Sound operated flip flop

This is a circuit 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 opamps in the IC1 LM 324 is used to amplify the sound picked by the condenser microphone. The third opamp 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 opamp, 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

Notes.

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