Hacking a flip dot display

While casually lurking on a famous auction website, [TeddyDesTodes] found the gem shown in the above picture and reverse engineered it. This is a flip dot display, the Brose Vollmatrix compact to be precise. It consists of a grid of small metal discs that are black on one side and yellow on the other, set into a black background. With power applied, the disc flips to show the other side. The disc is attached to an axle which also carries a small permanent magnet. Positioned close to the magnet is a solenoid. By pulsing the solenoid coil with the appropriate electrical polarity, the magnet will align itself with the magnetic field, also turning the disc.

After carrying the 25kg display from his post office to home, [TeddyDesTodes] opened it and discovered that the main control board was using two RS422 transceivers. So he fired up his bus pirate, started to sniff the traffic and noticed that several commands were repeatedly sent. [TeddyDesTodes] stopped the transmission, sent these particular commands and had the good surprise to see some dots flipped. From there, displaying something was a piece of cake.

If this is familiar to you it may be because it was shared in one of the Trinket Contest Updates. But the background details were just so much fun we think this deserves a full feature of it’s own. Do you agree?

Comments

  1. David says:

    Here’s a similar hack making a bus flipdot display work as a twitter feed http://www.behance.net/gallery/tweetDots/9206947

  2. zippora says:

    I think they have a similar project at OSAA. Bertho, Rohde: bring it on!!

  3. Matt says:

    That is the most epic USB-i2c converter ever.

  4. Sudos says:

    black and yellow black and yellow black and yellow black and yellow.

    Best geeky bathroom Occupancy sign I’ve seen yet!

  5. Stoneshop says:

    There;s an electromechanical 7-segment display (from a scoreboard or something; it’s quite large) somewhere in the space. The segments are hinged and move in and out of view using two magnets.

  6. JimBob says:

    I checked these out-a bit pricey. You would think someone with a 3D printer could make a cheaper version…

  7. Jonathan Wilson says:

    They have these on many of the buses around here (with a 3-digit 7-segment portion for the route number and a dots section like that one for the destination info)

  8. Bradley says:

    I used to work on those!

  9. j s says:

    What a silly name…”teddy of death”…

  10. tobias says:

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