(3 x filter) + (3 x led) = Color Organ?

Hi all.
I was browsing though my YouTube watch later playlist (300 videos!) and I came across some color organ videos. It made me wonder - is it possible to make a littleBits color organ with multiple filters and rgb leds? I have only one filter and can’t test this idea myself. Maybe an Arduino would work, but would that be cheating? Please reply with your thoughts and ideas. Oh, and if you have multiple filters, a video response would be icing on the cake.

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Hi Jude! Long time no see!

I think you’d be able to make a pretty cool light display with filter and LED bits, but it might fall a bit short from a true “color organ” effect. The first gotcha is that the filter bit is designed as a Low-Pass filter. You can use it to remove high-pitched content from an audio signal, but you can’t use it to remove low-pitched content. A filter bit would be perfect for making the Bass part of a color organ. However it couldn’t generate the Midrange or High parts, since it can’t remove the low-pitched content. Furthermore, to make a really good organ, you’d want to do some additional tweaking to the signal emitted by the filter bits. Ideally you’d want an “envelope detector” circuit, to convert the quickly moving audio waves into a smoothed out measure of amplitude. The sound trigger bit does all of this stuff for you, except for the critical part where the frequency filtering happens!

If you were open to a little soldering, this part on Sparkfun looks like it could help make the perfect color organ. Here’s an tutorial of how to use it.

Otherwise, your intuition of using an Arduino bit is a good one. (I too wrestle with whether this is “cheating” or not!). It could be a good excuse to dive into more advanced coding. I could see a few different ways to accomplish this. Something called a Fast Fourier Transform (FFT) is often used for this kind of thing, but takes a lot of processing power (I think our w6-arduino would struggle with it). Another scrappy way would be to use a few software filters on the arduino. This website has a really smart approach of using EMA filters. But with the filtering approach you’d still need to add the “envelope detector” part.

Whew, there’s a lot here, it’s a cool project idea!

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Good to see you @theterg! Thanks for the well thought out response. That Sparkfun chip looks sweet. If I pursue this idea myself, I’ll be sure to snag one. :smiley: