The 555 dual electric door bell circuit (1)

Published:2011/7/20 7:58:00 Author:Seven | Keyword: electric door bell | From:SeekIC

See as figure 15-27, IC1, R1, R2 and C1 compose a 800Hz audio oscillator circuit, when AN is pressed, the 2-pin of the trigger is connected with the earth, the 3-pin of the output terminal is reversed to be in a high LEV and starting to oscillate. Meanwhile, C1 is charged by R2, when the charge voltage is over the threshold LEV of 2/3VDD, the circuit is reset and stopping oscillating, the 3-pin is in a low LEV. The output of IC1 is sent to the 2-pin of IC2 and 13-pin of IC3, which makes IC2 and IC3 to be controlled by the output state of IC1.



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