Plug this circuit into an audio source and the LEDs will blink to the rhythm of the music. All it is really is using the voltage from the audio input to activate a transistor and turn on the LEDs.
This is circuit is very customizable. The setup of the lights is really up to you. The main thing to consider when choosing layout for the LEDs is your audio source and the power supply you will be using.
For this particular one I choose to make it run off a 9v battery and use an IPod for input.
Step 1: What You Need
Superbright LEDs, the number and color is up to you (I used 4 blue ones).
2 x TIP 31 NPN Transistor, the heart of the project.
Audio cord (a headphone cord will do or just an 1/8 inch jack)
case (I used a spare thick cardboard box)
9v battery clip (or the power supply you are using)
Step 2: Hooking up the LEDs and Transitors
***NOTE you can add more LEDs in series or a resistor depending on the voltage of the power supply.
2. Now connect the Cathode of the first LED to the middle pin of the TIP 31 (the collector).
3. Repeat steps 1-2 again (for the second part of the stereo input)
4. The Anodes of the last LEDs go to positive voltage.
5. The right pins of the TIP 31s (emitter) go to ground.