Introduction: Universal Box for Flashing LED's to Music

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!

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.

Step 3: The Transistor.

Picture of The Transistor.

Now we are attaching some wires to this intruiging piece of IC.

But before i go into serious B,C,E - writing, here is some info on how it works.

The transistor is like an amplifier.
It uses a small current to activate a bigger one.
When the small current gets bigger, the bigger one gets even bigger.

In this case, the small current is from my speaker-wires. When the base-lines roll it pushes more voltage through the wires, and this is what will make our "bigger" current to make the leds flash, or shine brighter.

This is why it's better to use a transistor for flashing with music, rather than just hooking it up straight to the speakercables.
I Measured my subwoofers Voltage-range, and it goes from 0V -> 12+V and if your LED's are made for 3V, you can imagine the poof they do. Since here we have a voltage-roof.

The transistor consists of three legs (can be more)

The Base
The Emitter
The Collector.


The current wants to flow through from the Collector to the emitter, but it can't unless we have voltage on the base.
Imagine a switch on a wire. You press on it with your finger, you then control the current inside the wires to flow, or stop.

Now a transistor is smaller. So imagine your finger is replaced with a current. (this way we can make it smaller)
The current turns the switch on. But instead of just I/O, you can push harder, and get more flow, and vice verca :)
When you have it pressed at max, you will get what you have it hooked up to. 12V-car battery, or maybe a 3V-battery? (if you have it directly to your subwoofers lines, there aren't really a max)


Just typing this makes my head spin, so let's continue!

My transistors pins from left to right are, Base - Collector - Emitter.

So solder one wire to each pin, and two wires to the emitter (think of it as the pin that emits the power, this will be connected later to the negative pool of the battery, and signal.)

When you are done with the soldering, glue it to the inside of the box.

Step 4: Wiring It All.

Picture of Wiring It All.
Here is where it gets VERY messy.

So follow these simple steps and you should make this work like a charm!
  1. First cable goes through the box from top left corner to the I/O switch (this is the cable you put on the + Pool on the battery)
  2. From the switch out the bottom left hole. Cut it here, this is where you connect the LED.
  3. The collectors wire you put through the bottom right hole. (Middle pin) This is where you connect the LED's other wire.
  4. Drag one wire from the emittor (right pin) out through the top right hole, this will be the negative pool on the battery or powersource.
  5. Drag the other wire out on the side of the box from the emittor. This will be the negative for the audiosource. (though it's AC "there is no negative")
  6. Final wire is from the base (left pin) this goes to the potentiometer.
  7. Then from the potentiometer out through the side hole.
Dont forget to solder it all in place.

You can use hot-glue to fix your wires to the holes so they can last a few tugs and don't break.

Step 5: Done!

Picture of Done!
Alright! You are done!

It looks .. like a crab, but it will get the work done! .. But yes, how does it work?

You are in luck, it's universal.

first you connect your LED's. (I'll use 12V-leds in this case) to the bottom wires.
Then you connect the powersource which in this case is max 12V DC.

Lastly connect the audiosource, and turn it on, crank up the volume!!!
Now you will notice it almost only shines brightly.
Mix with the potentiometer (Sensitivity stick) and watch it become more awesome :)


Other notes:

It IS POSSIBLE, to use a higher power-voltage to make lower-voltage LED's flash, but you will have to use the potentiometer carefully, so it stops enough power from the audiosource. (which controls the input voltage)

I have noticed that it's easier to make lower-voltage leds flash, than higher voltage.
If you, like me, use the speakerwires from the big stereo, it's not a problem with 12V LED's. since the audiowires spew enough voltage to make them flash, even too much when i crank the volume.


Dufva (author)2016-04-25

It's been a very long while ago since I made this, I'm sorry but I don't remember the values for the one i've used in the instructable.
And the transistor was already outdated when i made this, so you can find a better one than this one I guess!

Try a 10k ohm potentiometer, or a 100k ohm.
You can use almost any transistor you can find in the stores. But darlington is one you don't need, since it's like on and off when the current flows in those ones.

sohampatel (author)Dufva2016-04-25

did you use bux127 transistor

Dufva (author)sohampatel2016-04-26

Now when you mention it, I think I did.

sohampatel (author)2016-04-22

can you plesae give me the exact values of the transistor and potentiometer.means which transistor and how many ohms of potentiometer will work best for this project

i am new to electronics.

sohampatel (author)sohampatel2016-04-24

pls give the answer i want to make it

JP04294 (author)2015-07-01

Hello, I really like how you use just enough detail to break things down simply, it shows a solid understanding of the subject. I have been looking for something(like this) to integrate into my car led project, wherein led strips flash to the beat of the music played through the speakers. I was wondering, what do you think would be the best way to hook the speaker input and power source for this specific build? Also, would you be willing to make one and ship it, for a price?

Dufva (author)JP042942016-01-06


The most simple way would be just to pull another wire from the speaker through to the box.

Then pull one wire from the +Battery, and one to the metalframe for ground.

And I'm sorry, I don't make these on order :-)

DUDE123456789 (author)2014-12-02

where can i find suitable npn transistors

Dufva (author)DUDE1234567892014-12-03

At a store that Sells these kinds of electronic items :-)
RadioShack, etc

DUDE123456789 (author)Dufva2014-12-07

thanks, but I meant finding from broken electronics

Dufva (author)DUDE1234567892014-12-07

hmm.. An older radio perhaps.

Everything modern uses small smd sized components.

DUDE123456789 (author)Dufva2014-12-13


Dufva (author)DUDE1234567892014-12-03

At a store that Sells these kinds of electronic items :-)
RadioShack, etc

gianni leake (author)2014-04-16

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 leake2014-04-23

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'neal2 (author)2014-04-09

im not getting much of a difference with the light changes should I use a different potentiometer? ?

Dufva (author)to'neal22014-04-23


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

rubbish12 (author)2014-03-17

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)rubbish122014-04-23

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 :)

zomfibame (author)2013-09-23

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 hdmi (author)2013-09-11

salut tt ou je branche les deux fil de signal ,par ce que je suis débutant dans le domaine et merci

ijo3000 (author)2013-07-31

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)ijo30002013-08-01

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 :-)

ijo3000 (author)2013-07-31

oops I meant signal

EET1982 (author)2013-05-28

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)EET19822013-05-28

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 (author)Dufva2013-05-28

Very true.I'll try a 10k and go from there. Thank you for reminding me, I totally forgot. :)

Walkerion (author)2013-05-27

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)Walkerion2013-05-27

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 :-)

EET1982 (author)2013-05-26

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)EET19822013-05-27

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 (author)Dufva2013-05-27

Cool thank you. I'll be working on mine soon. Take it easy!

sailerj (author)2013-05-23

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)sailerj2013-05-23

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)sailerj2013-05-23


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 :) )

MadBricoleur (author)2013-05-22

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)MadBricoleur2013-05-22

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 :-)

Verticees (author)2013-05-21

Sweet job man! You can call it "Box of the Lords". Haha, just kidding, but great job on this Instructable!

Dufva (author)Verticees2013-05-22

Haha maybe later on :D, thanks!

About This Instructable




Bio: I'm an amature engineer, love to build things that use lights, lasers, LED's.. you name it. Other from that, i run a Photography ... More »
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