Sound Reactive LEDS




About: I love to build things, everything and anything that involves robotics, woodworking, metal working, anything that involves mechatronics. My education plan is to go to sierra college get my General Ed. and ge...

Sound reactive LED's are pretty cool, but you may be wondering what they are. Well there ordinary LED's Just Hooked up to a Transistor to make them flash to the beat of anything electrical. I think its coolest to use it hooked up to music. So I did some experimenting and found out that its possible with the help of a Tip31 transistor. (You can buy these at Radio Shack).
So I got my sound reactive LED's to work and i thought these are cool but there kinds boring. So I wanted to think of something more creative to do with them. So I installed them into my computer desk. i also put a switch box with a main power on/off (slide)  switch so they would either be lit or not lit. But the interesting thing is that I put another switch (toggle) on the box. The other switch acts as a on/on switch so the LED's will be sound reactive,or  have a solid light. I also installed a potentiometer in the box to resist how much power the LED's will intake while playing music so I don't fry them.

Step 1: Supplies

for exactly what I did you will need:

12V DC Wall transformer
On/off slide switch
On/On toggle switch
100 ohm potentiometer
20 ft of 22/2 gauge wire
Green and Blue LED'S
(I used standard Green LED's But High Power Blue LED's)

Step 2: Constuction

Ok  work with this schematic and start from there.

However I added 2 more High power blue LED's in addition to these and there are 15 green LED's in bunches of 3 to a resistor.  You will have to find out the number of ohm you need per resistor depending on your LED power usage. You can find this at


I installed 9 green LED's above my two monitors on my desk another 3 on each side of the monitors and finally the last 2 high power Blue LEDS behind my monitors so there would be a blue grow fade. I strung all the wires and ugly cords behind my desk.
Now of course these grow to the beat of music but I couldn't show that because i don't think I can upload videos.

Step 4: STUCK

Of course every ones project is a little bit different so some people may run into walls on this. if so i am happy to help you.



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7 Discussions


3 years ago

I don't have a tip 31, Wouldn't any transistor work? I would just need to change the current and voltage correct? I have an electronics class right now where i can get many T0-92 type transistors. I have a few larger ones similar in appearance to a tip 31 as well, but there are no markings on them as they were ripped from an old psu from one of my former pc builds. Any help would be greatly appreciated. I would like to make sound reactive leds to put inside my speakers of my stereo. And sorry for the oversized coment hehe.


4 years ago on Introduction

great instructable...I think you forgot to mention the TIP31 in the 'supplies'


4 years ago on Introduction

Hi... i haven't built this yet, but curious, if you plug in to your computer, it shunts the speakers correct? How did you hook up speakers to this?

1 reply

Reply 4 years ago on Introduction

Depending on your computer type and what software version you have it should have multiple options, for mine I run two aux outputs, one for my lights and one for my speakers.


Reply 6 years ago on Introduction

Well it was guess and check mostly, because before I installed the LEDs I had it all on a breadboard.