Remote powering implies that the power equipment is not local but some distance away. It is an alternative to commercial power, which can be hard to get and/or expensive. Remote means that the powering and powered equipment are in separate buildings or at different external locations inside same building.
This posting about remote powering in video applications.
Power over Ethernet term describes several standard or ad-hoc systems which pass electric power along with data on twisted pair Ethernet cabling. This allows a single cable to provide both data connection and electric power to devices such as wireless access points, IP cameras, and VoIP phones. Recently communications technologies (ICT) industry has seen an array of PoE-enabled devices and applications proliferate commercial buildings, such as Wi-Fi, surveillance cameras, commercial lighting and sensors. The power and data can be supplied up to 100 meters.
The original IEEE 802.3af-2003 PoE standard provides up to 15.4 W of DC power (minimum 44 V DC and 350 mA) supplied to each device. The IEEE standard for PoE requires Category 5 cable or higher (can operate with category 3 cable for low power levels). The updated IEEE 802.3at-2009 PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power. New IEEE 802.3bt standard that will be completed in 2018 will increase maximum power to almost 100 watts. The new IEEE802.3bt standard will increase the available power for the first time by using all four wire pairs in Ethernet cable.
HDBaseT Alliance has developed specifications for products that transport uncompressed, high-bandwidth multimedia content, 100BaseT Ethernet, power, and various control signals through a single LAN cable.HDBase can supply up to 10W power. HDBaseT’s ability to deliver up to 100W of power (over 100m, via a single LAN cable, without any additional power source) is actually very nicely aligned with trends in energy usage and demand. The power level is more than adequate for supporting today’s typical 40-inch LED TV, which requires 70W of power.
- Complies with the section 33.7.1 of the IEEE802.3at-2009 standard, which mandates that all PSEs conform to International Electrotechnical Commission (IEC) 60950-1:2001 specifications including classification as a Limited Power Source (LPS) carrying no more than 100 volt-ampere (VA) – or 100W – per port without the need for special over-current protection devices, and
- Performs Powered Device (PD) detection followed by PD classification to determine a PD’s consumed power level prior to its ignition.
In a typical HDBaseT implementation, the PSE is installed and powered by a 50 to 57-volt DC power supply, and all PDs receive power directly over the HDBaseT link across all four pairs of CAT5-or-better cables. Additionally, core PoE technology has been enhanced for HDBaseT to use a 1 amp current for every two cabling pairs, 3-event classification to identify compliant PSEs, and identify the cable length/resistance (draw more power when required not exceeding 100W, rather than assuming a worst-case cabling infrastructure at all times). This enables HDBaseT technology to transfer of up to 100W of continuous DC power, per port, from one side of the HDBaseT link to the other.
In addition PoE and HDBase-T there are also passive adapters to adapt CCTV signals to RJ-45 wiring. Those video over UTP adapters contains video balun (balanced-to-unbalanced conversion) for video signal and connections from power source to wires on the cable. This kind of systems are typically designed to supply 9-24V CCTV camera power up to few hundred mA to the CCTV camera to power it.
Links to more information:
HDMI video cable is designed to carry video signals for some distance. Typical length of the HDMI cable is few meter. Some sources claim that DVI and HDMI specs give a maximum distance of 15 feet, but this isn’t true. The HDMI spec, in fact, gives no explicit length limit, but the requirements of the spec implicitly give rise to some length limitations for “compliant” cables. This mean that quite decent distances are possible with carefully designed cable (something like 10-15 meters) and with active signal amplifying electronics.
In addition to video HDMI cable supplies also some power. Typically according to the HDMI specifications the 5V output on the HDMI connector should provide at least 50ma of current to the connected device (sink).
The HDMI power source shall (from AN-1998 How to Meet the HDMI 5V Source Requirement
• Provide a voltage between 4.8V and 5.3V
• Implement over-current protection of less than 0.5A
• Supply a minimum of 55 mA
Portpowered devices such as some HDMI video switches, splitters, or cable boosters/equalizers rely on the 5v from the source to provide enough current for them to work.
Sometimes some device combinations have problems to work together because the power supplying device it not able to provide enough current at 5V power pin or the voltage it provides drops too much when current is increased.
In case you have too little power on your HDMI cable, there are inserter devices that can substitute 5v from the external power supply to the downstream device.
There are local (within one building) applications where some low power DC is fed through the antenna cabling from the power supply to antenna amplifier. Using coaxial cables to deliver power to small-scale electronics is a common engineering practice. Typically the outer shield of coax cable is used as negative end of supply. Very many TV cable amplifiers (usually located on attic) use this method of delivering DC and antenna signal over a single coax cable.
Most typical power supply voltage used for this are 12V DC The power is inserted to the cable using DC power inserter. The available power is quite low (typical value around 12V 100 mA). Typical satellite TV setup operates at voltages between 13V and 18V DC on the antenna cable. 24 DC is used for powering large house common antenna TV amplifiers. Some set-top box devices and GPS receivers supply current limited 5V DC for the active antenna.
The method for inserting and taking power form antenna cable is based on “bias tee” circuit:
There is also higher power AC power feed used by CATV networks that I have already described in Remote Powering over communications cabling (part 1) posting.
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In TV studio is is typical that all the cameras are controlled from the main controlling room. Camera control unit (CCU) allows the camera settings to be controlled remotely. In this arrangement the camera operator just needs to do the sootin by aiming the camera to right direction and possibly doign shooting. All other camera settings are done through CCU from the control room. This allows that the techncian there can easily match the picture from different cameras to look the same, because he/she has access to control all of them.
The camera is connected to the CCU using a cable. This cable generally carries the video signal from camera (in suitable video format), audio, power to camera, intercom communications, tally light control and camera control signals. Traditionally CCU has been connected to the camera through a multi-core cable or throug Triax cable.
Multicore cable is a cable with multiple different kind of wires inside it. There are conductors for carrying video signals (generally miniature coaxial cables) and other signals (usually twisted pairs). Different camera systems use different kind of multicore cables. In addition to video multicore cable carries power (typically 12V), audio and control signal. For power there is typically own wire pair that carries the camera power.
Multicore cables are used with professional video cameras. In television studios, 26-pin cables are used to connect “cameras” to camera control units (CCU). Triaxial cables are used primarily in outside broadcasting however both are capable of delivering an HD-SDI feed and 30 – 40 Watts of power for the Cameras.
There has been many different multi-pin camera connectors. There has been for example many 10, 14 and 26 pin connector/pin-out variations. Typically the camera power in those systems has been +12V. The 26 pin Hirose round connector used on most studio cameras to connect back to the VCR or CCU.
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Triax cables are used in TV broadcast industry for TV camera interconnections (connecting camera to CCU and supplying power to camera). Triaxial cables are constructed with a solid or stranded center conductor and two isolated shields. The center conductor and the inner isolated shield make up a coaxial cable configuration that functions to carry the video signal. The outer isolated shield can be used for several separate signals by means of multiplexing that may include power feed, teleprompter feeds and control for automation.
There are two versions of triax cable commonly used in TV industry: RG59 (3/8″) and RG11 (1/2″). Typical triax camera system can send the picture from over a triax cable for up to 500 meters with no degradation. Camera set-ups that can be remotely adjusted though ta cable, as well as usually intercom functions.
When using triax cable, the overall system is powered by AC power at the CCU (some CCUs might also accept local DC power from batteries). Because the cable length can be very long (up to hundreds of meters) and considerable power needs to be transported (large camera and local monitor), the voltages transported through the triax cable can be quite high (up to 160V DC or 250V AC on some systems) to allow long distance power transfer (resistance can be 5-30 ohms per kilometer). The high supply voltage is converted in the camera adapter to 12V DC by a switched mode power supply. Because of high voltages on the cable, there are various special precautions that are taken in account to monitor earth leakage etc. to prevent electric shock under fault (damaged cable) conditions. Depending on the system, triax system can power up to tens of watts of power to camera (needed to power camera itself and accessories).
A typical triax system has the bi-directional signal multiplexing capability that provides power, genlock, return video, program audio, intercom, tally and complete camera control from the CCU to the CAU. In conventional Analog Triax the signals (component video, audio, intercom, control etc.) are modulated onto different frequency FM carriers which are carried through the same cable. Digital Triax is Component Digital video (plus other signals) running down the cable in digital format.
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Coaxial camera cables
Probably the most common way of installing SD CCTV is using RG59 coaxial cable. For the camera power, the traditional approach has been to provide power wires besides the coaxial cable (can be separate cable or integrated together with coax). The power is typically 12V over power feed wires (can be 24V on some systems). With this kind of system the maximum distance is around 100 meters for the video and power.
Because cable and installation costs easily more than some electronics, there is a trend to power up security camera by using Power Over Coax (PoC) without the need to use extra cables. Power over coax is the process allowing a specific power over coax camera to receive power via a specific PoC injector using RG59 or CT100 cable types. The injector injects power on to the Coax cable, negating the need to fit power local power supplies near the cameras. The marketers tells that this is very simple, just use a DVR and a camera that are compliant with the Power Over Coax standard. It is possible to get long transmission distance of 300m or 500m depending on cable used. For installers this means a much more time- and cost-efficient installation.
This technology is not new as there has been many proprietary powering over coaxial cable systems in use. Power and video over same cable has also been tried years ago with analogue composite video systems. EDN article Composite video and power on coax shows a the circuitry at the monitor end of the coax cable supplies all the power to the system. This circuit uses a gyrator (synthetic inductor) isolates the low-impedance power supply from the cable by maintaining a reasonably high impedance over the video bandwidth while contributing only 0.1 ohms of series resistance. The video is modulatedon the 20V-dc line and the camera end uses a 12V fixed-voltage regulator to supply 12V to a black-and-white CCD video camera (120 mA).
PoC a.k.a. Power over Coax, is a new power system that can supply energy to analog HD systems through coax cable, without any other power source. This Video highlights Microchip’s ability to send up to 3Gbit/sec simultaneous video, power and camera control over a single coaxial cable at very long distances.
There are also solutions that can converts IP camera signals (Ethernet) and power to coaxial cable. Check out this How to convert IP PoE over coax cable video:
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