A doorblell made from a stepper motor and a hard drive

Minimalistic Doorbell Doesn’t Need An Internet Connection – Or Even A Power Supply

Doorbells are among those everyday objects that started out simple but picked up an immense amount of complexity over the years. What began as a mechanism to bang two pieces of metal together evolved into all kinds of wired and wireless electric bells, finally culminating in today’s smart doorbells that beam a live video feed to their owners even if they’re half a world away.

But sometimes, less is more. [Low tech obsession] built a doorbell out of spare components that doesn’t require Internet connectivity or even a power supply. But it’s not a purely mechanical device either: the visitor turns a knob mounted on a stepper motor, generating pulses of alternating current. These pulses are then fed into the voice coil of an old hard drive, causing its arm to vibrate and strike a bell, mounted where the platters used to be.

Besides being a great piece of minimalistic design, the doorbell is also a neat demonstration of Faraday’s law of induction. The stepper motor is apparently robust enough to withstand vandalism, although we can imagine that the doorbell’s odd shape might confuse some well-meaning visitors too. If you’re into unusual doorbells, you might want to check out this one made from an old wall phone, as well as this electromechanical contraption.

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Jukebox Electromechanical Automation Explained

If you ever been curious how old-school jukeboxes work, it’s all electromechanical and no computers. In a pair of videos, [Technology Connections] takes us through a detailed dive into the operation of a 1970 Wurlitzer Statesman model 3400 that he bought with his allowance when he was in middle school. This box can play records at either 33-1/3 or 45 RPM from a carousel of 100 discs, therefore having a selection of 200 songs. This would have been one of the later models, as Wurlitzer’s jukebox business was in decline and they sold the business in 1973.

This may be the ugliest jukebox ever produced.

This jukebox is actually what turned me into the weirdo that I am today.

External appearances aside, it’s the innards of this mechanical wonder that steal the show. The mechanism is known as the Wurlamatic, invented by Frank B. Lumney and Ronald P. Eberhardt in 1967. Check out the patent US3690680A document for some wonderful diagrams and schematics that are artwork unto themselves. Continue reading “Jukebox Electromechanical Automation Explained”

A screenshot of pinball schematics

Get A Grip On Troubleshooting Your Vintage Pinball Machine

Restoring vintage technology can be a tricky business, especially without the appropriate schematics and documentation. To this end [Mark] has spent the past twelve months building a comprehensive schematic editor and circuit simulator library for electromechanical pinball machines.

Rather than explore each and every table in excruciating detail, the emSim software aims to examine how specific circuits work, and how they are used as part of the gaming experience. The aim of the project is to aid in the diagnosis and repair of vintage electromechanical pinball machines, the types that rely on a dizzying array of switches, gears, motors and coils in their operation, operating like clockwork underneath the play field. While these older pinball machines typically use alternating current, the game logic (for the most part) is still binary, and can be effectively described with Boolean operators.

Like any machine with moving parts, these systems will eventually wear down and require servicing, a task which may not be in the wheelhouse for your casual pinball enthusiast. [Mark]’s hope is that his circuit simulations will allow just about anyone to repair these classic tables, and keep them around for future generations to explore and enjoy.

If tinkering with pinball innards isn’t for you, then make sure to check out our coverage of this awesome virtual pinball table.

A man welds on a chassis

Electric Wheelchair Dump Truck Hack Really Hauls

Have you ever looked at a derelict electric wheelchair and thought “I bet I could make something great with that!” Of course you have- this is Hackaday, after all! And so did [Made in Poland], who managed to get a hold of a broken down electric wheelchair and put the full utility of his well equipped metalworking shop to work. The results? Lets just say it hauls.

What we really enjoyed about the build was that there wasn’t much that couldn’t be done by an average garage hacker with a drill press, angle grinder, and a stick welder. While it’s definitely nicer to have a lathe and a high quality welding table, plasma cutter, and everything in between, nothing that [Made in Poland] did in the video is such high precision that it would require those extensive tools. There may be some parts that would be a lot more difficult, or lower precision, but still functional.

Another aspect of the build is of course the control circuitry and user interface. Keeping the skid steer and castor approach meant that each motor would need to be controllable independently. To achieve this, [Made in Poland] put together a purely electromechanical drive controlled with momentary rocker switches and automotive relays to form a simple H-Bridge for each motor.

Of course you just have to watch until the end, because it really proves that a man will do anything to get out of hauling wood around! Old electric wheelchairs can also make a great base for big robots, as it turns out.

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The End Of The Electromechanical Era

When viewed from the far future, the early years of the 21st century will probably be seen as the end of a short era in human technological development. In the beginning of the 20th century, most everything was mechanical. There were certainly some electric devices, but consumer products like gramophone players and “movie” cameras were purely mechanical affairs. You cranked them up, and they ran on springs. Nowadays, almost every bit of consumer gear you buy will be entirely electronic. In between, there was a roughly 50 year period that I’m going to call the Electromechanical Era.

Jenny List’s teardown this week of an old Fuji film movie camera from 1972 captures the middle of this era perfectly. There’s a small PCB and an electric motor, but most of the heavy lifting in the controls was actually put on the shoulders of levers, bearings, and ridiculously clever mechanisms. The electrical and mechanical systems were loosely coupled, with the electrical controlled by the mechanical.

I’m willing to argue the specifics, but I’d preliminarily date the peak of the Electromechanical Era somewhere around 1990. Last year, I had to replace all of the rotted rubber drive belts in a Sony Walkman WM-D6C, a professional portable tape player and recorder produced from 1984-2002.

It’s not a simple tape recorder — the motors are electronically regulated to keep ridiculously constant speed for such a small device, and mine has Dolby B and C noise reduction circuitry packed inside along with some decent mic preamps. But still, when you press the fast-forward button, it physically shoves rubber-coated drive wheels out of the way, and sliding pieces of metal make it change modes of operation by making and breaking electrical contacts. Its precision lies as much in the mechanical assemblies and motors as in the electronics. It’s truly half electronic and half mechanical.

But that era is long over. The coming of the CD player signaled the end, although we didn’t see it at the time. Sure, there is a motor, but all the buttons are electronic, and all the “mechanism” is implemented almost entirely in silicon. The digital camera was possibly the last nail in the Electromechanical Era’s coffin: with no need to handle physical film, the last demand for anything mechanical evaporated. Open up a GoPro if you don’t know what I mean.

While I’ll be happy to never have to replace the drive rubber in a cassette recorder again, it’s with a little sadness that I think on the early iPods with their spinning metal hard drives, and how they gave way to the entirely silicon Zoom H5 recorder that I use now. It has a S/N ratio and quiet pre-amps, no wow or flutter, and a quality that would have been literally unbelievable when I bought the WM-D6C.

Still, if you find yourself in the thrift store, and you’ve never done so before, buy and take apart one of these marvels from a bygone era. A cassette recorder, even a cheap one, hides a wealth of electromechanical design.

Mechanical Seven-Segment Display, Smaller And Better Than The Original

One thing we love here at Hackaday is when we get to track the evolution of a project over time. Seeing a project grow over time is pretty typical — scope creep is real, after all. But watching a project shrink can be a real treat too, as early versions get refined into sleeker and more elegant solutions.

This slimmed-down mechanical seven-segment display is a perfect example of that downsizing trend. When we saw [IndoorGeek]’s first vision of an electromechanical display, it was pretty chunky. Then as now, each segment is a 3D-printed piece with a magnet attached to the rear. The segments hover over solenoid coils, which when energized repel the magnet and protrude the segment, forming the desired digit. The old version used large, hand-wound coils, though, making the display pretty bulky front to back.

Version 2 of the display takes a page from [Carl Bugeja]’s playbook and replaces the wound coils with PCB coils. We’ve seen [Carl]’s coils on both rigid substrates and flex PCBs; [IndoorGeek] used plain old FR4 here. The coils occupy four layers so they have enough oomph to extend and retract each segment, and the PCB includes space for H-bridge drivers for each segment. The PCB forms the rear cover for the display, which is also considerably slimmed down for this version. What’s the same, though, is how good this display looks, especially with strong side-lighting — the shadows cast by the extended segments are striking against the plain white face of the display.

Congratulations to [IndoorGeek] on a great-looking build and a useful improvement over the original.

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Building This Mechanical Digital Clock Took Balls

In the neverending quest for unique ways to display the time, hackers will try just about anything. We’ve seen it all, or at least we thought we had, and then up popped this purely mechanical digital clock that uses nothing but steel balls to display the time. And we absolutely love it!

Click to embiggen (you’ll be glad you did)

One glimpse at the still images or the brief video below shows you exactly how [Eric Nguyen] managed to pull this off. Each segment of the display is made up of four 0.25″ (6.35 mm) steel balls, picked up and held in place by magnets behind the plain wood face of the clock. But the electromechanical complexity needed to accomplish that is the impressive part of the build. Each segment requires two servos, for a whopping 28 units plus one for the colon. Add to that the two heavy-duty servos needed to tilt the head and the four needed to lift the tray holding the steel balls, and the level of complexity is way up there. And yet, [Eric] still managed to make the interior, which is packed with a laser-cut acrylic skeleton, neat and presentable, as well he might since watching the insides work is pretty satisfying.

We love the level of craftsmanship and creativity on this build, congratulations to [Eric] on making his first Arduino build so hard to top. We’ve seen other mechanical digital displays before, but this one is really a work of art.

Continue reading “Building This Mechanical Digital Clock Took Balls”