Open hardware · built in public

Project Horae

A miniaturized successor to Watchy: an open-source e-paper watch, rebuilt as thin as possible in a slim band form factor, like a Fitbit Charge instead of a square.

This page is the build log. It starts on day one and every milestone gets a photo or a screenshot.

GitHub Latest entry ↓
10 42 SAT 03

  1. Unboxing the Watchy

    The starting point: an original Watchy by SQFMI. ESP32, a 1.54" 200×200 square e-paper panel, four buttons, a LiPo, fully open hardware and firmware. Project Horae keeps the idea and changes the shape: thinner, narrower, and a better fit on a wrist.

    Unboxing photos coming later today

  2. Research: tools, batteries, displays research

    Before designing anything, we surveyed what's available. The first-pass picks:

    • Display: a 0.97" 184×88 bar-shaped e-paper (Good Display GDEM0097T61). It's 30×14×1 mm and uses an SSD1680, close kin to Watchy's controller. The runner-up is Sharp's 1.08" 160×68 memory LCD, which is the most Fitbit-like but hard to source.
    • Battery: a stock 2.4–3 mm, 100–130 mAh LiPo pouch. Sodium-ion is a no for now: the smallest cells sold are 18650s.
    • Electronics: fork Watchy's KiCad files into KiCad 10 and script everything with kicad-cli. Boards come from JLCPCB, 4-layer at 0.6–0.8 mm, assembled, shipped by DHL to Vancouver.
    • CAD: build123d (Python, STEP in and out) for the case. The KiCad board drops straight in for fit checks. Slicing and printing on the Bambu A1 mini run from the command line.

    The open question is the chip: keep the ESP32-S3 and Watchy's firmware, or switch to an nRF52/nRF54 for roughly 5× the battery life.

    DisplaysBar-shaped e-paper vs memory LCD BatteriesThin LiPo, sodium-ion, power budget ElectronicsEDA tools, fabs, ICs, import costs CAD & printingCode-CAD and headless A1 mini printing