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.

DSCN7847.AVI
Download

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.