TIMER_SWITCH_OFF_FOR_ENLARGER

Published:2009/7/13 3:46:00 Author:May | From:SeekIC

Circuit shows power supply designed to operate digital exposure timer using TTL. Since timer logic is needed only when enlarger lamp is on, power supply circuit will be turned off automatically when timer goes low and turns off enlarger lamp at end of exposure, Switch S is closed when timer cycleis activated, setting timer out-put at 5 V and turning on lamp. Transistor and diode types are not critical, Since D2 is con-netted to logic point of timer, power supply re-mains on when S is released, until completion of timer cycle.-E. R. Rumbo, Automatic Switch-Off Power Supply, WI'reless World, Feb.1976, p 77.



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