Instructables user ‘computergeek’ sent in this Arduino Charlieplexing tutorial. It’s a great technique for controlling a lot of LEDs without having to use up all your I/O pins. In this example, only 4 pins are used to control 12 LEDs.

I noticed that there weren’t many instructables on charlieplexing using an arduino, so i made this. I tried to keep the project simple, but that didn’t work very well. The soldering is complex, I wouldn’t recommend this as a first time soldering project.

In the Maker Shed:
Makershedsmall
Arduino Family
Make: Arduino