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I made this track timer for my son's 3rd birthday party. It's based on David's PDT (http://www.miscjunk.org/mj/pg_pdt.html), though with a few modifications.
- Single button operation
- Automated start gate, self resetting
- 1.2" tall green LED 7 segment displays
- Displays finish places, and winning time
- 4 lanes of Blutrack
- Red Laser Diodes
- Photo transistors mounted in black tubes pointed down, meaning full sun operation.
- Rechargeable Lithium Polymer battery pack for all day play with out plugging into the wall
The housing is made from garbage from the jobsite (I'm an electrician by trade). I 3D printed parts to fit PVC pipe to make the feet. The button is a 3D printed housing of a random button I had laying around, just to make it BIG and fun. The start gate is powered by a servo from an RC car. It's linked to the timer housing with a shield CAT5 patch cable, which supplies 5V, as well as the signal wire for the servo, and the input wire for the button. The single button makes it easy for the kids to have fun with the track with minimal input from an adult. The kids load up the lanes with cars, and hit the button. The timer displays a countdown, and the gate drops. Cars hit the laser beams, and the timer displays the places. Then it shows the winning time, and the start gate resets. The kids can run it all day all by themselves.
My son and his friends, as well as a few of the adults, had a blast with this at the birthday party!
See the next post for more build pictures.