When I was a teen, I joined an electronics club and built a disco board. I had 5 light bulbs, I painted them different colors. Then I built a board which was connected to these light bulbs. I'd connect my stereo to the board and the each light bulb would flash when a specific instrument would play (e.g. green for drums, etc...).

I want to build something similar with my son now, but I totally and utterly forgot how to do this. Can someone point me in the right direction?


You could look at triggering different lights with amplitude, like a VU meter. This is a cheap 5 LED digital VU meter ->


I've used it before to drive some LEDs on a kinda birthday card thing, I plugged the card into my Ipod output, and the 5 LED flowers on the card flashed with the music!

You could hook the output pins to some transistors which could then drive your colored light bulbs, it would be much cheaper and easier than using a micro controller. This would give you a regular audio level meter much like the one on a mixing desk, you could however change the order and color of the lights to mix it up a bit, so it's more of a light show. The lights also fade in with the increase of amplitude rather than just flashing on at a set value, so it would look cool.

Otherwise you would have to take a look at frequency analysis, whereby the lights could be triggered by the audio level at different frequency bands (one per light). This system would closest resemble a disco light that flashes with the different instruments in an audio track, but it's much harder to implement when compared to amplitude analysis. I'm sure a modern MCU would do the job with ease tho, with only 5 lights the resolution on the analogue inputs would not be a huge issue. If you could find some code to steal this option wouldn't be that hairy, if you're familiar with micro controllers.

|improve this answer|||||
  • \$\begingroup\$ If you give me a better idea about what result you're after, bearing in mind how complicated you wanna go, I could point you in the direction of something more specific. Peace \$\endgroup\$ – Jim Jan 18 '10 at 12:34
  • \$\begingroup\$ @Jim, It would be good if you could point me to board layout. \$\endgroup\$ – Angryhacker Jan 19 '10 at 15:59
  • \$\begingroup\$ No board layouts spring to mind, but there are loads of circuit diagrams for simple LED VU meters, for instance there's one in the data sheet for the LB1403N. Unfortunately you would have to modify the circuit in order for it to work with Light bulbs. I'll keep an eye out for something more suitable, tho. \$\endgroup\$ – Jim Jan 19 '10 at 17:30
  • 1
    \$\begingroup\$ If you want a convincing disco light you will probably need to delve into using a programmable chip. This example -> electronics.rory.co.nz/projects/lighting/disco_lights.php Shows a basic DIY implementation of a sound activated disco light using a cheap picaxe micro controller \$\endgroup\$ – Jim Jan 19 '10 at 17:39

Your question stirred some cobwebs deep in the recesses of my dusty brain. I seem to remember building such a thing myself way back when. I don't remember the specifics, but if I recall correctly, we used RC filters to segment the incoming audio signal and SCRs to trigger short strings of 110V AC Christmas lights. Probably a transistor to drive the SCR. These things were all the rage, along with strobe lights, back in the late 70's.

|improve this answer|||||
  • 2
    \$\begingroup\$ Hi again - my terminology brain kicked in and I remembered that we called these things "color organs". Discovercircuits (discovercircuits.com/C/color-org.htm) has a couple of schematics that might get you what you're looking for. The one by Randy Linscott looks pretty close to my recollection of what I built a million years ago. Good luck. \$\endgroup\$ – DuaneFBenson Jan 22 '10 at 22:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.