SOUND_OPERATED_RELAY

Published:2009/6/30 1:36:00 Author:May | From:SeekIC

Output of about 1.8 m VRMS from crystal orceramic microphone will energize relay when sensitivity control R4 is at maximum. First two stages form high-gain RC-coupled AF amplifier, output of which is rec-tified by silicon diode X1. DC voltage developed across diode is applied to gate of Siliconix U183 FETwhich acts as DC amplifier driving Sigma 5F or equivalent relay. To ad just, short microphone terminals, set R4 for maximum sensitivity, then ad just R10 until relay opens.-R. P Turner, FET Circuits, Howard W. Sams, Indianapolis, IN, 1977, 2nd Ed., p 111-113.



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