To create your own pinewood derby timer, you are going to have to custom build your track or even purchase one, which could already have timers installed. If your building your own, you are going to need a computer to plug the circuit board into using a USB port.
Step 1 - Connect the Trigger Switch and Light Sensors
Once you have the materials and have found a layout for your pinewood derby timer, you will want to mount your trigger switch to the starting gate. This will turn the sensors on, and make them look for movement on the bottom end of the track.
Step 2 - Operation
Your pinewood derby timer works on a light sensor in the bottom of the track in each lane. These sensors can reflect back the light from either an overhead mounted panel that is painted white, and when a car moves past it senses the light change and registers the first to cross the line.
Step 3 - Circuit Board Connections
You will mount the circuit board for your pinewood derby timer under the track and connect it to your computer. Use your computer to run the sensor tracking software which can determine movement within 1/1000th of a second.