Split-flap Train Display Uses Punch Cards; Serviced with Station Ingenuity

short but highly detailed documentary by [Krzysztof Tyszecki] explores the split-flap display system in place at the Łódź Kaliska train station in Poland as well as the efforts needed by the staff to keep it running and useful to this day. Split-flap displays might be old technology, but many are still in use throughout the world. But even by those standards, the unit at Łódź Kaliska is a relic you wouldn’t expect to see outside a museum. “I doubt you’ll find an original anywhere else,” says a staff member. It requires constant upkeep to remain operational, and meeting the changing demands of a modern station within the limitations of the original system takes some cleverness. “In general the failure rate of the device is terrible,” he adds.

Operator console for Czech PragotronThe system runs on punch cards. You can’t buy them anymore, so a local printer makes them – several hundred are needed every time there is a schedule change. The punching pliers (which also can no longer be purchased) get so worn out they replace the pins with custom-made ones from a local locksmith. The moving parts of the card reader have split-pins which need to be replaced every week or two – the stress of repeated movement simply wears them away. There’s nothing to do but replace them regularly. The assembly needs regular cleaning since dust accumulates on the cards and gets into the whole assembly. The list goes on… and so does the station.

There is no computation in the modern sense – it’s an electromechanical signing system managed and updated by human operators. It has more in common with a crossbar switch based telephone exchange than anything else. The punch cards are just a means of quickly, accurately, and repeatedly setting the displays to known states.

The short documentary goes into a lot of detail about every part of the system. The cards themselves are described in detail (1:07), as is the operator’s routine (2:27). We even see the back end controller (9:41), as well as see a split-flap module taken apart and tested (14:33) with an old tester the staffer isn’t sure will even work – but as with everything else we see, of course it does.

Split-flap displays are fascinating pieces of technology. We have even seen people build their own split-flap displays from scratch!

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Writing a Message in Hypnotizing Style

If you’ve ever encountered a rapidly spinning split-flap displays at an airport terminal, it’s hard not to stop and marvel at them in action for a few extra seconds. Because of this same fascination, [M1k3y] began restoring an old one-hundred and twenty character sign, which he outlines the process of on his blog.

Finding documentation on this old relic turned out to be an impossibility; the producers of the model themselves didn’t even keep it off-hand any longer. In spite of that, [M1k3y] was able to determine the function of the small amount of circuitry driving the sign through process of elimination by studying the components. After nearly a year of poking at it, he happened across a video by the Trollhöhle Compute Club, demonstrating the successful use of the same display model. Luckily, they were kind enough to share their working source code. By reverse engineering the serial protocol in their example, he was able to write his own software to get the sign moving at last.

Once up and running, [M1k3y] learned that only eighty of the sign’s characters were still operable, but that is plenty to make a mesmerizing statement! Here is a video of the cycling letters in action:

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Split Flap Display: If You Can’t Find It, Built It

It’s pretty hard to deny that split-flap displays are incredibly awesome. This one has been a long time coming, and it’s not a refab or surplus build. [Tom] fabricated these beautiful alpha-numeric split flaps from scratch.

Having recently seen an alarm-clock split flap hack just a week or so ago we found ourselves wondering where in the world people manage to find this type of awesome mechanical hardware. If you can’t get it out of grampa’s attic, the next best thing is to build it from the ground up.

This was not a build to be taken lightly. [Tom] started years ago, and part way into the project we looked at some of the control hardware for the installation. Make sure that you dig deep into his blog posts. It’s the only way you’ll put together the whole picture of how he ended up with each belt and stepper motor driven character module.

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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.

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