Via the Adafruit forums, user beermat shows a rules-compliant Pinewood Derby car that is decorated with lights, sound and video.
Presenting “The Light Fantastic v2”, a rules-compliant Pinewood Derby car that is decorated not with paint and stickers, but lights, sound and video, with (almost) all products obtained from Adafruit! Under the hood is a Teensy 3.6, powering 47 NeoPixel lights (3 Sticks, 1 Jewel, 1 Ring and 4x individual), one small LED back-light underneath, an Adafruit 1.54” 240×240 TFT display (removed from the breakout), a small “SugarCube” speaker, PAM8302 amplifier and a LSM9DS0 9DOF sensor.
User input comes via a small digital joystick and two micro push buttons, as well as tilt sensing. Various animations are programmed in to show on the display and/or NeoPixels, as well as the ability to play video at ~37 fps full screen (1:1) and ~50 fps letter-boxed (3:2). A custom built menu system adds additional goodies, such as a photo viewer, music player, video player, settings, calibration of 9DOF sensor, and access to games like Pacman and Flappy Birdz! A 400mAh LIPO powers this all for around 3 hours, but it can run off tethered USB power too.
The Teensy 3.6 has 256k of RAM, enabling the use of an in-memory buffer for fast screen updates, the heart of this project. Full screen 240×240 at 16 bits of colour requires ~115K of RAM for the buffer and using SPI with a bus speed of 90 Mhz (CPU clock speed 180 Mhz), the transfer to the display takes ~22 ms. Reading a full video frame from the Teensy SD card adds a further 6 or 7 ms, so playing video converted to a 23.98 fps rate is easily achievable! Semi-intelligent reduced data transfer allows for a 240×160 video to play at ~50 fps. This can be unnecessarily further improved by overclocking the Teensy up to 240Mhz/120Mhz, but the battery does not like this!
The electronics (display, lights, battery, Teensy, 9DOF sensor, switches, speaker, amp, joystick, wiring) weigh ~1.4 oz, so easily light enough to put inside a Pinewood Derby car and within the “legal” weight limit of 5oz. The wooden chassis, wheels and nails weigh ~1.3 oz, so additional tungsten weights totaling 2.2 oz were added. Track speed of car yet to be determined, but it rail rides, runs on 3 wheels and is weighted at the rear as much as possible, given the constraints of the electronics placement.