Raspbery Pi-newood Derby

Andre Miron’s Pinewood Derby Instant Replay System (sorry, not sorry for the pun in the title) uses a Raspberry Pi to monitor the finishing line and play back a slow-motion instant replay, putting an end to “No, I won!” squabbles once and for all.

Pinewood Derby

For those unfamiliar with the term, the Pinewood Derby is a racing event for Cub Scouts in the USA. Cub Scouts, often with the help of a guardian, build race cars out of wood according to rules regarding weight, size, materials, etc.

Pinewood derby race car

The Cubs then race their cars in heats, with the winners advancing to district and council races.

Who won?

Andre’s Instant Replay System registers the race cars as they cross the finishing line, and it plays back slow-motion video of the crossing on a monitor. As he explains on YouTube:

The Pi is recording a constant stream of video, and when the replay is triggered, it records another half-second of video, then takes the last second and a half and saves it in slow motion (recording is done at 90 fps), before replaying.

The build also uses an attached Arduino, connected to GPIO pin 5, to trigger the recording and playback as it registers the passing cars via a voltage splitter. Additionally, the system announces the finishing places on a rather attractive-looking display above the finishing line.

Pinewood derby race car Raspberry Pi

The result? No more debate about whose car crossed the line first in neck-and-neck races.

Build your own

Andre takes us through the physical setup of the build in the video below, and you’ll find the complete code pasted in the description of the video here. Thanks, Andre!

Digital making in your club

If you’re a member of an various after-school association such as the Scouts or Guides, then using the Raspberry Pi and our free project resources, or visiting a Code Club or CoderDojo, are excellent ways to work towards various badges and awards. So talk to your club leader to discover all the ways in which you can incorporate digital making into your club!


Andre avatar

Thanks for the shout out! It was a fun project for sure, looking forward to seeing how the scouts like it at our actual derby next weekend!

Alex Bate avatar

Excellent. Be sure to tweet us some photos.

Jason Ament avatar

This is really cool! These systems can be really expensive. it’s cool to see a maker community solution to it.

ameyring avatar

Nice and great to see it being tested on Matchbox cars to make sure the beams are tripped from smaller-than-wood derby cars so this could be applied to many different car races.

Andre avatar

Here is footage from our derby last weekend. This incorporates cell phone video along with the slow-mo instant replay. We discovered that lighting indoors wasn’t the best for the piCam, so I’m working on adding some bright LEDs to the system to illuminate the finish line and get us less speed blur next time around.


In addition to the LEDs, the next version will include a manual trigger to allow us to watch the instant replay again. Time permitting, I’m thinking of adding a second pi with a camera looking up at the start so we can get a full replay, as well as doing text overlays to display the elapsed times and differentials.

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