Sound-activated mp3

Thread Starter


Joined Oct 16, 2007
I am trying to design a circuit that will have a mic that triggers an mp3 player to play a message when it detects a sound.

There are some really cheap mp3 players now and I was thinking I could connect a mic to a potentiometer to give it some adjustability and then have it control the play button of the mp3 player with a transistor. As you can tell I'm a real beginner in electronics and I'm not sure if this is even possible. Would it just keep the play button on or is there a way to make this a "momentary" circuit like the play button on the mp3?

Also, can I connect the output of the mp3 player (speaker) back to the mic circuit so that it will prevent the mic from triggering again while the mp3 is playing? I imagine a transistor with an inverter so that while there is current to the speaker it keeps the mic circuit open. I think a 555 timer would do it but the disadvantage is that it would not automatically change the duration of blocking the mic with different mp3 durations.

I hope some of this makes sense. I'm still learning.


Joined Jul 22, 2007
A while ago, I bought a few 16 meg mp3 players, surplus store. I've got a simple circuit some place for making one play when power is applied, just a transistor, capacitor, and a resistor. Will post it if I find it, been a while. Never got around to finishing that project. Basically wanted to have it play a song after the sun went down, all solar powered. Needed a bigger amplifier, more battery power, and no idea how to turn it off after the song was done (would continously loop).


Joined May 16, 2005
Try an internet search using the terms "sound activated switch." You should find at leas half a dozen schematics if you dig long enough. Pick one or two that you think you could handle making, and we'll go from there.