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You ever go down the road wishing you could move to the beat? With this LED mod of your existing car stereo you can enjoy your music in sound and light. This modification uses the bass frequencies to alter the brightness of the LED's attached by the floorboard. We decided to use the bass as most beats are around bass frequencies. 

Step 1: Materials

1 car to be pimped out
1 source 12-14.4v power supply (look for two wires going to an unused fuse)
1 existing radio system

2 color wires (18-22 gauge)
4 Blue 4-Pin High Brightness Power LED model # 276-023 (radio shack) $2.49ea
4 Green 4-Pin High Brightness Power LED model # 276-027 (radio shack) $2.49ea
4 TIP31 NPN Transistor (radio shack) $1.69ea
4 resistors 330 ohm 1/4 watt (orange orange brown) $1.19 5pk

Soldering gun or electrical tape and wire nuts
voltage tester (ensure that you will not blow the LED's and that you have them in right direction)
Patience and a good flashlight is recommended but optional

Step 2: How It Works

To power your LED you need to have an external power supply besides the voltage from the audio cables. The LED's we used operate typically around 3.5-4v DC. An audio signal from your mp3 player is less then .4v AC. We will adjust the power supply from the car to give our LED a head start of 3.5v and the audio signal will increase the voltage +- .4v from 3.5. Transistors are used to limit the frequency range powering the LED's and only when those ranges are in effect will the LED's be on. Without the transistors the LED's would constantly be flashing and overall it would appear busy or noisy. Many cars have four speakers (Left Front, Left Rear, Right Front, Right Rear). Each speaker will have a unit spliced on consisting a transistor, resistor, blue 4pin led and green 4pin led. This is done that each LED unit blinks to its respectable speaker. Multitrack audio recordings split the music over the different speakers giving a surround sound effect. If only one transistor was used the LED system would be mono. 

Step 3: Diagram Hookup

Each speaker has its own transistor, resistor, blue led, and green led. The positive supply voltage goes to the resistor that goes to the positive anode which attaches to the other led anode that attaches to the collector of the transistor. The transistor emitter attaches to the speakers positive wire. The transistor Base attaches to both the ground of the supply voltage and the negative speaker wire. Thats it for one unit. Do this to each speaker and the hookup is complete. Once hooked up the music is ready to test.  

Step 4: Testing

Check out the youtube videos from my ipod camera demonstrating the system. It looks really cool at night although it may appear to dark on the video as ipod cameras are not made for low light conditions. 


U should hook it up to your car battery and put 2 led strips in each foot well and hook up to stereo and it will look better and have more light also put a standard switch so u can turn it off
Is there a way to wire a toggleswitch into this setup? IE if the switch is flipped "off" then the lights are completely disabled and do not flash/light up even if music is playing?
The buzzing noise is probably because you have the negative speaker wire conected to the Base conector of the transistor and the negative side from the power supply. Im dont know a lot about electronics but i am a mechanic. Whats going on is that the current from the alternator is feeding the speaker also so when the car is on it starts to buz. i havent given it much thought but u should probably check this out... XD<br>
It's challenging to help you with this situation based on the details described. Properly hooked up the LED's will not be on. Only when the radio has base frequencies will the LED's light up. It would be typical for the LED's to be off when the transistor is hooked up. However I don't think there should be a buzz from the speakers though. What may be happening is the speakers are drawing from the 12-14 v power supply, this is to do with how the transistor is connected. It's been a while since I have done the wiring for this connection so defiantly check the transistor hookup. Check on the bag the transistor came with to see what the wiring diagram looks like. locate the E (Emitter), C(colector), B(base) poles. I'm sure that the negative power supply is connected with the base. <br><br>My other idea why it might not work is that the transistor is hooked up with the speaker in series rather than parallel. You should be using both speaker wires in the hookup to the transistor. If you are only using one of the two speaker wires then that is most likely the case. I can't be too sure though. Is it possible to take a picture of your hookup. I might be able to get a better idea of what is wrong if I had a picture. Thank you for your comment.
When I hook up the LEDs to the power only, they work fine. However, once I hook up the transistor, my speaker buzzes and the LEDs are on for a moment, but once the radio turns on, the speaker and LEDs both turn off. Any suggestions?
I would mount them an inch or so further back, hiding the leds, but so you're still able to see the light. Otherwise, solid idea and solid diagram. You could use some more detail on the actual install, but other than that, I like it.

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Bio: I am MacGyver McDaniel, yes just like the tv show. Instructables is an awesome website to where I plan on sharing more great instructables.Technology ... More »
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