transistors audio controlled relay circuit

A circuit that fires a relay when it detects audio pulses from one channel of an mp3 player. I`m going to record audio pulses in sync with the music to control a motor for mouth movement. So for your stereo player, you`ll just mix music/whatever onto (arbitrarily) the left channel and have the right just be a series of loud sine pulses Nick T Oct 2 `10 at 4:14 Hey Pete - could you give us an idea about the kind and

size of motor or actuator you intend to use also could you comment a little on the mechanics - maybe just mention how you`d like the resulting thing to move - I just thought it might help people answer your question fully. Jim Oct 2 `10 at 15:14 You probably have to find the value of C1 experimentally. It probably depends on the output impedance of your MP3 player. Look at that point on a scope if you can. endolith Oct 2 `10 at 15:38 The problem you will run into is that there will be input signal levels that will put the 3904 into linear operation. To control a relay you want the transistor to drop either all the supply voltage or (very nearly) none of it. Intermediate states will just waste power cooking your transistor and won`t necessarily pull the relay in. JustJeff Oct 5 `10 at 1:43

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