Last year, I bought a robot arm and “modded” it a little bit with custom electronics. Specifically, I created a USB controller board for it to be able to programmatically control it from my computer. This was also aimed at getting some use out of my Arduino micro controller boards that I bought the summer before. So, the tightly scheduled two-week USB controller project was created. In the end, it took a bit longer because of a redesigns of the input power supply but the final design looked like this:
You can have a look at the USB Robot Arm Controller page for more information. The article currently focuses mainly on the electrical design of the board. I might add a second page later this year that will focus more on the controller software for the robot arm.