The folks over at blondihacks are gearing up for an event called “The 24 Hours Of LeMons” which is a form of low-budget endurance racing involving cheap cars, heroic repairs, wacky themes, and a lot of serious driving. The format of the race is pretty simple, the cars race around the track continuously for a set amount of time (usually 12 or 24 hours), and the goal is to complete as many laps as possible in that time.

In order to be racing that long each team has multiple drivers, and a in car timer would be especially helpful. While commercial models cost a pile of money, the team was able to source a dual clock / stopwatch with a nice big display, and hack it up with an Attiny13. The stopwatch is deactivated when the engine is off, and reactivated when the engine gets turned back on.

Now when one driver’s turn is up they come in for a pit stop where the engine is shut down for saftey reasons. When the new driver is ready to leave, the clock automaticly resets for them and they can get on with the race.