Audio Detection.

For a while now, I have been trying to find an easy solution for a robotic ‘ear’. I used to use the BASIC Stamp a lot, but now that I am learning the Arduino, I finally have an easier way to do this: A/D! I was asking around in their forums (, and came up with an easy circuit ( When I connect it to the Arduino, all I have to do is use the leads that are supposed to go to the LED in the schematic, connecting + to an analog pin, and - to GND. The problem is, when it hears a really loud sound, it takes a really long time even after the sound is gone for the value from the A/D converter to settle down again. And the odd thing is, when I test this with an LED, the LED does NOT stay lit and slowly dim from the input just as the value from the Arduino A/D shows. What’s going on? I tried using different value resistors connected to the output of the audio circuit, but that didn’t help. Does it have to do with the caps? Or with the Arduino itself…?

You could try it with a smaller capacitor (say .01 uf )and/or with a resistor across the cap (say 1 megohm)

Cool. Thanks; that worked! I figured that might work. I used a 1.5m resistor across the smaller cap.