Infrared anti-theft alarm circuit diagram

Published:2011/5/17 3:44:00 Author:Ecco | Keyword: Infrared, anti-theft , alarm circuit | From:SeekIC

Infrared anti-theft alarm is composed of the radiating circuit and receiving circuit. This circuit is sensitive and reliable, anti-interference, it can work in bright light. In radiating circuit, the multivibrator composed of F1, F2, and R1, C1 can produce 1 ~ 15KHz high frequency signal. After amplified by the BG, itdrives IR LED,emits a high-frequency infrared light (IR) signal. In the receiving circuit, when there's someone passing or stopping in front of the launch head, the part of high-frequency IR signal from the transmitter will be reflected back by boby. DU photocell receives the signal, then it is amplifiered by the amplifier circuit composed of BG1, BG2, BG3 and RC components. And then it is decoded by the audio decoder LM567 and it produces low level on pin 8 of IC1 to stop BG1. Power charges for C1 by R1D1, ICdTWH8778 isimmediately turned onto make an alarm sound. At this time, even if the person has passed the restricted area , photodiode DU has no turn signal reception to make BG4, D1 cut off.



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