FET_TIMER_WITH_RELAY

Published:2009/7/13 2:12:00 Author:May | From:SeekIC

With values shown, circuit gives delay of several seconds. Increas-ing C1 bv shunting with 20-μF capacitor delays energizing of relay to over 1 min. C1 is charged to -4.5 V when switch S1 is closed, biasing gate to cutoff and deenergizing relay. When S1 is open, capacitor begins discharging at rate determined by RC time constant of circuit. When voltage across capacitordrops to point at which 01 conducts, relay is energized and power is applied to load.-E. M. Noll, FET Principles, Experiments, and Projects, Howard W. Sams, Indianapolis, IN, 2nd Ed., 1975, p 215-216.



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