The Rossio railway station in Lisbon (Portugal) uses little colored cylinders for parts of their displays (marked in red).

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I'd be really interested in getting more information about them, but I couldn't find anything about them online.

The only reference for something similar is http://tpdomain.blogspot.com/2017/08/full-color-mechanical-display.html where someone proposes to build such a display (apparently not knowing, that it already exists).

What are they called? How exactly do they work?

  • \$\begingroup\$ Mechanical display? \$\endgroup\$ – winny Sep 10 '18 at 13:04
  • \$\begingroup\$ I wonder how many folk here have been to the main station in Lisbon and, if they have, would they know it was the main station and, would they have taken much notice of the displays (assuming we know what displays you refer to). \$\endgroup\$ – Andy aka Sep 10 '18 at 14:01
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    \$\begingroup\$ @Andyaka, not many I'd wager. But I'm booking the next plane to Portugal to check it out, sounds pretty sweet. \$\endgroup\$ – Wossname Sep 10 '18 at 14:21
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    \$\begingroup\$ Neat concept in your link. They seem to be forgetting that notwithstanding they use paint on the cylinder, it's still reflecting light that adds across pixels, so they should use an RGB basis, not a CMY (printing, subtractive) basis. \$\endgroup\$ – Neil_UK Sep 10 '18 at 15:34
  • \$\begingroup\$ Adius, My article was published a year ago on tpdomain so maybe it was the inspiration for the display in Portugal. Do you know when was it installed ? \$\endgroup\$ – Rami Rouhana Sep 10 '18 at 17:37

My company uses something similar as an indicator. The flip disc has a magnet in it, and one side is brightly colored while the other is black. Current is directed through an electromagnet just behind the disc briefly, one way, to align the magnetic fields and get the brightly colored side to flip forward. When current flows the other way, the magnetic field flips, as does the disc, and the black side shows.

The discs themselves are mechanically designed so that a quick magnetic burst will flip them, and they stay in a mechanically stable state so that you don't have to continuously apply current to the electromagnet to keep them in place.

Our 'discs' are basically small cylinders. To answer your actual question, they are called "flylinder".

  • \$\begingroup\$ So, what do you call it? Without that information, this is not an answer to the actual question. \$\endgroup\$ – Dave Tweed Sep 10 '18 at 15:26
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    \$\begingroup\$ @DaveTweed A flylinder. Why do you ask? \$\endgroup\$ – K H Sep 10 '18 at 17:32
  • \$\begingroup\$ I can confirm they're called flylinders. \$\endgroup\$ – schadjo Sep 10 '18 at 18:21

Many years ago I used 7-segment displays which were electro-mechanical. They were large, heavy and expensive, but retained the information without power.

I have found something similar at https://flipdots.com/en/products-services/large-7-segment-displays/ However, these are not alphanumeric - I feel a dot array is the best solution for such applications.


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