Gutting And Rebuilding A Classic Watch

No, that watch isn’t broken. In fact, it’s better.

[Lukas] got so used to his binary-readout ez430 Chronos watch that when the strap disintegrated he had to build his own to replace it. But most DIY wristwatches are so clunky. [Lukas] wanted something refined, something small, and something timeless. So he shoe-horned some modern components, including an MSP430, into a Casio F-91W watch.

The result is a watch that tells time in binary, has a built-in compass, and with some more work will be updatable through an IR receiver that he also managed to fit in there somehow. Now he has the watch that Casio would make today, if fashion had stayed stuck firmly in the early 1990s. (Or not. Apparently, Casio still makes and sells the F-91W. Who knew?)

Anyway, back to an epic and pointless hack. Have a look at the tiny, tiny board that [Lukas] made. Marvel in the fact that he drove the original LCD screen. Dig the custom Kicad parts that match the watch’s originals. To get an accurate fit for the case, [Lukas] desoldered the piezo buzzer contact and put the board onto a scanner, which is a great trick when you need to get accurate dimensions. It’s all there, and well-documented, in his GitHub, linked above.

All in all, it’s an insane hack, but we love the aesthetics of the result. And besides, sometimes the hacking is its own reward.

47 thoughts on “Gutting And Rebuilding A Classic Watch

    1. My 3 Chronos watches, one for myself, my wife and nephew… they have drifted by maybe 3 seconds in the 3 months since I replaced the batteries in them. The appear to drift more as it gets warmer outside so I’ll blame that on AGW.

    2. Even with my sweet pebble I still find use for my Chronos, and I also use the 430 in two other ‘time piece’ in the house.
      I like the 430 for any (more than basic) timekeeping device on battery.
      In my experience the drift on those is less than 1s/month (External Crystal).

      Hey, that why I sync them once a month.

  1. Now this is hardcore, great project. No matter how fine it keeps time, syncs with iPhone or runs WoW. No matter how practical it is. I love it, because he chosen quite unique project and finished it, probably being more expensive than buying decent smartwatch or whatever.

    In fact, one of key points in hacking/making is… the hacking/making. It doesn’t need to be useful. We all have to do useful, organized and logical things every fucking boring day. Those irrational, pointless and weird projects are way to deal with this devastating routine.

        1. I’m not sure TSA has a clue what a stock vs custom PCB would even look like. Now, if that watch was attached to a bundle of cylinders, then they have a 92% chance of detecting it.

    1. Whatever the original lure (cost or maybe it’s easier to get the signal off the watch board), it makes sense that they stick with the same watch type. No need to figure out a new watch, the work has been done already. This is a plus for the less technically inclined.

      I’d point out that any modifications will likely make the watch no longer waterproof. I once changed the battery on a Casio, and it was never properly waterproof afterwards.

      On the other hand, my twenty dollar Casio Waveceptor is now a decade old, and keeps on ticking. It has a solar cell to keep the battery topped off. I thought it was a gimmick, but there have been times when the voltage dropped a bit, and placing it in better light got it back to “normal”.


  2. I wonder if the under $5 metal watches on ebay listed as “Retro Vintage Digital Metal Classic Style Unisex Men Women LCD Watch” are a close enough clone of the Casio to use them? I suspect the “water resistant” claim may be a little dubious, but not that hard to test if you are going to gut it anyway.

    1. Cannot speak for the metal ones, but I don’t like the extra weight and free wrist depilation that comes free with it anyway! Bought an original F-91W off eBay for $6 or so, and I really, really love it. While it’s really simple in features (single LED backlight), it does its primary job exceptionally well thanks to its extra-sharp LCD. The UI seems to be optimized to perfection, it’s also as indestructible as a Nokia 3310. No worries showering with it, or smashing it against something for a millionth time, it will always just work. Plus nobody knows the terrorist related trivia here in Poland ;)

    2. The clones are not watertight and can drift badly (30sec a month or more). but the metal is nice. and the hinges/straps dont brake as fast as the plastic ones. But for the upside the housing has the same dimensions as the real ones. so you can easily swap them. (did it with mine)

      1. You should be able to find them for as low as 9.00 Euro, delivered, from a certain Jersey, United Kingdom ebay seller.

        But if you want to get the most from a cheap watch the calculator watches are better as they have way more buttons and LCD segments.

  3. did we forget the calculator + infra red remote control model, i still have one somewhere, the wristband has seen better days but the remote and time still work(+7years on battery and counting). I’ve noticed too there are extra pads that possibly could be programming points, but never tried to hack it, waiting for someone else to try first.

  4. My girlfriend visits schools to teach kids to ride bicycles safely on roads. The schools often prohibit staff from using mobile phones (sometimes they prohibit having a mobile phone, which is absurd given the necessity in emergencies).

    We went to the retailer Argos before her first day on the job and picked out the legendary F-91W which I had such fond memories of owning and losing. I believe I may have lost at least 2 of them in my youth. At a price of about 8GBP, I decided to buy one for myself too, having lost the amazing 200GBP (Costco) Citizen Ecodrive stainless steel watch (with cool hexagonal PV) my ex gave me a few years earlier.

    At the checkout, the employee offered us the extended warranty, at only 3GBP each. I replied “But… they’re *eight* pounds!”

    Sadly, I have since lost my latest F-91W. I have given up on wearing watches.

    My girlfriend’s F-91W bears a few battle scars but soldiers on.

  5. I have trusty Casio A158W on my wrist, while typing this, as usual. Got it as graduation gift and have wore it since, watch that has come inseparable. Having stop watch and alarm clock always on hand is handy (pun not intended) and I often find myself checking time from wristwatch even if other clocks are around (like holding phone in the other hand).

    I have changed the old dim green backlight to super bright white led, that is more readable yet uses less power. I have also thought making new board with advanced features, but it is not easy to make design as low power/long-life and remain simplistic but be still useful in everyday life as the original watch.

    Also these Casios are only water resistant, not water tight, so officially they should not be used under water, but mine have survived even from soaking hours in sauna and outdoors hot tub (as it being hackerspace party, there was also toughbook for bath coding) ;)

    1. I can say with confidence that the A158W is very water resistant. I wore mine every day at work at a bodyshop where it’d be submerged regularly for hours on end when wet-sanding and resoaking the sponge. It never skipped a beat and is still my favorite watch for going to the gym. I mostly wear mechanical analogue watches for the sake of the microengineering that goes into them but I always keep my casio around for those rough activities. I’ve got the model used in this hack on the steering wheel of my car as the radio is very low and gets blocked by the shifter. Its very nice for measuring those 0-60 times when you can start and stop it with your thumb.

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