CURRENT_DRAIN_SENSOR

Published:2009/7/2 2:57:00 Author:May | From:SeekIC

Current drawn bydome light when door is open or by ignition when turned on triggers current-sensing stages Q1 and Q2 to start 555 timer and apply power to horn relay. Initial15-s delay in sounding horn allows owner to enter car and open hidden switch S1 to deactivate alarm. If S1 is not opened during delay interval, horn sounds for about 90 s, then circuit automatically resets itself. C5 and R5 control duration of initial 15-s delay.C2 and R4 control total time that horn sounds.-R. F. Graf and G. J. Whalen, The Build-It Book of Safety Electronics, Howard W. Sams, Indianapolis, IN, 1976, p 57-62.



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