Racing Toward Christmas
The North Pole Circuit is a hyper-festive electronic Christmas card featuring a magnetic sleigh racetrack and synchronized lights and music.
Every holiday is an opportunity for hardware hackers to ply their trade as they create eye-catching and unexpected gadgets that make the season even brighter. And with Christmas right around the corner, everyone — from the armchair engineer to the professional — is racing to get their projects built while there is still time. We have certainly seen our share of festive builds this year, like this energy-harvesting electronic Christmas card that lights up when it gets near a Wi-Fi router or microwave oven.
More recently, a very unique Christmas card made by the Janky Jingle Crew caught our attention. In years past, these holly jolly souls have brought us unusual creations like the Reindeer Volume Meter and a microcontroller-powered model fireplace. This year, they went all out with what they call the North Pole Circuit. It is an electronic Christmas card that is not just festive, but hyper-festive. It has the usual (for unusual custom electronic cards, that is) lights and music, but it does not stop there. It also features a race track that loops around a tiny village where Santa and his reindeer can get some practice for the big night.
The card, of course, is powered entirely by Christmas magic. End of story. Nothing more to see here. Unless you are the sort of person that likes to peek at presents before Christmas morning, that is. In that case, read on.
The card features a pair of dual-core, 32-bit CH32V003 RISC-V microcontrollers and is powered via USB-C. Users can interact with it by placing the 3D-printed sleigh and reindeer on the track and controlling their motion with buttons that adjust their speed and direction. A separate button activates a Christmas jingle (played on a buzzer) accompanied by synchronized movement.
The propulsion system is based on the Lorentz force, which generates motion by creating a perpendicular force where an electric current interacts with a magnetic field. Magnets with vertically aligned poles are attached to Santa and the reindeer, and they work in conjunction with PCB traces laid perpendicular to the track’s direction. Depending on the direction of the current, a forward or backward force propels the magnets along the track. For optimal propulsion, sinusoidal waveforms with a 90-degree phase shift are applied to the tracks, mimicking the microstepping technique used in stepper motors. Guard rails run parallel to the tracks to stabilize the magnets through curves.
The electronic design is divided into two primary circuits: the driver circuit and the decoration circuit. The driver circuit controls the propulsion system, including the phase tracks and guard rails. DRV8833 motor drivers replace traditional components, offering lower resistance and improving the efficiency of the system. The decoration circuit controls the LEDs and buzzer. This circuit uses I2C communication to synchronize with the driver circuit, allowing the lights and music to be synchronized with the sleigh and reindeer’s motion.
To finish off the build, a 3D-printed village was added to the card, with some LEDs underneath for illumination. The Janky Jingle Crew made a total of 50 of these cards. If you were not lucky enough to receive one (join the club!), then be sure to check out the project write-up to learn how you can make your own.