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Can i make a LED to fade with music?

I want to have a LED alwais on and with the tempo of the music the LED will turn off or fade.
to make this i have a npn a pnp and a SINGLE OPERATIONAL AMPLIFIER the led is 3v.
i don't have an Arduino o another tipe or controller

jpacquing3 years ago
You can get the controllers from:
http://www.elwirepros.com/
Connect up the opamp as an adjustable rail to rail comparator it is a circuit like this one only instead of diodes and transistors just resistors and the music on the opamps input.

https://www.instructables.com/id/Photo-Components-Testing/step5/Building-the-Tester/

Joe
clowreed (author)  Josehf Murchison3 years ago
thank you very much for your answer, could you please explain better what you mean with adjustable rail and how to connect the opamp and the led to the circuit you posted?
Your audio input voltage goes up and down with sound and is higher or lower by adjusting the volume.

This makes the voltage go up or down at point A with the incoming sound.

The adjust; is adjusted to match the voltage at point A where you want the LED to turn on and off.

So when the voltage at the adjust is above the voltage at point A nothing happens, if the voltage at the adjust is the same or below point A the LED turns off.

To change this around swap the opamp inputs.

Sound goes up and down as many as a thousand times a second this is too fast to see so cap A is needed to keep the voltage up and down long enough to see.

This circuit needs to be tweaked so build it on a bread board so you can swap out the parts you need to change to make this work the way you want.

Joe
shmit trigger.gif