My first robot was a line follower built on the plastic base I had built a few months earlier. It uses Pololu’s infrared emitter/detector to “see” the line below it. Because its a simplified version of their popular 3pi robot kit, I called it a 2pi.
I wrote about it as my second Instructable, which was also featured and earned me another free t-shirt.
For version 2.0, I switched from an H-bridge IC to building an optimized version from transistors and diodes. I also switched from a home-etched circuit board to an outsourced OSH Park PCB.