DIY Modder Creates Stirling Engine-Powered Computer Running Tetris on 150mW

Off-Grid Computing Innovation

Reddit user PickentCode constructed a unique "heat engine computing device" that operates entirely off-grid. This custom microcomputer integrates a miniature Stirling engine to generate power for its functions, moving away from conventional power sources like solar panels or batteries.

Stirling Engine Mechanics

The core of the power system is a Stirling engine, a device patented in 1816 by Robert Stirling. This engine converts heat into mechanical energy by using temperature differences to expand and contract air within a sealed cylinder, driving a piston that spins a flywheel. This mechanical rotation is then converted into electricity by a simple generator.

Construction and Components

The project involved a month of design, building, and programming. The physical case was crafted from wood, with a laser engraver used to etch a portrait of Robert Stirling and his patent sketch. Custom 3D-printed parts were used for structural elements and keycaps. The system's intelligence comes from an ESP32 C3 microcontroller paired with a 2.42-inch monochrome OLED display and a 16-key keypad. Capacitors stabilize the electrical output from the generator.

Power Management and Performance

The Stirling engine provides only 150 milliwatts of power, necessitating significant hardware and software optimizations. Wi-Fi and Bluetooth were disabled, and screen brightness was kept low to conserve energy. The ESP32's CPU frequency was adjusted, running at 80 MHz for screen updates and opcode interpretation, and down to 10 MHz during idle periods, allowing the device to run simple games like Tetris, Snake, and Pong.