Ding-Dong sound generator

This is the circuit diagram of a ding dong sound generator based on two NE555 timer ICs.The circuit is designed to toggle between two adjustable frequencies to produce the ding dong sound. The first NE555 (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.

Circuit diagram.



  • 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
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10 Responses to “Ding-Dong sound generator”

  • ahmed nabil says:

    hey , please i wanted to ask about the capacitors function in this circuit specialy C2 ….. ?

  • Amit Khobragade says:


    Is there any replacement for C1 & C4, as I am not able to get those capacitors, the min available are from 25v onwards.

    What will be the diagram changes if I used one of those.?


  • jack says:

    are c1, c2, c3 are milar capacitors?
    if not, what are its corresponding voltage values? thnx!

  • Alan says:

    Is this circuit supposed to make a “higher pitched DING, lower pitched DONG” sound like a doorbell? All I get is “beep beep beep beep beep beep” and I can use the variable resistors to change the length of time of the tones (long beep with a long pause, or very quick), and the other variable resistor to change the tone, higher or lower pitched. But all the tones are the same pitch. Or did I wire it wrong?

  • rendy says:

    where is the (-) pole??

  • frank says:

    There should be a 100k resistor between pin 3 IC1 and pin 5 IC2…also you need a button for it to work like a doorbell