Vernier Photogate
Contributors:
bri_huang
bri_huang 
Our First Prototype
Using a standard Arduino UNO, an LCD screen, and a pair of Photo Interrepters, we started with a proof of concept design.
This prototype was a great success. We modified stopwatch code from Dan Thompson. Unfortunately, this prototype was far from ready to be put in the hands of kids. I still needed to find a cleaner, tighter solution. The first part I needed to replace were the small photo-interrupers (photogates) you see in this picture.