555 two-tone electronic doorbell circuit (1)

Published:2011/6/7 4:08:00 Author:TaoXi | Keyword: 555, two-tone, electronic doorbell | From:SeekIC

As the figure 15-27 shows, the 800Hz audio oscillator is composed of the IC1, R1, R2, C1, when you press the button AN, the trigger port pin-2 connects with the ground, the output port pin-3 has the high electrical level and starts oscillation. At the same time, the C1 is charged through R2, when the charging voltage is higher than the threshold level 2/3VDD, the circuit resets and stops oscillation, pin-3 has the low electrical level. IC1's output adds to the IC2's pin-2 and IC3's pin-13 to make the IC2 and IC3 controlled by the IC1's output state. When the IC1 outputs the low electrical level, pin-3 of IC2 has the high electrical level, C2 is charged for 1 second through R3, pin-6's voltage is higher than 2/3VDD, the circuit resets again. That is to say during the 1 second delay time, the IC2 starts oscillation, the oscillation frequency is 400Hz.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Basic_Circuit/555_two_tone_electronic_doorbell_circuit_1.html

Print this Page | Comments | Reading(3)