Flip-Dot Display Brought Out Of Retirement By New Drivers

November 21, 2017 by Dan Maloney 16 Comments

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

September 20, 2017 by John Baichtal 15 Comments

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

September 7, 2016 by Donald Papp 40 Comments

[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

June 17, 2016 by Kristina Panos 5 Comments

[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.

Most 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.

Wheel Of Resistors Form Unique Rotary Encoder

June 15, 2016 by Dan Maloney 75 Comments

Continuing his tradition of making bits of wire and scraps of wood work wonders, [HomoFaciens] is back with a unique and clever design for an electromechanical encoder.

There are lots of ways to build an encoder, and this is one we haven’t seen before. Not intended in any way to be a practical engineered solution, [HomoFaciens]’ build log and the video below document his approach. Using a rotating disc divided into segments by three, six or eight resistors, the encoder works by adding each resistor into a voltage divider as the disc is turned. An Arduino reads the output of the voltage divider and determines the direction of rotation by comparing the sequence of voltages. More resistors mean higher resolution but decreased maximum shaft speed due to the software debouncing of the wiped contacts. [HomoFaciens] has covered ground like this before with his tutorial on optical encoders, but this is a new twist – sort of a low-resolution continuous-rotation potentiometer. It’s a simple concept, a good review of voltage dividers, and a unique way to sense shaft rotation.

Is this all really basic stuff? Yep. Is it practical in any way? Probably not, although we’ll lay odds that these encoders find their way into a future [HomoFaciens] CNC build. Is it a well-executed, neat idea? Oh yeah.

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Retrotechtacular: A Mechanical UART

November 13, 2015 by Al Williams 44 Comments

We’ve heard it said that no one invented the old mechanical Teletype. One fell from the sky near Skokie, Illinois and people just duplicated them. It is true these old machines were similar to a modern terminal. They sent and received serial data using a printer instead of a screen. But inside, they were mechanical Rube Goldbergs, not full of the electronic circuits you’d think of today.

Teletype was the best-known name, but there were other mechanical monster terminals out there. [Carsten] recently took some pictures of his 99 pound Olivetti mechanical terminal. According to him, there’s only one electronic component within: a bistable solenoid that reads the data. Everything else is mechanical and driven with a motor that keeps everything at the right baud rate (110 baud).

Like the Teletype, it is a miracle these things were able to work as well as they did. Lacking a microcontroller, the terminals could respond to an identity request by spinning a little wheel that had teeth removed to indicate which letters to send (TeleType used a similar scheme). Things that are simple using today’s electronics (like preventing two keys pressed at once from being a problem) turned out to be massive design challenges for these old metal monsters.

Turns out that when [Carsten] last fired the terminal up, a capacitor finally gave up its magic smoke. He plans to fix it, though, and as long as it isn’t a mechanical problem, we bet he will.

We’ve talked about Teletypes a few times in the past, including using them for text messaging and even Twitter.

Relays Calculate Square Roots

May 8, 2015 by Bryan Cockfield 23 Comments

After seeing an exhibit of an old relay-based computer as a kid, [Simon] was inspired to build a simple two-relay latching circuit. Since then, he’s been fascinated by how relays can function to do computation. He’s come quite a long way from that first latching circuit, however, and recently finished a huge five-year project which uses electromechanical relays to calculate square roots.

The frame of the square root calculator can hold up to 30 identical relay modules, each of which hold 16 relays on PCBs, for a total of 480 relays. The module-based setup makes repair and maintenance a breeze. Numbers are entered into the computer by a rotary dial from an old phone and stored in the calculator’s relay memory. A nixie tube display completes the bygone era-theme of the device and shows either the current number that’s being entered, or the square root of that number as it’s being calculated.

The real magic of this project is that each relay has an LED which illuminates whenever the relay is energized, which shows the user exactly where all of the bits of the machine are going. [Simon] worked on this project from 2009 and recently completed it in 2014, and it has been featured at the San Mateo Maker Faire and at Microsoft Research in Redmond, WA. We’ve seen smaller versions of this before, but never on this scale and never for one specific operation like square roots.

Video below. Thanks to [Bonsaichop] for the tip!

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