How to Make LED Lights Flash to Music in a Car.




Posted in TechnologyLeds

Introduction: How to Make LED Lights Flash to Music in a Car.

This Instructable will show you how to make a LED Controller that can be directly wired to a car sub woofer amplifier or standard speaker output. It is constructed entirely of recycled parts and may cost you nothing.

I chose to make this Instructable as I was unable to find a device similar to this available for purchase

A Video of it in action is attached as it takes too long to convert. You probably need Quicktime or VLC.

The controller uses a 12V SLA battery and a transistor to control when the lights should be active by monitoring the speaker output. It works best when wired to a subwoofer as it only activates the lights when a beat is present.

You will need:

A box to put it in (I used an old Pioneer home theater speaker)
A Heavy Duty Transistor( The transistor I used was a ST W14NC50 from an old Compaq power supply unit)
A soldering iron
A switch (optional)
3 Speaker input ports(don't know what their actually called)
A 12 Battery. (Make sure the voltage isn't to high over 12V as you may blow the LED's)

Step 1: Constructing and Soldering the Circuit

Construct and solder the circuit using the transistor you have sourced. It is best if the transistor is attached to a heatsink in order to prevent it from overheating and failing.

Step 2: Test the Circuit.

To test the circuit find a battery with a 12v charge. Connect it to the red and black wires. Connect the two orange or amplifier wires to a smaller battery such as a 3V computer battery. If all goes well the LED's will light up. If not, try reversing the polarity of the 12V LED strips or testing them with the battery itself.

Step 3: Making It Look Nice.

In order to make it look neater and to easily mount it within a car you should mount it within a box. I used an old speaker as it already had a port that could be used to wire the LED's into. Any small box should do though.

Step 4: Add Any Finishing Touches

To my LED controller I added some aluminum checker-plate and engraving to make it look more solid and personalised.

Step 5: Installing the Controller

To install the controller mount it to a suitable place in your car. I would not recommend connecting it directly to the car battery unless you add some sort of circuit that regulates the voltage as it will otherwise blow the LED's.

Connect the LED's to the controller.
Connect the two wires to the subwoofer or speaker amplifier, ensuring the channel they are connected to is active.

A Video of it in action is attached as it takes too long to convert. You probably need Quicktime or VLC.

Do not use this system while driving as it is likely you will get defected and have to uninstall it. Try to keep it off when on the road. I DO NOT ACCEPT ANY RESPONSIBILITY for any damages it causes you, be it damage to your car, damage to your lights, battery, etc.

It works well as a show-off piece with friends as it is difficult to purchase a similar system.

And that's it. I hope this tutorial was useful to you.



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    hi i built this but when connecting the power up the led just stays on? pllease help!!

    Hey, so I'm looking to do something to make a mounted light bar sound reactive. Would you recommend this process or are there any other ideas? I'm stumped...

    Hey, so I'm looking to do something to make a mounted light bar sound reactive. Would you recommend this process or are there any other ideas? I'm stumped...

    All very good points. I'd just like to add/correct however, that it's mainly current you're actually concerned about with leds, not voltage... Generally, limit an led to 10-20ma depending on the type of led. Also, as they are a diode, each one will cause a slight drop in voltage and/or current. Which it drops is dependent on whether they are wired in series or parallel, or both. Nice work though! Simple, fun, rewarding little project.

    you sir are awesome :D
    btw its called "diamond plate" lol

    Do us a favor and make a video of you making it please. Also im hooking it up to my subs in my house, so it will only light up when the sub is going but i plan on adding other lights to the regular speakers to.

    Hi I really like your 'ible, I don't have a subwoofer or an amp in my truck
    Would I just find a wire the outputs to any speaker and tap into that? Thanks in advance for your reply, or anyone's.

    Here is a simple addition to your circuit to provide voltage regulation.


    Voltage Regulator1B.jpg

    F.Y.I. --- good quaility and reasonably fast video conversion program free here:;1 Using this only took about 40 secs to make your video into .avi format that will play on windows media player. I have attached the result to this comment so it's ready for other readers to view. You have my permision to cut it from my comment and add it to your instructable if you like!!Also, I agree that you should add a voltage regulation curcuit to your design between your battery negitive and your transister to prevent an overload to your leds and burning them out prematurely. Otherwise,nice able! Happy brainstroming!

    Quote of the day--"Pirates are always cooler than Ninjas"

    G'day mates

    you sould put in some sort of voltage regulator. normally in a car the alternator will push the overall voltage as high 15 vols which could result in blown LEDs. of course a resistor works just as well or even a relay connected to the REM the has a resistor iat the end of it. I may be able to draw u a schematic but honestly im just thinking out loud here.

    anyway great instructible! I will definatly look into building this for my soon-to-be sub system for my car

    2 replies

    Thanks for that, I forgot about the varying voltage. Was also thinking that you could just use an external battery such as a small SLA 12v and you would not have to rely on cars varying voltage,

    True. What you could do as well is just get like a 12v battery charger and use that for the power source. I would think that would have a voltage regulator as well