Picture of Universal box for flashing LED's to music
Alright, in this Instructable I will show you how to create a box for making any led flash to music.

The difficulty of this is a bit above average of understanding.
BUT, i will try and make this as easy as possible, so anyone can build it!

This box will be universal, and you can hook up any lighting to it (that uses DC-voltages of max 50V and 15A) and make it flash.  <---

In action!
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Step 1: What do I need?

Picture of What do I need?
First of all, we need a set of tools.

A Dremel can be useful but is not necessary.
A Drill.
A Gluegun.
A soldering device :)
Cablestripper, and anything else you think you need. .. like good music.

1. Transistor. (NPN)
These come in all sizes and shapes, from my large one, to 35 nanometer.

2. Potentiometer.
I'm using a slider. One with a knob works just as fine.

3. On-Off switch.
Well, self-explanatory, but it's used to cut power.

4. A box.
To hide it all in and protect with.

5. LED's.
To test and party with!

6. Cables.
Because you can't get enough of wires.

Step 2: Preparing the box.

Picture of Preparing the box.
First, we will prepare the box.

We need 6 holes for this particular design. It's possible with fewer, but it requires some homework :) 

I put 4 on the short-sides and two on the longside.

The top two will be where you hook up the power.
The bottom two will be where you connect the LED's.
And the two on the side will be the signals going in. (Speaker wires from the stereo or amplifier)

After the holes are drilled, you either drill a hole on the lid for a potentiometer (knob version) or carve a longer hole for a kind like mine.
Aswell as a hole fitting for the on-off switch.

Make sure your potentiometer fits and slides without anything obscuring the way.
When done, glue it in place or use screws.
DUDE1234567893 months ago

where can i find suitable npn transistors

Dufva (author)  DUDE1234567893 months ago
At a store that Sells these kinds of electronic items :-)
RadioShack, etc

thanks, but I meant finding from broken electronics

Dufva (author)  DUDE1234567893 months ago

hmm.. An older radio perhaps.

Everything modern uses small smd sized components.


Dufva (author)  DUDE1234567893 months ago
At a store that Sells these kinds of electronic items :-)
RadioShack, etc
gianni leake11 months ago

what transistor did you use? also, if i wanted to use loads of led's would i need to use a different transistor or would i just need to change the voltage??

Dufva (author)  gianni leake11 months ago

BUX 127 (or 121) It's a rare transistor. but anything similar works :)
If you want loads of leds, i suggest putting them in parrallell [Spelling??]
To a certain point though, the transistor has to be able to handle the power.

if you hook them up in series, you need to crank the voltage and there are more risks to that.

to'neal211 months ago
im not getting much of a difference with the light changes should I use a different potentiometer? ?
Dufva (author)  to'neal211 months ago


Is it only bright, or is it very dim?
And is the volume turned up to "normal" ?

rubbish121 year ago
Hi I listened to a lot of classical-orchestral music, based on your frequency pot I assume this will only work on bass heavy music? Thanks for posting.. Will try it out but looking for a more high frequency sensitive module.
Dufva (author)  rubbish1211 months ago

Hi! sorry for the late reply :)
It will work for higher freq's. However, you will have to play at a louder volume, and it might not be as responsive and jumpy as when the bassline plays. (depending on the music ofc)

But it works :)

zomfibame1 year ago
I like this. nice n' simple. and it's not going all crazy with all sorts of over-kill to do something very cool but very simple. and I love how simple and basic the graphic for the schematic is as well. nice and easy to follow.
mehdi hdmi1 year ago
salut tt ou je branche les deux fil de signal ,par ce que je suis débutant dans le domaine et merci
ijo30001 year ago
OK I'm confused. im new to this whole thing, so where do I hook the source wires to? in between the radio and the amp? or in between the amp and the sub?
Dufva (author)  ijo30001 year ago
Alright, let's untangle the confusion then :-)
First the signal comes from your radio to your amplifier, then from the amplifier to the speaker.
All that way you have a signal.
You can split a wire at any point, after the radio or after the amplifier, and still make it flash.

The DIFFERENCE is that you get a higher signal (brighter flash) after the amplifier, due to well, it amplifies :-) ..

What I've done myself is I've put two extra cables from the speakerterminal of my subwoofer that is connected through an amplifier and a low-pass filter, so the light flashes with the base-line :-)
ijo30001 year ago
oops I meant signal
EET19821 year ago
I used 2 TIP31C's to add both left and right channels, a switch, and an led to know when it is switched on. Also added the ability to tighten down the wires to the board so I don't have any wires hanging out when I store it. Thank's for the idea!
Dufva (author)  EET19821 year ago
Looks nice, but don't forget a potentiometer, or two, otherwise the LEDs are only controlled by the stereos volume :-)

And thank you too for posting the pic!
EET1982 Dufva1 year ago
Very true.I'll try a 10k and go from there. Thank you for reminding me, I totally forgot. :)
Walkerion1 year ago
That's so cool. I wonder if there's a way to wire it so there are three lights for three different frequencies. Like a bass, mid and high. That would be awesome.

Is the audio source just the positive of any speaker cable?
Dufva (author)  Walkerion1 year ago
Oh yes, it's possible :-) !
But it gets a little more complicated than this basic version.

From the top of my head I'd say you need to have an audio split where the cables from the audio source come in, then have a low-pass filter for one, high pass for the second and a bandpass for the third, then each one connected to one individual transistor which powers your three colors :)
It's not harder than that I believe!

Now, you can make those filters for 3$ from 2-6 parts. So it's not that hard, and I'm thinking of building it myself later on.

And yes, the audio source is the positiv AND negative speakerwire :-)
EET19821 year ago
What size pot did you use? I am really wanting to make this but unsure of the size. Thank you for the very cool instructable :) I think when I make mine I will make it work with left and right channel audio. Adding a dual gang pot and 2 high voltage transistors. Going to be epic :). All thanks to you lol.
Dufva (author)  EET19821 year ago
My instrument says it's 22k at max.
I tried it hooked to my subwoofer, and when it's going at very loud volumes, around half of the slider is enough to make the LEDs go black.

Sounds nice with left and right :-)
I will do that myself sometime in the future, but in a smaller size!
EET1982 Dufva1 year ago
Cool thank you. I'll be working on mine soon. Take it easy!
sailerj1 year ago
Cool concept! I think the only improvement might be a resistor placed at the base of the (transistor of your choice). Believe me, I have had enough of these blow up in my face! I suggest starting in the 1K range! :)
Dufva (author)  sailerj1 year ago
Oh I almost forgot, I have the potentiometer connected to the base-pin, so whenever it's too loud or signal too strong, I can tweak with it :-)
Dufva (author)  sailerj1 year ago

Okay okay, I'll take that into consideration when I'm making them in the future :^)
But this particular transistor can handle 50V and 15A, so it melting by normal volumes won't be a problem.. (I hope :) )
you wouldn't be able to use this with a regular house light or lamp, correct? Do you have any insights on getting that to work in a way that wouldn't burn out the circuit?
Dufva (author)  MadBricoleur1 year ago
I'm afraid that it won't work, at least with this transistor. Find one that can handle the voltage required (110-230) with some headspace and it should work.
Then, I don't know how transistors work with AC power. But a rectifier should solve that :-)
Verticees1 year ago
Sweet job man! You can call it "Box of the Lords". Haha, just kidding, but great job on this Instructable!
Dufva (author)  Verticees1 year ago
Haha maybe later on :D, thanks!