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Arduino Input

I am writing an Arduino program to read speaker inputs for a test station.  I need only to know when a speaker lead is on or off. This will be done by using the fade and balance.  Originally I was connecting the speaker leads to the analog inputs and could get a single line to work as a simple VU meter. Multiple lines gave issue.  Since I don't need to know the actual level, just whether they are on or off I'd like the speaker lead to trigger a transistor connected to a digital I/O pin on the Arduino.  Any thoughts or quick schematics on how to do this? 

All you need is a simple clap circuit using an op amp. Set the gain pretty high on teh clap circuit and any time anything comes through the speaker the LED will light.

dbirky (author)  mpilchfamily3 years ago
I haven't done much with opamps. Something like this?
clamping circuit using op amp.jpg

No, something like this.

Also see the follow up video to this as it may have some info that may help to take your project to the next level.

On the circuit the output to the LED can be fed to the base of a transistor to trigger it allowing a full 5V to trigger a digital pin on the arduino to do anything else your looking to do.