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Sound Sensitive LED Sequencer

ClncyFshSlayer

Jul 4, 2012
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I have a circuit that I designed and it has been giving me total fits to get working. It runs off an electret mic, that runs though a high pass filter, then is sent through an LM358 op amp to boost the signal by roughly 100X, then through a switching diode acting as a max voltage sensor and into another op amp used as a comparator, then to a decade counter to advance 1 LED per beat of the music.

I can get the circuit to work, however is does not follow the beat well and it appears that multiple LEDs light at the same time. Any help on this circuit would be great. A better schematic or PCB layout would be amazing.

The whole idea is to sequence 10 strings of 4 to 6 LEDs with the music using a 12V 4.2A computer power supply, preferably using direct audio input from the back of a stereo, but a mic will work too.

Here is a video of what I want to make this circuit do.

Thanks! CFS
 

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KJ6EAD

Aug 13, 2011
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Shouldn't you be using a low pass filter if you want to track the beat?
 

ClncyFshSlayer

Jul 4, 2012
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I really was not completely sure, I had seen a tutorial someone had made that responded to claps of the hand, they used a high pass filter, which was my reasoning here as to why I used one. I am not entirely sure the difference between a high and low pass filter, other than the layout having the resistor and capacitor switched.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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A high pass filter will detect sharp abrupt transitions (like the sound of a clap). The beat of music is a much slower signal, and a low pass filter (perhaps VERY low pass (up to 3Hz?) may be required. You want the signal that changes between (say) 1 and three times per second)
 

ClncyFshSlayer

Jul 4, 2012
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How would I go about calculating the resistor and capacitor needed in order to get the right sensitivity?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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You need to reverse the position of the resistor and the capacitor and then pick something that will give you a correct rolloff frequency.

It is complicated a little because the mic is probably less sensitive to low frequencies, and you're probably looking for effectively a modulation of the signal at low frequencies. Start with 100k and 0.47uF and see if you detect anything. Then reduce the resistor value (you might even use a pot) to get an optimum value.
 
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