Modding A Casio W800-H With A Countdown Timer

Stock, the Casio W800-H wristwatch ships with dual time modes, multiple alarms, and a stopwatch – useful features for some. However, more is possible if you just know where to look. [Ian] decided to dive under the hood and enable a countdown timer feature hidden from the factory.

The hack involves popping open the case of the watch and exposing the back of the main PCB. There, a series of jumpers control various features. [Ian]’s theory is that this allows Casio to save on manufacturing costs by sharing one basic PCB between a variety of watches and enabling features via the jumper selection. With a little solder wick, a jumper pad can be disconnected, enabling the hidden countdown feature. Other features, such as the multiple alarms, can be disabled in the same way with other jumpers, suggesting lower-feature models use this same board too.

It’s a useful trick that means [Ian] now always has a countdown timer on his wrist when he needs it. Excuses for over-boiling the eggs will now be much harder to come by, but we’re sure he can deal. Of course, watch hacks don’t have to be electronic – as this custom transparent case for an Apple Watch demonstrates. Video after the break.

28 thoughts on “Modding A Casio W800-H With A Countdown Timer

  1. I’ve never bothered with countdown timers, too much effort to set them up.

    So if I’m timing something, I just use the stopwatch function. No setup, and I just need to check occasionally.

    1. Or, if you have the ability to do 2nd grade math, you would really only need a clock/watch. The same trick of looking at it occasionally to determine how much time has passed still applies – without having to interact with the stopwatch function at all.

      The point I’m trying to make here, is you’re polling a system intended to measure time with an previously unknown duration to determine if you’ve reached a known, fixed duration. That’s the job of an event-based (interrupt) system.

      The inverse is equally as ridiculous: set a countdown timer for a time guaranteed to be longer than the unknown duration you’re trying to measure. When the event would normally stop your count-up, you instead look at the countdown – subtracting the current value from your original, and boom: you’ve turned a countdown timer into a stopwatch.

      Setup of either on a Casio watch is impractical, requiring manual input on a tiny HID – these days we just ask our smart assistant devices to do the thing for us, setup be dammed.

    2. The countdown timer, and especially in the auto-repeating mode, is great in the darkroom. When you get the rhythm, the timer beeps you to shift one step further in the enlarger – developer – fixer – washer pipeline.

      1. I came here to say the same thing. I used to have a nice Casio watch with an auto-repeating countdown mode and it was great for roll film processing. Every so often it would chime and I would agitate, drain, rinse, fill, whatever the next event was. The auto-reset was helpful because the last thing you want to do with your hands covered in chemicals is to have to touch stuff.

        Nowdays, I would probably write a little app for a tablet. It could do the whole proces flow w/timers as well. If I still did film processing.

    3. I use a bizarre watch that emits a ticking sound while in operation. It features a rotating bezel that can be set to either the current position of the “big hand” for count-up function, or set ahead the required amount of time. When the big hand makes it to the indicator, time is up! And it “automatically” counts up at that point.

      For my purposes, it is very rare I need to time something over 1 hr, and +/- 30seconds or so is an acceptable error. Parking meters, cooking pasta, no decompression time limits, things like that.

      These types of time pieces are pretty cool. They used one on Apollo missions. I think they still make them.

      1. I have one like that. I also have a battery-powered analogue watch on which the bezel is a slide rule. Sadly, a self-winding mechanical chronograph costs more than any car I’ve owned (Omega does still make the watch that went to the Moon, it’s about $10k new, I’ve paid between $800 and $8000 for used cars), and the fully-mechanical flywheel-wound equivalent of my $500MSRP Seiko SNA411 costs … $Breitling.

  2. I use a countdown timer, through Alexa, to alert me my clothes washer and dryer are done since I don’t always hear the end of cycle buzzer.

    How does one discover these ever present omnipotent jumpers on something as microsized as a watch? I don’t imagine schematics are freely available.

    1. when ever I buy something new I always take it apart and study it’s layout, if i see jumpers I prod, if i see shorted pads I unshort to see it’s effects , a lot of consumer electronics have this style of “configuration” from a coffee pot to a remote for a no name brand TV to top of the line sony tech. it’s also now a habbit of mine that if i see a spi eeprom in a device I dump it, already this trick has saved my TV which has committed software suicide twice already from factory “updates” and having the original dump just ment i could reset to factory each time.

  3. Wasn’t this taken from my old (approx. 2013) post on :-O The principle is extremely simple: select any possible combination of jumpers and look at the result. Recently I discovered the same on a popular specialized calculator, Calculated Industries Construction Master 4 (Model 4045). Switching its three jumpers can transform it to four different models (Conduit Calc, Pocket Handyman 4, Ultra Measure Master, Trig Plus 2) as well as select three different software versions of Construction Master 4 (by the way, the factory selected version was not the highest one).

    1. Was it? Or is it just that someone in the western world happened to make the same finding, a concept that seems to utterly baffle Russians?

      I’ve seen the same level of astonishment from Russians that the MAME team more or less had to reverse-engineer how to electronically dump the microcontrollers used in Game & Watch games. But the reality is that that Igor guy who dumped a bunch of Elektronika games (Game & Watch bootlegs from the Soviet era) wasn’t exactly forthcoming with information at the time.

      1. >>Was it? Or is it just that someone in the western world happened to make the same finding, a concept that seems to utterly baffle Russians?

        No one will know…

  4. UHHHHHHHHHH there are guys in gitmo for having this watch and this is exactly what they are accused of making but connected to and IED…. wtf HaD

      1. You are looking at the wrong side of the PCB. The jumpers are all on the display side, not on the battery side! I’m going to bet though it shares the control chip with F-91W and A168W, since the display layout is the same as well, which means you probably won’t find any useful functions to unlock. You may just find jumpers that calibrate the quartz precision.

  5. My old Sekio digital watch has much better UI than my replacement Casio. It is a lot more intuitive and consistent. I still have to read the manual for my Casio from time to time. The old Sekio has a great alarm feature, it can be selected on/off for each weekday. i.e. Don’t want to be waken up for work or school on the days you don’t need to.

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