I don't yet know what frequencies I plan on using. I'm still looking into it. Any recommendations?You'll need to build several bandpass filters. Active filters will be easier than passive filters.
Did you have frequency ranges in mind?
You might consider using "eggcrate" type fluorescent light diffusers, like on this page:I'm going for aesthetics with this project. I'm hoping for something about the size of a standard piece of printer paper, about 1"-1.5" deep that I can mount on my wall. I'll put it in a picture frame of some sort. The front of the board, instead of just LEDs, will be offset from the top of the LEDs by about 1/4". The front will consist of a sheet of plexiglass with white paper beneath it (to diffuse each LED's color). I'll use 14 bands and 10 LEDs for each band. Each LED will be seperated by little cubbie-like dividers (almost like in a fishing tackel box) so that the color doesn't bleed through into other squares on the front. Each LED will be centered in a .795" square.
Sure. You might use Cadsoft's Eagle Layout Editor to work it up. Unfortunately, the freeware version is limited to 3"x4" boards, but your circuit is basically going to be many repetitions of the same thing.I'm probably not going to start with the hardware for about a month, but maybe if I create a schematic, you guys could give it a quick lookover to make sure everything checks out? (I haven't taken on a project like this before. I can't wait to see the finished product)
You could record a .wav file with various known frequencies in it, then play it back in WMP to find out.What about the WMP visualization, "Bars". It uses 50 different bands. Is there any way to tell what frequency ranges they are?
Every 3db is a half power point. That means when each successive LED lights, the power level has doubled.Could I run my audio through this in a parallel circuit, and measure only a fraction of the input? I know that the chip runs in 3dB intervals, and I don't want to use more than 10 LEDs, and don't want to cascade chips.
See... I called it.Yes you did! You have connected the ground of the filter to the signal input and the output of the filter to ground. Change them and it will work fine.
Okay. I'll fix my diagram and post it again (probably not until tomorrow). Granted, it will probably be 800% more screwed up.I mean that it has to vary between 0 and a positive value voltage.
Well, my stereo has a 7-band equalizer on it.
Frequency ranges are:
63 Hz
160 Hz
400 Hz
1 kHz
2.5 kHz
6.3 kHz
16 kHz
It's a '93 vintage Technics that was the best bang for the buck in it's day.
You could use that as a basic guideline for your spectrum display. You'll need to design wide bandpass filters for each frequency range. For example, for the 63Hz filter, you might go from 20Hz to 100Hz, for the 160 you might go from 105Hz to 220 Hz or so, etc.
TI's Filter Pro will help you a great deal in designing the filters. You can download it for free here:
http://focus.ti.com/docs/toolsw/folders/print/filterpro.html
Use Wide Band-pass, MFB Single Ended or Sallen-Key, Chebychev. 2 poles for both the low-pass and high-pass. Allow up to 1dB ripple in the passband.
The filters will be very sensitive to values of RC. You'll need a good cap meter to verify your caps before installing them.
Well, it would be good to keep things more focused on a novice level - after all, he wants to build the beastOr if you really want to get hi-falutin' fancy, you can build a parametric equalizer...you can then scoot your bandpass centers around at will.
by Aaron Carman
by Jake Hertz
by Duane Benson