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We created a modern Pinewood Derby Car that could be controlled with Silicon Labs' Thunderboard React MCU and app.




We wanted to utilize Silicon Labs' Thunderboard React MCU which contains a Bluetooth Low Energy module, two LEDs (green and blue), two switches, an accelerometer/gyroscope, and plenty of GPIO pins. The app can connect to the Thunderboard via Bluetooth and can display the orientation and speed of the car in real time. You can also turn the two LEDs on/off via the app. Initially we intended on using the orientation and speed data to trigger lights and sounds, i.e. when the car is accelerating a revving sound could play and when decelerating a braking sound/light could trigger. We quickly found out that accessing the real time car data was beyond our software skills, so as self respecting engineers we created a hack!




Since the only inputs we had access to via the app were turning the LEDs on/off, we decided to use those as triggers for our lights and sounds. When a LED was turned on, the respective GPIO pin would drop from 3.7 V to 0 V. This was used to send a signal to a connected Arduino that was then connected to an Adafruit Soundboard module. The Arduino would listen for either a high or low signal and send that signal to the Soundboard, which would play either the revving or braking sound file on loop. 






Wiring Diagram.jpg                                                                                                                                                                Software:


You can check out the Arduino code and sound files on GitHub:



Derby Car Body:


Both the derby frame and outer shell were 3D printed (Ultimaker 2+) so that we could secure all the electronic hardware in an organized way. The wheels were machined on a desktop CNC (Nomad 883 Pro) out of acrylic sheets. Keeping with our pickup truck theme, we added a payload to the bed of the truck body using stainless steel balls. The idea was to increase the total mass of the car so that it would have higher inertia coming off the derby ramp. The front hood of the truck has vents cut out for the speaker underneath.





Thanks to Silicon Labs for providing the Thunderboard React module and thanks to everyone at the Derby Race that helped us win Hottest Design!

  • Bluetooth Low Energy
  • Projects
  • Interface
  • Wireless
  • Sensors