A Relay Calculator With DIY Neon Displays, Just Because

This looks like one of those projects that started out as a glimmer of an idea and led down a rabbit hole. But it’s a pretty cool rabbit hole that leads to homebrew neon seven-segment displays on a calculator with relay logic.

It’s a little thin on documentation so far, but that’s because [Mark Miller]’s build is one of those just-for-the-fun-of-it things. He started with a bag full of NE-2 tubes and the realization that a 3D-printed frame would let him create his own seven-segment displays. The frames have a slot for each segment, with a lamp and current limiting resistor tucked behind it; with leads brought out to pins and some epoxy potting, these displays would be hard to tell from a large LED seven-segment. Rolling your own displays has the benefit of being able to extend the character set, which [Mark] did with plus-minus and equal sign modules. All of these went together into a two-banger calculator — addition and subtraction only so far — executed in relays and vacuum tubes. Version 2.0 of the calculator regressed to all-relay logic, which must sound great.

We heartily regret the lack of a satisfyingly clicky video, but we’ll give it a pass since this is so cool. We’ll be watching for more on this project, but in the meantime, if you still need to get your click on, this electromechanical BCD counter should help.

The Noisiest Seven-Segment Display Ever

Few mechanical clocks are silent, and many find the sounds they make pleasant. But the stately ticking of an old grandfather clock or the soothing sound of a wind-up alarm clock on the nightstand are nothing compared to the clattering cacophony that awaits [ProtoG] when he finishes the clock that this electromechanical decimal to binary to hex converter and display will be part of.

Undertaken as proof of concept before committing to a full six digit clock build, we’d say [ProtoG] is hitting the mark. Yes, it’s loud, but the sound is glorious. The video below shows the display being put through its paces, and when the clock rate ramps up, the rhythmic pulsations of the relays driving the seven-segment flip displays is hypnotizing. The relays, one per segment of the Alfa Zeta flip displays, have DPDT contacts wired to flip a segment by reversing polarity. As a work in progress, [ProtoG] hasn’t shared many more details yet, but he promises to keep us up to date on the converter aspect of the circuit. Right now it just seems like a simple but noisy driver. We’ll be following this one with interest.

If you prefer your clocks quieter but still like funky displays, check out this mixed media circus-themed clock.

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A Gloriously Impractical Electromechanical Display

For this year’s office holiday party, [Gavan Fantom] wanted to do something really special. Coworkers were messing with LEDs to come up with displays and decorations, but they lack that old-school feel of mechanical displays. He wanted to create something that had retro look of moving elements, but didn’t want to just recreate the traditional flip mechanism we’ve all seen over and over.

The mechanism to drive a single “pixel”.

What [Gavan] came up with is breathtakingly impractical 8×8 display that sounds as cool as it looks. Each “pixel” in the display is a 3D printed screw mechanism rotated by a hobby servo. As the pixel is rotated in its case, it becomes progressively more visible to the observer. The opacity of the pixel can even be adjusted by varying the degree of rotation, allowing for rudimentary display of grayscale images.

Each element in the display is made up of seven 3D printed parts and two nails, which the mechanism slides on to move forward and backward. An 8×8 display needs 64 elements, which means the entire display needs 64 servos, 128 nails, and a whopping 448 3D-printed parts. Even with two printers attacking the production in parallel, the printing alone took over two weeks to complete.

The display is powered by a Raspberry Pi and three “Mini Maestro” controllers which can each handle 24 servos. [Gavan] found some sample code in Python to pass commands to the Maestro servo controllers, which he used as a template when writing his own software. The Python script opens image files, converts them to grayscale, and then maps the value of each pixel to rotation of the corresponding servo. He says the software is a little rough and that there’s still some calibration to be done, but we think the results are phenomenal so far.

Mechanical displays are a favorite of hackers, due in no small part to the awesome noises they make while in operation. While we’ve seen some very creative approaches to this type of display before, what [Gavan] has created here is certainly in a league of its own.

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Flip-Dot Display Brought Out of Retirement by New Drivers

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.

You may recall [John] from a recent edge-lit Nixie-like display. Looks like he’s got a thing for eye-catching displays, and we’re fine with that.

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Hackaday Prize Entry: MOLBED Braille Display

Electromechanical braille displays, where little pins pop up or drop down to represent various characters, can cost upwards of a thousand dollars. That’s where the Modular Low-cost Braille Electro Display, aka MOLBED, steps up. The project’s creator, [Madaeon] aims to create a DIY-friendly, 3D-printable,  and simple braille system. He’s working on a single character’s display, with the idea it could be expanded to cover a whole row or even offer multiple rows.

[Madeon]’s design involves using Flexinol actuator wire to control whether a pin sticks or not. He designed a “rocker” system consisting of a series of 6 pins that form the Braille display. Each pin is actuated by two Flexinol wires, one with current applied to it and one without, popping the pin up about a millimeter. Swap polarity and the pin pops down to be flush with the surface.

This project is actually [Madeon]’s second revision of the MOLBED system. The first version, an entry to the Hackaday Prize last year, used very small solenoids with two very small magnets at either end of the pole to hold the pin in place. The new system, while slightly more complex mechanically, should be easier to produce in a low-cost version, and has a much higher chance of bringing this technology to people who need it. It’s a great project, and a great entry to the Hackaday Prize.

Amazing Meccano Pinball Machine Fully Functional Before Meeting Its Fate

[Brian Leach] of the South East London Meccano Club has put an impressive amount of ingenuity into making his pinball machine almost entirely out of Meccano parts. He started in 2013 and we saw an earlier version of the table back in 2014, but it has finally been completed. It has all the trappings of proper pinball: score counter, score multiplier with timeout, standing targets, kickouts, pot bumpers, drop targets, and (of course) flippers and plunger.

The video (embedded below) is very well produced with excellent closeups of the different mechanisms as [Brian] gives a concise tour of the machine. Some elements are relatively straightforward, others required workarounds to get the right operation, but it’s all beautifully done. For example, look at the score counter below. Meccano electromagnets are too weak to drive the numbers directly, so a motor turns all numbers continuously with a friction drive and electromagnets are used to stop the rotation at specific points. Reset consists of letting the numbers spin freely to 9999 then doing a last little push for a clean rollover to zero.


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Denver Mini Maker Faire: Fun With Pinball

[Mark Gibson] probably has nothing against silicon. He just knows that a lot that can be done with simple switches, relays, and solenoids and wants to share that knowledge with the world. This was made abundantly clear to me during repeat visits to his expansive booth at Denver Mini Maker Faire last weekend.

In the sunlight-filled atrium of the Museum of Nature and Science, [Mark] sat behind several long tables covered with his creations made from mid-century pinball machines. There are about two dozen pieces in his interactive exhibit, which made its debut at the first-ever Northern Colorado Maker Faire in 2013. [Mark] was motivated to build these boards because he wanted to get people interested in the way things work through interaction and discovery of pinball mechanisms.

fun with pinball thumbMost of the pieces he has built are single units and simple systems from pinball machines—flippers, chime units, targets, bumpers, and so on—that he affixed to wooden boards so that people can explore them without breaking anything. All of the units are operated using large and inviting push buttons that have been screwed down tight. Each of the systems also has a display card with an engineering drawing of the mechanism and a short explanation of how it works.

[Mark] also brought some of the original games he has created by combining several systems from different machines, like a horse derby and a baseball game. Both of these were built with education in mind; all of the guts including the original fabric-wrapped wires are prominently displayed. The derby game wasn’t working, but I managed to load the bases and get a grand slam in the baseball game. Probably couldn’t do that again in a million summers.

fun with pinball baseball game
Take me out to the Maker Faire! Click to embiggen.

About five years ago, we covered [Mark]’s build of an atomic clock from pinball machine parts. It’s about time we featured his work again. We have shared a lot of pinball-related builds over the years from the immersive to the gigantic to the dankest of the dank.