The Beginnings Of A Geeky Wristwatch


Wow, we’re seeing all kinds of good stuff from NYC Resistor today. [Caleb] found this link to [Hudson’s] early work on a geeky wristwatch. It is based around an HDSP-2112 eight-digit alpha-numeric display. Each digit is a 5×7 array of LEDs, but the look of it really reminds us of [Woz’s] Nixie Wristwatch. The nice thing about using a display like this one is it’s much easier to drive and the power requirements don’t really call for special consideration either.

The display happens to be nearly the same footprint as the Teensy 2.0. In fact, the display is a bit longer. That makes it a perfect backpack, bringing everything necessary to drive the display. Check out the video after the break to see it scrolling the time as words, and displaying numbers.

This needs to have an RTC and portable power source before you can wear it around. But the proof is there. Perhaps [Hudson] will spin his own board with a uC that includes RTC capability and a charging circuit for a tiny Lithium cell.

18 thoughts on “The Beginnings Of A Geeky Wristwatch

    1. I have that exact display! Pulled it from a laundromat card reader I bought for $4. Its got some strange onboard processor that I couldnt figure out though. Very bright too, there was a darkend plastic window infront of it when I tore it down.

  1. These displays can often be obtained on eBay for around $5-$10 each. Equivalents are also available from Osram/Infineon. They do have some special power requirements in that they use heaps of power (hundreds of mA) and most versions are 5V only. A bit of a challenge for a battery powered design.

    1. They are the gold pads where the bond wires from the LED dies attach to the display substrate. Normally there would be a tinted filter over the display and these wouldn’t be visible.

    1. That’s an awesome build. You should submit it for a HaD article.

      How do you prevent shorts? Having a LiPo cell right against your arm with the possibility of pulling big current sounds like a recipe for a bad time.

      1. Thanks.

        Yeah, it is entirely possible to short the battery terminals, but I don’t find myself pressing the top of my wrist against any sort of conductive surface. I imagine that the 30’ish AWG wire I’m using to connect the battery to the watch would blow before the battery does. I could always just use a PTC resettable fuse to prevent damage. I’m already using one on the USB +5V in…

    2. That is a nice build. I used to have a bunch of those displays too (or similar ones) a long time ago. Boy I wish I still had all that old stuff I tossed out. Grrrr……. The tiny “bubble” displays like they used to use in the first LED watches are next to impossible to locate.

      I have some older HDSP-2000 displays, which are similar to those in the article above, but smaller. Serial input/output for cascading. Easier to use. But God they’re power hogs! I think they’d burn your arm if they were on for more than a few seconds. You have to be careful how you use them, you have to use a big old PCB to act as a heat sink. Look great though.

  2. i have 8 of these HDSP displays ( yellow ) i am wanting to use 2 displays to build a GPS clock that shows time on 1 display and date on the other display.
    i am willing to trade a few of them for someone to help me build one.
    i can assemble it, i just do not know how to write the code for it. i can be reached @ make sure to mention GPS clock or HDSP display.

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