Are you familiar with this distinctive type of display, at one time often found at railway stations? Some time ago I presented a series of "railway" devices, including a GPS and on-board computer, and today I continue this theme and show a display I obtained from the same source, after decommissioning.
An electromagnetic display, also often referred to as a flip-dot display, as the English-language name suggests, consists of two-coloured flaps that are rotated by electromagnets. Each flip-dot has two sides in different colours (usually yellow and black) and its position is changed by a short current pulse applied to a coil. After such a pulse, the flip-flop remains in the set position even when the power is removed, which means very low power consumption - current is only needed when changing the displayed information. This whole process is associated with a characteristic mechanical 'rattling' sound.
My copy was damaged and from scrap anyway, so I opted for a slightly more destructive presentation and also looked under the coils themselves.
You can see the two diodes there, which allow the polarisation to be controlled in an array fashion and also simplify the wiring of the array. This makes it possible to address points in a row and column arrangement without running separate wires to each coil.
(schematic source: https://electronics.stackexchange.com/questio...is-the-purpose-of-diodes-in-flip-dot-displays )
Finally, a short video presentation - I simply controlled the whole thing by hand by applying the wires from the lab power supply - you can watch from the audio:
In summary , this was a fairly old flip display from scrap. It had already come to me in such poor condition that I simply decided it wasn't worth running any further. You can't see it very well in the pictures, but it's missing a lot of dots, and the connectors are also only suitable for replacement. The hardware itself appears to be quite old, the date on the sticker indicates 05.11.2006, so it is almost 20 years old. Judging by the contents of the display when I got it, it's still only one of at least a few segments. And here comes the conundrum - what could this display have been showing in the first picture? I don't seem to have any concrete ideas on this....
Have you used this type of display, either at work or perhaps for DIY? Where else can these be found?
PS: Related 'railway' topics:
Polish company's railway on-board computer - construction, interior and commissioning
Polish company's ISM 868 MHz RM-2 railway modem module - interior and construction
Polish made extension module - interior and exterior
Railway GPS module by Polish company - construction and interior
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