OpenChronograph Lets You Roll Your Own Smart Watch

At first, smartwatches were like little tiny tablets or phones that you wore on your wrist. More recently though we have noticed more “hybrid” smartwatches, that look like a regular watch, but that use their hands to communicate data. For example you might hear a text message come in and then see the hand swing to 1, indicating it is your significant other. Want to roll your own? The OpenChronograph project should be your first stop.

The watches are drop in replacements for several Fossil and Skagen watch boards (keep in mind Fossil and Skagen are really the same company). There’s an Arduino-compatible Atmega328p, an ultra low power real time clock, a magnetometer, pressure sensor, temperature sensor, and support for a total of three hands. You can even create PCB artwork that will act as the watch face using Python.

You can see a video of how you’d replace an existing watch’s PCB with the new version. You’ll also need a special tiny POGO pin programmer since there isn’t much room in the little case.

Honestly, opening the watch looked a little frightening to us, but at least the hybrid watches aren’t usually that expensive. You can usually find a Hagen or a Men’s Machine for under $100. A Fossil Q Activist looks as though it might come in at just a little bit more.

Of course, you could skip the existing watch and build one all the way. Some are easier to build than others.

32 thoughts on “OpenChronograph Lets You Roll Your Own Smart Watch

  1. I like this. I neither need not want a smaller phone on my wrist to complement the one in my pocket.

    I’ve got a Fossil Q Grant, and I find it’s exactly as ‘smart’ as I need my watch to be: it notifies me when someone I actually want to hear from communicates with me, it counts steps, and it helps find my phone when I drop it down the sofa.

      1. I have already seen people looking for the phone when it slipped into the sofa. In fact, one possibility is enough, the sofa needs not to be extra big for this: The phone is out of sight.
        Not that I myself had that problem up to now – fortunately equal to the (non)occurrence of “spider web design” on the display. :-)

          1. Not to belabor it too much; there’s always some alternative. But having a device on my wrist which I can use immediately is much more convenient than finding someone to call me.

    1. Yah I got $30 of walmart chinesium that does that. It’s kinda showing it’s age at 2.5 years in use now, already had to squish it into an applewatch replacement strap. I am frustrated that I am not finding anything better to replace it with really.

      1. Buy a secondhand Pebble watch. I’m using mine daily (Pebble Time). I got a few scratches on the bezel, sadly, but even with scratches it still looks the part. And the bezel is steel, so I could remove the paint and just have a polished steel bezel.

        Add a leather strap (from a Fossil watch, by the way), and you’re there. I paid $50 for it, secondhand.

        Still can’t believe that Pebble just threw the towel in the ring like that.

  2. Luckily digital technology allows us watches without hands, other moving parts or ticking noises since “a few” years. I don’t have any urge to give this up. Be it a normal digital watch or a smart-watch.

  3. The real reasons hybrid watches suck is the associated phone software and not so much what’s going on on the watch itself.
    God I wish I could have the new Fossil Hybrid with the features that make sense to me. But since Pebble nobody ever made a sensible phone software stack ever (RIP)

  4. (Guy who modifies Seiko watches here) There are 3 watchmaker tools readily available on Amazon that would make the case opening video 100X less terrifying. Case holder, case knife, bezel tool. Just a plastic case holder alone would make the use of the vice safer or unnecessary. YMMV.

  5. Pretty cool, curious about the battery life, what kind of battery is inside these? Also, there’s no connectivity from what i can see. An NRF52832 would cover all of this and still be Arduino compatible, maybe in a future version?

  6. The battery in this watch is a CR2430, and life is very usage dependent. If you were to run the MCU constantly and leave the IMU on, the average power draw is ~6500uA and the battery drains in less than a day. The MCU, altimeter, and IMU have sleep currents of 4.5uA, 2uA, and 8uA, respectively. For a standard 12-hour watch display (1 tick every 10s), these boards draw ~21uA on average. For comparison, the consumer watch seems to draw an average of ~16uA and claims 6-months to a year of battery life “based on usage”. I’ve wired it up so that the RTC can gate power to the IMU to shut it off completely, and when you do this the average power draw falls to 7.7uA. However, I haven’t found a way to reliably bring the IMU back up after you’ve turned it off this way.

    There is indeed no connectivity in the current design, and the haptic has been removed to make room for sensors. I will probably not pursue those features, but I’d be happy to support anyone who’s interested.

  7. These micromotors are slightly different than the Soprod ones that you can find in other hybrid smartwatches (Withings, Garmin). Could they be manufactured by another company? It’s a real pity that they cannot be sourced easily, at least, I haven’t been able to find a supplier for these kind of motors anywhere.

    1. I’ve been spending hours already trying to look for the Soprod movement or something similar but I couldn’t find anything. I guess it’s still very early. But it would be very helpful if someone can point out a source.

        1. Very interesting, thanks. I still can’t find a way to source these kind of bidirectional micromotors. I really want to put my hands on them and try to make something out of it. I think I’m going to contact Soprod directly.

          1. I don’t think that they will reply you except in the case that you buy some hundreds. Let us know your findings. From my point of view the best way to get these micro motors is to recycle/hack current hybrid smartwatches, this is what Scott? has done in the great OpenChronograph project.

            I have the feeling that there are two big watch groups that produce these motors:

            – Festina Group (Soprod)
            – Fossil Group

          2. The only way I have found to purchase these motors is to purchase smartwatches that contain them. If you find a better source, or if Soprod get back to you, I’d be really interested to hear about it.

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