SOUND_ACTIVATED_SWITCH

Published:2009/7/2 3:20:00 Author:May | From:SeekIC

Can be used as sensor for burglar alarm or for turning on su'-veillance tape recorder to monitor conversa-tions. R8, is adjusted to give desired sensitivity at which A2, triggers switch Q1, to provide 200-mA load current and turn on indicator LED. First section of LM339 quad comparator serves as amplifier and detector providing gain of 100. Second comparator compares DC output of first with reference level selected by R8.-D. ft. Mor-gan, Sound Turns Switch On, EDN Magazine, Aug. 5, 1978, p 82 and 84.



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