Flip dots are driven by a pair of electromagnetic posts that attract or repel a magnet embedded in the dot, and [Larry Builds] version is no different. For the electromagnets, he used M3 threaded rod with enamel wire wound around them using a drill. At first, he used a large magnet in the center of the 3D printed dot, but the magnetic field was large and strong enough to flip the surrounding dots in an array. He then changed the design to a small 4 mm diameter magnet in the edge that aligns directly with the electromagnets. This design looks very similar to those used by Breakfast for their massive installations. By modifying electromagnets and adding spacers around the magnets, he was able to reduce the operating current from 2 A to below 500 mA. [Larry Builds] also breadboarded a basic driver circuit consisting of H-bridges multiplexed to rows and columns with diodes.
We will be keeping a close eye on this project, and we look forward to seeing it evolve further. It’s definitely on our “things to build” list. We’ve embedded multiple videos after the break showing the progress thus far.
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.
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.
We love electromagnetic displays: take the modern look of a digital readout, combine with the low-tech coil mechanism that you theoreticallycould create yourself, add a dash of random clacking sounds, and what’s not to like? Evidently, [Nicolas Kruse] shares our affection for these displays, because he’s taken it beyond theory and created a 7-segment magnetically-actuated display from scratch.
The display is 3D-printed, as you would expect these days. Each segment contains a small neodymium magnet, and each coil a 1 mm iron core for flux concentration. The coils are driven with a 1.6 A peak current, causing the segments to flip in less than 10 ms. [Nicolas] provides STL files for the display base, segments, and spools so you can print your own display. He’s also released the schematics and code for the driver, which uses an ATtiny44 to drive the coils through N- and P-channel MOSFETs. Initially designed to drive a passive 4×7 matrix of displays, the driver couldn’t quite manage to flip one segment without affecting its neighbors. However, for a single display, the driver works fine. We hope he figures out the matrix issue soon, because we really want to see a clock made with these displays.
You can see (and hear) a short video of the display in action after the break. The clacking does not disappoint!
LED matrix displays and flat-screen monitors have largely supplanted old-school electromechanical models for public signage. We think that’s a shame, but it’s also a boon for the tinkerer, as old displays can be had for a song these days in the online markets.
Such was the case for [John Whittington] and his flip-dot display salvaged from an old bus. He wanted to put the old sign back to work, but without a decent driver, he did what one does in these situations — he tore it down and reverse engineered the thing. Like most such displays, his Hannover Display 7 x 56-pixel flip-dot sign is electromechanically interesting; each pixel is a card straddling the poles of a small electromagnet. Pulse the magnet and the card flips over, changing the pixel from black to fluorescent green. [John] used an existing driver for the sign and a logic analyzer to determine the protocol used by the internal electronics to drive the pixels, and came up with a much-improved method of sending characters and graphics. With a Raspberry Pi and power supply now resident inside the case, a web-based GUI lets him display messages easily. The video below has lots of details, and the code is freely available.
Flip-Dot displays are so awesome that they’re making a comeback. But awesome is nothing when you can have an insane flip-dot display that is three-dimensional with the dots floating in mid-air. Researchers at the Universities of Sussex and Bristol have built what they call JOLED, an array of floating pixels that can be controlled via a combination of ultrasonic standing waves and an electrostatic field. These “voxels” can be individually moved in space via ultrasonics, and can also be individually flipped or rotated through any angle, via the electrostatic field.
The key to the whole thing is something they call Janus Objects – hence JOLED. Janus particles have different features or chemistry on two opposite sides. A portion of each voxel is speckled with a small amount of titanium dioxide nano powder. This gives it a bipolar charge that makes it respond to the variable electrostatic field and hence capable of axial rotation. Half of each white voxel can then be covered with a contrasting color – red, blue, black – to achieve the flip dot effect. Each voxel appears to be a couple of millimeters in diameter. The ultrasonic actuators appear to be regular piezo transmitters found in every hacker’s parts bin. Transparent glass plates on opposite sides apply the variable electrostatic field.
While this is still experimental and confined to the research lab, future applications would be interesting. It would be like breaking e-ink displays out of their flat glass confines and giving them a third dimension. The short, two-minute video after the break does a good job of explaining what’s going on, so check it out. Now, who want’s to be the first to build a JOLED clock?
Admit it, you’ve always wanted to have your own flip-dot display to play with. Along with split-flap displays, flip-dots have an addictive look and sound that hearkens back half a century but still feels like modern technology. They use a magnetic coil to actuate each pixel — physical discs painted contrasting colors on either side. It means that you really only need electricity when changing the pixel, and that each pixel makes a satisfyingly unobtrusive click when flipped. The only problem with the displays is that they’re notoriously difficult to get your hands on.
Breakfast, a Brooklyn-based hardware firm known for creative marketing installations, unveiled their Flip-Disc Display System this morning. Used displays have come up on the usual sites from time to time, but often without a controller. Traditional flip-dot manufacturers haven’t sought out the individual hacker or hackerspace, and a click-to-buy option has been difficult if not impossible to find.
Flip-dot displays are grand, especially this one which boasts 74,088 pixels! I once heard the hardware compared to e-ink. That’s actually a pretty good description since both use a pixel that is white on one side and black on the other, depend on a coil to change state, and only use electricity when flipping those bits.
What’s remarkable about this is the size of the installation. It occupied a huge curving wall on the ooVoo booth at 2015 CES. We wanted to hear more about the hardware so we reached out to them they didn’t disappoint. The ooVoo crew made time for a conference call which included [Pat Murray] who coordinated the build effort. That’s right, they built this thing — we had assumed it was a rental. [Matt Farrell] recounts that during conception, the team had asked themselves how an HD video chat for mobile company can show off display technology when juxtaposed with cutting edge 4k and 8k displays? We think the flip-dot was a perfect tack — I know I spent more time looking at this than at televisions.
Join us after the break for the skinny on how it was built, including pictures of the back side of the installation and video clips that you have to hear to believe.