Index
Alarm Technology Page
The purpose of any alarm system is to either protect life or property or to detect an intrusion. Many buildings and complexes being constructed today are equipped with some type of intrusion detection and fire alarm systems. Numerous detection and fire alarm systems are in existence today.
- Remote Alarm Signaling - It is usually desirable to connect building alarm systems to a remote receiving station manned at all times by competent personnel who can take the proper action-to extinguish the fire and evacuate the building if necessary. These connections are usually in the form of auxiliary relay contacts that can be connected to operate an alarm transmitter. Rate this link
- Smoke Detectors - This is an introduction to smoke detectors. Smoke detectors are frequently used in fast-acting automatic fire detection systems that incorporate an extinguishing agent release function to protect high value or highly combustible storage and work areas. Rate this link
- Heat Detectors - Heat detectors are probably the most widely used initiating device for general-purpose automatic fire alarm systems. Rate this link
- Alarm Systems - Numerous detection and fire alarm systems are in existence today. This Construction Electrician book chapter discribes the function and operation of a typical detection system and of various fire alarm systems. Rate this link
General information
- Tiny 2-Zone Alarm - build a really small alarm that could easily fit inside a pocket, this alarm supports two wire loop zones Rate this link
- Motorcycle Alarm - This is a mercury switches as bike movement detectors based alarm circuit. Any number of normally open switches may be used. Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Rate this link
- Miniature Loop Alarm - The aims of this alarm circuit were simple construction, reliable operation, very small power consumption, and, most of all, small size. This circuit is utterly primitive and consists of two identical transistor switches. Each has its own alarm LED and they're coupled to a neat 82dB buzzer. Rate this link
- Gate Alarm System Rate this link
- House Security System - Here is a low-cost, invisible laser circuit to protect your house from thieves or trespassers. A laser pointer torch, which is easily available in the market, can be used to operate this device. Rate this link
- Doorknob alarm - metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door, anyone grabbing the knob from the outside is detected by the electrical capacitance change that occurs from the human hand contact between the knob and the box, operates years from set of batteries, pdf file Rate this link
- 5 Zone Alarm System - a complete alarm system with 5 independent zones suitable for a small office or home environment - a complete alarm system with 5 independent zones suitable for a small office or home environment Rate this link
- Wire Loop Alarm - This circuit is a simple wire loop alarm that can be used in doorways, hallways, or any other place the tripwire will be broken by intruders. The circuit has a built in siren, but it can be replaced by a relay to drive an external siren, commercial alarm, etc. Rate this link
- Ultrasonics: remote control and Intruder detector Rate this link
- Single chip detects optical interruptions Rate this link
- Micro power temperature alarm - sounds an alarm when the temperature exceeds a certain point (around 65 degrees celsius), can be powered for years by a single 3 volt lithium battery, pdf file Rate this link
- Light Alarm - Detects very small amounts of light and sounds the piezo alarm, pdf file Rate this link
- IR Light Fence/Door Minder - Set up an invisible infra-red light beam to monitor doorways or any other area. When the beam is broken a relay (maims rated) is tripped which can be used to sound a bell or alarm. Rate this link
- Crystal Locked Ultrasonic Movement Detector - sensitive circuit with few components, pdf file Rate this link
- An Ambient-Light-Ignoring Infrared Active Motion Detector - using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned to detect all sound in that area Rate this link
- Piezo device generates buzz, beep, or chime Rate this link
- Very loud piezo alarm beeber - sweeps the drive frequency slightly to produce a very annoying sound, uses a transformer to increase the drive voltage across the piezoelectric device to more than 200 volts peak to peak, cranks out an ear splitting 120db when measured at 12 inches, pdf file Rate this link
- Very loud beeper circuit - but generates a continuous tone, delivers about 110db (12 inches away) from a 9v battery using a single inexpensive C-MOS IC and off-the-shelf piezoelectric beeping device driven at resonance, pdf file Rate this link
- Inexpensive LED drives flash-and-beep circuit Rate this link
- Alarm Siren Driver - This kit is based on the ZSD100 siren driver chip from Zetex. With the addition of a few external components, this chip will produce an ear piercing 120dB siren using an 8 ohm horn speaker. It will operate from supplies of 4V up to 18V, making it ideal for security systems in battery powered applications, burglar alarms and car anti-theft systems. Rate this link
- 9V Siren - A surprisingly loud siren for such a simple circuit. Uses voltage controlled oscillator, 1/2 Watt, 8 ohm speaker and operates form 9V DC. Ideal to attach to an alarm system which needs an sound module. Rate this link
- 9 to 12V Piezo Screamer - Powerful 9V to 12V piezo alarm. Uses 556, auto-transformer and two piezo alarm elements. Circuit will deliver 108-110dB at 1M. Uses sweep circuit so there is no need to trim the circuit to match the cavity resonant frequency. Rate this link
- Combination Lock - A basic but fully working combination lock. Separate touch pad with 9 pads. Lock is reset if an incorrect digit is pressed. Rate this link
- Discover Circuits Alarm Circuits - Alarm circuits collection Rate this link
- Pyroelectric Infrared (PIR) Motion Sensor - This document includes circuit design as well as an excellent tutorial on PIR devices. Rate this link
- Passive-Optical Person Detector - Ordinary proximity detectors use infrared sensors which respond to the warmth of the human body. But there???s a simpler way: we can use ambient lighting and detect changes in illumination. Any move a person makes causes a change in the ambient lighting. This circuit uses an ordinary phototransistor as its "eyes" to detect these changes. Rate this link
Alarm circuits
Alarm systems
Sensor circuits for alarms
Alarm sound circuits
Electronic lock circuits
Other circuits
Person movement detection
Ordinary proximity / movement detectors use infrared sensors which respond to the warmth of the human body. Those are usually called passive infrared motion detectors or Pyroelectric Infrared (PIR) Motion Sensor. There are also other techniques for this. Thos include detection of lighting changes, using ultrasound and using microwaves.
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