Sound operated flip flop.


Here given is a circuit in which the status of the output pins of a Flip Flop IC can be toggled by using sound. A condenser microphone is used for picking up the sound. The first two op-amps in the IC1 LM 324 is used to amplify the sound picked by the condenser microphone. The third op-amp inside LM 324 is wired as a level detector. When ever the voltage produced due to sound have a level more than that of the reference voltage at pin 5 of the third op-amp, its output (pin 7) goes high, triggering the flip flop IC1 CD 4027.As a result the state of the output pins of CD 4027 ( pin 1 & pin 2) toggles for each burst of sound.

Circuit diagram with Parts list.



  • Assemble the circuit on a good quality PCB.
  • The circuit can be powered from three 1.5 V cells in series.
  • The ICs must be mounted on holders.
  • All capacitors must be rated 10V.
  • The mic M1 is a condenser mic.
  • The sensitivity of the circuit can be adjusted by varying the preset R9.
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