Chronio DIY Watch: Slick and Low Power

[Max K] has been testing the battery life of his self-designed watch under real-world conditions. Six months later, the nominally 3 V, 160 mAh CR2025 cell is reading 2.85 V, so the end is near, but that’s quite a feat for a home-engineered smart watch.

We’ve tipped our hats to the Chronio before in this Hacklet, but now that the code is available, as well as the sweet 3D-printed case files, it’s time to make your own. Why? It looks sweet, it plays a limited version of Flappy Bird (embedded below), and six month’s on a button cell is a pretty great accomplishment, considering that it’s driving a 96×96 pixel LCD display.

The Chronio is more than inspired by the Pebble watch — he based his 3D model directly on theirs — so that’s bound to draw comparisons. The Pebble is color, and has Bluetooth and everything else under the sun. But after a few weeks away from a power socket, ask a Pebble wearer what time it is. Bazinga!

19 thoughts on “Chronio DIY Watch: Slick and Low Power

    1. Might not actually. E-ink requires some exotic voltages (15V, 22V, -20V, -15V) and generating all of these means major losses in the conversion. Although it would only be on for once a minute (or less, because this one isn’t even displaying time constantly), I’m not sure if you would end up with a net energy savings. Also, maybe really small screens don’t have the same voltage requirements. I think it’s amazing to get such life out of such a small battery.

    2. It’s a Sharp memory LCD. It only needs power to switch, like E-ink. E-ink needs a voltage convertor to operate, which takes up space and isn’t easy on battery life. If he gets 3 months out of 1 battery, we can certainly say he’s succeeded in his aim.

    1. It’s programmable. Writing software for a watch isn’t too difficult. I’d love an affordable watch that I could write code for. If someone would reverse-engineer the cheap GT08 Chinese ones that’d be fantastic! Colour LCD touchscreen, camera, Bluetooth, and 2G + GPRS cellphone. CPU something like 200MHz ARM. Not the greatest platform in the world, but you can buy them for $7 from some places, fot $15 there’s a hundred places dying to sell them to you.

      The hardware’s great, for all sorts of uses. Way better than anything we could make ourselves for any sort of price like that. But currently nobody seems to know how to program them. It’s a shame.

        1. What, for a watch-phone like GT08? It just needs to spend most of it’s time in sleep, that’s all. You could still add things like calendars, or even games. The power supply is a lithium battery.

    1. Despite its name, the “memory” LCD has a write-only memory. You cannot read it, you have to either save its state in a separate memory accessible by the micro-controller, or recreate the entire display every time you want to update it.
      96×96 pixels is 1152 bytes, but 128×128 is 2KB, i.e. all the memory available to the ATmega 328.

      I managed to get a LS027B7DH01A (400×320) to sort of work with an Arduino, but only as an old school 25×20 text only display. I only store the characters in RAM and the 16×16 bitmaps for the fixed font are stored in EEPROM.

      It is manageable, but not pretty.

      Now with a Cortex M0 and mbed…

  1. Cool. How does this compare to something like Texas Instrument’s Chronos dev platform when looking at battery life and performance? The Chronos only has a 96 segment LCD, but probably has to update it more frequently. Would be interesting to see this Sharp display on the Chronos.

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