F-V converter LM324
Electronic

ICs quite natural that you assume if there is a V-F converter there should be an F-V converter also. You're right, and we're going to make it in this project. With this converter, you can convert the frequency of your voice to a voltage and light up the LED.

See schematic, U1:A is a voice amplifier that amplifies the voice signal from a microphone (the earphone is used as a microphone).

U1:B is a comparator that maintains the amplitude constant to make the converter work smoothly. This comparator produces a square-wave output.

U1:C and U1:D work as an F-V converter where the frequency is converted proportionally to a voltage. Let's see how this converter works.

Turn power ON, and whistle at the microphone at the same pitch. You'll notice the LED lights up but its brightness doesn't change even if you give a strong, loud whistle, and that's because the frequency (pitch) of your whistle doesn't change.

Try changing the pitch of your whistle. Can you see the difference in LED brightness?