LOW_CURRENT_INTRUDER_ALARM

Published:2009/6/30 2:05:00 Author:May | From:SeekIC

Use of programmable μA776 opamps reduces standby current of infrared alarm to 300 μA, permitting operation from small rechargeable cells. Detector is Mullard RPY86 that responds only to wavelengths above 6 μm, making it immune to sunlight and backgrounds intermittently illuminated by sun. Low-cost mirror is used instead of lens to concentrate infrared radiation on detector. Rd is chosen to make input to first opamp between 2 and 6 V. Circuit energizes alarm relay RL only when incident radiation is changed by movement of intruder in monhored space.- Ceramic Pyroelectric Infrared Detectors, Mullard, London, 1978, Technical Note 79, TP1664, p 8.



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