Reverse Engineering Solari Soft Flap Displays

This is a side view of the guts of a one character Solari soft flap module. This is the type of mechanical display used in some transportation hubs that have a flap for each letter. The motor turns the flaps through the alphabet until it gets to the target letter. Recently [Boz] had a client approach him who needed a custom controller for a 20-character soft flap display. (Link fixed in 2022. Thanks Wayback Machine!)

The process started out with a magnifying glass and multimeter which yielded a rather complicated hand-drawn schematic. An optical encoder is used to judge which character is currently displayed. After analyzing the output using an oscilloscope [Boz] designed a PIC based driver board which is controlling the display seen in the clip after the break.

The great thing about these displays is that they don’t use any electricity except when they change letters. This sounds like the predecessor of ePaper and makes us wonder if there are any companies developing high-contrast ePaper to replace soft-flap digits?

25 thoughts on “Reverse Engineering Solari Soft Flap Displays

  1. Nice work!

    Always love seeing someone reverse engineering stuff…

    As of the thing with the companies doing high-contras ePaper…. I would REALLY miss that awesome flipping sound!!!

    1. Some of the boards that used to use this type of displays often get a set of speakers & a circuit installed to “simulate” the sound of the real deal.
      And sometimes also the visual animation to boot.

  2. Where do you get these for individual purchase? I haven’t been able to find the flip modules or the electromechanical dot matrix modules anywhere online.

    There are a few manufacturers, but they seem to only be business-to-business – or through integrators, who definitely aren’t interested in individual sales.

  3. Hi Guys

    Again sorry for the video, It and the pictures were filmed by the customer from his old phone once it was partially dismantled and after a few beers.

    It’s with the carpenter now, once its all back in a few weeks I promise I will get better pictures with all the flappers going – and some more appropriate wording :-[

  4. I have wanted to build a retro 1970s styled home audio deck to display mp3 id3 tag information (file name, track number) for a long time. I suppose it could also pull information from hd radio signals.

    These types of displays’ style fit many retro projects better than Nixie tube, LCD, or VFDs.

    Just for fun, I’d like to see someone build a calculator using these

  5. These flap displays have always fascinated me ever since I was a little boy (and that was a VERY long time ago). I could sit and watch in an airport for hours (or so it seemed) how the info on the display is changing. It always reminded me of some kind of a roulette – until the entire text change is complete, you never quite know if your flight is on time or delayed. Those last moments before the flaps settle could be pretty intense when it’s already been delayed a few times…

    I am also wondering where people get these? These days it seems anything can make its way on ebay but I never came across these flap-display digits.

  6. If you want to play with split-flap displays just go to this site. These are 30 split-flap letters and a clock in our office that can be controlled from anywhere.

    Because of the daylight only illumination the text will only be visible during german daylight (typical 6am to 4pm UTC)

  7. Hello from Algeria, I would like to thank you a lot for this informative post , i’m working right now on a similar project in Algeria ( Oran city train station) . I asked some youtubers but .. no answers .
    My split flop displays are from Bodet ( a French company ) with 48VAC synchronous motors and 12VDC for the circuit, a I have 16-pin output from the motor controler, I was thinking about controlling it using an arduino then I saw your post I was thinking about controlling it with an old window everything in my plan changed !!! I have some question in my mind, and I know it’s a lot to ask but I hope you’ll understand that I’m so enthusiastic to see the result of this project ,
    You did some reverse engineering to know the the functionality of the motor control ? can you please help me !

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.