Wristwatch Made Of Sandwiched PCBs


Here’s a wristwatch concept we haven’t seen before. Instead of trying to sandwich everything inside of a case it uses a stack of PCBs as the body of the watch.

[Mats Engstrom] wrote in to tip us off about his build. The design goes with LEDs which is nothing new. But unlike previous offerings [Mats] didn’t go with one LED for each minute. When the touch sensor in the middle of the watch is activated the twelve LEDs on the face will let you know the hour and the nearest five minutes. A video of this is embedded after the break.

The design uses three different circuit boards. The bottom board is the largest and provides slots through which the wrist bands can connect. It also serves as one of the two battery connectors. The second PCB is a spacer with a cutout for the coin cell that powers the device. The top board is where all the magic happens. It’s dual sided to host the LEDs and touch senor, with the PIC microcontroller and support circuitry on the other side.

27 thoughts on “Wristwatch Made Of Sandwiched PCBs

  1. nice work!

    i’d be a little worried about dragging the face of the watch against something and breaking some of the led’s and their solder pads off, as it seems to happen all too often for me, but i guess that’s why i just don’t wear watches anymore.

    1. That was one of my first thoughts. Maybe adding a clear plastic layer above the top PCB would work well. Either cut out to clear the LED’s and touch pad, or vacuum formed around them.

      It still is a cool build nonetheless.

  2. I’d like to see the pcb interconnections. He wrote that he used wires to connect the bottom PCB with the top one. I wonder how he managed to squeeze wires in there. I can’t imagine it’s very service-friendly.

      1. I can just extend my hand to reveal my watch under my sleeve (now that’s almost summer I don’t even have a sleeve). If I have to use my right hand to touch the watch on my left then I’ll just pull my phone and check the time using just one hand. Nice design but awkward to use. There’s a reason there are no commercial touch-watches.

          1. Except after dark to activate the LCD back light!

            But yes indeedy, there is nothing unusual to pressing a button to see the time, especially for LED watches. I would love an LED watch that constantly displays the time, but currently this would need a rechargeable battery pack strapped further up my arm! Also there are some practical situations where you’d need to turn off the LEDs, such as driving.

            Very old farts had to press a button too – to flip open the cover on their (pocket) watch AND they had to take it out the pocket first! (Inspiration – Maybe a LED pocket watch could pack a bigger power source, and stay lit, but only while the cover is open for viewing? No doubt it’s been done and on HAD already!)

  3. I suggest you coat the watch with polyurethane to prevent glass fibers from the circuit boards digging themselves into your skin.It’s not a pleasant experience, and the polyurethane will make the watch look more finished as well.

    Also – dust collection when machining PCB material is a must! You don’t want to be breathing those fibers either.

    1. The only problem is that it really needs a very hard poly. Most polys scratch easily. I am wondering if an epoxy would not be a better choice as the board is already an epoxy/fiberglass product.

      1. When working with epoxy I often mix it up on a transparency sheet. When set it’s pretty well stuck to the sheet, but with care you can peel it off (to reuse the sheet) and have a really smooth epoxy surface. Splodge of epoxy on transparency sheet, set watch down in it, add a weight to squish most out, wait for cure, delaminate then round over any sharp bits of epoxy with a file?

        but epoxy can cause contact type allergic reactions.

        1. To eliminate the contact reactions when I use epoxy on something that people touch, I slap a layer of nitrile over the side that’ll be touched. Thin latex doesn’t work as well, the fiberglass particles puncture it pretty easily when pressed against, but nitrile holds up really well and is designed specifically to avoid allergic skin reaction. Nitrile also has that nice smooth blue look to it that goes well with flashy lights.

  4. this is, by far, the FIRST geek-watch
    i could _actually_ see myself wearing!

    a quick coat of epoxy would finish it up good.
    epoxy wont be easy to spread evenly tho.

    as to the top board idea;,,
    you could just add a board that is (almost) clear
    and mill enough from underside to leave room
    for LEDs below. LEDs would have enhanced contrast?
    thus adding a cover and not changing the existing parts :)

    PS: why oh why arent these kind of watches
    sold at the (in person) store???

  5. I’ve seen this before. Dave Jones does exactly the same thing with his calculator watch. Not a bad idea of a hobby project, but not really suitable for production IMO. Solder Mask just isn’t that resilient.

    1. Solder mask is not resilient? Hm…. then please tell me how to get rid of it from a PCB. I’ve immersed a PCB in hot (~80C/176F) acetone, paint thinner, white/mineral spirits and MEK for an hour and the resist resisted (pun intended) all attempts to get if off from the board. It didn’t even get softened enough to be even partially removed when scrubbed with a one of those steel wool scrubbers.

      I’m quite sure that some light rubbing against skin and some sweat would have any effect at all.

      But as you say, a pcb enclosure is probably not the best for production volumes, a die cast enclosure would be so much cheaper – but not necessarily thinner and more stable. Even 0.8 mm FR4 is really strong and hard to bend and break.

      I could probably have made this watch with 0.6+1.6+0.6 mm pcbs = 2.8 mm in total thickness and still be ok for daily usage. But 0.6mm pcb is more expensive than 0.8 and I already had the 4 mm long screws that’s why I ended up with a 0.8+1.6+1.6 stack.

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