The dark room timer circuit

Published:2011/8/15 22:24:00 Author: | Keyword: dark room timer | From:SeekIC

The 555 is the timing circuit, the timer has 12 basic marks, each interval is half-gear. The switch S1, resistors R1-R12 and capacitors C1 and C2 compose the timing component, the adjusting gear can be divided into 1/4 by C2, i.e when S2 is closed, the exposing time is reduced to 1/4 gear. The switch S3 controls the starting of the timer. When the switch is closed, the 3-pin of IC1 is turned into a high LEV, the solid relay IC2 is conducting, the bulb in the shadow amplifier is lighted.



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