INTRUDER_ALARM

Published:2009/7/2 3:05:00 Author:May | From:SeekIC

Input is from Mullard RPY86 infrared detector responding to wave-lengths above 6 μm, making it immune to sun-light and backgrounds intermittently illumi-nated by sun. Output signal is produced only when ihcident radiation is changed by movement of intruder in monitored space. Mirrors rather than lenses concentrate incident radia-tion on detector because mirrors do not require high-quality surface finish. Preamp is followed by two amplifier stages, with R10 varying gain of second stage between 10 and 100. Band-width is 0.3-10 Hz. First trigger, having thresh-old of about 1 V, drives second trigger through diode pump to energize alarm relay when in-truder is present.- Ceramic Pyroelectric In-frared Detectors, Mullard, London, 1978, Tech-nical Note 79, TP1664, p 8.



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