dimmers (e.g., replacements for standard wall switches) widely available at hardware stores and home centers    Rate this link
      • Basic Lamp Dimmer - Lamp dimmers using traics can be quite simple, nothing more than a potentiometer, resistor, capacitor and triac with a built-in diac. This circuit is similar to designs using unijunction transistors to generate the triggering pulse. The basic circuit is designed to be controller using a potentiometer, but the article has also information how to adapt this circuit to do controlling using external control voltage.    Rate this link
      • CMOS gate implements reverse phase control - this circuit implements a "reverse" phase control, using only a single CMOS 4001 quad NOR gate, conduction begins at the zero crossing of the ac sine wave and the turn-off timing is adjusted based on dimmer setting    Rate this link
      • Dimmer switch 230V / 50Hz - This dimmer switch is suitable for 230V incandescent lamps with a total power of up to 300 Watts. The circuit is wired in series with the lamp so it can directly replace the wall switch.    Rate this link
      • Electric power controller - suitable as simmer for 100V lamp up to 1200W    Rate this link
      • Homemade neon dimmer    Rate this link
      • Independent dimming from two locations - kludge #3251 - Here is a scheme which will permit dimming with independent control from two locations. Each location will have a normal switch and a dimmer knob. The toggle essentially selects local or remote but like normal 3-way switches, the actual position depends on the corresponding setting of the other switch.    Rate this link
      • Light dimmer circuits - schematic for 120V AC and 230V AC dimmer with description how light dimmer works    Rate this link
      • Novel circuit controls ac power - simple fan dimmers can only handle about 100W, but this circuit increases the load capacity to 3000W    Rate this link
      • Odd application of neon glow lamps: The Dimmer - neon glow lamps can also be used only for their U/I characteristic and not for producing light    Rate this link
      • SCR phase control yields solid-state switch - SCRs (silicon-controlled rectifiers), or thyristors, have higher current and voltage ratings, lower conduction losses, and more robustness than triacs. For these reasons, SCRs are better suited to high-power applications. This is high power dimmer circuit for 115V AC.    Rate this link
      • TRIAC Light Dimmer - dim 115V lights up to about 350 watt    Rate this link
      • TRIAC Light Dimmer - This little circuit can be used to dim lights up to about 350 watts. It uses a simple, standard TRIAC circuit that, in my expirience, generates very little heat. Please note that this circuit cannot be used with fluorescent lights.    Rate this link
      • Triac Light Dimmer - This is a very basic dimmer circuit for 220V AC.    Rate this link
      • TRIAC Light Dimmer - This little circuit can be used to dim lights up to about 350 watts of 110V AC lighting. This uses a simple, standard TRIAC circuit.    Rate this link
      • Varying brightness AC lamp - SCR is used to slowly vary the intensity of a 120 volt light bulb by controlling the time that the AC line voltage is applied to the lamp during each half cycle    Rate this link
      • The dimmer - Neon glow lamps can also be used only for their U/I characteristic and not for producing light. In this circuit of a dimmer the diac is replaced with a neon glow lamp, but it works exactly in the same way than a classic one: an RC network delays the trigger pulses on the gate of the triac. The glow lamp rises the trigger voltage from about 40 V to about 80 V. Some adjustments to R and C values may be required to match specific glow lamps and triacs. This circuit is designed for 220Vac and can control up to 1000W.    Rate this link

      Touch dimmers

      A touch dimmer is a combination of touch sensor and dimmer. With a touch dimemr can change the brightness of lamb, with a only touching the dimmer device itself. Typically touch dimmers have one touch contact, and when you touch it you can turn the light on/off and control the brightness. Different touches do different things, typical operation being the following: A light tap on its sensor will turn the light ON or OFF. A longer touch will either increase or decrease the light level. This kind of dimmer module typically incorporate a memory and will switch the light on at exactly the same level it was before switching it off.

      • Electronic Touch Dimmer - With this circuit we can change the brightness of lamp, with a only key of touch. This circuit is based on S566B IC from SIEMENS. This IC, it processes the information of duration of touch and then it checks the brilliance of lamb, according to this information. If we touch upon the key for a small period of time (60 until 400 ms), the lamb simply only changes situation, that is to say from OFF in ON or on the contrary, depended from the situation is found itself before the unit. In one of bigger duration of touch (more from 400ms), is altered the brilliance of lamb, late from dark in luminous or on the contrary.    Rate this link

      Multichannel dimming systems

      Multi-channel dimmers are generally used to control a set of lights.This kind of dimmers are most often seen as dimmer packs as used instage lighting. Such dimmer pack is generally controlled fromlighting desk (DMX-512 or 0-10V interface). The dimmer packusually consists of control electronics, set of switchingcomponents (triacs/scrs/whatever), filters and overloadprotection components (fuses, circuit breaker, overheat protection).The control electronics takes the DMX or 0-10V or whatever and turns that into the right stuff to wiggle the triacs/scrs/whatever. In 0-10V analog lighting control systems the dimmers typically create a ramp signal (looks like |\|\|\|\|\|\|\|\, goes linearly from 10V to 0V and then quickly back to 10V during mains power zero cross). The dimmer has a comparator circuit that triggers a signal if the two input voltages are the same. The comparator circuit circuit ompares the control voltage to the ramp signal that falls from 10 to 0 volts over time of one half cycle of mains power. Example: Control desk "sends" 8V to the dimmer, because it should dim the light to 80%. When ramp signal reaches 8V, the comparator signals the load part of the dimmer (where the lamps are attached) to start the current.

      • Three-phase power regulator - This three-phase linear power regulator can control resistive loads or induction motors. Drive outputs are optoisolated and regulation from zero to full load is via a single potentiometer so interfacing to a PC should be easy, assuming all mains isolation is properly implemented.    Rate this link
      • Three-phase power regulator - This three-phase linear power regulator can control resistive loads or induction motors. Drive outputs are optoisolated and regulation from zero to full load is via a single potentiometer so interfacing to a PC should be easy, assuming all mains isolation is properly implemented.    Rate this link
      • Velleman K8064 DC controller dimmer - This electronics kit is AC mains voltage dimmer that features a simple brightness adjustment by means of a DC voltage. It is suitable for incandescent lamps, mains voltage halogen lighting and low voltage halogen lighting in combination with a conventional transformer. Adjustment voltage: 0 to 12Vdc max (0-10V works well), adjustment current 2.25mA at adjustment voltage of 12V and adjustment input is optically isolated. Operating voltage range is 110-125V or 230-240V AC (50/60Hz). Maximum load is 750W/230V or 375W/110V, 0-98% adjustable. Documentation includes full circuit diagram.    Rate this link
      • 1 x 3.000 W dimmer voor theater-spot's - This circuit uses 0-10V control signal.    Rate this link
      • An Experimental Cross-Fader - ideas to modify simple rotary light dimmers to make a cross-fader    Rate this link
      • Dimmer mit TCA785 - The project description of this dimmer card is in German. Circuit diagram is included.    Rate this link
      • Four channel dimmer rack - 4 channels, 900W maximum per channel, 2300W maximum total, operates at 230V 50Hz mains supply, uses standard 0-10V analogue control signal    Rate this link
      • Light dimmer - This is a simple dimmer circuit that can be controlled with 0 - 10 VDC. This design is for 4 channels.    Rate this link
      • Light dimmer circuit with 0 - 10 volt input - This is a simple dimmer circuit that can be controlled with 0 - 10 VDC. It is designed for 110V AC.    Rate this link
      • N-channel light dimmer - schematic of 0-10V DC controlled 230V AC light dimmer in postscript format, the circuit is designed by    Rate this link
      • LightProcessor has a    Rate this link
      • LX-800 LIGHTING SYSTEM - inexpensive 8 channel lighting controller for small theatre groups or musicians, includer dimming and sequencer, sound to light, designed for 240VAC 50Hz supply, fed domestically from 3-pin 16A sockets    Rate this link
      • LX-800 power control section - 8 channel 0-10V DC controlled dimming pack with 5A at 240V power rating per channel    Rate this link
      • Remote Control Lighting - up to four channels of light dimmers to be remotely controlled with IR remote    Rate this link
      • Velleman K8003 DC Controlled Dimmer Kit - This is a 0-10V DC controlled dimmer module. Putting many this kind of modules inside on case makes a multi channel light dimmer. This circuit works from 220V, 110V and 24V. The Maximum current this circuit can control is 3.5A. Now obsolite and replaced with newer kit K8064.    Rate this link
      • Velleman K8003 DC Controlled Dimmer - This small but handy circuit is ideal for replacing an existing dimmer or switch, in order to be able to control a lamp, set of lamps or even a motor via an adjustable DC voltage. This kit can take standard 0-10V control voltage input (opto-isolated). This products is sold as electronics kit but this page has the full kit documentation, including full circuit diagram. This circuit is suitable 24V, 110-125V or 220-240V, 50 or 60Hz. Maximum load is 3.5A (750W/220V,380V/110V, 80W/24V).    Rate this link
      • Velleman K8064 - This kit gives you simple brightness adjustment by means of a DC voltage. It is suitable for incandescent lamps, mains voltage halogen lighting and low voltage halogen lighting in combination with a conventional transformer. The adjustment voltag range is 0-12Vdc max. Maximum load is 750W/230V or 375W/110V, 0-98% adjustable.    Rate this link
      • Digi Pack - This unit recieves DMX 512 data and Analogue (0- 10v) data and uses these to phase angle control four mains outputs. This design is based on PIC16F870 microcontroller. This devices has 3 Modes of operation: Digital Lighting Data, Aanlogue Lighting Data and Internal Presets. This circuit supports linear, S-curve and switching dimming curves. This circuit is designed to operate at 240V 50 Hz power.    Rate this link
      • Basic Lamp Dimmer - Lamp dimmers using traics can be quite simple, nothing more than a potentiometer, resistor, capacitor and triac with a built-in diac. This circuit is similar to designs using unijunction transistors to generate the triggering pulse. The basic circuit is designed to be controller using a potentiometer, but the article has also information how to adapt this circuit to do controlling using external control voltage.    Rate this link

      Fluorescent and neon lamp dimming

      Fluorescent dimming requires special planning. Dimmable ballasts, 4-pin lamps and compatible controllers are required for successful fluorescent dimming. Some old fluorescent light dimming systems have supplied continous heating power (for example 6.3V AC) to the fluorescent light heating filaments and then controlled the current coing through the lamp itself using some phase control dimmer. This kind of control works with careful planning, but has quite limited dimming range. Nowadays the best approach to dim fluorescent lights is to use a commercial electronic fluorescent ballast that has built-in dimming capabilities. The operation of those is based on a controllable switch mode power supply that can send the needed amount of high frequency AC (typically around 30 kHz) to the fluorescent lamp tube. This kind of electronic ballast provides typically better efficiency, better light quality (no flickering), wider dimming control range and longer fluorescent lamp life than the old dimming fluorescent light controlling systems provided. The dimmable fluorescent light ballasts are typically controlled through 1-10V voltage control system. Many ballasts supply a low voltage (12-15V typically max) limited current (typically 0.5-0.6 mA) to their control outputs, so that the dimming can be controlled with just a potentiometer (1.8 kohm gives around 10V and 200 ohms gives 1 volt to the ballast). There are also other control system in use, including interfaces to house control bus systems on some ballasts.

      Dimmer circuits for low voltage DC lamps

      There are generally two ways to dim a DC light bulb. One is to reduce the voltage reduction method what uses somesuitable component in series with the bulb to limit the voltage(series resistor, voltage regulator, current limiter etc.).This method is simple, but is only usable with very low powerlights because this wastes lots of power.A more efficient light dimming is to use pulse width modulation (PWM)to reduce the average voltage which goes to the lamp. Dimmers designed to dim DC light bulbs generally using pure pulse width modulation, they just have an adjustable free-running oscillator with variable pulse width to control the light output. When PWMis used, the dimmer circuit acts like a very fast switching components(just on or off), thus it does not waste much power. When the powerto the bulb is switched on and off fast enough (100 Hz to few kHzgenerally), you will not see any flickering on the light output.

      LED light dimmers

      LEDs are normally operated from current regulated DC power source. LED intensity can be changed by controlling the LED current directly or by using PWM method. For dimming only one LED the simplest method is to use variable resistor as the current limiting resistor. For more efficient operation a PWM method is preferred. Full-range dimming is typically done by pulsing the LEDs and adjusting the pulse-width. If you do this at a high enough frequency, it appears to be "flicker-free". LEDs can be driven to very high frequencies easily (up to tens of kHz to MHz depending on LED and driver circuit designs).

      LEDs can be dimmed with a continuous current. In this case there is no flicker from the LED. The trick is to make a variable current source with high efficiency. This is done all the time by using a PWM circuit inside the power converter and then smoothing (filtering) the current before it is applied to the load. You get a continuously variable, high efficiency current source that has very little modulation on its output - and hence no flicker. Usually this kind of power supplies are constructed as switched mode continuous current sources. A switched-mode current source can use relatively small inductors to smooth the current to something approximating DC.

      • Constructing a linear constant current dimmer for a white 24-LED array - This simple Linear circuit provides continuously variable regulated current (~25-400mA) from a 4-6 Volt source. The linear design for selected for mplicity, reliability, ease of repair, and to avoid switching EMI. The circuit requires only 0.2V headroom above the parallel LED Array voltage to provide regulation at maximum current.    Rate this link
      • White-LED driver provides 64-step logarithmic dimming - This circuit is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as four white LEDs from a 3.3V source and adjusts the total LED current from 1 to 106 mA in 64 steps of 1 dB each.    Rate this link
      • A linear Constant Current LED Lamp Dimmer - This simple Linear circuit provides continuously variable regulated current (~25-400mA) from a 4-6 Volt source.    Rate this link
      • Circuit controls intensity of reflex optical sights - A popular category of aiming/pointing aids is the reflex, or "red-dot," sight. This system finds use in such diverse applications as astronomy, archery, and shooting. In the reflex sight, light from an internal source?typically a high-intensity red LED reflects from a curved, transparent optical (reflex) element through which you view the target. The result of this geometry is that the image of the LED (the red dot) appears superimposed on the target image, thus indicating the point of aim. When you correctly adjust the aiming point of the telescope, bow, or gun, the target and LED images coincide. For best sight performance, the intensity of the red-dot light source must at least roughly match the illumination level of the target. This circuit adjust the LED intensity based on the target.    Rate this link
      • Fading Red Eyes - can be used to slowly illuminate and fade a pair of red LEDs    Rate this link
      • LED Lamp Dimmer - This circuit provides 32 steps of brightness control from 0 to 100% for a backlight or instrument panel using just two general purpose microprocessor signals. In addition, very little board space is required since only three SOT23's and a uMax package are used. Although shown in the figure below driving white LED's, the load could also be a DC motor or an incandescent lamp. The circuit is based upon a modified Schmitt Trigger relaxation oscillator    Rate this link
      • LED dimmer uses only two lines - This circuit provides 32 steps of brightness control (from 0 to 100%) for a backlight or instrument panel, using just two general-purpose-microprocessor signals. Although the circuit shows the circuit driving white LEDs, the load could also be a dc motor or an incandescent lamp. The basis of the circuit is a modified Schmitt-trigger relaxation oscillator controlled by MAX5160 digital potentiometer.    Rate this link
      • LED Lamp Dimmer - This circuit provides 32 steps of brightness control from 0 to 100% for a backlight or instrument panel using just two general purpose microprocessor signals. In addition, very little board space is required since only three SOT23's and a uMax package are used. Although the example circuit is driving white LED's, the load could also be a DC motor or an incandescent lamp.    Rate this link
      • Single FET controls LED array - White-LED backlights are gaining acceptance because they offer higher reliability and simpler drive circuitry than backlights based on CCFL (cold-cathode-fluorescent-lamp) and EL (electroluminescent) technology. This circuit shows a switch-mode boost design that regulates current instead of voltage and switching off individual LEDs or groups of LEDs is not a problem.    Rate this link
      • Circuit delivers dimming control for white-LED driver - This Design Idea presents a more widely adaptable approach to the dimming challenge. Although the LM4811 headphone amplifier is not designed to operate as a DAC, you can tweak it to do so. The implementation is straightforward. The output current from the LM4811 is directly proportional to the digital value stored in the digital-volume-control block. The rising edge of the clock, along with the polarity of the Up/Down pin, sets the appropriate output current of the LM4811 and, thus, the output current of the white-LED driver. The resultant approach requires only two general-purpose input/output lines, which are available in all modern baseband and application processors.    Rate this link

    Light control interfaces

    In almost all stage lighting situations, luminiares are not used constantly at full power. are generally required to fade in and out, and to be used at different brightnesses, or intensities, at different times under control of lighting operator. The actual dimming is done using the light dimmer, but it needs to be controlled in some way, usually form remote location. The control desk, or simply the desk, is the front-end of the lighting control system, and provides an interface between the dimmers and the operator. The state of each dimmer can be changed from the desk, thereby controlling the output from the luminaires. The control desk must communicate with the dimmers in order for the changes made by the operator to take effect on the stage. There are many communication system in use between the lighting desk and the dimmers. There are both analogue and digital systems in use. Analogue systems use a control signal that varies in voltage or current in direct relation to the required intensity. Digital systems use control signals that send the required control level numerically for each channel. The control information could be communicated to the dimmers by using one control wire for each channel: this is called multicore control. Alternatively, each control channel can be instantaneously measured, and the resulting values sent down a single control wire to the dimmer in sequence. This procedure is called multiplexing. Digital systems are more reliable than the analogue equivalent, faster and can be used for more accurate controlling. Besides light dimmers digital light control protocols (most often DMX-512) are used to control devices light intelligent lighting (like roboscanners), foggers and many other lighting devices.

      DMX 512

      DMX is a lighting industry standard way of controlling lighting equipment. The whole idea behind DMX as a standard is that it allows equipment from one manufacturer to talk to that made by another. DMX-512 allows for one controller (like a lighting desk)to control many lights. DMX is limited to controlling 512 separateparameters, that's where the name DMX-512 comes from. DMX-512 is a protocol for controlling (at a basic level) the brightness oflights in a theatre (it is vary capable and can be used for controlling moving lights, smoke machines, strobe lights etc.). It basically consists of one 8-bit (on or off) signal for each light whichsets the brightness level (0-100%) of the light to one of 256 levels.

      DMX-512 is the standard interface and protocol used in the theatre and entertainment industry. DMX-512 allows control systems to communicate with dimming systems, automated luminaires, color scrollers and with other equipment. Equipment from different manufacturers can be connected toghether nicely and they work together. Practically any DMX-512 control board can be connected to any dimemr or other equipment with DMX-512 interface. DMX is pretty straightforward as a protocol, there are some details at the bit level regarding frames and packets, but they are typically not of concern to the general user. More importantly, DMX fundamentally provides 512 channels of 8-bit resolution (0-255) level control (which constitue a DMX 'universe' of which various gear supports various numbers.) DMX runs over a cousin of our familiar serial port (RS-232) known as RS-485 allowing for up to a (theoretical) 4000 feet cable run (around 1200 meters). In the practical systems is is not a good idea to use longer than around 250 meter cables (realiabity drops on very logn cables). The transmission rate is fixed at 250 kbaud. Electrical characteristics are accoding RS-485 standard. Accroding to RS-485 there can be up to 32 devices daisy-chaines to one line, and in DMX-512 system if you need more you need to use signal splitters or repeaters (or use some new devices with special high impedance inputs that allow up to 256 devices on one cable line).

      A working DMX rig typically consists of a DMX-enabled controller (lighting board or computer,) cabling, one or more DMX addressable dimmers and lights plugged into AC outlets on the dimmers. Since DMX is really just a bunch of values associated with channels, often channels are used to select a gobo, select a gel, set an X-axis postion, set a Y-axis position, set a strobe rate or do some other task. Many/most of the DJ/Club scanner head lights are DMX these days, allowing for a variety of sync'd movement and chase activity.

      DMX512 is connected using a daisy-chain methodology where the source connects to the input of the first device, the output of the first device connects to the input of the next device, and so on. The standard allows for up to 32 devices on a single DMX link. The DMX512 communications protocol is very simple and robust. DMX512 was created in 1986 by the United States Institute for Theatre Technology (USITT) as a standardized method for connecting lighting consoles. It was revised in 1990 to allow more flexibility (this is the version in use today). The Entertainment Services and Technology Association (ESTA) has assumed control over the DMX512 standard. ESTA is making revisions to clarify and further extend the standard. Special care is being taken so that existing DMX512 equipment will work under any new standard. Although the DMX512 standard is being updated, existing equipment will still work the same under any new revision.

      DMX512 is designed to carry repetitive control data from a single controller to one or more receivers. This protocol is intended to be used to control dimmers, other lighting devices and related non-hazardous effects equipment.Since this Standard does not mandate error checking, DMX512 is not an appropriate control protocol for hazardous applications. So do NOT use DMX-512 to control devices like moving platforms or pyrotechnics.

      Officially DMX is carried on 5 pin connectors, which carry the data(RS485) on pins 2 & 3, screen (and common mode reference) on 1. Thereis a second data link on pins 4 & 5 the format of which has never beenwell defined and it is seldom used in practice.This means that at an electronics level, the signal is sent through 5-core cable (but only 3 are ever used) consisting of 0v, +ve and -ve signal wires. Cable for DMX-512 installations should be 110 ohm impedance shielded twisted pair cable. A normal microphone cable (shielded twisted pair) works OK for short runs, but can cause problems in long runs (so using it is not recommended). In DMX-512 world there has been a long debate on 3-pin vs 5-pin connector.The ofifcial standard says 5-pin connector.Unfortunately some manufacturers use a cheaper 3-pin XLR connector instead of standard 5-pin. Cheaper/budget lighting kits (like many disco effects) are almost always 3 pin, probably because the plugs are cheaper!It seems that 3 pin is becoming the modern de-factor norm (although not conforming to the DMX512 standard) and 5 pin is becoming more unusual. Current Martin kit uses 'pin 3 +ve' but older Martin stuff is the other way round. It'stherefore worth carrying 'change-over' connectors as well as 3-to 5-pinadaptors if you are workign with systems consisting of components frommany different manufacturers. Standard DMX-512 connector (5-pin XLR) wiring is:

      • Pin 1 - Ground (shield)
      • Pin 2 - Data complement (Data -) (D1-)
      • Pin 3 - Data true (Data +) (D1+)
      • Pin 4 - Optional Second Data Link Complement (Data 2 -) (D2-)
      • Pin 5 - Optional Second Data Link True (Data 2 +) (D2+)
      The pins 4 and 5 are reserved for spare data. There are also some application where 3-pin XLR-connector is used to carry DMX-512 data. A male XLR jack is used for input DMX signals and the female jack are for output DMX signals.

      Use of 3-pin connector is not defined in the DMX-512 standard, but the industry de-facto pinout for 3-pin XLR connector is the following:

      • Pin 1 - Ground (shield)
      • Pin 2 - Data complement (Data -)
      • Pin 3 - Data true (Data +)
      NOTE: There are some kit using 3-pin xlr connectors that had Data +/- reversed.Which one of the connector you see on the equipment depends on the manufacturer and to what market those equipment are made for. In professional theatrical lighting applications the users and manufacturers prefer the standard 5-pin XLR connector. Practically all all the theatrical consoles, dimmer packs, PDU's, etc. use 5-pin connector. The new version of the DMX spec is very clear on connector issue - 5 pinonly, anything else just makes life difficult for the end user. Go for 5-pin. Anything else will render your product non-compliant with theUSITT DMX512 standard.However, 3 pin DMX exists and will no doubt continue to be widely usedeven in new products. 3-pin XLR connector is typically found on DJ/club type lighting instruments- One of the big reasons 3-pin XLR has become sopopular is because manufacturers of intelligent lights targeted DJ's,clubs, etc. who already had 3-pin XLR's for their audio gear. 3 Pin XLR do not conform with the USITT DMX-512(1990) standard. The DMX512 standard has always been clear about it being a 5-pin XLR.The reason many of the companies were using 3-pin is because they hadtheir own native protocols that predated DMX and DMX was just anadditional feature. The problem with using 3-pin XLR connectors is that you can easily confuse the DMX-512 cables with microphone cables that do not meet the needs of DMX-512 data cable. If you just use "any microphone cable" for DXM-512 connestions, you might be able to get it to work with few instruments on short ditances, but when distances get longer and number of instruments increase, things do not run smoothly anymore. The only rationalization for continuing to build any new product using 3-pin is to allow the inappropriate use of low-grade mic cables. Nota good reason in my book. The new version of the DMX512 standard in the works by ESTA specifically disallows the 3-pin XLR (not that it was ever allowed tobegin with). If you don't comply you can't mark your product as complying to the new standard. Because there are this two connector model situation, many people working on this field need to use 3-to-5 and 5-to-3 pin adapters quite often.

      DMX512 uses EIA-485-A (commonly refered to as RS485) which is abalanced system. Normative references for electrical specifications at ANSI/TIA/EIA-485-A-1998 Electrical Characteristics of Generators &Receivers for Use in Balanced Digital Multipoint Systems.The electrical specifications of DMX-512-A standard are those of EIA-485-A with some minor exceptions. The DMX-512 interface is electricallyRS-485 bus where there is one transmitter all the time transmitting andmultiple receives along the bus. There is always one transmitter (usually lighting desk or signal repeater) and there can be up to 32 receivers in a single bus.The signal voltage is is between the 2 data lines (pin 2 & 3). The difference between the pin 2 and 3 voltages is what isimportant: data high (digital 1)is if pin 3 is at a higher voltage than pin 2,data low (digital 0) is if pin 2 is at a higher voltage than pin 3.Typicaly the pin 2 and 3 are at either +5 or -5 Volts, but the RS485limits are +12 and -7 Volts. In other words, the data is carried over a twisted pair (connected topin 2 & 3).The transmitting device has a RS485 driver (transmitter) connected topins 2 & 3, and transmits uses +5 and 0 volt levels with respectsto the transmitting devices ground. In receiver side pins 2 & 3 need to be within a few volts with respect tothe receivers 0V reference. (pin 1) There must be a difference of at least 200mV between pins 2 and 3 for the logic state to be reliably detected.The main advantage of using a twisted pair is the ability accept acertain amount of common mode voltage (external noise/interference)and still get the data through. However there are limits to muchcommon mode voltage it can accept, and the cable screen is used tohelp limit how much gets onto the data lines. The DMX512 standard that is not clear is exactly how pin 1 (shield ground)should be used. There are guidelines to manufacturers on how to implement electricalisolation between devices. There is an ideal situation discussed, andalternatives, but unfortunately not every manufacturer has implementedthe ideal. Ideally, the shell of the connectors should be connected to thechassis of the device its plugged into.The cable screen should be connected to pin 1 at both ends, with thetransmitting device provide a connection to ground. The receivingdevice provides no connection to avoid problems with devices havingdifferent ground references.

      The wiring for what DMX-512 is designed to is 120 ohm shielded twisted pair wiring. In practice DMX-512 works very well on wiring that has impedance at 100-120 ohms range, meaning that is can be used with nowadays common 100 ohm wiring. DMX-512 is designed to use 5-pin XLR connectors, but some implementations use 3-pin XLR connectors.

      It is also possible to use CAT 5 wiring to carry DMX512 signals. In response to a perceived industry requirement for lower cost DMX512 cable installations, the DMX-over-Category 5 Cable Task Group was formed by ESTA?s Control Protocols Working Group (CPWG) at the January 1998. Accoding the performed tests the Category 5 cable, or "generic premises cable" as it has become known, could be used as a low cost substitute in permanently wired DMX512 installations. It should be noted that while the nominal impedance of Category 5 cable is normally quoted as 100 ohms this is referenced to signals in the 10 to 100 MHz range. The Category 5 cable is also specified as having an impedance of 107 ohms at 256 KHz. This has been verified in measurements by ESTA Control Protocols Working Group. It can be suggested that the minimal reflection from the transition between Category 5 and low capacitance 120 ohm EIA-485 cable is too small to be of any noticeable effect in DMX512 transmission and reception.

      The use of IEC 60603-7 8-position modular connectors (commonly referred to as RJ45 type connectors ? plugs/jacks) and associated punchdown terminal blocks shall be limited to connections that are part of a fixed installation and not normally accessible except to qualified, authorized users, nor intended for regular connection and disconnection. The wiring for RJ-45 connector is the following:

      • Pin 1 (white/orange) - Data 1+
      • Pin 2 (orange) - Data 1-
      • Pin 3 (white/green) - Data 2+ (optional)
      • Pin 6 (green) - Data 2- (optional)
      • Pin 4 (blue) - Not assigned
      • Pin 5 (white/blue) - Not assigned
      • Pin 7 (white/brown) - Signal Common for Data 1 (0 v)
      • Pin 7 (brown) - Signal Common for Data 2 (0 v)
      Warning: Accidental connection to non-DMX512 equipment likely to be encountered (e.g., an Ethernet Hub at a patch bay) may result in damage to equipment. Pins 4 and 5 may carry voltages outside the EIA-485 range in telecom applications (e.g., telephone ringing). Pins 4 and 7 may carry voltages outside the EIA-485 range in other applications (e.g., some manufacturers whose distributed DMX512 buffering products require low voltage DC power may use these wires for this purpose). Because of these various uses, misplugging unlike systems could cause serious damage.

      A DMX network is restricted to 32 devices in a daisy chain (includingsource), and the far end of the network should be terminated witha 120R resistor between pins 2 & 3. If more than 32 devices needs tobe connected, suitable active signal repeaters and/or splitters needsto be used to split the wiring to parts with less than 32 devicesin each part.For reliable operation of DMX-512 system use right kind of cable. DMX may, or may not, work with microphone cable. This depends on the cable and on the run lengths. So microphone cable is not recommended. DMX512/1990 suggests Belden 9841/2 and Alpha 5271/2 cables, depending on if you want one or two pairs.There are many other cables around which work well with DMX512 system. You need a shielded cable approved for EIA-485 use. You are looking for a cable with shielded twisted pair construction and impedance in 100-120 ohms range. Conductors connected to connector pins 2/3 and 4/5 should be twisted together. At 250K bits per second (DMX-512 data rate) the max cable length is about 1000 ft for DMX512 in good conditions.

      The DMX512 communications protocol is very simple and robust. The protocol used in DMX-512 bus is similar to normal serial communications(like RS-232 with 8 data bits + 1 stop bit) and operates at 250 kbps speed. DMX-512 is basically serial transmission via rs485 with 250KBit with 8N2 (8 data bits, 1 start bit, 2 stop bits) format. Transmitting DMX-512 data involves transmitting a reset condition (indicating the start of a new "packet"), a start code, and up to 512 bytes of data. A frame start is indicated with 88 ?s break (low) (typical value) followed by 4 or 8 ?s mark (high). Then a config byte follows (normally 0) and up to 512 data bytes. Normally data packets are transmitted continuously. As soon as one packet is finished, another can begin with no delay if desired (usually another follows within 1 ms, but it can take longer if needed).

      A NULL START Code identifies subsequent data slots as a block of un-typed sequential 8-bit information. Packets identified by a NULL START Code are the default packets sent on DMX512 networks. Each NULL START Code packet contains no formal data or addressing structure. The device using data from the packet must know the position of that data within the packet. There is no guarantee that all NULL START Code packets will be delivered to all devices. Data sent using NULL START Codes should be of a type where loss of packet does not greatly affect the operation of the device. Dimmer level data should be sent in NULL START Code packets. Valid dimmer levels shall be 0 to 255 decimal (00 to FF hexadecimal) representing dimmer control input. Value 0 shall represent a dimmer output of OFF or minimum and 255 shall represent an output of FULL. A dimmer shall respond to increasing the DMX512 slot value for 0 to 255 by fading from its minimum level (off) to its maximum level (full). If nothing is changing (i.e. no lamp levels change) the same data will be sent out over and over again. The DMX-512 equipment expect see that constant flow of data. The general advice is nowadays that those NULL START packets should be sent in such way that the data in all used dimmer channels are updated at least once a second. Typically the data rate on updates is in order of tens of timer per second (for example 50 updates per second). The DMX-512 system just sends the data to the dimmers with the minimum framing information with no error correction or checking information. This means that DMX signal has absolutely no fault tolerance or error correction/detection. Because the data is sent over and over again, randoms error do not cause typically serious problems (get corrected quicly). Because DMX-512 system does not have any error detection or correction systems, it should not be usd to control devices that can be dangerous if they do somethign unexpected with strange data.

      Not all 512 channels need to be output per packet, and in fact, it is very uncommon to find all 512 used. For example, most simple lighting consoles only output 16 channels or less. The fewer channels are used, the higher the "refresh" rate. DMX needs to transmit all Channels up to the highest Channel-number used. So in theory if you leave gaps in your DMX numbering it won't hurtanyone but it will lower your refresh rate (more channels to transmit, so at fixed speed the transmissions take more time andthus you get less repeats per time interval.) In practice you don't have this amount of choise, because on nearly all lighting control desks the number of dmx channels is fixed and the refresh rate is fixed. On really posh and expensive control desks you can go into the setupand alter the maximum DMX channel transmitted and therefore increasethe refresh rate. DMX is a very accurately timed stream of repeating data that loops continuously. To create this continual stream of data at 250,000 bits per second takes alot of processing power and finely tuned software, and as such most commercial PC to DMX modules use on board memory and a processor to churn the data out continuously leaving the PC free to work on level sand update the module as required.

      The communications path for DMX-512 system shoudl be well built to guarantee error free data transmission. Error free data transmission is needed for reliable operation, because DMX-512 does not include any error detection or error correction capabilities in it. This means that if some error happens on the signal on the line, then one dimmer channel some dimmer channels receive incorrect values. Random errors that happen very rarely do not cause too much problem, because the data sent to dimmers is repeated very often (typically tens of times in second). If the dimmer gets wrong data at one data packet, the next packet with correct value will make the dimmer setting right again. So the transmission errors typically do not cause any noticeable problems in light controlling, usually at works cases maybe some random flashing of lights. DMX controlled dimmers either hold the last value or go to zero when a control signal is lost (i.e. when someone turns off the board with the dimmer packs still on). Because DMX-512 does not have any error control or detection capabilities, it should not be used in any application where the reception of wrong control value can cause permanent damage or danger (for example you should not use DMX-512 to control mechanical movemement of any heavy objects).

      In order to provide for future expansion and flexibility, DMX512 makes provision for 255 additional non NULL START Codes (1 through 255 decimal, 01 through FF hexadecimal), henceforth referred to as Alternate START Codes. Where it is required to send proprietary information over a DMX512 data link, a packet starting with a registered Alternate START Code shall be used. A DMX512 transmitter interleaving NULL START Code packets with Alternate START Code packets shall send a NULL START Code packet at least once per second. DMX512 processing devices or any device that receives and re-transmits DMX512 shall state in the manual for the product how they process Alternate START Code packets. The devices can:

      • Block all packets containing particular Alternate START Codes
      • Pass unmodified all packets containing particular Alternate START Codes.
      • Process the information contained in packets containing particular Alternate START Codes.

      The receivers for DMX-512 needs to be carefully designed, because a DMX512 receiver MUST properly decode ANY possible DMX512 transmitter. If the standard does not say that a transmitter can't do something someone has designed one that does! All receiving devices other than in-line processing devices shall process the START Code and differentiate between those packets with NULL START Codes and those with Alternate START Codes. Devices shall not ignore START Codes by assuming that all packets received are NULL START Code packets.

      The original intention of using DMX512 for controlling dimmers only , has now been stretched to include a whole range of equipment. The 8-bit data structure, which was originally used to specify 256 levels of dimming only, is now also used to define many different parameters in different equipment. Typical applications include mirror position and gobo position on moving mirror light instruments, gelstring position on color changers, shutter position and focus motor position on many intelligent light instruments, smoke machine, sometimes even laser effects and RC servo motors. Equipment for generating DMX512 have also taken different forms. Nowadays you can most often see it done with lighting consoles or with a standard PC that has suitable adapter. In addition to those applications use back-up equipment for consoles, architectural lighting controllers and test instruments or DMX multiplexor (takes in . In addition there are special equipment with receive and transmit capabilities: lighting protocol converters (converts between DMX-512 and some other protocol), DMX multiplexors, DMX de-multiplexors, DMX splitters, intelligent DMX-512 signal combiners etc.

      The console converts data collected by it from the various tactile controls on it into a 8 bit form using Analog to Digital converters or other devices and then computes the required output data. The PC software works using the same principle but uses software control of the parameters (usually either GUI or control algorithm). Not all 512 channels need to be output per packet, and in fact, it is very uncommon to find all 512 used. For example, most simple lighting consoles only output 16 channels or less. The fewer channels are used, the higher the "refresh" rate. It is possible to get DMX512 refreshes at around 1000 times per second if only 24 channels are being transmitted. If all 512 channels are being transmitted, the refresh rate is around 44 times per second.

      DMX SPLITTERS generally provide multiple DMX outputs from one input and can drive a large number of units. DMX MERGE units take two or more DMX512 inputs and merge them into one DMX output stream placing one input stream AFTER the other. DMX MIX units take two or more DMX512 inputs and mix them together channel to channel and produce one DMX512 output. The mixing is usually done in the HTP (Higest Takes Precedence) mode, but some devices can also be programmed to work using other algorithms.

      There are various ways how different light instruments handle the received DMX-512 data:

      • Dimmers recieve DMX512 data and use it to control the width of a pulse which then triggers a power control device such as a triac or a set of thyristers. The DMX data-to-phase angle ratio is often compensated over the entire 256 step (8 bit digital) range. These compensating curves are called dimmer curves and are often user selectable in the dimmer or from the console.
      • Moving lights se DMX512 data to determine the relative angle of a motor shaft. Those motors are most often stepper motors that are controlled by the light control electronics. There may be several such motors turning the mirror, gobos,lenses,lamp shutters etc in a moving light. Each needs it's own channel of DMX data and thus separate channels are used. In addition to motor controlling, one DMX-512 channel may be used for a traditional dimmer that controls the lamp intensity.
      • A color scroller has one or two motors with a reel shaft on each across which the gelstring is strung. Based on the DMX512 data recieved , they reel the gelstring in or out, changing the color coming in front of the lamp.
      • DMX512 is also used to control smoke machines. Usually or or more channels are used. The basic channel is used to trigger the smoke machine to blast away smoke when it receiver value over the tigger limit (for example halfway of control range). One more channel may be used to control smoke quantity (pump pressure).
      • DMX512 can control some stroboscopes directly. Typically two control channels are used, one controls the strobo speed and another is strobo brightness.
      • DMX512 channels are used to activate relays on relay controller (usually value 128 or higher activates relay, lower value turns them off). Relay controller offers a relay closure control based on the signal on DMX-512 control bus. Those relay output can be activate whatever device you want (confetti dispensors, snow machines, strobe flash etc.). For DMX-to-relay converters, you should always consult the manual for details about how the channel values are interpreted as far as relay closure and opening.
      • DMX-to-analog converters take in a number of DMX-512 channels and convert the numeric values to corresponding output voltages in 0..+10V votlage range. Those control voltages can be then connected to an equipment that originally was designed to be controlled with analogue lighting desk (for example old light dimmer packs with only analogue inputs).
      • DMX512 can be used to control various laser projector functions, just as it was used to control lamp brightness levels, voltage levels, panning and tilting and other things. To do this, the laser projector would need to have a DMX-to-analog or DMX-to-TTL converter within the projector.
      • DMX-512 can be used tio control small animatronics with aid of a DMX-512 to RC servo converter. This kind of converter converts a number of DMX-512 channels to a PWM signal suitable to control RC servo motor position. Those servo motors can then move some small objects as needed.

      There are some equipment that you should not control with DMX-512. Infact , any thing which compromises the safty of human (or animal !) lives due to failure to recieve and interpret DMX512 correctly, is prohibited. The following equipment are SOME of many which are prohibited from using DMX512 as a trigger source as specified by the standard: pyrotechnics, set shifting equipment and truss motion control.

      DMX512 data link works quite reliably when properly used, but there are some DMX512 "gotchas" - general aspects of DMX usage to watch out for.

      • 3-pin vs. 5-pin connectors: In some places 3-pin XLR cables are used instead of 5-pin XLR cables. Sometimes you will need to create a 3-pin to 5-pin converter.
      • Watch out those rare revices that use pins 4 and 5 of 5 pin XLR connector for something. The way different devices use those spare pins can vary and devices that use them differently mught not like being in the same daisy-chain.
      • Data link termination: Since DMX512 uses relatively high data transmission rates, the end of the cable needs to be terminated, particularly if it is over 25 feet long.
      • Refresh rate too fast: Although the DMX512 standard provides for very fast transmission where each data packet can immediately follow the last data packet with no delay, very few DMX devices can actually work with such a fast data rate. Most devices require some delay between packets or a lower refresh rate to process the data received in the last packet.
      • The receiver can "drop data bits" in a channel or channels in case of electrical noise gets too much to the control cable. The consequences of dropped data bits depends on the device being controlled. For simple lamps, this would result in the lamp level fluctuating. A similar thing would happen for any kind of color selector or a relay output.
      • If there are a lot of transmission errors a DMX-512 receiver can "drop channels". No matter what is being controlled, the results of dropped channels would probably be very visible.

      In reality, things like dropped bits occur very rarely; dropped channels almost never occur. When you add the "continuous transmission" aspect of DMX512, data link errors are essentially unnoticed. As long as good quality cable is used, and as long as the end of the data link is terminated, you should never see any of these problems.

      The SIGNALING in DMX is a "real" standard - virtually anything can coexist with virtually anything else and DMX will control it all and things stay out of each other's way nicely. Up to 512 devices, or functions on a device, can be controlled with 8-bit resolution. All channels are continually being "refreshed", which increases safety. Although the DMX512 standard is being updated, existing equipment will still work the same under any new revision.

        DMX-512 circuits

        • DMC 4ch Receiver - Receives four DMX channels and drives four 220V outlets. This circuit is based on PIC16F84.    Rate this link
        • DMC 4ch Receiver - Receives four DMX channels and drives four 220V outlets. This circuit is based on PIC16F84.    Rate this link
        • DMX512 Receiver 1 - Channel 1 drives 8 LEDs. This circuit is based on PIC16F84 and SN74176.    Rate this link
        • DMX512 Receiver 1 - Channel 1 drives 8 LEDs. This circuit is based on PIC16F84 and SN74176.    Rate this link
        • DMX Receiver 2 - Receives any DMX channel from 00h to oFh data and drives 8 LEDs. Built around PIC16F84.    Rate this link
        • 8 channel DMX / RS485 controller (rev. 2.0) - With this circuit DMX-512 based dimmerpacks, switchpacks, PWM controller and controller for laser devices can be realized. The circuit is only made of an AVR and few other parts.    Rate this link
        • Base Code to Transmit and Receiver DMX512 channel on 8051 based microcontrollers    Rate this link
        • 12 button DMX-512 flasher    Rate this link
        • 8051 + AVR + DMX HARD - DMX-Transmitter, DMX-Receiver, 0-10V Converter, 1 Kanal DMX-Dimmer, text in German    Rate this link
        • benoit.bouchez.free.fr - This site is maintained by the author of the DMX control programs SoftController 1 and SoftController II (demo versions available for download). The author has designed a full range of DMX interfaces and modules, described in the ELEKTOR electronics revue.    Rate this link
        • DMX-512 booster schematic - This circuit gives you optoisolation and four DMX-512 outputs    Rate this link
        • DMX 512 Printerport Interface page - This page contains schematics and software to build your own cheap 64 channel DMX 512 printerport interface. This is a very popular homebuilt PC to DMX-512 interface supported by many free control software applications. This web page also contains the schematics for a 4-way DMX booster / splitter and a 12 channel DMX flasher.    Rate this link
        • ftp.armory.com DMX-512 hardware directory - DMX-512 technical documents and example circuits    Rate this link
        • How to build DMX512 terminators    Rate this link
        • Kelly Kohls, N5TLE Homepage - DMX 512 Light control circuits including 16 channel 0-10volt demultiplexer based upon a PIC16C76/PIC16F876, also a Analog to DMX512 multiplexer based upon a PIC16F876    Rate this link
        • Kristof's Webpage: Home of the DMX-512 printerport interface - PC parallel port to DMX-512 adapter circuit and control software for Windows    Rate this link
        • Simple Oscilloscope trigger circuit for DMX signals - This is a simple O'scope trigger circuit for checking DMX signals. It is based on a 4528 CMOS monostable multivibrator.    Rate this link
        • Konverter RS 232 - DMX 512 - This circuit takes in RS-232 signal and outputs DMX-512 signal. The circuit is based on PIC12F675 microcontroller and is isolated from PC. This circuit documentation gives also idea how to interface this circuit to USB port. The description of this circuit is in German language.    Rate this link
        • LPR2DMX - Open-Source DMX512 interface - One of the smallest DMX512 interfaces connected to the computers printer port is the LPR2DMX. It features all 512 slots and any start-code as it will be apart from the coming DMX512-2000 specifications. The start-code is also not fixed, it can be changed from frame to frame. That allows one to transmit every 0.1 second a frame with none zero start-code and the rest of the time frames with start-code equal to zero. All that was included into a PIC16F84-10 or PIC16F84A-20 in a way, that in-circuit reprogramming and firmware updating is possible. The LPR2DMX is released as free software under the GNU General Public License.    Rate this link
        • DMX43 Interface DMX43 Interface is a DMX512 Interface based on the TI MSP430 microcontroller. DMX43 features two DMX In and Output. Connected to the ECP/EPP parallel port the DMX43 is the fastest parallel port interface on the market today. DMX43 1.0 includes the firmware, schematics and development docs (currently in german) for the DMX43 interface.    Rate this link
        • DMX30 Interface - This is a small dmx-interface for do-it-your-self. This is a very old design based on very old hardware (AT89C2051).    Rate this link
        • Open DMX USB Interface - The open DMX USB hardware solution provided to the community by ENTTEC. This DMX USB interface is based on the FTDI 232BM chip, it's a USB to serial convertor. Using a simple application on a PC or MAC you can send and receive DMX512.    Rate this link
        • OksiD DMX 3/1 - OksiD DMX 3/1 is a Standard Parallel Port DMX 512 interface for IBM compatible PCs. The OksiD DMX 512 controller has 3 output Universes and 1 input Universe (a Universe is a set of 512 DMX channels). Both input and output have fully buffered 512 channels. This DMX 512 interface works under Windows 95, 98, XP and Linux. This is an Open project. All source code and schematics are available for free. The DMX512 interface is based on 3 Microchip PIC18F452 running at 32MHz. You can build the circuit with only one PIC18F452 if you only need one Input and one Output Universe. You don't need to modify the software.    Rate this link
        • MANOLATOR DMX512 Free Interface - This is an easy to make (it uses the schematics of the interface designed by kristof Nys), can be powered by computer (by the ps2 or usb connector), interfaces to parallel port and supports 256 Channels (all buffered). This interface works with Manolator software and with Freestyler software. This design is based on pic16f88 microcontroller.    Rate this link
        • Digi Pack - This unit recieves DMX 512 data and Analogue (0- 10v) data and uses these to phase angle control four mains outputs. This design is based on PIC16F870 microcontroller. This devices has 3 Modes of operation: Digital Lighting Data, Aanlogue Lighting Data and Internal Presets. This circuit supports linear, S-curve and switching dimming curves. This circuit is designed to operate at 240V 50 Hz power.    Rate this link
        • DMX PC Keyboard Interface - This is the Design for a DMX512 to computer keyboard interface. It sits in line on the computer keyboard and on the DMX 512 chain. Decoding The Lighting data and if one it's set channels is set above 1/2 value this unit will output a sequence of keyboard keys to the connected PC. It is primarily designed to be used with PC connected to video projectors, where the lighting controller may require control of a presentation on the video screen but the PC for the presentation is located in a different location to lighting control. This unit allows a presentation to be controlled form a standard DMX lighting desk. The DMX Keyboard interface has 6 Channels that can be selected to any group of addresses from 1 - 512 in the DMX Universe. This unit is designed around a standard Micorchip PIC chip PIC16F627 running at 20MHz.    Rate this link
        • Open DMX project - The open DMX projects goal is to produce a low cost USB-DMX control unit under a GPL license.    Rate this link
        • DMX 4ch Receiver - This PIC16F84 based circuit receives 4 DMX channels and controls four 220V AC outputs on/off based on data on those control channels. The description of this circuit is in French.    Rate this link
        • Un r?cepteur canal x DMX512 - This is a simple PIC16F84 based single channel DMX-512 receiver circuit. This circuit can be set to receive channels 1 to 15. Circuit description is in French.    Rate this link

        DMX-512 control software and information on products

        A PC can nowadays used as a feature rich light control system. You need a suitable DMX-512 interface for your PC and a suitable control software. In general you need to look at the control software and the itnerface as one system, because there are no standards for DMX-512 interface interfacing. The DMX-512 interface hardware has to be built into the application, and different software applications support different sets of hardware. There are both commercial and free PC light control software, many alternatives with different feature sets. Depending on you application a PC may look like a better or worse light controller as the traditional lighting board. With PC screen you don't have the "feel" of the real controls in he lightin desk, you just have an application that looks like a lighting desk that you manipulate more or less conviently with your mouse/keyboard. The benefits of PC light control comes when you need board where you have to store many lighting settigns (there is lots of mory and hard disk space on PC for those) and when you need to do complex control of moving lights (som software allows graphical definition of moving light movement effects easily). Most PC based light control systems run on Windows, but there are also software that runs on Linux.

        PC has some disadvantages as lighting controller. The basic trouble is that PCs running under Windows, are not terribly reliable. Most of the time, they are fine, but this isn't good enough for lighting control. If your show depends on the operation of he control PC, you want something that works for sure. PC's are as reliable or unreliable as the people who use and control them. If you want a reliable PC, get someone who knows what they are doing to help you make it reliable and keep it reliable. PC's deserve at least as much attention as a car (you need to change oil and do repairs on time). If people who don't know what they are doing load software and don't address the problems that may arise, the PC becomes trash.

        To make Windows more reliable, it is best to use a dedicated machine that is optimized for the light control application. No unnecessary software and no system update all the time. If you keep a control PC outside the Internet and LAN networks, you don't have to worry about all Windows safety updates (they are mostly not needed in PC that is not connected to network and used for only one special application). Keep an up to date backup of your data and setting, so that you can quicly bring the PC up again in case you hard disk crashes. Or keep another PC as spare unit you can use for light controlling if the first one fails. PCs are cheap enough that if you want to use one as just a lighting controller, its a practical thing to do. Just load the lighting controller software, plug in the interface, and allow absolutely nothing else to be loaded or attached. Ever.

        If you don't have the luxury of a dedicated control PC then you have to work with what you have and you will probably want Word, Excel and a CAD package loaded in order to document your lighting designs etc. Best way of working with a single PC would be to have a a dual-boot system and to maintain a second minimalistic installation of Windows on a separate partition with absolutely no frills or optional components and only install the absolute minimum of features for any applications such as Office components. When you boot up you could then choose between the "show" system (with just the control software) and the "plot/rehearsal" system with everything else as well. You can then keep this squeaky-clean by periodically re-formatting the partition and reloading from a backup image, using your main installation. When you boot up you could then choose between the "show" system (with just the control software) and the "plot/rehearsal" system with everything else as well.

        • DMX512 PC-Interfaces - information on some commercial interface card products and general programming tips, take also look at    Rate this link
        • DMX4Linux - A DMX device driver package for Linux    Rate this link
        • DMX-512.com downloads - DMX DIP switch buddy and DMX shapes generator    Rate this link
        • FreeStyler - FreeStyler is software running on Windows 98/2000 and XP systems. The software controls all DMX512 equipment like scans, movingheads, dimmers... FreeStyler is compatible with many free DMX interfaces that can be found on the internet, therefore the number of users keeps on growing rapidly. The software can be downloaded freely.    Rate this link
        • DMXControl - DMXControl is a is a freeware project that creates Windows based software for control of any DMX-equipment. Thsi software features Sound-to-Light control, Scenes and light effects administration and manual control of the light show. This software supports many DMX transmitters, both commercial and homebuilt devices.    Rate this link
        • StageLight Basic - StageLight Basic is simple easy to use lighting scene editor and sequencer designed so anyone that has operated a basic lighting console will be able to learn how to use it in about 10 minutes. It has been designed for schools, churches, traveling performers, shops, homes (Christmas lights anyone), and really small theaters. Using the DMX4Linux drivers it will have access to a variety of DMX512 interfaces, including some freely avaliable parallel port designs. StageLight Basic is being developed on the GNU/Linux operating system using the FLTK Graphical User Interface Library and the DMX4Linux Hardware drivers. SLAVE Lighting (previously Light-n-Easy) has released StageLight Basic under the GNU/GPL Licencing.    Rate this link
        • Linux Lighting Software and Hardware links    Rate this link
        • Q Light Controller 2 - Q Light Controller 2 (QLC2/QLC) is a derivative of Q Light Controller Project. QLC2 like its predecessor is an application that can be used to control various stage/show/club/venue lighting systems like scanners and dimmers on a Linux/X11 platform. QLC uses the dmx4linux driver suite to access various hardware interfaces.    Rate this link
        • DMX4Linux - DMX4Linux is a DMX device driver package for Linux. DMX4Linux gives you access to a wide range of DMX interfaces with the Linux operating system. Currently DMX512, Analog 0-10V and MIDI control systems are being supported by dmx4linux.    Rate this link
        • DMX512 Interfaces supported by dmx4linux    Rate this link
        • SLight - This software controls professional theater dimmers with the DMX-512 protocol using the DMX4Linux drivers, and is meant to write and run relatively simple shows with a minimum of hassle and feature-bloat. Useful features include automated follow and cue looping, but the real gain is in consistency: 90 second crossfades happen smoothly and precisely. This software is written using the QT toolkit. It will be available in source-code only. This software is designed to be used in Linux operating system.    Rate this link
        • ProZic - DMX - This is a free DMX-512 control software. It works with a parallele interface to DMX : ParZic DMX available on this site or LPR2DMX from lighting Solutions (schematic supplied). Software runs on Windows 95, 98, NT, 2000 and XP.    Rate this link
        • DMX Desk - This is a Computer based lighting control Desk for two easily available Adapters. DMX Desk is designed to provide up to 512 channels of lighting using several adapters designs available on the internet. DMX desk is deigned to work with kristofnys design, the Oksid PC DMX Adapter or Enttec Open USB DMX Interface. The Desk is based on a design by for a light jockey desk, but is now designed to be an computer version of a normal lighting desk.    Rate this link
        • Manolator Software - This is an upgrade version of Kristof Nys? DmxDesk9 Software, compatible with MANOLATOR 256 Interface and with KRISTOF?S 64Ch. The newest version also supports Enttec OpenDmx interface.    Rate this link
        • XL12 - 256 emulator by Kristof Nys - This is a virtual version of the Zero 88 XL12 lighting console made by Kristof Nys to use with the Manolator interface. You can manage only 12 different channels at time, like the real console, but those channels can be patched to any of the 256 output channels of the interface.    Rate this link
        • The MasterPeace Project - This is a free software version of a well known light desk. This software supports parallel port DMX512 interface and EnTTec Usb OpenDmx interface.    Rate this link
        • SoftNode - SoftNode converts Ethernet DMX Protocols to DMX ready for your lights. This software allows you to use older PCs as ethernet-dmx stagebox's or even a cheap wireless dmx rig. This software supports both Art-Net and ESP-Net Ethernet DMX Protocols (can also convert ESP-Net into ART-Net). This software supports Open DMX USB Widgets.    Rate this link
        • Office Wing - Control the lighting in your home or office! Open source.    Rate this link
        • Simple 16 DMX - Simple 16 DMX is a simple 16 channel 2-scene preset light board with cue memory and timed cross fades. This software is written using Visual asic and released to the public domain. This free software works with the Enttec OpenDMX USB interface.    Rate this link
        • DmxDesk9 by Kristof Nys - A Lighting console ported to Enttec Open DMX USB (Open source)    Rate this link
        • DMX 512 software links    Rate this link
        • DMX 512 software links    Rate this link
        • MagicQ PC - A fully working moving light console, which has native support for the widget, and also working art-net universes support!    Rate this link
        • MagicQ PC - A fully working moving light console, which has native support for the widget, and also working art-net universes support!    Rate this link
        • STL-DMX - Sound-To-Light. This program rocks! Audio detection with Several operating modes (free, manual, modulating, random with or without music, copy of another channel) with many parameterslinear Modification of the evolution of the values of each channel Transistions slow (Insipid Time) in manual and random mode with curve s?lectionnable. Site is in French but it's easy to figure out.    Rate this link
        • dmxusb - send and receive DMX512 using the Open DMX USB Interface. Available for Windows, Linux and Mac OS X.    Rate this link
        • MAX MSP External - Send or receive DMX512 data using the Open DMX USB Interface    Rate this link
        • Receiving DMX with ENTTEC Open DMX-USB unit - A guide to error-free dmx reception with code in C    Rate this link
        • C Interface & ActiveX control for ENTTEC Open DMX-USB unit - The bin should contain everything required. OpenDmxUsb.dll is the C interface library and OpenDmxUsbCom.dll is the COM wrapper.    Rate this link
        • C Interface & ActiveX control for ENTTEC Open DMX-USB unit - The bin should contain everything required. OpenDmxUsb.dll is the C interface library and OpenDmxUsbCom.dll is the COM wrapper.    Rate this link
        • Steve's software for DMX-512 theatrical lighting control - Dmx4Linux driver for FTDI-based interfaces    Rate this link
        • Open DMX USB Linux 2.6 Driver - the driver and programming examples for Linux    Rate this link
        • LuX - light up - LuX stands for "Light up X" and provides a fully integrated Light controll center (an enhanced virtual Light Console) for a Linux Machine running GTK and X. Designed to work with a Parport AVR Dongle. The LuX-Client is free software, developed under the terms of the GPL.    Rate this link
        • Light up X - LuX (Light up X) is a full-featered Virtual Light Console for Linux. It communicates with a DMX Device and can be used in Theatres, Concerts or Parties for complex light effects.    Rate this link
        • dmxconsole - simple dmx manipulating program for DMX4Linux DMX-512 device driver package for Linux    Rate this link
        • dmxconsole - dmxconsole is a simple curses console application for manipulating DMX-512 data to be sent using DMX4Linux DMX-512 device driver package for Linux. You can manipulate dmx channels directly and store them in different cues. Cues are crossfaded.    Rate this link
        • midi2dmx - midi2dmx will translate midi messages to dmx slots    Rate this link
        • dmxpanel - dmxpanel is a simple X dmx console for Linux. dmxpanel displays faders which manipulate the dmx device directly.    Rate this link
        • dmxdisplay - dmxdisplay monitors the dmx device. dmx channels are displayed with a ledbar. Designed to work with Linux.    Rate this link
        • MANOLATOR 256 Ch. Free DMX512 Interface - upgrade version of Kristof Nys? DmxDesk9 Software, compatible with MANOLATOR 256 Interface and with KRISTOF?S 64Ch    Rate this link
        • ArtNet Project - a library that implements ArtNet on POSIX systems    Rate this link
        • DMX 512 WinAmp Light Show - Synchronize your DMX-512 controlled lighting system with music played with WinAmp    Rate this link

      AMX192

      AMX192 is a control protocol standard for dimmers first introduced around 1975 as Strand proprietary multiplexed dimmer control system. This sytem became widely used with Strand's extremely popular Light Palette and CD80 dimmers that first appeared in 1979. The AMX192 standard, adapted by the United States Institute for Theatre Technology, is non proprietary and may be used by all manufacturers. The AMX192 standard was introduced at 1985. The origins of this standard come from a control protocol originally developed by Strand Lighting (Strand Century Inc.). This protocol is used by a large installed base of equipment manufactured by Strand and many other manufacturers.

      AMX192 uses a small twisted pair cable to communicate with a maximum of 192 dimmers. Depending upon the type of console, a single AMX192 data line can handle either 96 or 192 dimmers. Dimmer levels (0-5V) are sent sequentially on one wire, referenced to a signal common wire that the other conductor is paired with. A synchronizing clock signal is sent differentially on a second pair of wires. The data signal is 'de-multiplexed' (usually at the dimmers) resulting in individual 'analog' control signals (usually 0-10 volt, DC). When AMX first appeared on Strand products, it used the tiny Switchcraft TA4 connector. Its pinout was clock- on pin 1, common on pin 2, clock+ on pin 3 and mux analog on pin 4. Many rental companies have replaced with connector with 4-pin XLR connector. The standardized AMX-192 uses 4-pin XLR connector with the following pinout:

      • 1 = Screen
      • 2 = Clock +
      • 3 = Analogue
      • 4 = Data Clock -
      This is how it should be: input connectors are female and outputs are male; pin 1 is common, pin 2 is clock+, pin 3 is analog, and pin 4 is clock-.

      The name AMX192 would incate that this USITT analog multiplex would be 192 channel system, but some sources indicate that AMX192 would be able to support up to 384 channels. Because the original protocol has undergone many slightly different versions. There are substantial differences between the receive timing and the transmit timing. New controllers adhering to this standard must produce a signal acceptable to a wide variety of dimmers, and new dimmers must be able to listen to a number of different controller signals. As an example, note that new controllers should provide a wide "analog valid" window, but new dimmers must be able to cope with the differences in existing consoles, and use a narrow "sample window". Although widespread adoption of this Standard is sought by USITT, compliance with the standard is strictly voluntary. One real gotcha with this multiplexed analog schemes is that the cable radiates a fair amount of interference, and so wireless intercomms can get blocked if you are close by.

      Anyone who has dealt with AMX192 gear for any length of time will tell you that they've had more than their share of problems getting things to communicate properly. No one console, for example, will talk to all receivers out there, and vice versa. The age and condition of receiver cards and power supplies can affect how well the data link works. The type and length of cable can also be a factor when changing to a different transmitter, such as a protocol converter. Designers of new AMX controls usually pick a set of signal timing parameters that are known to work well with most of the existing dimmer racks; you might just be one of the unlucky ones that gets a mismatch.

      AMX192 has been very widely used in USA markets, both in theatrical and architectural markets. Virtually every North American Strand product designed until very recently included at least one AMX port. As well, a number of their competitors made compatible products over the years AMX192 is virtually non-existent outside of the U.S. and Canada

      Microplex (MPX)

      As for the control system for the dimming system, today's industry-wide lighting protocols are multiplex (MPX) and DMX-512. Multiplex is known by a variety of names by different companies; it may be called microplex or LMX-128. This communication signal is normally transmitted from your lighting console to your dimmer via a standard microphone cable. Multiplex can offer a maximum total of 128 channels, and the distance between the console and the dimmer should not exceed 125 feet. If your application can accept these limitations, then multiplex is a valid option.

      The Micro-Plex (MPX) method is aimed at low-cost, short-run, dimmer control applications where standard XLR mic cables can be used with the dimmers and the controller chained in a way that's very similar to MIDI communication. NSI Micro-plex is capable of supporting up to 100-128 dimmer channels. However, the more channels, the slower the refresh rate. NSI Microplex (MPX) is proprietary control protocol used by NSI (Leviton). Some devices from some other companies support this protocol also. The pinout for Microplex 3-pin XLR connector is the following:

      • 1 = Common
      • 2 = +12V DC (+15V on some information sources)
      • 3 = Micropex data
      Here is a quick overview of protocol (unofficial information): The Microplex signal line swings from around +8v to -6v. +8v is Fully ON and 0v is Fully OFF. Negative voltage, -6v, is a sync pulse. The protocol starts off by sending a 5ms sync pulse (-6V). This sync pulse resets the channel counter in the dimmer boxes to zero. After the pulse, the level for the first light is send for 0.25ms. If the light is to be off, then the level will be zero volts, if light full on the voltage is +8V. Next a 0.25ms sync pulse (-6V) is sent. This increments the channel counters on the dimmer boxes. The dimmer signal levels and 0.25ms pulses are repeated until all the channels have been sent. The process begins again with the 5ms sync pulse. The actual specification could be slightly different than this quick overview.

      There are two basic Microplex variants: NSI's version normally supports 64 dimmers, but in certain cases does 96; the Leprecon and Lightronics versions support 128 dimmers. The version used by Lightronics is called LMX-128. The 3 companies supporting this protocol seem to agree on almost everything but basic signal timing parameters, making interoperability a bit dicey. They all use 3-pin XLRs wired as follows: common on pin 1, console power on pin 2, and signal on pin 3. The mux control signal is 0-10 volts.

      0-10V DC voltage controlling

      DC voltage control is very much used in simple light effects and small light dimmer systems. It is a very simple and easy to understand system which can be troubleshooted with just a multimeter. The most commonly used DC based light controlling interfaces are 0-10V control for light dimmers and 1-10V control used to control dimmable electronic fluorescent lamp ballasts. Strand, who pioneered desks with semiconductors, decided on their 0 - -10V control back in the days of p-n-p germanium transistors, when this was natural. Being stubborn, they stayed with this protocol long after it was out of date. Other manufacturers in the industry have used different voltages, but have later sellted to 0..+10V control voltage range.

      This type of multicore analogue systems were prevalent before digital DMX-512 control became more popular in large systems. In multicore analogue system the console was physically connected on a channel by channel basis to the dimmers. Most modern light controlling desks still emit 0 - +10V, on their analogue lines (usually 15-pin D-connector). Very many modern light dimmers can accept 0-10V control voltage in addition to DMX-152 controlling. For example many 6-channel dimmer packs use 8-pin Bleecon connector (8-pin DIN or 8-pin XLR) for 6 channel analogue 0-10V control voltage. Bleecon connectors ("Bleecons", by Belling Lee) are widely used on dimmer packs of six or less channels for analog control input. The Bleecon is basically an 8 pin DIN plug and socket. The sockets will accept ordinary 8 pin DIN plugs, and also those with a locking ring. The most often pinouts for this Bleecon connector is the following:

      PinStandard
      1Channel 1
      2Channel 2
      3Channel 3
      4Channel 4
      5Channel 5
      6Channel 6
      7Power
      8Earth
      Like all good widely used connectors, there are a few variations by manufacturer of just what the various pins do. Power polarity tends to follow control polarity, so Strand supply -ve power here, everyone else supplies +ve power.

      There are also other connectors types in use. Dimmers or receiving devices shall use connectors with male contacts (pins). Controllers or sending devices shall use connectors with female contacts (sockets). If suitable connectors are not available in both sexes, the same connector may be used on dimmers and controllers. For most multipin connectors are wired in such way that the different control channel signals start at pin 1 (channel 1 on pin 1, channel 2 on pin 2, etc.) and the highest number pin is signal common. Sometimes several of those highest number pins are used as ground, and sometimes free pins between highest used channel and ground pins are used to supply power though te cable (usually around 12-24V range). Pinout of all control connectors are often labeled adjacent to connector showing all pin assignments or listed on the equipment manual.

      Typical multi-channel light controlling system which uses 0-10V DC controlling uses thick multicore cables containing a core for each channel, as well as power supplies and ground leads. 0 to 10V cables can be almost any type of conductor or cable.

      Many DC controlled light control systems (not all) can be connected in parallel in highest takes precedence (HTP) manner. This refers to the way in which a channel is controlled. When a channel is controlled by two or more sources (for example, if two sub-masters on a lighting desk contain the same channel) the highest value is used. HTP channels are normally used for controlling intensity.

      The standard approach in 0-10V controlling is that the controlling source (lighting desk) supplies power to the line and the receiver (dimmer) just looks at the voltage it gets. The control signal sources have typically their output quite low impedance (1-5 kohm typically) while the devices to be controlled have typically high input impedance (typically around 47 kohms, but can be lower on some some devices). In 0-10V analog lighting control systems the dimmers typically create a ramp signal (looks like |\|\|\|\|\|\|\|\, goes linearly from 10V to 0V and then quickly back to 10V during mains power zero cross). The dimmer has a comparator circuit that triggers a signal if the two input voltages are the same. The comparator circuit circuit ompares the control voltage to the ramp signal that falls from 10 to 0 volts over time of one half cycle of mains power. Example: Control desk "sends" 8V to the dimmer, because it should dim the light to 80%. When ramp signal reaches 8V, the comparator signals the load part of the dimmer (where the lamps are attached) to start the current.

      The American National Standards Institute's Board of Standards Review approved E1.3-2001, Entertainment Technology - Lighting Control Systems - 0 to 10V Analog Control Specification, on 21 March 2001, is a standard for using DC voltages from zero to 10V to control lighting devices. This used to be a very common control method, but earlier there was no widely accepted standard. It has been superceded in parts of the entertainment lighting market by DMX512 and other digital protocols, but a significant portion of the entertainment industry still makes, sells, and uses 0-10V equipment. It is particularly important in the custom market on projects where specifiers want a simple and easy to trouble-shoot protocol.

      The signal intepretation is the following: Zero volts is considered the "off" condition. When dimmer receives zero volt input signal, it should turn it's output off (there can be some idle voltage if defined on dimmer itself). In case of motion control, the receiver should position itself at one extreme. In case of speed or rate control, the receiver should set speed to minimum or stopped. In case of audio volume zero voltage could be off or maximum attenuation. Note that when a console or other sending device is powered down or disconnected, it sends zero voltage to all receivers. The "off" condition of a receiver should always be a safe condition. Ten volts is considered "on" condition. When a controller is sending a level od 100% or "full", it should place ten volts on the output. When dimmer receives 10V input, it should tur its output fully on (can be less than full line voltage if maximum is defined so on dimmer). In the case of motion control, the receiver should position itself at the opposite position form "off". A rate or speed control should go to it's fastest speed. The 0 to 10V control is intended to be linear. The output of a receiver should be "half" when it receives 5V control voltage. A dimmer at half may bring lamp to half intensity or output ar half it's maximum voltage (in productions the response curve form control voltage to lamp intensity should be defined).

      The output of the controller shall be a steady DC voltage. When the control level is constant, the output shall not change by more than +/-20mV. The output shall vary between 0 and 10 volts. Zero voltage represents off condition and then volts is full on. The output voltage shall never be less than -0.5V and nor more than +10.50V. Output voltage levels are to be measured with a load of 20 kohm. Passive controllers, with unbuffered outputs, shall use potentiometers with a resistance value of 10K ohms or less (=output impedance of 5 kohms or less). Active controllers with buffered outputs must have an output impedance of 100 ohms or less and be capable of continuously sourcing at least 2.0 milliamperes. Controllers and output devices shall be provided with a blocking diode (or similar circuit) such that each output presents an open circuit to any source voltage of more than itself. The blocking diodes allow multiple controllers or outputs to be paralled to control the same dimmers or receivers on a "highest takes precedence" basis. It is recommended that controllers and output devices have current limiting on all outputs such that they are not damaged by short circuits to signal common. The control signal and all control connector pins shall be isolated from AC mains (line and neutral). It is encouraged that the control signa be isolated from earth ground.

      Those specifications above generally apply to the new devices. Please note that there is a lot of old 0-10V devices that might not meet all of those specifications.

      There is a one variation connonly used at variation normal 0-10V control approach, this is used widely for controlling fluorescent lighting dimming ballasts. The dimmable fluorescent light ballasts are typically controlled through 1-10V voltage control system. Many ballasts supply a low voltage (12-15V typically max) limited current (typically 0.5-0.6 mA) to their control outputs, so that the dimming can be controlled with just a potentiometer (1.8 kohm gives around 10V and 200 ohms gives 1 volt to the ballast).

      The definition of 1-10V ballast controlling method is included to IEC 60929 standard. In this system one controller can control up to 50 ballasts. Active control voltage range is 1-10V (voltages in 0-10V range are allowed). In this system every ballast is a current source that feeds 0.2-1 mA current to the line (0.3 mA typical). The controller is a current sink that sinks current so that the voltage on the line drops to ne wanted control voltage level. The controller current sink must be able to sink up to 100 mA at 1V output and up to 50 mA at 10V output to be able to control many ballasts (up to 50). The controller must be able to work with as low as 0.2 mA current to work reliably with only one ballast connected. The standard is only designed for lamp dimming level controlling (no special on/off controlling).

      • ANSI E1.3-2001, A New Standard for an Old Protocol - The American National Standards Institute's Board of Standards Review approved E1.3-2001, Entertainment Technology - Lighting Control Systems - 0 to 10V Analog Control Specification, on 21 March 2001. It is a standard for using DC voltages from zero to 10V to control lighting devices.    Rate this link

      Ethernet in light controlling

      Ethernet is the most commonly used standard computer communications protocol used in local area networks. Moving lights, modern dimmers and lighting control desks all contain computers, so it coming to wide use for lighting control as well. Ethernet is capable of controlling massive numbers of lights, but at the moment Ethernet light controlling suffers from slightly lower reliability and less standardization than traditional DMX-512 interface. Ethernet using twisted pair wiring is coming to the lighting industry controlling, but the manufacturers have not yet have agreed on a common Ethernet protocol. Current Ethernet standards define the pyical network and addressing, but there are no standard for the format and content of the packets to be used for lighting equipment controlling. Nowadays there are some implementations of Ethernet based light controlling but those are proprietary solutions which are not compatible with each other. Some implementations run on Ethernet level and need their own Ethernet segments, while some other rely on using TCP/IP protocol running on top of the Ethernet. Generally speaking Ethernet cabling is cheaper than currently used cabling systems and it can replace many different control cabling, so in not-too-distant future Ethernet an take an important role in theatrical and lighting control technology. There are nowadays several protocols cometing on the Ethernet lighting control. ACN (or the ANSI BSR E1.17 standard) is the next generation control protocol that is under development by ESTA (Entertainment Services and Technology Association). It will operate using Ethernet and is intended partly to address the limitations of DMX512. This standard is under development at the moment. Art-Net is a protocol used, for example, for things like theaters to transport lighting data over Ethernet. The protocol is designed by Artistic Licence and put into the public domain. Its purpose is to allow transfer of large amounts of DMX512 data over a wide area using standard networking technology.

      MIDI Show Control

      MIDI is short for musical Instruments digital Interface. It was originally used to link keyboards and music syntetizers. MIDI is now used for linking lighting boards together, controlling dimmers and running shows. MIDI is event based, that is messages are sent to indicate what must changed, and the value to which it must be changed, rather than constantly updating the receiver. The data rate of MIDI is 31.5 kBaud. MIDI interface is based around opto-isolated current loops. A typical application for MIDI in show lighing is to leave the "controller" as a device that stores sets ofdimmer levels (called a "scene" memory or "preset") and you could selectwhich scene to play from any MIDI device. This would imitate the functionality found on a lot of lighting boards (some advanced boards have even MIDI interfaces). Depending on the application the controlling can be done using MIDI Show Control messages (standard for control messages being passed over MIDI) or justsimple note-on note-off messages with different notes triggeringdifference memories on your controller. MIDI can be used to control the dimmers directly. There are a couple of MIDI dimmer packs out there. Technically MIDI a lot easier protocol to work with than DMX, since the bit-rate is so much less.But the use of MIDI is not really the standard for lighting control, which means your options will be limited if you plan to use MIDI for this (you are limited to few manufacturers, and changing to use devices from other manufacturers later can be hard).

      RS-232 lighting control

      RS-232 is not widely used for controlling lighting instruments in the lighting industry. There are some disco effect (quite rare) that can take in RS-232 signal. In some lighting applications controlling lighting through RS-232 interface could be useful. Usually this is accomplishes by using a special converter box which takes in RS-232 signal and outputs suitable control signal that the lighting instruments can use. There is a lot of entertainment kit designed to takeRS-232. Any company which is trying to get out of straight theatre ofdiscos will have such kit, because it allows them to be used in museums,commercial developments, shopping malls and restaurants with boutiquediscos run off central time cues. RS-232 systems generally allow the signal source to generate a one word string (or sometimes longer control word). The RS-232 listening devices are simplyprogrammed to respond to that string. It is very basic really, but veryeffective because it allows you to interface anything - all device suppliers will give you a documentation or library of commands for their kit (different manufacturers use different commands). In many special applications which combine technologies from different technology areas then RS-232 is usually the only sensible interface to use. It is universal for interfacingAV/Lighting/Comms/Networking/Blinds/Doors/HVAC and everything else in abuilding management systems (BMS). There are variousprotocols by specific BMS manufacturers, but ALL of them have RS-232modules. Why? It is the universal protocol for such equipment.

      Other professional lighting control interfaces

      Here is some description of some lighting protocols that have been once widely used but not used much nowadays. The descriptions are mainly based on article LIGHTING CONTROL PROTOCOLS that appeared in ESTA's Protocol, Fall 2000 issue (it's on-line reprint).

      Proprietary multiplex protocols are the manufacturer-specific console-to-dimmer data communication schemes that preceded establishment of the universal DMX512 standard. Most of these protocols came into being in the early 1980s, which, for better or worse, coincided with good times in the entertainment and architectural lighting markets. Dimmer-per-circuit systems became the industry standard. Everyone was using microprocessors. A lot of consoles and dimmers were sold!

      Nearly 20 years later, most of those consoles are gone, but the vast majority of dimmer racks and packs are still in service, and will probably remain so for another decade or more. But keeping those dimmers working means that, when a new control console is purchased, its DMX output must be translated to whatever the dimmers' native language is.

      Strand's extremely popular Light Palette consoles and CD80 dimmers first appeared in 1979, and with them came a new multiplexed analog control scheme that would later evolve into USITT AMX192. It was soon incorporated into Mantrix consoles and Environ architectural dimmers; in fact, virtually every North American Strand product designed until very recently included at least one AMX port. AMX192 is virtually non-existent outside of the U.S. and Canada.

      Strand's R&D group in the U.K. devised a somewhat different analog mux protocol they designated D54 (an internal standards number) to work with their Galaxy and Gemini control desks. D54 never made inroads into North America, but it ended up everywhere else in the world. D54 runs over 2 wires, a signal conductor that carries both the dimmer levels and the clock signal, and signal common. it uses only 3-pin XLRs and one pinout: common on pin 1, no connect on pin 2 and signal on pin 3. 384 dimmers are supported. D54 uses 0-5 volt dimmer levels.

      Possibly the earliest digital lighting control protocol to appear was from Avab of Gotheberg, Sweden. In the late 1970s, the company developed an asynchronous digital output card for their 2000 series console (later known as the Viking), which could communicate with a remote analog demultiplexer. In 1980 the technology was applied to the DD-I digital dimmers. In the early 1980's most of Avab's equipment utilized this protocol. Avab protocol runs at 153.6 Kbaud and 8-bit resolution. FFh is reserved as a frame header, so the maximum signal level is FEh (decimal 254). Early control consoles sent 128 dimmers per packet, later increased to 240. The Expert series consoles were capable of sending 252 dimmer levels. RS422 was used for the data link. All consoles sold in North America were modified to incorporate a "console present" output, which, by changing from a high to a low state, signals the dimmer racks that the console is sending valid dimmer data. The dimmer rack data connection used either a DB25 or circular connector with the following pinout: common on pin 7, data+ on pin 8, data- on pin 9, and console present on pin 12.

      CMX (sometimes called C-156) traces its beginnings to an innovative control console called Channel Track that Colortran unveiled in 1979. A digital data stream, sent from the CPU over a coaxial cable, was decoded by a local D/A converter into individual 0-10 volt analog levels. These products utilized RS422 differential data transmission for remote D/A's or direct control of dimmers. CMX receivers included a 108-channel D/A card produced in the early to mid-1980s and the popular D192 high-density dimmer rack introduced in 1985. Virtually all control and dimmer products sold by Colortran were user-configurable for either CMX or DMX operation by 1989. Two slightly different transmission speeds were used: 156.25 Kbaud for early systems and 153.6 Kbaud from about 1985 on. There's not enough difference between the two rates to matter, so a controller running at either speed will work with any dimmer rack. CMX protocol was the prototype for today's DMX512. The only major difference is the data rate, which was increased to 250 Kbaud for DMX. design team designated the first word of the data stream as an identifier for the type of information to follow (now DMX512's start code!). CMX pioneered the familiar 5-pin XLR and pinout later adopted by DMX512: shield/common on pin 1, data- on pin 2, data+ on pin 3. Some products such as Status consoles received their DC power from the dimmer pack on pin 5.

      Electro Controls entered the digital protocol race in 1983. They introduced ECmux protocol, originally known as "Celebrity Protocol" after the console that it was developed for. The protocol was expanded in 1985 to carry channel/dimmer softpatch information. Strand acquired EC in 1986. By 1992, Strand had stopped production of all EC-designed equipment except a new Premiere architectural control system. ECmux was an asynchronous protocol operating at 187.5 Kbaud and 8-bit resolution. EC employed a single-ended (one wire plus common) transmission line for their data signal, which limited the practical control cable length to 150 feets (50m). ECmux used a 4-pin XLR connector, wired as follows: shield or common on pin 1, data (minus) on pin 2, rack overtemp sense on pin 3, and no connection on pin 4. ECmux can carry level data for 512 dimmers in one continuous packet. All protocol versions reserved FFh for a start code, so the maximum value that a channel can reach is FEh (decimal 254).

      ETC/LMI is a synchronous protocol utilizing two wire pairs. One pair is used for dimmer data and the other carries a sync signal. A 4-pin XLR connector is used for the signal lines, and signal common is ground-referenced at each end of the transmission line. LMI's pinout was data+ on pin 1, data- on pin 2, clock+ on pin 3 and clock- on pin 4. ETC consoles generally swapped the functions on pins 1 and 2. Data rate is 250 Kbaud. The protocol was originally designed to handle 144 dimmers, but ETC expanded its capacity to 1000 or more with the addition of softpatch functionality.

      Kliegl Bros. introduced their new digital control protocol along with the popular K96 fully digital dimmer rack system and the Command Performance console in 1981. K96 was a powerful protocol that incorporated data compression, high level commands and dimmer talkback features, although these advanced features were generally not used. It also carried softpatch data for storage in the rack processors. K96 runs at 83.3 Kbaud with 7-bit resolution. The protocol handles up to 512 channel levels and provides softpatching for thousands of dimmers. The electrical interface is RS422 with one pair used for control and the other for talkback. The Entertainer console is the only one that used the talkback feature. Entertainer and P-3 consoles had a 7-pin Viking connector with following pinout: pins 1-3 common, pin 4 talkback-, pin 5 talkback+, pin 6 data-. and pin 7 data+. P-4 consoles used a DB9 with common on pins 1 and 2, data+ on pin 3, and data- on pin 4. Wall plates generally had a 5-pin XLR where the shield was on pin 3, the data pair on pins 1 and 2, and talkback on pins 4 and 5.

      Teatronics introduced their own analog multiplex protocol in 1981 (used in Director and Producer series lighting consoles). The only dimmers that received the Tmux protocol were the first generation of Genesis 6 and 12-packs. Analog was transmitted as a balanced, low impedance signal on a pair of wires, and the synchronizing clock was a high impedance signal on one conductor paired with the signal common. 5-pin XLRs were used: common on pin 1, analog+ on pin 2, clock on pin 3, analog- on pin 4 and no connect on pin 5.

      LMX-128 is a multiplexed lighting control protocol used mainly by Lightronics. It is an industry standard 128 channels 3 wire multiplex protocol (also known as NSI/Sunn three wire multiplexed protocol). The control interface used 3-pin XLR connectors and normal microphone cables. The control signal pinout is: LMX common on pin 1, console power on pin 2 and multiplex signal on pin 3. The protocol is basically same as Microplex MPX. The data sent through the cable is analogue multiplex signal. The mux control signal is 0-10 volts.

      Bit Serial Protocol (BSP) is a protocol for transmission of data to lighting devices. It was introduced by Siemens Lighting (now Transtechnik.) at late 1970's for their B40 product line. BSP uses the standard serial transmission via rs422. BSP is asynchronously clocked with 250KBit. The Sender (Master) issues the clock rate via a clock line. Transmission uses the 8N2 schema. The connector has 5 pins assigned with symetric clock and data and gnd. (+clock, -clock, +data, -data, gnd). Transmission is divided into frames of up to 512 bytes. Valid data bytes have values from 1-255. Value 0 is invalid and used to mark a new Frame. A typacal frame is three Frame Start characters (value 0) followed by up to 512 data bytes (value 1-255).

      IEC 60929 PWM standard is one controlling protocol for controlling electronic lamp interfacing components (other protocols in this standard are 1-10V and DALI). This pulse width modulation (PWM) method uses a signal that has two levels: low level (0-1.5V) and high level (10-24V). When the line is at high level 5% or less of the time the lamp is at highest output level. Lamp is at minimum level when signal is 95% of time at high level. If signal is more than 95% at high level, the lamp is turned off. The response from puse width to ligh level is logarithmic. The pulse time can be at 1-10 ms range. This PWM method is standardized but not widely used as general controlling protocol, but it is quite much used with cold cathode fluorescent lights and LED light source controlling. Most often the PWM signal is generated using a controlling interface converter that is controlled though DMX512 or DALI bus.

      Home automation and lighting control

        X-10

        X-10 is a power line carrier protocol that allows compatible devices throughout the home to communicate with each other via the existing 110V wiring in the house. Using X-10 it is possible to control lights and virtually any other electrical device from anywhere in the house with no additional wiring. X10 is a communications "language" that allows compatible products to talk to each other via the existing 110V electrical wiring in the home. X10 devices can be categorized into 3 distinct groups: Transmitters, Receivers and Transmitter/Receivers (2 Way X10 devices). X10 Transmitter devices send a coded low voltage signal that is superimposed over the 110VAC current. Any X10 Receiver device plugged into the household 110V power supply will see this signal. However, the Receivers will only respond when it sees a signal that has its address. Up to 256 different addresses are available. If you want more than one device to respond to the same signal, simply set them to the same addresses. X-10 operates at 120 kHz frequency range. X-10 adds short bursts of 120 kHz carrier after each mains zero crossing to send data. Each data bit takes two zero crossings, so the data rate is 60 bps. This is enough for slow control applications.

        DALI

        The drive for Energy Conservation and Intelligent Building Automation has led to the development of the DALI standard for control of Lighting Networks, especially those involving Fluorescent Ballasts. Backed by the major Lighting manufacturers in the world, the DALI interface allows for low cost control of large networks. DALI (Digital Addressable Lighting Interface) is a quite new industry standard to lighting control systems. DALI is supported by the main lamp and ballast manufacturers in Europe (Helvar, Osram Philips, and Tridonic). Backed by the major lighting manufacturers in the world, the DALI interface allows for low cost control of large networks. The DALI system mentioned as extension to IEC60929 standard.

        DALI is a dedicated communication interface for the control of lighting systems at local room level. It has been developed specifically for optimum lighting control, both in Local Room Control applications and when interfacing with Building Management Systems. The DALI protocol is exclusively designed for lighting and aims at filling the gap between the standard 1-10 V analog control interface and the more complex universal bus systems, which are too advanced for many applications. DALI interface is suitable for mid-size rooms and stand-alone systems. DALI system is the combination of ballast switching and dimming via the control wire with ballast addressing. The key feature of DALI is individual ballast addressability, which enables up to 64 different luminaires on the same control circuit to be switched and controlled independently. The luminaires on a single circuit can be combined in up to 16 freely definable groups, in which individual light can be assigned to one or more groups. Programmablity allows installations to be reconfigured without the need for costly wiring changes.

        Wiring using DALI is very simple: all the luminaires in a room are simply connected to the nearest unswitched power supply, as well as to a single control cable from a lighting controller. DALI is the de facto industry standard for the control of lighting systems. The system concept and communication protocol are now accepted as a draft IEC document with preparations for the definitive IEC standard at an advanced stage.

        DALI operating voltage is 9.5-22.4 V and DALI system current is max. 250 mA (limited on power supplying bus master). In general the control line voltage in a DALI system is normally 16 V (between 22,4 and 9,5 volts) when there is no communication (idle state). DALI bus power is supplied from additional power supplies. The DALI power supply must limit the supply current to max. 250 mA under all circumstances. In practical installations the current is good to limit to a lower level in order to maintain the flexibility of changing the layout and increasing the system at later stages. There is no limitation to having several power supplies on the same DALI control line as long as the current limit is not exceeded and the supply polarity is taken into account. Since the DALI signal varies between 0V and 16V the polarity is important to maintain also with power supply. A typical DALI equipment consumes around 6 mA of current from the bus. Good practice is to allow sufficient margins for the supply current. This will guarantee reliable system functionality under different conditions and also allow the flexibility.

        DALI data transmission speed is 1200 Baud. Data is transported through one wire pair. The transmission circuit consists mainly of a power transistor switching the bus power on and off. The digital signal becomes low when the voltage level in the DALI system becomes zero.

        Digital interface in devices is insulated in accordance with EN 60928 (basic insulation). Guidelines for SELV installations do not apply to the DALI signal. The low voltage installation requirements apply. DALI uses standard mains rated cables for electrical installation (supply and control). Supply and control wires can be laid together in one cable or duct. There is no special wiring required with regard to wiring topology (star, series and mixed networking allowed). Maximum cable length of DALI control wires 300 m (for 1.5 mm2). All devices in a DALI system must comply with the following European standards: EN 55015, EN 61547, EN 61000-3-2 and EN 63000-3-3.

        Some major characteristics of the DALI protocol are (from http://www.freescale.com/files/microcontrollers/doc/ref_manual/DRM004.pdf and http://www.dali-ag.org/c/manual_gb.pdf and http://www.semiconductors.philips.com/acrobat_download/applicationnotes/AN10225_2.pdf):

        • Asynchronous serial protocol
        • Data is sent at 1200 bits per second speed, bi-phase encoding, half-duplex
        • Because of bi-phase coding every very bit takes two periods T (1/2400 seconds),
        • A message is started by a start bit, and ends with two high-level stop bits (No change of phase). Data is being transmitted with the MSB first.
        • Between frames, the bus is in idle
        • Two-wire differential interface
        • Voltage difference above 9.5 V means high level (transitter sends 11.5-20.5V, receiver expects 9.5-22.5V)
        • Voltage difference below 6.5 means low level (transmitter transmits in range -4.5V..+4.5V, receiver expects voltage in -6.5..+6.5V voltage range)
        • The master unit controls the communication
        • 64 slave units can be connected
        • Each slave unit can be individually addressed
        • The master unit sends 1 start bit, 16 bit data, and two stop bits
        • The slave unit sends 1 start bit, 8 bit data, and two stop bits
        • The maximum lead length between two connected systems must not exceed 300 meters.
        • Bus wiritng can be 0.5mm2 up to 100 meters, 0.75mm2 up to 150 meters and for distances above 150 m 1.5 mm2 wire must be used
        • The control input is separated galvanically from the mains voltage (corresponds to the requirements of the base isolation)
        • No termination resistors required
        • Dimming range 0.1 % ?100 % ? the lower limit depends on the manufacturer.
        • The dimming curve is standardized and adapted to the sensitivity of the eye (logarithmic dimming curve)
        • Star-shaped and mixed structures are possible besides linear or tree-shaped structures
        • The digital interface connecting leads can be wired jointly with the mains supply leads on the same cables
        • Within a DALI-system each ballast has its own address (64 individual addresses exist in the DALI-system, 16 groups, the assignment of the addresses and with that the assignment of the group addresses is effected by a software)

        The DALI communication is serial using two wires for communicating in both directions. The voltage difference between the wires indicates if it is a high or low level. A voltage difference above 9.5 V is a high level and a voltage difference less than 6.5 V is a low level. The master unit communicates with the slave units by setting the level high or low according to the serial protocol. When no communication takes place the master unit keeps the level high.

        The slave unit responds to the master unit by setting the level high or low. A high level is simply achieved by not interfering with the high level set by the master unit. A low level is obtained by forcing a short circuit across the wires. This is possible to do since the DALI standard states that the current supply for the DALI communication has to be limited to 250 mA.

        There are a number of parameters stored in each slave unit. These parameters indicate how the lamp should behave in different situations. Messages can be sent over the DALI communication wires to change or check the values. All communication is controlled from a master. Every lamp is connected to a slave unit that is silent until the master requires an answer. The 16-bit data from the master unit consists of an 8-bit address part and an 8-bit command part. Up to 64 slaves can be connected to the same network and each slave can receive an individual address, which is called the short address. There is also the possibility of assigning a slave unit to a group. Up to 16 groups can exist and a slave unit can belong to several groups. A message can also be broadcasted to all slave units.

        More information on DALI protocol can be found in the document A.C.-Supplied Electronic Ballast for Tubular Fluorescent Lamps, Performance Requirement, Requirements for Controllable Ballasts which can be obtained from IEC. DALI stands for Digital Addressable Lighting Interface and is a protocol set out in the technical standard IEC 60929 under Annex E. AG-DALI is a working group set up by leading manufacturers and institutions in the field of digital lamp/luminaire control to promote DALI technology and applications.

        EIB (European Installation Bus)

        The European Installation Bus (EIB) is an open, comprehensive system which covers all aspects of Building Automation. It is managed by the neutral EIB Association. The European Installation Bus is designed as a management system in the field of electrical installation for load switching, environmental control and security, for different types of buildings. The InstallationBus can be installed in large buildings such as business premises, schools, hospitals, factoriesand administration premises as well as in domestic residences. Its purpose is to ensure themonitoring and control of functions and processes such as lighting, window blinds, heating,ventilation, air-conditioning, load management, signaling, monitoring and alarms. The EIB is an intelligent building control system which is able to control, regulate, measure, switch, service and monitor. Its basis is a communications bus which lies in parallel with the 230V mains network. EIB is a fully peer-to-peer network, which accommodates up to 65?536 devices. The logical topology allows 256 devices on one line. The EIB system allows the bus devices to draw their power supply from the communication medium, like Twisted Pair or Powerline (230 V mains). The EIB protocol is today supported by several media, like Twisted Pair, Powerline, RadioFrequency and Infra-Red. It is of course always possible to connect gateways to other media. Possible media types:

        • EIB TP (Twisted Pair): This uses single pair of twisted pair wiring. Bit-level collision detection with dominant logical 0 ensures that in case of collision, the transmission always succeeds for one of the communication partners. Fast polling allows up to 14 devices to be polled for 1 byte status-information within 50 ms. A physical TP segment may be up to 1 000 m long.
        • EIB PL (Powerline): This technology allows to use 230V AC power line for communications. EIB PL uses a novel Spread Frequency Shift Keying (SFSK) modulation technique. Maximum distance between 2 devices (without repeater): 600 m. Communication on powerline is influenced by electromagnetic pollution conditions in the installation. This system uses 105,6 - 115,2 kHz frequency range.
        • EIB RF (Radio Frequency): Infree field conditions, the transmission distance is about 300 m. Retransmission ensures that large volumes can also be covered inside the building. Different lines are physically separated by a different carrier frequency.
        • EIB.net (Autiomation Networking): The EIB.net specification realizes EIB on all media with a logical link layer according to ISO/IEC 802-2, including Ethernet and Arcnet. An enhanced specification catering for routing based on the Internet Protocol (IP) is being reviewed. This means that EIB.net allows transparent usage of existing LAN infrastructure.
        Twisted pair electrical segments can have an arbitrary topology (i.e. linear, star, tree, loop or combinations of them) consisting of individual wiring sections as long as the electrical requirements (resistive and capacitive length) are not exceeded.This means that the connection of the bus can be in linear, star or tree configurations which allows flexibility in the applications in all forms of modern electrical installation. The bus needs 1 twisted pair to work. When standard control cables with 2 pairs are used, oneis dedicated to signal transmission, the second one may, for instance, be used forcomplementary power feeding services. Up to 64 bus devices may then be connected to each of these lines, allowing a total of 64.000 components to be connected. The total cable length shall not exceed 1000 m per electrical segment. The maximum length allowed is 700 m between two devices and 350m between a power supply unit and a device.Intelligent system components, operating by distributed control, are coupled to this communications bus. The Bus system is usually implemented as a decentralized system butnevertheless it still allows, whenever it is required, centralized application implementations.Decentralized management is implemented within the devices whether they are transmitters orreceivers, they communicate directly to each other without recourse to hierarchy or networksupervisory device. This type of management makes the system highly flexible. The aim of communication is the interworking between sensors and actuators. The information exchange between two devices is achieved by transmission of data packets. Each data packet must be acknowledged. Management of EIB Bus devices connected to the Installation Bus can be addressed using physical addressing and group addressing. Every bus device is identified by a unique physical address. The physical address is generally only used as destination address for initialization, programming and diagnostic operations (connection oriented transmission). Group addressing corresponds to the normal operation mode. Functions ofEIB Bus devices belonging to the same group, may be controlled by only one message sent by a "source" EIB Bus device. The group addressing is a logical link between bus devices. A sensor can only transmit on one group address and an actuator can receive several.Each system component can be programmed to perform prescribed functions in combination with other system components, either from controlling elements within the system or via PC control. Together, these form the infrastructure of the basic functional level of the system. Two types of system component are used: Sensors (Transmitters) and Actuators (receivers).EIB is used in intelligent buildings for example to control lighting. The European Installation Bus (EIB) is an open, which means that EIB may be implemented by anyone, on any chip orprocessor platform chosen - both as proprietary implementation for individual products, as well as for OEM BAU?s (Bus Access Unit). Conformity tests are defined, and EIB Certification is open to all members of the Association.

    Light effect controllers

      Sound to light circuits

        Light organs

        A "light organ" sound to light unit converts music signals into light pulses. In most cases, three channels are used to cover different frequency ranges. The bass channel will then indicate the ?beat? of the music by a more or less rhythmical flash, while the two other channels represent the higher frequency ranges of the music channel.

        The typical color organ had three (3) channels. Different colored lamps would be attached to each channel. Each channel would be controlled by a separate audio input, tuned to a specific audio frequency. A typical three (3) channel unit might be wired as follows:

         Channel    Lamp Color        Frequency    
        ------------------------------------------
        1 Red Hi (10-20 kHz)
        2 Green Mid ( 5-10 kHz)
        3 Blue Low ( 0-5 kHz)
        When activated, the 3 channels of lights would automatically dance and respond to the beat of the music. The freqency ranges used on different implementations can vary. For example the response of bass channel on some designs can go only up to few hundred Hz.

        More advanced color organs might contain as many as 15 individual channels. This color organ became popular for discotheque and psychedelic lighting applications. Today, many entertainment lighting control boards now also contain advanced color organ functions.

        Other sound to light circuits

        • Disco VU effect - light a big sound level meter, uses a LM3914 bargraph display driver, together with an automatic level control, 10 channels, 250W per channel, uses control at zero-crossing    Rate this link

      Sequencers

      Light sequencer circuits are used to implement simple light chasing effects and also more complicated sequential light effects. What kind of circuit to use for this depends on how many lamps do you want to drive, how many steps to the sequence, AC orDC. There are thousands of simple circuits that can do this. Most light sequencer circuits are simple counter or sequencer circuits that have a steady clock signal applied to them. This signal determines how quickly the lamps are switched. The most common devices to use to impemenent the sequence itself is either a counter or a shift register. The counter type can run a single lamp (usually) chasing along in some series of lamps, such as 4 to 10. Applying the clock signal makes the counter advance and moves the"lit" lamp down one place.Shift register types can have a block of lamps move in a pattern. You canload one, two, or any number of lamps and make that pattern move along. A typical lamp sequencer will consist of a counter such as the CD4017 chip,a clock generator like a 555 chip, and some sort of lamp drivers to allow thechips to turn them on. Most microchips do not put out enough current to lightany large lamps, so they are controlled through some power electronics circuits like transistors, power transistors, power FETs, thryristors, triacs or SSRs. Many times when small DC lamps are used a simple transistor can be used for each lamp as a driver. This same scheme can be expanded to drive mains voltage lights by replacing that small bulb with a coil of a relay capable of switching the mains voltage safely (remeber the protection diode in parallel with relay coil!). Relays work quite well on slow lighting applications, but when lights are swiched often, you should use SSRs instead because they will give much longer relay life (a normal relay will wear out quite quicly if you turn it on and off very often). Here are links to some light sequencer circuits:

    Strobe and Flash Lights

    The stroboscope is a device for viewing a rotating object by making the object appear to be at rest. In its simplest form, it consists of a rotating disk with one or more viewing slits, through which the object can be viewed. The stroboscope is of great use in engineering studies of moving parts, as they can actually 'freeze' and view the image in real time. Modern stroboscopes no longer use the rotating wheel with slits. Instead electric lamps are utilized that produce short flashes of light at the same rate that the object is revolving. The high speed gas discharge lamp, stroboscope was developed by Harold Eugene Edgerton and his associates at the Massachusetts Institute of Technology around 1926 to 1931. Today, neon lamps are also commonly used for low power stroboscopic applications, producing a flash rate synchronized with a 50/60 cycle frequency, of the standard AC power line (for example used on some phono players to check the rotation speed). The higher power stroboscopes generally use xenon flash tube. On a darkened stage in a theatre, a single flashing light source can provide a very striking and dynamic - stop action effect, of all moving objects on stage. During the 1960's the 'Strobe' was frequently used for discotheque lighting applications.

    A stroboscope is a special kind of light that flashes in a very regular way. Each flash of the strobe light is the result of an electrical discharge (sort of like a spark) traveling through the special gas contained in the strobe "flash bulb". To the electronics industry, it's simply a high-voltage plasma discharge in a low-pressure gas container. The electrical current flowing through the gas causes it to emit light. Generally we need about 300 volts or more at some decent current to make a flash tube used in a typical stroboscope to flash. A xenon flash tube is initially a very high resistance component that is typically connected in parallel with the energy storage capacitor. When the tube is triggered with a trigger pulse (typically few kilovolts), the tube starts to conduct and the resistacne between tube ends drops to a very low value (typically to around 1 ohm). The charge from the main capacitor discharges through the tube very quicly. When the voltage drops below a voltage that can sustain the discharge, the tube reverts to high resistance state. The time in which the power goes through the tube is typically very short (typically one millisecond or few milliseconds) and the currents are high, over 100 ampere currents and less than 3 ohms loop resistance (tube + capacitor ESR + wiring) are typical values. The flash tubes are typically both maximum per flash energy rating (higher than this rating can make the tube to "explode") and heat limited (this limits how often the tube can flash at needed flash energy before overheating).

    The usage field of stroboscopes is varying. Stroboscopes are used as disco in disco lighting, for lighting effect purposes, for special photography and for engineering/laboratory use (for timing lights, to "stop" moving objects etc.).Pilots have found an equally beneficial use for electronic strobes: fending off other airborne objects. The same principle is used in electronic camera flash units. Photographers were among the first consumers to benefit from strobes - for lighting their subjects. Camera units normally only flash once and the flash energy is is quite large (makes very bright flash). Usually the discharge happens very quickly, lasting only a tiny fraction of a second.

    In disco and effect lighting applications there are several different ways to control the flashing of the stroboscope.

    • Simplest stroboscopes have just a potentiometer in them to set the flash rate plus a switch to turn them on/off.
    • There are some dual-function stroboscopes that can work on flashes on power down and constinuous flashing modes. The first operation mode flashes on power down, for use in combination with a light effect generator that are designed to flash normal light bulbs. The second operation mode flashes continuous with adjustable speed.
    • The 10V pulse controlling allows controlling the stroboscope flash rate of one or more stroboscopes easily with one central controller. The idea on this controlling is that there is normally no power on the line, and when the strobo units needs make one single flash, the controller sends a truigger pulse to line (typically 8-12V pulse, length of few milliseconds to tens of milliseconds typically). This pulse makes the stroboscope or stroboscopes conneted to control line to make a singl flash. Sending pulses at wanted rate (controllable with controller) the stroboscopes or multiple stroboscopes connected in parallel to control line are made to flash at wanted rate all at the same time.
    • Analogue 0-10V control is used on some high power stroboscopes. Typically two control channels are used, one controls the strobo speed (typically 6.3 mm stereo jack tip) and another is strobo brightness/dimmer control (typically 6.3mm plug ring). Both control signals have common ground (6.3 mm jack body).
    • Digital DMX-512 control is used in many modern hign power stroboscopes. Typically two control channels are used, one controls the strobo speed and another is strobo brightness.

    WARNING: Strobes can be DANGEROUS. Strobes can induce epileptic fits. Use sparingly and with caution. The main energy storage capacitor(s) of even a small camera flash is typically charged to 250-330 volts. Many professional photographic flash units use voltage of around 500V or higher. In strobe light main capacitors the voltage is usually around 300 volts but may be as high as 600 volts in some smaller party strobes and flashing alarm lights. The longer flashlamps used in some lasers and photocopiers require even higher voltages. Some of these use voltages over 2000 volts. It is generally considered that the amount of energy stored in a capacitor roughly represents how badly it can shock you. Many sources state that a discharge of 10 joules into the human body can be fatal. Some sources state that a shock as little as 1 joule has some chance of being fatal. If the voltage is high enough to burn through your skin, or your skin is especially conductive due to perspiration, then a higher percentage of the capacitor's energy will be dissipated in your vital organs, and such a shock is more likely to be fatal. It is recommended to avoid shocks of even 1/4 joule. The energy storage capacitors aren't the only thing that can kill you. The source of high voltage DC that charges them up can also cause dangerous electric shocks. Furthermore, consider the hazards of high voltage and line voltage AC. The bright light of some xenon strobes may be hazardous to your eyes. In most cases, things are safer if you test strobes in a brightly lit work area. Brighter ambient light will make your eyes' pupils constrict, which lets less strobe light into your eyes. In the event you need to look at particularly bright flashtubes or you think you might be looking at one as it goes off, you may want to wear goggles used for acetylene welding. Xenon flashes emit a wide range of electromagnetic radiation, mainly mid-infrared to shortwave UV. Longwave UV and the shorter visible violet wavelengths are not completely safe to the human eye. If you are building your own strobe with a quartz flashtube, you must use glass to block the shortwave and mediumwave UV. Most transparant plastics at least two millimeters thick also work, but may be discolored by heavy UV exposure. It is common for some strobe parts to get really hot. In a repeating strobe, the flashtube is likely to get burning hot. Cheap glass flashtubes can safely operate with part of the tube surface close to the melting point of solder. A few better glass flashtubes safely operate with parts of the glass surface well above the melting point of solder. Most power resistors used to limit current in stroboscope circuits get burning hot in normal use. Please note that if things go wrong, xenon flash and strobe units have components that can explode. For example the xenon flash tube and/or the capacitors can expode if improperly used. Wear any safety goggles for safety, so you probably won't get seriously hurt with small circuits.

      Strobo circuits

      Use extreme caution in building and using stroboscope circuits. A xenon flash tube is a triggered discharge device. A voltage may be impressed across the tube and it will not conduct until the xenon gas is ionised by an external high voltage (typically 3 to 5kV). Stroboscope circuits include high voltage (hundreds of volts) stored to large storage capacitors. This Voltage Can Kill You! In addition to this there are low power trigger voltages of few kV present in many stroboscope circuits.

      The circuitry in the strobe devices operate at very high DC levels. These voltages are LETHAL. Take adequate precautions when testing, fault-finding and so on. If you are unsure of how to work with potentially lethal voltages, do not attempt to build any strobe circuit! In many strobe circuits the DC operating potential is about 300-600V, and in many circuits there is more than enough stored charge to kill you many times over. Ask a competent person for help.

      The stroboscope circuits should be built with caution and you should place them in a suitable insulating plastic case or well grounded metal case. For safety reasons remember to put some protective material (for example transparent plastic) in front of the stroboscope tube, because stroboscope tubes can explode sometimes (if damaged, very old or you push too much power to them). The strobe circuit is dangerous, and the internal wiring can kill you on contact. Every safety precaution must be taken to ensure that you do not cause injury or death to yourself or anyone else.

      Many stroboscope circuits connect directly to, and operates at, mains voltages or above. It is potentially lethal. Since most strobo circuits operates at greater than mains potential and they are not isolated by a transformer, they are extremely dangerous. Expect always that the entire strobe circuit is LIVE and take all the necessary precautions during construction to ensure safe operation. Never work on the circuit while it is plugged into the mains outlet, and remember that capacitors can hold a charge for a long time. Make sure that all caps are fully discharged before attempting to work on the circuit.

      Strobe lights can cause epileptic fits and disorientation. This can happen even with people who are not "epileptic" as such. Many countries have laws governing the use of strobe lights in public places, and effects such as nausea, vomiting and epilepsy have been directly linked to the excessive use of strobes at the right (wrong?) flash rate. Use of this or any such circuit is entirely at your own risk.

      Information on camera flash units

      There are many places where there is not enough light to get good photographs. Typical traditional compact film cameras and digital cameras have built-in flash unit to give needed illumination when encironmental light is not enough. Professional photographers use typically external professional flash units to get the lighting they want. This lighting is crucial for yielding good photographic performance and requires careful consideration. A typical camera flash tube will usually produces a flash which lasts about one millisecond. The energy used to produce the short flash comes from discharging a special capacitor, charged to several hundred volts. Typical small compact camera flash unit features around 100-150 uF flash capacitor that is charged to 300-500 V voltage. Bowens are flash unit as used by professional photgraphers. It produces a bright flash, but requires 10 - 20 seconds charging time between flashes. Bowens use higher capacitors, special high power flash tubes and electronics to control the light output power.

      The electronic flash uses a solid state oscillator to step up a low voltage to the needed 300-500V voltage. The oscillator uses a transistor(s) to chop the low voltage DC into pulsating DC which can be stepped up by a transformer, the output of the transformer is then rectified (converted to DC) and used to charge a capacitor. The whistling you hear is mostly due to the transformer vibrating at the oscillator frequency although some capacitors are also capable of making some sound. The pitch rises after each flash because the oscillator isn't very well regulated and the discharged capacitor presents a heavy load to the oscillator, as the capacitor charges the load decreases and the frequency rises.

      High-quality photographic capabilities are also coming to cellular phones. To support their improved image sensors and optics, they will need high-quality "flash" illumination, which requires special design attention. This lighting is crucial for yielding good photographic performance and requires careful consideration. Two practical choices exist for flash illumination in cellular phones: LEDs and flash lamps. LEDs feature continuous operating capability, low-density support circuitry and low voltage operation, among other advantages. Flash lamps, however provide advantags like easy to get diffused light over a wide area, light output is hundreds of times greater than point-source LEDs and flash lamp's color temperature of 5500-6000 degrees Kelvin is close to the temperature of natural light.

      Camera stroboscopes have typically trigger interface that allows the camera unit to trigger the stroboscope device when needed. A typical interface is the interface built to camera hotshoe: there is a big pin in the center and metal rail (trigger pin) along both sides of the hotshoe (ground), combine to create the flash-triggering circuit. Every "standard" hotshoe, from every manufacturer, will have those same two connections. The camera shorts the center contact (sometimes called X contact) to ground when the shutter is fired. Electronic SLR cameras use a thyristor for this function, and the X-terminal short-circuit output current from the strobe(s) must be limited to no more than about 1.5mA to allow the thyristor to de-latch after firing. Old mechanical cameras used a electromechanical switch that makes contact then camera shutter it open. The strobe input is typically a logic-gate with a pull-up resistor to the logic B+ rail, and the value of the pull-up resistor sets the X-terminal current in the logic-low state. Up to 2 strobes can be connected in parallel, so strobe designers should choose the pull-up resistor so that the X-terminal short-circuit current is no more than about 750mA (e.g., the pull-up resistor for 5V logic is 6.8 kohm). Some earlier strobes which used for example 3.3kohm pull-up resistors (or less) must be modified for dual-strobe use with electronic cameras.

      Some flash unit can have also extra pins. All the other pins are there to send extra signals back and forth between camera and strobe, according to proprietary methods set by each camera manufacturer. If your camera strobe has more than one pin, those extra pins may be hazardous if connected to to camera that the device is not designed to work with.

      One commonlt used extra signal is the Quench signal. In a conventional TTL flash system, the camera integrates the light falling on the film (using a phototransistor and a capacitor), and when the integrated level reaches a threshold determined by the film ISO (ASA) setting, the Quench line is shorted to ground via a transistor. The Quench signal tells the strobe to switch-off the flash-tube current.

      The trigger voltage is the amount of voltage between the strobe's two primary hotshoe contacts (center pin and rail). This voltage will be discharged by the strobe through the camera's hot shoe when the strobe fires. According to ISO 10330 (1992), "Photography ? Synchronizers, ignition circuits and connectors for cameras and photoflash units ? Electrical characteristics and test methods," strobe voltages up to 24V should be generally permitted in triggring circuits. This is not standard, but not all meet those standards. Some strobes (and infrared strobe triggers) use high voltages in the trigger circuit (even in 100-200V range). For mechanical cameras, this is fine ? but many newer, electronically-driven cameras can be damaged by excessive strobe voltages. The trigger voltage is typically positive in the rigger pin compared to ground contacts (hotshoe rail or other connector outer shield).

      With modern electronic cameras you should be carful what flash unit you connect to it. Fo example Canon specifies no more than 6V trigger voltage for EOS cameras, including the Powershots. Some sources say that Nikon specified the maximum voltage to be 12V for most of their models. Never put a strobe onto the Powershot (or any other modern electronic camera) without first checking to be sure that the strobe's trigger voltage is within an acceptable range for the camera, and that the strobe doesn't have any "extra pins" that were designed for a different flash system.

    LED based lighting circuits

      Building lamps out of LEDs

      LED bulbs are emerging as the hottest and newest light sources. The small size of LEDs allows designers to develop creative and compact styles. The average service life of LED bulbs is about 100,000 hours. When encapsulated and integrated with electronic boards, the bulbs can last for about 50,000 hours. The downside with LEDs, though, is the initial cost. These bulbs are said to be five to 10 times more expensive than halogen bulbs. However, if their long service life, high energy efficiency, and low maintenance costs are factored in, LEDs will still come out more cost-efficient.

      • Economical circuit drives white LEDs - this circuit provides a means of efficiently controlling LED current in a series-connected string    Rate this link
      • LED driver delivers constant luminosity - . The output current is almost constant over an input-voltage range of 1.2 to 1.5V and is insensitive to variations of transistor gain.    Rate this link
      • LED Headlamps - This article includes circuits of DC-DC LED drivers (click pics for bigger ones) step downs to run LEDs on less than Battery Volts, Boost for above.    Rate this link
      • LED Mood Light - This circuit makes a nice lamp that is low power, runs cool, and has a long lifetime, based on LEDs and runs from 12V DC    Rate this link
      • LED Torch - A white LED torch that consumes just 24 mW    Rate this link
      • Light a white LED from half a cell - White LEDs are rapidly gaining popularity as sources of illumination, as in LCD backlights, but with forward voltages typically ranging from 3 to 5V, operating them from a single cell presents obvious difficulties. This design exploits the ultralow operating voltage of a single-gate Schmitt inverter based switching LED driver.    Rate this link
      • Make a Joule Thief - In the November 1999 issue of EPE (Everyday Practical Electronics), a small and intriguing circuit was published in the Ingenuity Unlimited section by Z. Kaparnik. It was a very small implementation of a typical transformer feedback single transistor invertor. The transformer was a standard ferrite bead with two windings wound on it and the circuit was using the high voltage pulse generated when the transistor turns off to light an LED from a single 1.5V battery. This page has two variations on the original design to use the simple circuit in a useful manner.    Rate this link
      • Single cell lights any LED - This circuit allows you to light any type of LED from a single cell whose voltage ranges from 1 to 1.5V. This range accommodates alkaline, carbon-zinc, NiCd, or NiMH single cells. The circuit's principal application is in LED-based flashlights, such as a red LED in an astronomer's flashlight, which doesn't interfere with night vision. White LEDs make handy general-purpose flashlights. You can use the circuit in Figure 1 with LEDs ranging from infrared (1.2V) to blue or white (3.5V).    Rate this link
      • Special Lighting - experiments with white LEDs    Rate this link
      • White-LED driver touts high efficiency - White LEDs, the most recent addition to the LCD backlight, find common use in providing backlight for color LCDs. Thanks to their size and white-light output, they appear in small, portable devices with color displays, such as PDAs and cellular phones. Like other LEDs, a white LED needs a constant-current source?typically, on the order of 15 to 20 mA. The forward voltage of a white LED is approximately 3.5V.    Rate this link
      • White LED Flashlight    Rate this link
      • IR illuminator for night sights - This source uses LEDs and an astable oscillator to control the switch, duty cycle, and effective IR illumination output.    Rate this link
      • http://www.electronicsforu.com/EFYLinux/circuit/feb2003/circuit-2.pdf - This ultra-bright LED lamp works on 230V AC with minimal power consumption.    Rate this link
      • Mains LED - Ever come across an application where all that is needed is some indication the power is applied. An LED would be perfect as they have proved their exceptional reliability. But there is no low voltage in sight. current limiting resistor at 230VAC, even with a super-bright LED running at 10mA, will consume a massive 2.3W. There is another means to generate the required current without dissipating heat - a series capacitor.    Rate this link
      • Constant-current, constant-voltage converter drives white LEDs - LEDs usually take their drive from a constant dc-current source to maintain constant luminescence. Most dc/dc converters, however, deliver a constant voltage by comparing a feedback voltage to an internal reference via an internal error amplifier. The easiest way to turn a simple dc/dc converter into a constant-current source is to use a sense resistor to convert the output current to a voltage and use that voltage as the feedback. The problem is that 500 mA of output current with a 1.2V drop?the typical reference voltage?in the sense resistor incurs relatively high power losses and, thus, a drop in efficiency. One approach is to use an external op amp to amplify the voltage drop across a low-value resistor to the given reference voltage. A better approach is to use the LT1618 constant-current, constant-voltage converter, which combines a traditional voltage-feedback loop and a unique current-feedback loop to operate as a constant-voltage, constant-current dc/dc converter. Example circuit shows the LT1618 driving a 1W, white Lumileds LXHL-BW02 Luxeon LED.    Rate this link
      • Power-supply IC drives multiple LEDs - Bright LEDs are becoming prominent sources of light. They often have better efficiency and reliability than do conventional light sources. This circuit uses the integrated offline Viper22A switching regulator in a constant-current configuration to drive two to eight 1W LEDs.    Rate this link
      • 1.5V battery powers white-LED driver - Although white LEDs are common in a variety of lighting applications, their 3 to 4V forward-voltage drop makes low-voltage applications challenging. Charge pumps and other ICs are available for driving white LEDs, but they generally don't work with the low supply voltage of 1.5V in single-cell-battery applications. This circuit provides a current-regulated output suitable for driving white LEDs.    Rate this link

      Multicolor LED controlling

      It is well-known that simultaneously mixing two primary-color light sources, such as red and green, creates a secondary color, such as yellow. This mixing process commonly occurs in tricolor LEDs.

      • Circuit efficiently switches bipolar LED - This article represents two methods to switch a bipolar, two-color LED using an SPDT mechanical switch or relay.    Rate this link
      • Create secondary colors from multicolored LEDs - It is well-known that simultaneously mixing two primary-color light sources, such as red and green, creates a secondary color, such as yellow. This mixing process commonly occurs in tricolor LEDs. This Design Idea proposes a sequencing method to generate balanced secondary colors from bicolor, tricolor, and RGB LEDs, using only one LED's operating current.    Rate this link
      • Rainbow LED indicates voltage with color - Meters that indicate analog levels via a moving-pointer meter, a numeric display, or a column of LEDs typically occupy considerable panel area and require more than a casual glance to read. An indicator lamp or LED takes little space but indicates only an on or off condition. However, an unobtrusive LED that changes color as a function of a measured value would enable an observer to easily assess the measurement.    Rate this link

      Misc circuits

      • 28 LED Clock Timer - programmable clock timer circuit that uses individual LEDs to indicate hours and minutes    Rate this link
      • A High Current Pulsed LED - Using this circuit will create a very sharp high current pulse to an LED at various Frequencies. With the values shown, and a 20 Volt supply, the Frequency is aproximately 10Khz and the current is about 525 mA.    Rate this link
      • A linear Constant Current LED Lamp Dimmer - This simple Linear circuit provides continuously variable regulated current (~25-400mA) from a 4-6 Volt source.    Rate this link
      • Circuit controls intensity of reflex optical sights - A popular category of aiming/pointing aids is the reflex, or "red-dot," sight. This system finds use in such diverse applications as astronomy, archery, and shooting. In the reflex sight, light from an internal source?typically a high-intensity red LED?reflects from a curved, transparent optical (reflex) element through which you view the target. The result of this geometry is that the image of the LED (the red dot) appears superimposed on the target image, thus indicating the point of aim. When you correctly adjust the aiming point of the telescope, bow, or gun, the target and LED images coincide. For best sight performance, the intensity of the red-dot light source must at least roughly match the illumination level of the target. This circuit adjust the LED intensity based on the target.    Rate this link
      • Circuit drives mixed types and quantities of LEDs - Portable systems often use LEDs of different colors and in varying quantities of each color. Some examples are white for the display backlight, green for keypad illumination, and red for power. Typically, the LEDs derive power from at least two power supplies: one for "standard" LEDs (red and green) and one for white LEDs. (White LEDs exhibit a higher forward voltage.) This circuit mixes LEDs of different forward-bias requirements, yet keeps the loads reasonably well-balanced.    Rate this link
      • Fading Red Eyes - can be used to slowly illuminate and fade a pair of red LEDs    Rate this link
      • Fantastic Atom Expander - "exploding atom" effect using 98 LEDs    Rate this link
      • LED dimmer uses only two lines - This circuit provides 32 steps of brightness control (from 0 to 100%) for a backlight or instrument panel, using just two general-purpose-microprocessor signals. Although the circuit shows the circuit driving white LEDs, the load could also be a dc motor or an incandescent lamp. The basis of the circuit is a modified Schmitt-trigger relaxation oscillator controlled by MAX5160 digital potentiometer.    Rate this link
      • LED Lamp Dimmer - This circuit provides 32 steps of brightness control from 0 to 100% for a backlight or instrument panel using just two general purpose microprocessor signals. In addition, very little board space is required since only three SOT23's and a uMax package are used. Although the example circuit is driving white LED's, the load could also be a DC motor or an incandescent lamp.    Rate this link
      • LED Mood Light - this LED circuit makes a nice lamp that is low power, runs cool, and has a long lifetime, operates from 12V, puts out a warm yellow shade of light, the color may be adjusted by changing the number of red or green LED strings    Rate this link
      • Led Pilot Light - LED current is constant between 6 and 8 mA at 5 to 30Vdc    Rate this link
      • Light Pollution Meter - LED brightness control circuit and a multimeter to compare light levels to LED level.    Rate this link
      • McMurtrie's self powered flashing LED - circuit which uses a LED as solar panel to charge a capacitor which flashes a LED, the LED will blink when the circuit is placed in bright light    Rate this link
      • Resources for Bike Light Builders    Rate this link
      • Single FET controls LED array - White-LED backlights are gaining acceptance because they offer higher reliability and simpler drive circuitry than backlights based on CCFL (cold-cathode-fluorescent-lamp) and EL (electroluminescent) technology. This circuit shows a switch-mode boost design that regulates current instead of voltage and switching off individual LEDs or groups of LEDs is not a problem.    Rate this link
      • Stroboscopic Tachometer using LED - use a LED, resistor and function generator to make a very small stroboscope    Rate this link
      • Velleman MK103 Sound-to-Light Unit - This kit is a device that transforms sound into light.Sensitivity is adjustable, and when set at it?s maximum it is really very very sensitive, even the smallest whisper will make the four high-intensity LEDs glow bright red. This page has some theory of the kit operation.    Rate this link
      • LED driver provides software-controlled intensity - Recent advances in operating efficiency have expanded the use of LEDs from one of mere indicators to becoming driving forces in electronic lighting. Increased reliability and ruggedness (versus other lighting technologies) gives the LED a bright future indeed. Vendors in recent years have introduced many ICs for driving LEDs, but the problem of driving serial chains of LEDs has received less attention. One approach to that problem adapts a bias-supply IC for APDs (avalanche photodiodes) to provide adjustable-current, software shutdown, and logic indication of open-circuit faults. The three-wire serial interface controls the DAC in this circuit. The circuit also provides an output-voltage limit and limits the open circuit voltage to 50V.    Rate this link
      • Mains LED - Ever come across an application where all that is needed is some indication the power is applied. An LED would be perfect as they have proved their exceptional reliability. LEDs are low voltage devices and can be easily powered from low voltage source with simple series resistor. A current limiting resistor at 230VAC, even with a super-bright LED running at 10mA, will consume a massive 2.3W. There is another means to generate the required current without dissipating heat - a series capacitor.    Rate this link

    Other light projects

    Electronics kits for light controlling

    Here is a small list to pages which contain information on ready made electronics kits which might be usable for experimenters who want to build light controlling electronics themselves. Sometimes it is a good idea to use ready made design for the parts which are directly connected to mains voltage. If you would rather build ready made light controlling electronics then it is best to check lighting companies link page and laser links page.

    Related pages


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