The ChronodeVFD Wristwatch

VFD Wristwatch

Not just another steampunk fashion statement, [Johngineer’s] ChronodeVFD wristwatch is as intricate as it is beautiful. Sure, we’ve seen our share of VFD builds (and if you want a crash course in vacuum fluorescent displays, check out Fran’s video from earlier this year) but we seldom see them as portable timepieces, much less ones this striking.

The ChronodeVFD uses a IVL2-7/5 display tube, which in addition to being small and low-current is also flat rather than rounded, and features a transparent backing. [Johngineer] made a custom board based around an AtMega88 and a Maxim DS3231 RTC (real time clock): the latter he admits is a bit expensive, but no one complains about left-overs that simplify your design.

The VFD runs off a Maxim MAX6920 12-bit shift register and is powered by a single alkaline AA battery. A rechargable NiMH would have been preferable, but the lower nominal voltage meant lower efficiency for his boost converters and less current for the VFD. [Johngineer] won’t get much more than 6-10 hours of life, but ultimately the ChronodeVFD is a costume piece not meant for daily wear. Swing by his blog for a number of high-res photos and further details on how he built the brass tubing “roll cage” enclosure as well as the mounts for the leather strap.

47 thoughts on “The ChronodeVFD Wristwatch

  1. very cool and you said that NiMH don’t provide enough power have you thought of using NiZn rechargeable batteries there base voltage is 1.6volts and are very hard to damage they will not explode when hot they are recyclable and made of the two most common metals Ni Zn

      1. NiZn and LiFePo sounds amazing. I love when my Batteries dont explode.
        To bad there is no charger Module available like for the LiPo Batteries. Is there a chip to charge NiZn or LiFePo? I have a Charger for NiCad & NiMh (MAX712CPE)

        1. Charging LiFePO4 is just a matter of connecting a 3.5V or so supply to it, current limited to less than the charging current rate and preferably less than half that. In fact, there are LiFePO4 packs that are drop in replacements for lead acid.

        2. I designed my own smart charger. Stand alone or controlled + logging + programmable battery parameters from Windows. Just never got around writing the graphing part. :P

          Microchip MCP73123/MCP73223 does LiFePO4 charging. Leadless DFN packages which requires a hot air tool + PCB. These days you can get good quality PCB made in China cheap, so that’s not an issue any more.

          There are other chips that can do that too. There are also LiFePO4 charger from China.

    1. While an alkaline battery starts out higher in voltage than a NiMh or NiCd, its rated end of life voltage is actually lower. If something works on alkalines but not NiMh, it’s not getting the full life out of the alkalines.
      If you could find a boost converter that works well down to 1V or so, it would give longer life from alkalines and allow working with NiMh.
      This is a very common problem in consumer electronics (I’m talking to you, Gameboy!)

  2. This is a really nice build. I think you could get closer to the steampunk look by getting rid of the modern looking parts, like
    – the silkscreen on the PCB
    – the purple solder mask (brown to match the strap would be ideal, otherwise black I guess)
    – putting heatshrink over the battery, or stripping off the plastic covering to leave a silver cylinder

    1. Another solder mask option: none! Just put a flood fill on the stop layers. You’d have to be careful not to route signals under components that might touch the trace, but a fully ENIG plated board would look awesome.

      1. If there are issues of copper touching conductive parts of a component (e.g. metal shields etc), you should have an restrict on those footprints already. Don’t rely on solder mask alone for insulation.

        Not having a solder mask IMHO is a good idea for wearable electronics. sweat, splashes from water, drinks etc. along with an electric field can have corrosive effects for the non- gold plated things – leads, solder joints etc.

    2. I think that the only thing that could make this look more steampunk is to ditch the pcb all togethor and air-wire it, using 10M resistors as standoff seperators.
      Might make it a bit fradjile tho :)
      If you put a tight spring around the pipe when bending it, it shouldnt colapse.
      iirc, the mercury cells have the highest power/weight of non-li-ion batteries, high resistance, I wonder how many of them it would take to power that (high voltage config)

  3. Very nice looking build.

    My one worry is the VFD fill nipple on the right side. The brass roll cage doesn’t protect it as the glass nipple ends further out. If you snag that on clothing and it breaks then the VFD will die.

        1. In truth, I considered that during the design phase, and originally the right-side brass rail was going to be bent in the middle (like an arrowhead pointing to the right). However, during test fitting I found that the nipple doesn’t stick out far enough to cause a problem. It doesn’t extend past the edge of the leather cuff either. I’ve worn the watch for about a week and it (surprisingly) hasn’t snagged on anything, so I’m not too worried about it now.

  4. If you fill the tubing with fine salt or sugar before bending you can reduce is not eliminate the collapsing of the tubing. The wash it out with water. You can also anneal brass by heating it red hot and then quenching in water, it is the opposite of steel, quick cooling softens brass and copper.

        1. You can’t get a radius that tight on 1/8″ tube without collapsing the tube. It’s a roll cage on a wristwatch, not an exhaust pipe, after all. Mechanically it’s still sound, and it’s reinforced with a solder fillet on the underside.

          1. Great build! That looks amazing!

            If you do make another one, there was a link to a small OD pipe bender article on here a while ago:

            This tool shape has worked well for me, and I’ve succeeded in getting 1/8″ brass tube to bend at a 1/8″ radius without collapse. It took filling the tube with melted wax, and using a version of this pipe bender design, though.

            Like macona mentioned, you can also fill it with powdered salt, heat it up gently with a torch and do the same thing, but the bending rig *really* helps avoid point stress collapses.

          2. Yes, but consider that if I had a machine shop at my disposal I would have already done that. I’ve lived with this project for 2 months, and I made the choices I had to make. There is really no suggestion you can make which I haven’t already thought of and dismissed because it was impractical.

  5. National Semiconductor made a VFD clock module
    that was smaller than this build. Only it ran of 12 volts.
    I have 4 of the units sitting on my bench now. The
    devices are of late 1970’s vintage if I recall correctly.

    1. Your bench sounds like my desk. I often have to dig around to find the keyboard and mouse. When I do, I stumble on chips and other tech stuff dating back to the 80’s.

      I get about 2 inches of height for each decade lol. Found an old FDC765 floppy controller chip from the 80’s the other day. Old EPROMS, DRAM, CPU’s like the Z80 6xxx. Even saw a 6845CRTC a month or so ago all from the bottom layer. Top layer is modern uC, CLPD/FPGA, development boards and programmers etc. Several things ending in duino.

      Yes it’s a total mess and things often get lost when they fall a decade or two deeper but it’s entertaining at times, like a private museum.

      Unfortunately no VFD’s but I did see some of those old 8 or 9 digit matrixed 7 Seg LED displays with the magnifying bubbles over the tiny LED units. There in there somewhere lol.

  6. 14500 Protected Li-Ion batteries provide 4.2 volts fresh off the charger, and are the same form factor as the AA battery already included in the design. The protection PCB also makes them mostly non-explody (prevents over-draining the battery, etc).

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