Current Schematic:
**broken link removed**
The idea is to detect music from the electret mic, amplify it and send it through a low pass filter and full wave rectify it, and then smooth it to compare to a sawtooth wave, in order to drive some LEDs using Pulse width modulation. The point is to have the lights glow dimly when there is a low amount of noise and shine brightly when there is a loud noise.
The circuit works, sort of. It just needs a lot of fine tuning. One problem I have is that when I don't include c8, which is meant to be a smoothing capacitor, the LEDs flash visibly and rapidly. When I do include c8, they work well at full strength, but instead of glowing dimly at half strength, they flash slowly at a rate dependent on the value of c8. I then tried to attach a resistor in series with this cap, which produced very desirable results, only to fry my op amp after a few minutes use. The chip was not hot, but it did stop functioning, and had to be replaced. This happened twice, and I don't know whether it was the cap or the resistor that caused it. What I need help with here is either a better way to rectify and smooth the audio wave, or a way to include this without frying anything.
Another thing I wanted to do was to drive the LEDS a tiny by default, so they were always glowing, but the get bright during bass hits. I tried to do this by dividing the voltage at the "plus" input of U3A, in an attempt to base the audio wave at say 1V or 2V instead of 0V, but this didn't work. Is there any way to do this?
If anyone could give me ideas on either thing I would greatly appreciate it.
-Dave
**broken link removed**
The idea is to detect music from the electret mic, amplify it and send it through a low pass filter and full wave rectify it, and then smooth it to compare to a sawtooth wave, in order to drive some LEDs using Pulse width modulation. The point is to have the lights glow dimly when there is a low amount of noise and shine brightly when there is a loud noise.
The circuit works, sort of. It just needs a lot of fine tuning. One problem I have is that when I don't include c8, which is meant to be a smoothing capacitor, the LEDs flash visibly and rapidly. When I do include c8, they work well at full strength, but instead of glowing dimly at half strength, they flash slowly at a rate dependent on the value of c8. I then tried to attach a resistor in series with this cap, which produced very desirable results, only to fry my op amp after a few minutes use. The chip was not hot, but it did stop functioning, and had to be replaced. This happened twice, and I don't know whether it was the cap or the resistor that caused it. What I need help with here is either a better way to rectify and smooth the audio wave, or a way to include this without frying anything.
Another thing I wanted to do was to drive the LEDS a tiny by default, so they were always glowing, but the get bright during bass hits. I tried to do this by dividing the voltage at the "plus" input of U3A, in an attempt to base the audio wave at say 1V or 2V instead of 0V, but this didn't work. Is there any way to do this?
If anyone could give me ideas on either thing I would greatly appreciate it.
-Dave