idlehandsdev/pps-watch

This repository contains the full design for a physical wristwatch that does not display the time at all. Instead, it is a precision GPS timing device you wear on your wrist, built to output an extremely accurate one-pulse-per-second signal. It is a joke on the idea of a watch, paired with genuinely serious timing hardware underneath. The device receives GPS signals to get a position and time fix, then outputs a one-pulse-per-second signal directly from the GPS module's hardware pin. That signal stays silent until the GPS locks on, then starts pulsing once per second with high accuracy. The pulse is distributed out through a BNC connector so it can be used as a timing reference for other equipment. The watch can also accept an external PPS signal and compare it against its own GPS-derived pulse using a hardware comparator chip, lighting LEDs to show whether a signal is present and whether the two pulses are in phase. Notably, there is no microcontroller and no firmware anywhere in the design: the GPS module's own hardware pin drives the LEDs and outputs directly through simple logic buffer chips. The hardware is built around a u-blox GPS module, an external antenna connected through an SMA connector, buffer and comparator chips, indicator LEDs, a coin cell battery, a switch, and a small connector for one-time configuration. The circuit board was designed in KiCad, with the mechanical case and 3D assembly modeled in Fusion 360, and the repository includes a full bill of materials with specific part numbers for ordering components. To build one, you would order the parts, have the circuit board manufactured, 3D print a frame and watch band mount from the included files, and assemble everything with a standard 22mm watch band and a handful of small screws. This is a from scratch electronics build project, not software you install, so it requires soldering skill, PCB fabrication, and a 3D printer or printing service to complete.