Racing is a lot of fun. But if you want to compare the results of multiple races, you need be able to accurately record the finishing times of each one. To do this, I designed a timer circuit that will automatically record the finishing times.

Two light sensors are mounted on a track. The first one is positioned just in front of the starting line. The second is located at the finish line. When the car crosses the first sensor, it starts the timer. Then when the car crosses the second sensor, it stops the timer. This lets you automatically record the finishing time of each car.

The system that I built is tailored to toy car races (such as pinewood derby or CO2 Dragsters), but it can easily be adapted for other kinds of races.

Step 1: Watch the Video

Here is a video walkthrough of this project.

Hey there, would using N.O switches work instead of sensors?
The trick would be how to activate the button with out interfering with the car. You could use a normally open switch at the finish line pretty easily. Just set up a backstop with switches facing the cars. Then when the car crosses the finish line, it would run into the button and press it.
<p>amazing idea!!</p>
<p>I like the idea, but we have 3 tracks for our pinewood derby track. </p>
Oh what a great idea! :)

About This Instructable




Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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