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PIR Sensor Based Security System Posted: 13 Jul 2011 12:49 AM PDT The circuit of an inexpensive and highly secure electronic security system is explained below. This electronic security system can be used in banks and other high security areas. A normal electronic security system will have a transmitter and a receiver. The transmitter sends out an IR laser and this will be received by the receiver. When an intruder walks past the device, the IR beam is cut and thus the alarm is activated. But, this system has some major disadvantages like limited range and poor line of sight. These disadvantages are eliminated through the PIR sensor circuit explained below. Working Instead of infrared or laser transmitters and receivers, PIR (Passive Infrared Radial) sensors are used in this circuit. The sensor is basically a pyroelectric device. When the device is exposed to infrared radiation, it generates an electric charge. The device is made of crystalline material. According to the change in the amount of infrared striking the element, there will be a change in the voltages generated, which is measured by an on-board amplifier. The infrared light explained here refers to the light radiating from all objects in its field of view. The reason for not having a transmitter and receiver...

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