Why Security system uses Infrared Camera? Fact File 37

Infrared camera is used to capture the image of a moving person in darkness as a measure of security. The surveillance systems used in home, office and commercial establishments uses infrared camera to monitor the premises. The infrared camera utilizes the infrared radiation generating from the body heat. The system senses the infrared and generates a video image of the moving person using the infrared camera. This device is sensitive to only the infrared range of the electromagnetic spectrum.

The system uses a Photocathode sensitive to infrared. The Photocathode consists of a thin layer of metal that can give out electrons by accepting energy from the infrared rays. The thin layer of metal is coated on a flat glass plate. A lens system is provided to focus the infrared light from the source into the photocathode plate. The metal coating in the photocathode is too thin so that when the infrared energy hits the front layer of the metal, electrons will be emitted from its back layer. Thus the photocathode generates an electron pattern based on the infrared photons hitting on the photocathode.

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Design your Circuit. Part IV – IR Transmitter

Most of the consumer electronic devices use Infrared remote control for easy operation. The Carrier frequency of such remote control may be 36 kHz or 38 kHz. The Control codes are sent to the receiver of the device in Serial Format. This format is Modulated to the carrier frequency by the On / Off method. In the Remote, the IR signals are generated using an IR LED which emits Modulated IR rays. This part explains the details of IR transmission protocol and the design of IR Transmitter.

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PIR Sensor based Alarm

This Passive InfraRed Alarm system can switch on a Lamp or Alarm when it detects the heat from an object like moving person. The name PIR (Passive Infrared) is given to the sensor because it receives the infrared rays passively and do not emit any infrared ray. The lamp or alarm remains on few minutes depending on the mono time setting of the PIR Sensor used. Ready to fix PIR Sensors are available with Fresnel lens to increase sensitivity and to filter ambient light. Its range is around 5 meters at 45 degree cone angle.

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Trick to See Infrared

Have you seen Infrared rays so far? It is difficult to see because it is beyond the spectral response of our eye. Our photosensitive cells in the retina detect only the visible light in the range 450-750 nm. But many animals can see infrared spectrum lying above 900nm.Then what we can do to check whether, the Infrared LED in our project is working or not. A Digital camera can solve the problem. See how it detects the infrared.

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IR Sensor Tester

Most of the Remote control systems use TSOP 1738 IR Sensor module to control various functions. This IR Sensor is highly sensitive and may damage easily, if is supply voltage increases above 6 volts. This tester is useful to check the working of the IR Sensor. It gives audio-visual indications when the IR sensor is working properly.

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