OuijaCNC: Raspberry Pi 3 and ESP32 power automated magnetic Ouija board

A Halloween-themed open hardware project combines a Raspberry Pi 3 Model B+ with a custom-built core XY CNC machine to create an automated Ouija board. The system uses an ESP32 microcontroller to drive stepper motors via G-code commands received over USB serial from a Python Flask web application running on the Pi. The planchette is moved magnetically from beneath the board surface, with ball bearings embedded in its base to reduce friction against a heavy wooden piece.

The software stack includes Raspberry Pi OS Trixie, Raspberry Pi Connect for remote access across changing networks, and a Python Flask web UI that converts typed text into G-code coordinates mapped to letter positions on the board. The ESP32 handles real-time motor control while the Pi manages network connectivity, web serving, and G-code generation. The project demonstrates how commodity single-board computers and microcontrollers can be integrated for precision mechanical control in home-built CNC applications.

Hardware architecture and control flow

• Raspberry Pi 3 Model B+: Serves as the primary controller running Raspberry Pi OS Trixie, handling network connectivity via Raspberry Pi Connect, web UI serving, and G-code generation through a Python Flask application.
• ESP32 microcontroller: Acts as the real-time motor driver, receiving G-code instructions over USB serial from the Pi and translating them into stepper motor commands for the core XY mechanism.
• Core XY CNC mechanism: Built with 3D-printed parts, fishing line as drive belts, and multiple magnets on both the CNC head and planchette; spring-loaded magnet mounts maintain consistent pressure against the board underside.
• Friction reduction system: Free-spinning ball bearings embedded in the planchette base address the challenge of moving a heavy wooden piece with large surface area across the board.
• Coordinate mapping: Letter and word positions on the board surface are stored as G-code coordinates in a JSON file read by the Flask application, requiring manual calibration for each board layout.

Why it matters

This project illustrates the continued utility of older Raspberry Pi hardware in embedded control applications, with the Pi 3 Model B+ finding new purpose after years as a print server. The combination of a Linux SBC for high-level networking and UI with a dedicated microcontroller for real-time motor control reflects a common and accessible pattern for hobbyist CNC and robotics builds. While the Ouija board itself is a novelty, the underlying core XY design was already reused by the builder for a CNC plasma cutter, suggesting the mechanical and software framework has broader applicability for open hardware fabrication tools.