I'm looking to create an audio controlled PWM setup for red, green and blue lighting of a particular object (think a CD lamp, but way cooler). I'd like the option of taking input from an electret mic, splitting it into low, mid and high frequencies with the appropriate low, band and highpass filters. I'm figuring I'll need a basic mic preamp, but I can probably scrounge together a CMoY-like design with what I have lying around. It doesn't exactly have to sound good. What I need help with is figuring out how to use the audio signal to control the PWM lighting controller. Right now I'm thinking of using a simple 555 timer, whose frequency is adjusted by input voltage. How do I go from an AC audio signal to a DC signal that roughly represents the majority of the sound in the given band? Doesn't have to be high quality or anything, but it should certainly be enough so that when bass notes go off, you see that in the blue light, an acoustic guitar in the green, and maybe a high vocal in the red. The audio controllers they have for CCFLs would probably work damn near perfect, but I'm not about to buy three CCFLs for this project, plus I'd rather make something myself. So how do I go about doing this? Can I use the multitude of 555 ICs I have lying around, or is there a better solution? Cheers, -Matt
a nicer way is buying a simple programmable chip, and making some software to read out an A/D convertor level, and push a PWM signal towards the leds. the only thing you then need to fix is getting an DC signal to send to the chip out of the AC audio signal. My guess is that 4 fast diodes and a small capacitor would work.
if i where to do it this is what i'd do..... Audio Signal ---> Filters (Low, Mid, High) Then each filter's output would undergo conditioning and clipping Then each component would be fed into a voltage to frequency converter which would drive the LEDs through a transistor. From my initial estimates parts shouldnt cost you more than $20 USD if you already have the LEDs
You might find this thread helpful. A search for "Color organ" will show you lot's of threads here (googling it will give you dozens of hits as well).
Thanks, that's got me in the right direction. I can't believe I forgot to search, I've even read that LED thread before!
actually for PWM, an easier way to do it is to build a little sawtooth generator with a 555 (use a transistor as a constant current source), then feed it to a comparator, sawtooth into the +, your signal into the -. out goes to driving transistor. make sure they're in the same amplitude range though, or things get wonky.
Easier? I think it would be way easier to modify one of the circuits in that other thread for three channels. Likely this will be one of three modes, the other two being constant on (with adjustable brightness for R, G and B, which is easy) and adjustable pulsating brightness.
