help with Led music sync with tip31C,usb powered

[captianxawsome]

so what method do you propose to bias the transistor?

 

[audioguru]

Two resistors will bias the transistor so it is almost turned on. then a warm temperature or a signal will turn it on.
Adding an emitter resistor will reduce the temperature effect.

Then if the signal source is at 0V it will kill some of the bias for the transistor, so a coupling capacitor can be used to block the DC voltages.

Then since the base-emitter of the transistor is a diode it will cause the capacitor to charge and slowly turn off the transistor.

It better to use an opamp to automatically bias the transistor. The opamp needs an input coupling capacitor and two resistors to bias it. It needs 2 negative feedback resistors.

 

[captianxawsome]

so.......

 

[captianxawsome]

so i have it working its is a 6,000mcd blue led and it is only peaking at around 100mcd how do i increase the mcd?

 

[audioguru]

The extremely simple transistor driving an LED is garbage.
It shows only half of a waveform and the LED is dark for the other half. Narrow spikes in music have a duration so small that our vision can't see it but you can hear it.

I designed my Sound Level Indicator project properly so the LEDs are always bright. It uses a peak detector which holds the voltage on a narrow spike long enough for our vision to see it and it holds all signals long enough so there is never a dark half of a waveform.
It picks up all sounds with its microphone. Of course it uses opamps to drive its transistors. It is fairly complicated.

 

[captianxawsome]

so have any advice on any minor inprovements i can make on it?
thanks for your help

 

[audioguru]

One Instructable project for this garbage circuit was "designed" by a 10 years old kid who knows nothing about electronics.

 

[captianxawsome]

so can i add any more resistors anywhere to improve the effect of the lights?

 

[audioguru]

so can i add any more resistors anywhere to improve the effect of the lights?

You need a proper circuit using opamps that amplify very low level signals properly then drive a peak detector circuit.