Universal Box for Flashing LED's to Music




About: 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 business, and i L0V3 taking pics :D

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.

http://p.videofy.me/v/1811736  <---

In action!

Step 1: 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.

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.

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.

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!

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.



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    39 Discussions


    3 years ago

    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.

    2 replies

    Reply 3 years ago

    did you use bux127 transistor


    Reply 3 years ago

    Now when you mention it, I think I did.


    3 years ago

    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.

    1 reply

    3 years ago on Introduction

    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?

    1 reply

    Reply 3 years ago


    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 :-)


    Reply 4 years ago

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


    Reply 4 years ago

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

    gianni leake

    5 years ago on Introduction

    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??

    1 reply
    Dufvagianni leake

    Reply 5 years ago on Introduction

    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.


    5 years ago

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

    1 reply

    Reply 5 years ago on Introduction


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


    5 years 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.

    1 reply

    Reply 5 years ago on Introduction

    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 :)


    5 years ago on Introduction

    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.