Driving an 8-digit split flap display

[Markus] got his hands on a split-flap display and built a controller for it. These sometimes can be found on really old alarm clocks, but [Markus] was a lucky-duck and managed to acquire this large 8-digit display which previously made its home in a railroad station. They work like a Rolodex, mounting flaps around a cylinder for a full alpha-numeric font set.

A PIC 12F683 was selected to control the display, using optoisolation to separate the 42V display motors from the driver circuit. From the video after the break we think he did a wonderful job of getting this working. It only takes six I/O pins to control and the sound and look of the digits scrolling leaves us quite jealous.

So what’s he got in store for it? The first thing he did was use it to count down to the New Year.


  1. Andrew F says:

    I wonder how he knows where zero is, if the display is reset, does he manually have to reset zero?

  2. Jordan says:

    I’ve always wondered what those where called… now I know.

  3. Jordan says:

    Curse you, Hack-A-Day, and your lack of a comment-editor.

  4. me too, I love these displays :-)

  5. Benjamin says:

    WOW! Total retro!

    Nice work and cool video Markus.

  6. J. Peterson says:

    If anybody finds a source for these, please let us know!

  7. Colecago says:

    I like how he has to go from x9 to (x+1)2 because of the time it takes to reset the numbers.

    Pretty wesome though

  8. David says:
  9. Nemo says:

    Seems like it wouldn’t take too much effort to make a design for this kind of display using a laser cutter or CNC machine. The mechanism is simple, everything except for the motors and sensors could be created from laser-cut wood. I’m sure a kit for this kind of display would have high demand.

    Someone with access to a laser cutter, get on it quick!

  10. mowcius says:

    Whoa, I want one!

    That’s such a cool display to have!

  11. Hirudinea says:

    Mabye he could turn it into a scrolling display for an rss feed or twitter (ugh, twitter. :p )

  12. bluewraith says:

    Great.. now I have to go find an old railstation and do some reallocation of property in order to feed my want of one of these. I wonder what the duty cycle on the mechanics are, as I would probably just have it flip around randomly for the fun of it.

  13. Desmond says:

    You can make your own ‘Lost at Home’ game where you have to push a button every 108 minutes or else a bunch of red hieroglyphics appear.

  14. trike says:

    I’ve waited months for something like this!

    I want to use something like this for a portable MP3 player, automobile receiver, or Hi-Fi set fashioned like something out of the 1960s or 1970s. Move over steampunk, there’s a new retro modding scene.

  15. sam says:

    reminds me of lost……..

  16. HackerK says:

    Cool.. yea. I was also wonder what those things call…

    But yup, it is too noisy to use as a clock.

    Now it would be even cooler if it is the dot matrix version (often seen on older buses)

  17. Osgeld says:

    they used them for “digital” clocks for many years in the home (obviously smaller) though the seconds were usually on a wheel that just rotated from 00 – 59

  18. Whatnot says:

    I’m sure there are many available on ebay and such sites, since most stationdisplays and other public displays are going digital in droves the last years

  19. medwardl says:

    This made me think of using it in the back of my car for either telling people off “instead of an electronic led version” or some weird James Bond license thing but I don’t think it would work.

  20. Markus Gebhard says:

    > I wonder how he knows where zero is, if the display is reset, does he manually have to reset zero?

    There are two reflective IR-sensors: One for counting the characters and one for finding “zero” position.

  21. strider_mt2k says:

    I LOVE these displays.

    Lucky LUCKY duck!

  22. Peter says:

    Thought those only displayed: “CANCELLED”, “DELAYED” or, very rarely: “ON TIME” :-)

    Nice job!

  23. NatureTM says:

    I’ve wanted one of these for awhile. After a lot of time spent googleing, I realized I can’t afford one anyway.

  24. vorn says:

    Toooo cool! Yeah, if there was some DIY kits available of these I can imagine that person making a small fortune!

  25. uC says:

    Here is a nice datasheet that includes some info on the number of flaps (up to 84, addressable < 9 seconds)


  26. sati says:

    I think it might be possible to make the flaps using something.

  27. boz says:

    Hi, Nice project but a lack of info, I had to do my own controller recently for a client and here is my write up of it.

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