Sometimes you just need a wristwatch, and sometimes you come across a bunch of super-sweet retro LED displays pulled from old calculators. I mean, what else am I going to do with my time?


Back in late 2009 my roommate was heckling me about never finishing my projects. At the same time, technologically absurd wristwatches were all the rage in the Maker community. Nixie Tubes, high-res OLEDs and discrete LEDs were the thing to have, battery life be damned.

I wanted a slightly different aesthetic and found exactly what I was looking for.

What it does

  • Displays time in a variety of formats

What it’s made of

Theory of operation

Push the “Display” button and the time glows at you for 3 full seconds.

That’s all the tutorial I have for now – you can read through main.c to see what the setting fields mean.


The watch worked well. One thing to note is the LED segments aren’t very bright when used with a coin-cell battery because those ultra long-life batteries can only source about 2mA sustained and 10mA pulsed. Attach a reasonable battery and things will lighten up.

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