I found out about a special chip that's designed to read in a signal and split it into 7 filtered frequency, the MSGEQ7, and it's the heart of the analyzer combined with the LM3915, a 10 segment LED driver. So in a nutshell, you read in audio, split it into 7 bands (63Hz, 160Hz, 400Hz, 1000Hz, 2500Hz, 6250Hz, 16000Hz), output the info to the LED driver to light up some cool LED bar graphs. The MSG chip outputs a voltage that represents the level of each frequency band one after another so the micro is used to time the MSG chip to keep outputting the 7 bands while also turning on and off the appropriate LED bar graphs.
There's 2 3.5mm jacks that are connected together for pass-through and off those jacks I tap the signal into a couple buffers, then send it to the MSG chip. The system runs off 9V, 5V internally. The micro is an ATMEGA228P which I program using an Arduino Uno and the Evil Mad Science ISP shield. (feel free to ask away if you have questions about that Arduino stuff, happy to share what I know about the hardware etc. The ISP shield is really handy for burning the boot-loader onto new micros then programming them all from the Uno.)
You can plug in pretty much anything like your phone, iPad, MP3 player, computer, guitar, drum machine, synth, and whatever you plug in you will see the frequencies of without altering or doing anything to the signal, it's totally unobtrusive and just monitoring from a distance kinda thing. You can also use it with a built in microphone to monitor the sound around you, like in a band room. There's a little volume pot on the side to adjust the threshold of the display and inside there's a trimpot to adjust the idle noise plus a push-button switch to select line/inst or mic inputs.
I'll have more pics and a demo vid soon... sooo... anybody else like flashing music lights?
