LIGHT_BLOCK_SENSOR

Published:2009/7/15 22:30:00 Author:Jessie | From:SeekIC

In this circuit, relay RY1 remains open until the light source is blocked. As long as the IR light source is uninterrupted, phototransistor Q1's collector voltage is near zero. The voltage at zener diode D2's cathode is too low for conduction, keeping transistor Q2 off and the RY1 open.



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