Enormous Fluid Simulation On Flip Dots Is Also Enormous Amount Of Work

September 27, 2026 by Donald Papp 5 Comments

Flip dot displays are cool, and more people realize that after [mitxela]’s fluid simulation on flip dots installation was on display at EMF 2026. As glorious as the result is, it was also an amazing amount of work!

Not only did [mitxela] need to source a large number of flip dots, he also needed to find a solution for driving them that didn’t end up more trouble than it was worth. Just about everything about the surplus flip dots — from electrical requirements to mounting — was a pain to work with in one way or another. Even his optimized method of integrating a custom backpack-style driver board into the existing PCB involved a staggering amount of soldering. This project was a long time coming, and the work never really let up.

The payoff, however, is exquisite. Check it out in the video (embedded below) which really shows it off. Flip dots are like nothing else, and the subtle rippling of sound that accompanies their physical movement is oddly soothing.

The installation at EMF 2026 had a GRAVITY CONTROL joystick that allowed folks to interactively shift the display, but [mitxela] also has an accelerometer mounted so that the display physically reacts to being moved. It’s a fantastic spectacle, even more impressive in light of the work it involved.

Unsure how, exactly, flip dots work? We’ve covered all the details about how these devices function. And while a large number would be prohibitively expensive for most projects, if your project can get away with only one dot you’re probably in luck.

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A Close Look At How Flip-Dot Displays Really Work

March 3, 2023 by Chris Lott 19 Comments

[Mike Harrison] has an upcoming project which will combine a large number of flip-dot displays salvaged from buses. [Mike] thought he knew how these things worked, and had a prototype PCB made right away. But while the PCB was being manufactured, he started digging deeper into the flip-dot’s flipping mechanism.

As he dismantled one of the flip-dots, he realized there was a lot going on under the hood than he realized. The dots are bistable — staying put when power is removed. This is achieved with a U-shaped electromagnet. The polarity of a driving pulse applied to the coil determines which way to flip the dot and saturates the electromagnet’s core in the process. Thus saturated, each dot is held in the desired position because the black side of the dot is made from magnetic material. But wait, there’s more — on further inspection, [Mike] discovered another permanent magnet mounted in the base. He’s not certain, but thinks its job is to speed up the flipping action.

Besides curiosity, the reason [Mike] is studying these so closely is that he wants to build a different driver circuit to have better and faster control. He sets out to better understand the pulse waveform requirements by instrumenting a flip-dot and varying the pulse width and voltage. He determines you can get away with about 500 us pulses at 24 V, or 1 ms at 12 V, much better that the 10 ms he originally assumed. These waveforms result in about 60 to 70 ms flip times. We especially enjoyed the slow-motion video comparing the flip at different voltages at 16:55 in the video after the break.

[Mike] still has to come up with the optimum driving circuit. He has tentatively has settled on a WD6208 driver chip from LCSC for $0.04/ea. Next he will determine the optimum technique to scale this up, deciding whether going for individual pixel control or a multiple sub-array blocks. There are mechanical issues, as well. He’s going to have to saw off the top and bottom margin of each panel. Reluctant to unsolder the 8500+ joints on each panel, his current idea is to solder new controller boards directly onto the back of the existing panels.

This video is a must-watch if you’re working on drivers for your flip-dot display project, and we eagerly look forward to any future updates from [Mike]. We also wrote about a project that repurposed similar panels a couple of years ago. There are a few details that [Mike] hasn’t figured out, so if you know more about how these flip-dots work, let us know in the comments below.

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30 FPS Flip-Dot Display Uses Cool Capacitor Trick

February 24, 2021 by Mike Szczys 35 Comments

Most people find two problems when it comes to flip-dot displays: where to buy them and how to drive them. If you’re [Pierre Muth] you level up and add the challenge of driving them fast enough to rival non-mechanical displays like LCDs. It was a success, resulting in a novel and fast way of controlling flip-dot displays.

Gorgeous stackup of the completed display. [Pierre] says soldering the 2500 components kept him sane during lockdown.

If you’re lucky, you can get a used flip-dot panel decommissioned from an old bus destination panel, or perhaps the arrivals/departures board at a train station. But it is possible to buy brand new 1×7 pixel strips which is what [Pierre] has done. These come without any kind of driving hardware; just the magnetized dots with coils that can be energized to change the state.

The problem comes in needing to reverse the polarity of the coil to achieve both set and unset states. Here [Pierre] has a very interesting idea: instead of working out a way to change the connections of the coils between source and sink, he’s using a capacitor on one side that can be driven high or low to flip the dot.

Using this technique, charging the capacitor will give enough kick to flip the dot on the display. The same will happen when discharged (flipping the dot back), with the added benefit of not using additional power since the capacitor is already charged from setting the pixel. A circuit board was designed with CMOS to control each capacitor. A PCB is mounted to the back of a 7-pixel strip, creating modules that are formed into a larger display using SPI to cascade data from one to the next. The result, as you can see after the break, does a fantastic job of playing Bad Apple on the 24×14 matrix. If you have visions of one of these on your own desk, the design files and source code are available. Buying the pixels for a display this size is surprisingly affordable at about 100 €.

We’re a bit jealous of all the fun displays [Pierre] has been working on. He previously built a 384 neon bulb display that he was showing off last Autumn.

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Towards DIY Flip Digit Clocks

June 18, 2017 by Brian Benchoff 31 Comments

Seven segment displays and Nixies are one thing, but the king of all antique display technologies must be electromechanical flip dots. These displays, usually found in train stations or rarely on old bus lines, are an array of physical disks, black on one side, light on the other, that ‘flip’ back and forth with the help of an electromagnet. They’re expensive and impressive, driving them is a pain, but oh man do they look awesome.

While flip dot displays can be bought new if you know where to look, [sjm4306] had the idea to build his own out of inexpensive materials. It might just be a prototype, but we’re saying he’s succeeded. He has the workings of a seven flip-segment display, and the techniques he’s using mean it shouldn’t be too expensive to build your own.

Instead of building a matrix of flip dots, [sjm] is building a mechanical seven-segment display. Each of the segments are 3D printed in black PLA, and mounted to a piece of cardboard via a thin wire ‘axel’ going through the length of the segment. Where normal flip dots use an electromagnet to change each dot from one state to another, [sjm] mounted a very small vibrating pager motor to one end of the segment. When one half of a tact switch h-bridge is activated, the segment flips to the front. When the other half of the h-bridge is activated, the segment flips back.

Right now, this hardware is in the ‘extreme prototype’ stage, but results so far are encouraging. [sjm] has already designed a single-segment ‘module’. Plans for the electronics include optocouplers for two microcontroller pins for each segment and reed relays for each individual digit. For a four-digit display, these flip digits will only require 18 I/O pins.

You can check out [sjm4306]’s video for this project below. It’s a little bit long, but watch those things flip!

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