ATtiny Watch is Tiny

[陳亮] (Chen Liang) is in the middle of building the ultimate ring watch. This thing is way cooler than the cheap stretchy one I had in the early 1990s–it’s digital, see-through, and it probably won’t turn [陳]’s finger green.

watch-gutsThe current iteration is complete and builds upon his previous Arduino-driven watch building experiences. It runs on an ATtiny85 and displays the time, temperature, and battery status on an OLED. While this is a fairly a simple build on paper, it’s the Lilliputian implementation that makes it fantastic.

[陳] had to of course account for building along a continuous curve, which means that the modules of the watch must be on separate boards. They sit between the screw bosses of the horseshoe-shaped 3D-printed watch body, connected together with magnet wire. [陳] even rolled his own coin cell battery terminals by cutting and doubling over the thin metal bus from a length of bare DuPont connector.

If you’re into open source watches but prefer to wear them on your wrist, check out this PIC32 smart watch or the Microduino-based OSWatch.

27 thoughts on “ATtiny Watch is Tiny

    1. Actually, you would probably want a rigid-flex board and not a full flex. Hobbyist numbers are not the problem, but the price tag could be out of your comfort zone. Depending on the number of layers you probably have to run with something between 300-500 Euros for a single run. Hacking something together with just rigid boards and wires is defintely easyer and cheaper if you’re not trying to mash up a concept without mass production in mind.
      What could maybe work too is to use just very thin circuit boards and try to bend them. I’ve used the 0.4mm thick photocoated material from CIF before (ordered at Farnell/Newark) and it can bend pretty well (as long as you don’t try to constantly flex it but just bend it into shape once and lock it in place, it could work).

      1. That’s right, there is also a technology called “semi flex”, where normal FR4 is milled thin in some zones, so it can be bent one time during installation. But in the cheaper version you have only one routing layer in this zones. Probably it helps to apply moderate heat when bending the 0,4mm material.

      2. Quite on the mark with the prices, by Euro Circuits calculator, anyway.

        Also available from PCB-Pool, and as mentioned, iTead too! PCB-Pool (Aka, Beta Layout) have been a real treat to work with previously, and if you ask nicely, will do you a single piece run for free on your first design with them. That was the deal previously anyway. Top guys!

    2. Maybe you can make your own. Take a piece of paper, glue some Mylar tape over it, then use epoxy to glue a thin sheet of copper. Then use either photoresist or thermal transfer method to get the circuit design on it, etch it gently, and then leave it to dry under some weight so drying paper won’t warp it. After that just solder components in, and use PVA glue to bend and glue board to your ring or any other element. PVA will impregnate paper, my wife tested it with DIY bookbinding…

  1. I really wish that those OLED displays like that were easier to find. That one would be perfect for my Motorcycle helmet HUD project. I am using a MuVu half right now but color is not needed, I need brighter monochrome like that OLED will deliver

  2. I have been trying different builds for a watch based on the ATTiny85 myself and I cannot get it accurate enough without an external crystal. I’m not exactly comparing it to a perfectly built atomic clock, but the best I can do with the internal oscillator deviates from my phones stopwatch by over a minute after only 2 hours.

    1. The internal osc is very temperature and voltage dependent (see the datasheet, at the very back). Even with OSCCAL adjustments, it’s going to wiggle all around.

      With good temp/voltage control you can get less than a second per day, probably. If you’re go skiing and then hit the sauna, forget it.

  3. This reminds me of an old Dilbert, where he built a “internet ring” and could sure the web “one letter at a time”. I didn’t realize just how close technology has progressed to making this a reality.

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