A few years ago the finish line detector at my church’s AWANA Grand Prix track bit the dust. AWANA Grand Prix is the same thing as the Pinewood Derby to scouting folks. We did without for a couple years until I finally got all the pieces together for a new one. First I’ll explain the end product; then comment on my wish list for a future version. Special thanks to my coworkers Gerry Powell and David Fowler for their electrical engineering design help on this project.
This article was submitted by Ed Wilson as part of the “Hobby parts for articles” program. Write something of interest to electronic hobbyist and receive parts for your next project.
Here is the finished system in action. It worked flawlessly.
The system uses two thru-beam optical sensors to sense the cars as they break the beam at the end of the track. The sensors were tied up with two D-type flip-flops. The flip-flops were wired so that the winner would light an LED and hold the other flip-flop in reset. A simple push-button switch was used to clear the flip-flop’s for the next race.
Here is the schematic and parts list. The LED’s we used were too small and dim; it’s what we could find at the time. Hope this helps if anyone is looking for a simple finish line detector. Hopefully you’ll have more time to spin a proper board and make things a little neater. Good Luck.
- +12v power source,B1
- Sensor—-Q1,Q2 (SunX EX-13EBD)
- LED source (not shown)