A Whole Lot Of Stepper Motors Make The Most Graceful 7-Segment Displays

Over the years we’ve seen many takes on the 7-segment display. Among the most interesting are the mechanical versions of what is most often an LED-based item. This week’s offering is from [John Burd], who published a very odd video showing off the clock he made. But look beyond YouTuber antics and you’ll see the stepper motors he used to turn the segments are dripping with graceful beauty. (Video, embedded below.)

Okay if you want to hear [Charlie Sheen] say “Raspberry P-eye”, this is the video for you. [John] used Cameo to get the (former?) star to talk about what was used to build the clock. Like we said, the video is weird. Let’s embrace that right away and then never talk about it again.

The thing is, the build is such a good idea. [John] went with some stepper motors you can source relatively cheaply from Ali Express and the like. Typically they’re around a buck or two each and have a couple of wings for screw mounting brackets. This builds on the segment displays we’ve seen that use hobby servos by allowing you finer control of how the segments move. Sure, the 90° rotation isn’t all that much to work with, but it will be much smoother and you can get fancy with the kinematics you choose. The only place we see room for improvement is the alignment of the segments when they are turned “off” as you can see the center segment in the video thumbnail below is not quite level. Maybe a linkage mechanism would allow for a hing mechanism that aligns more accurately while hiding the servos themselves behind the mounting plate? It’s in your hands now!

In the demo video you’ll also find some interesting test rigs built to proof out the project. One just endurance tests the mechanism, but the other two envision water-actuated segments. One pumps a hollow, transparent segment with colored liquid. The other tried to use water droplets sprayed in the air to illuminate laser segments. Both are cool and we’d like to see more of the oddball approaches which remind us of the ferrofluid clock.

23 thoughts on “A Whole Lot Of Stepper Motors Make The Most Graceful 7-Segment Displays

  1. Absolutely mesmerizing motion, entertaining video. I have not heard of Cameo and found it to be an amusing addition to the presentation. I really had not expected the clock to be that large, but in the appropriate setting (not a living room), I can see it working.

    1. I have a number of those and similar steppers, and they’re all almost entirely silent. Don’t think Nema 17 like in most 3D printers. When testing smaller motors, I always put a small piece of tape on the shaft so I can see that it’s working, they’re pretty much inaudible.

    1. …and even then, you don’t get to see it actually change properly. As far as I could tell, nowhere in this video do you see it as a clock changing from one minute to the next, as you expect a clock to do.
      As a viewer I feel sort of let down by that, just a waste of 5 minutes of my time.

  2. Oh man. I have been thinking about building a 7segment clock for so long.

    I its an invasive thought I just cant shake from my mind. its been developing over over a few years now and one day im going to have to find the time to make it a reality.

    I want a fully mechanical digital clock.

    I think a bearing or marble ball lift that releases one ball a second should give it a nice mechanical “tick”, maybe with a flip/flop on the output so every other second has a “tock”.

    The “tick” balls will be sent to run the time keeping registers that will consist of a series of counters. The first will use some sort of indexed Geneva mechanism to count balls passing and divert every 30th ball (once a minute). This will cause the decade counter pre primed with the overflow balls to be incremented, and if it rolls over this will be fed onto the next counter for the next segment in a cascading manner.

    The “tock” half of the balls will be sent to a series of mechanical 7 segment decoders. These will take the output of the decade counters and work out which segments must be flipped in order to increment the displayed number. This will in turn release a bank of marbles which will cascade down to the segments and flip them correctly.

    Hopefully i can engineer this to be as flat as possible and ideally a single layer thick so that it can be wall hung and all the mechanical working is visible. not sure on the scale yet but im thinking that the smaller the marbles the harder it will be to make them behave predictably.

    It will likely be loud, very annoying, and a single mechanical mishap will cause chaos with timekeeping, but that’s what makes it interesting right?

    1. You might want to look into TIs TPIC6-series of shift registers (TPIC6x595, TPIC6x596, where x: none, A, B or C).
      They behave like 74HC595/596, but have open drain outputs rated from 100mA/33V to 350mA/50V.
      They are also avalanche rated thus they might not need external diodes when switching inductive loads if the current is low enough.
      It should be possible to drive 2pcs. 12V 28BYJ-48 steppers from one chip without external diodes.

    2. Hi Alex. I’m trying to built the clock. If you are trying too and you wanna chat about suggestions and so on, please write me on IG: filippo_ghisio. Thanks a lot, I’ll really appreciate it.

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