I'm looking to create a cheap photogated timing circuit to measure the time it takes model cars to go down a short ramp. It's based on an idea we saw at Legoland, where you can build different cars and test them down a ramp to see which design is fastest.
Technical photogating equipment is very expensive. For this application, something imprecise would be fine. I thought about hacking a stopwatch (
as in this project), but using infrared beams (cheaper/safer) instead of lasers. I didn't fully understand the circuit in that project, and wondered if the first beam needs to latch or shutoff once it's broken to prevent a false second signal that would stop the watch -- for example, from a second axle.
Does anyone have a simple idea on how to do this? Maybe there is a kit that does this already?
I'm a novice with circuits but do understand soldering, switches, and basic components.
Thanks!