A Tiny Bubble Display Alarm Clock

LED

For one reason or another, we’re starting to see a lot of projects featuring some old seven-segment HP bubble displays. Yes, those displays once relegated to ancient electronic calculators are making a comeback for reasons we can’t understand why, other than speculation that someone found a bunch of NOS displays. [Markus] picked up a few of these olde tymie displays and built a very nice bubble display alarm clock.

To keep things simple, [Markus] didn’t go the usual ATMega with RTC route. Instead, he’s using an MSP430, a 32kHz crystal, and a few buttons to construct this tiny alarm clock. It’s powered by a single AAA battery, and in a nice change of pace from fancy, professionally made boards, [Markus] built this on some perfboard with a little bit of enameled wire.

It’s a neat little clock, and with the speaker and most likely extreme battery life thanks to the MSP430, a wonderful portable, classic-looking alarm clock. Video of [Markus] manipulating the time below.

40 thoughts on “A Tiny Bubble Display Alarm Clock

  1. Not surprising that there’s a little surge of projects with these since Sparkfun is selling them, apparently new stock. Also went from 1000 in stock to backordered in a few days.

    There is a definite period feel — and unlike with Nixies, not really a pleasant one — if you remember working with these when they were all that existed. They were small, with the LED’s of the 1970’s not all that power efficient and still dim. I remember doing the happy dance when I was able to switch out my bubble LED TI-30 for a TI-35 (and later better a HP-11C) which would work for months instead of just days on a set of batteries because of the LCD display.

    1. TI-30? How about a TI SR-11 (ca. 1974) … batteries would last about 85% of an hour exam if you were careful…. Love the 11C though; many of those are still $100+ on Ebay.

      1. I put in 2x 9V batteries in parallel to replace their battery pack for exams back in the days of the old TI LED calculators.

  2. Throw in some magnetic bubble memory and retro is go…

    I remember the LED watches from ’78 or ’80 maybe, they got my “ohhh…shiny” vote at the time

  3. The display is really pretty, so much nicer looking than a standard 7-segment.

    A nice, simple, case and it’d make a handy travel alarm clock.

  4. I had similar wristwatch project with same LED display: http://ketturi.kapsi.fi/2013/11/watch-project/ but I didn’t have time nor money, and I still do not have time. Major problem is if real time counter and descent battery life would work with low power/sleep mode and how to wake up the MCU when button is pressed (and time calculated from RTC). Also casing and PCB need some work, and after all I have good old al-qaida casio watch so my diy watch would not have much use.

  5. You’d be correct to guess that Brian, 5 seconds with google reveals that Sparkfun got a sizable shipment of these awesome little displays in from HP or some really good generic parts maker because these are dirt cheep compared to the other parts resellers who are offering them for upwards of $70(!) I don’t understand why more people haven’t used these yet in projects. if enough people did it would spark interest in manufacturers to begin making these classic style displays again.(I’ve already got some fun ideas for these and that STM32F0 that has been kicking around my room as of late

    1. “I don’t understand why more people haven’t used these yet in projects”

      Those of us old enough to remember using them back in the day likely have no desire to relive the squinting, shading, and even magnifying needed in order to actually see what is displayed on these tiny LEDs. No thanks.

      1. Do you realize that the height of the font in the browser on which you’re reading this page is most likely smaller than the height of those digits? And I’m talking of a PC, not even a smartphone.
        In these days of high resolution displays we’re much more used to tiny text than in the ’70s. I bought some of those displays and… to me they look big.

        1. Do you mean that people in the 70s didn’t read? I learned to read in 1980, so from my unique perspective you’re 100% correct.

          These displays are not appreciated by many not because of the size as such but because of the tunnel vision effect caused by those bubble lesnes. They are readable only if you’re looking directly into them And at even the smallest angles they distort horribly. They would probably be more readable without the lenses at all. I still like them a lot, but I’m glad that they are not the only display tech in existence.

          1. I would not fully agree with the “more readable” part, although the bubble could have been more shallower to allow for a wider viewing angle.

          2. I wasn’t comparing the size of bubble displays with the font size of books, but with the font size of other display technologies of the era. Nixie tubes, VFDs, and other kind of LED displays were substantially bigger, and even (most of) the computer screens of the era didn’t have the tiny fonts of today’s full HD screens.

      2. You definitely do *not* speak for me !
        I love those old school displays. They bring back fond memories of reading Popular Science in the 70’s, and of annoying my parents to buy me the electronic widgets of the time that used them (since I was i like 12 yrs old when I convinced my mom/dad to get me a new “digital” watch that used those LED displays).

        And I still have my HP-25 (and later acquired HP-67) calculators.

        Still debating if I “really” want to get an HP01 watch (that I used to drool over as a kid).
        Since they’re on that auction site.

  6. wondering how the battery life is if the display draws 20mA? The battery used is a 200mAh one, so I assume 10 hrs of use?

    1. The display only turns on when pressing a button (and remains on for 4 seconds) or when the alarm goes off. In idle mode it consumes about 1.6 uA, making it last for years.

  7. Some clever person should work out the die for these and start producing some modern, bright, high-efficiency types (preferably in more colours than just red!). They would be fantastic whenever a small display is needed.

    Last year, I built a digital pressure gauge and was able to make all the circuitry really tiny, but then needed to slap on a rather humungous 4-digit 7-segment display (0.7″ height). Would’ve looked so much nicer with one of those little bubble displays.

  8. I’ve ordered some of these, and from everything I can tell, there is no way they are NOS. Someone is fabbing these again – brand new. Kinda cool! And super cheap on ebay. Have a look!

  9. I have an old, huge 7 or 8 digit one I pulled from a calculator. Oddly I was just thinking of making a watch out of it!

  10. Cool little clock. I’ve always loved bubble displays. I applaud you for not going the route of many other clocks and watches I see here on HaD that unnecessarily employ an RTC ASIC. A simple 32768 Hz crystal is all that is needed for reasonably accurate timekeeping.

    For those complaining about the bubble displays being very directional / hard to read. I’ve used some tiny discrete 7-segment digits in one of my watch builds : http://bitpuppy.com/megawatch/.

    To reduce current consumption / extend battery life, only switch a single segment at a time. This keeps the current consumption closer to 1-2mA. It also has the added benefit of keeping the digits a uniform brightness…”8″ tends to be dimmer than say “1” when taxing the MCU’s drivers if the segments are all switched simultaneously. I also have used something like your glyph delays, but they never work as well as I’d like.

    1. Nice build. I like your design! Can I ask where you sourced those little 7-seg’s from? Also, you mentioned that you’re using a flexible LiPo; Can I ask which one? All of the thinergy-esque cells I’ve seen have rarely been in stock at any of the usual distributors!

      1. Flexible LiPos (primary cells and rechargeables) are available from : http://www.powerstream.com/. My one caution is that the metal leaf tabs break-off easily after just a few flexes, so I’d *highly* recommend some strain relief if you do use them in anything that flexes (like a watch band).

        I wiped-out the supplier’s stock of those NOS 7-segment displays a a couple of years ago. But since then, I’ve found many similar components on ebay.

      2. @Markus; Thanks for the pro-tip, but there are no answers to either of my questions there. Hence my asking.

        @dizot; Cheers, thanks for the link. Again, nice build.

      1. Rare? SparkFun alone has over 3.000 of them in stock. They can further be found also on Tindie and eBay.

  11. “To keep things simple, [Markus] didn’t go the usual ATMega with RTC route. Instead, he’s using an MSP430, a 32kHz crystal, and a few buttons to construct this tiny alarm clock”

    Why is that simpler than an AVR with a 32kHz crystal (not the built-in since that would probably be way to inaccurate)? The keep things simple, he used an uC without the tinyRTC-board (DS1307), but the choice of a MSP430 is arbitrary compared to an AVR.
    Of course, I might be interpreting the sentence incorrect…

    1. I think the implication was just that the mcu (regardless of architecture) is using a 32768Hz crystal, rather than a dedicated ASIC for the timekeeping.

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