Jeff McBride's "Gauss Speedway" Propels Magnetic Cars Along a Clever "Stepper Motor" PCB

Electronics engineer Jeff McBride has built the Gauss Speedway, a compact racetrack powered by an STMicroelectronics STM32F051 microcontroller and Rust, which sends 3D-printed magnetic cars whizzing along as though they were components in a stepper motor.

"I prototyped this months ago, and now finally did the re-spin into a better package without the mess of wires," McBride writes of the project. "Controlled by an STM32F051 on the back running Rust [language]. "Designed in KiCad, with my CurvyCad Python library. The cars are 3D printed, with 2mm diam[eter] axial magnets glued in."

The Gauss Speedway itself is shaped like a gently-curving racetrack, while the cars are shaped like little lozenges. Magnets on the underside of each stick the cars to the track's surface, but it's magnetism that sends them whizzing round under the control of a simple user interface: two capacitive sliders to control speed and direction plus a handy stop button to bring everything grinding to a halt.

"It works exactly like a bipolar stepper motor, just laid out flat," McBride explains of the race track's operation. "You alternate the current direction so that the trace under the magnet is constantly pushing it along. The silkscreen isn't functional at all; it's just for looks. There are two 'guard rail traces' running just outside the magnets, with the current direction in them set to push the car towards the center. So if it deviates a bit one way or the other, it moves more over the guard trace and gets a net restorative force to center it.

"The guard rails are connected in series, such that current in one rail runs CW [clockwise] and the other CCW [counter-clockwise]. If you run the current in the right direction, these create a force pushing the magnet back towards the center, and since the rail is just outside the magnets, the centering force increases when the car deviates onto the rail."

"I'm running at 2.5W at low speed, and up to 5W at high speed," McBride adds. "Its a terribly inefficient motor because at any given time 2-4 short copper sections are doing work and the rest are just resistive heaters!"

The operation of the speedway is effectively identical to Kevin Lynagh's micro-robotics project from February of this year, in which tiny magnetic "robots" could be walked around the surface of a PCB through alternating magnetic fields — but with a focus on accuracy of movement in tiny steps, rather than the high-speed and surprisingly smooth racing available from McBride's Gauss Speedway.

A video showcasing the project in action is available on McBride's YouTube channel, with more information available in the project's Mastodon thread.