[General] Arduino Digital Trigger

[dbirky]

I am programming an Arduino Mega to turn on an LED when there is audio signal present on a speaker lead from a stereo. I'd like to use an LM324 opamp. I need to have a 5v signal when audio is present, and 0V when the line is muted to trigger a digital IO pin. Once I have this working I intend to duplicate the circuit for all 4 channels from the stereo. Any help with the circuit would be greatly appreciated.

 

[dbirky]

Well, after more experimenting I have something that works. Taking the +Signal through a filter to the LM324 works well. I'll be able to trigger 4 different inputs on the Arduino with one LM324 opamp. This will indicate which channel the stereo is faded to. Any comments on the schematic would be appreciated.