BATTERY_BACKUP_POWER

Published:2009/7/11 1:47:00 Author:May | From:SeekIC

Provides 60-Hz square-wave output for driving electronic timekeeping circuits from battery during AC power failure, 555 timer is connected as square-wave astable MVBR normally locked to incoming 60-Hz power frequency. Rt should be trimlned for zero beat wiih 60-Hz soulco. When primary power fails, reference voltage disappears and effect of C1 on frequency is minimized. 555 now oscillates at frequency determined by Rt and Ct, Which is 60 Hz. Use 6-V battery.-W. G. Jung, IC Timer Cookbook, Howard W. Sams, Indianapolis, IN, 1977,p 201-203.



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