This is the circuit diagram of a ding dong sound generator based on two NE555 timer ICs.The circuitis designed to toggle between two adjustable frequencies to produce the ding dong sound. The firstNE555 (IC1) is wires as an astable multivibrator operating at 1Hz. The frequency of the second NE555(IC2) is modulated by the output from the first IC. This is attained by connecting the output of first IC to the control pin (pin5) of the second IC. The tone of the sound depends on the frequency of the second IC and the changeover time depends on the frequency of the first IC.
Notes.
The circuit can be assembled on a Vero board.
Use 9V PP3 battery for powering the circuit.
POT R4 can be used to adjust the tone of the sound.
POT R2 can be used to adjust the change over time.
IC1 and IC2 must be mounted on holders.
K1 can be a 8 ohms, 1/2 watt tweeter.
source:http://www.circuitstoday.com
