RAIN_ALARM／DOOR_BELL

Published:2009/6/25 22:37:00 Author:May | From:SeekIC

With S1 open the circuit functions as a doorbell. With S1 closed, rain falling on the sensor will turn on Q1, triggering Q2 and the thyristor and activating the bell, R4 provides the holding for the thyristor while D1 prevents any damage to the thyristor from back EMF in the bell coil. The sensor can be made from 3 square inches of copper clad board with a razor cut down the center. C1 prevents any mains pickup in the sensor leads.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Control_Circuit/RAIN_ALARM／DOOR_BELL.html

Print this Page | Comments | Reading(3)