SMOKE_DETECTOR_2

Published:2009/7/7 7:18:00 Author:May | From:SeekIC

This circuit comes from U.S. Patent 3,778,800, granted to BRK Electronics in Aurora, IL. The circuit provides a smoke detector with an alarm for both smoke and low batteries. The R6/R7 voltage divider monitors the battery and will turn Q2 and Q1 off when the battery voltage falls too low. The smoke-detec-tor chamber will also cut Q1 off when it senses smoke. Q1 via Q3, triggers SCR Dl and sounds the alarm. Capacitor C1 provides feedback that causes the alarm to sound intermittently. The smoke detector and low-battery circuits sound the alarm at two different rates.



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