Pikul Servo Powered Falling Dominoes Pushing a Cube

Domino Row Goes With The Flow

May 30, 2022 by Michael Shaub 1 Comment

Around here, we’re always excited about a new actuator design. Linear actuators are particularly hard to make cheap, fast, and good, so it’s even better when something new that we can build ourselves slides onto the scene.

Researchers at U Penn’s Pikul Research Group took inspiration from the cascade of falling dominoes for an innovative take on linear motion. This article on IEEE Spectrum describes the similarity of the sequential tipping-over with the peristaltic motion of biological systems, including you, swallowing right now.

The motion propagation in falling dominoes, called a Soliton Wave, can be harnessed to push an object at the front of the wave, just like a surfer. See the videos after the break for examples of simple setups that any of us could recreate with laser-cut or 3D printed parts. Maybe you won’t be using them to help a robot swallow (a terrifying idea that the article suggests), but you might need a conveyor or a novel way to help a device crawl like a shrimp. The paper is behind a paywall on IEEE, though you readers likely see enough in the videos to get started, and we can’t wait to see where your dominoes will lead us next.

RIP John Birkett, Parts Vendor Extraordinaire

May 20, 2022 by Jenny List 56 Comments

It is with sadness that we note the passing of John Birkett, proprietor of the legendary eponymous surplus radio and electronics store on an unassuming street in the British city of Lincoln, at the age of 93. He has been a fantastic source of esoteric parts and electronic assemblies for many decades, and though many of you from beyond where this is being written may never have heard of him the chances are that if you follow electronics enthusiasts from the UK you will have unwittingly seen parts which passed through his hands.

A typical Birkett advert from 1986 — Gateway to a world of wonders: a typical Birkett advert from 1986.

There was a time when surplus stores were a relatively common sight, given their window of opportunity by the huge quantity of post-war and Cold War military gear at knock-down prices. My town had one when I was a kid, but though it sold its share of electronic goodies it was more of a place for sturdy olive green outdoor wear or all the 1930s British military uniform items you might ever need. J. Birkett was different, as a purely electronics store the shop rapidly became the go-to place for both the most necessary and the most unexpected of parts.

His motto was “Not a piece of junk in sight”, and though as with much surplus equipment there is plenty of junk to be found it was his eye in managing to stock the junk which was most interesting and useful that made his selection special. Such was its reach that most of his customers including me never made it to Lincoln and the store itself, instead we came to him through his mail-order business and attendance at radio rallies. I fondly remember the anticipation of receiving a Birkett parcel, and I still have plenty of parts that came from him. An FM tuner converted for use as a 2 meter receiver is still in a box somewhere, and I’m pretty certain my storage unit still holds a pair of Pye Cambridge VHF transceivers he supplied.

According to Google the shop remains open, and we hope that state of affairs will continue. Surplus may not be what it once was, but we thank John Birkett for what he gave to generations of British hardware hackers. May he rest in peace.

Header image: Oliver Mills, (CC BY-SA 2.0).

Autogyro Models Are Hard — Even For [Peter Sripol]

May 9, 2022 by Adam Fabio 12 Comments

Aviation consists of two major groups. Airplane enthusiasts, and helicopter enthusiasts. The two groups rarely get along, each extolling the virtues of their chosen craft. Somewhere in between are autogyro folks. People who like vehicles that blend the best (or worst) of both airplanes and helicopters. Aviation master [Peter Sripol] has dipped his toes into the autogyro world, but not without some trouble.

Autogyros are propelled by a propeller, like a plane. They also have a tail section that works similar to a fixed-wing aircraft. That’s where the similarities end though. Lift for autogyros comes in the form of a rotating set of blades, much like a helicopter. Autogyro rotors aren’t powered during flight. They utilize autorotation. The blades freewheel, spun by the air as the craft moves forward.

[Peter] recently got his hands on a full-scale autogyro. So it made sense to build a model to help learn to fly. This isn’t [Peter’s] first attempt with autogyro models. He’s built a few in the past, with limited success. This time he started from scratch and ran into even more problems!

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Prusa’s Official Enclosure Pulls Out All The Stops

May 8, 2022 by Tom Nardi 50 Comments

It’s well known in the desktop 3D printing world that you get what you pay for. If you want to spend under $300 USD, you get a Creality Ender 3 and deal with its slightly half-baked nature. Or if you’ve got the money to burn, you buy a Prusa i3 MK3 and know that you’ll remain on the cutting edge thanks to a constantly evolving slicer and regular hardware revisions.

Now it stands to reason that an expensive product will have expensive accessories, but even still, the recently unveiled “Original Prusa Enclosure” is sure to induce a bit of sticker shock in even the most ardent of [Josef Průša]’s fans — the most bare-bones configuration of the 10 kg (22 lbs) box rings up at $349 USD. You read that right, just the enclosure for Prusa’s flagship machine costs more than the average Chinese 3D printer. In fact it costs as much as the kit version of the Prusa Mini, which incidentally, is set to get its own version of the enclosure sometime in the future. If you select all the bells and whistles, a fully-decked out Prusa Enclosure will cost you $700 USD, plus shipping.

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Re-imagining The Resistor Color Code Cheat Sheet

May 7, 2022 by Donald Papp 108 Comments

Some people look at a venerable resource like resistor color code charts and see something tried and true, but to [Andrew Jeddeloh], there’s room for improvement. A search for a more intuitive way is what led to his alternate cheat sheet for resistor color codes.

Color code references typically have a reader think of a 560 kΩ resistor as 56 * 10 kΩ, but to [Andrew], that’s not as simple as it could be. He suggests that it makes more sense for a user to start with looking up the colors to make 5.6 (green-blue), then simply look up that a following yellow band means resistance in the 100 kΩ range (assuming a four-band resistor); therefore 560 kΩ is green-blue-yellow.

The big difference is that the user is asked to approach 560 kΩ not as 56 * 10 kΩ, but as 5.6 * 100 kΩ. [Andrew] shares a prototype of a new kind of chart in his post, so if you have a few minutes, take it for a spin and see what you think.

Is his proposed method more intuitive, or less? We think [Andrew] makes a pretty good case, but you be the judge. After all, just because something has always been so doesn’t mean there isn’t room for improvement. This happens to apply nicely to resistors themselves, in fact. It may seem like through-hole resistors have always had color bands, but that is not the case.

ElectriPop Turns Cut Mylar Into Custom 3D Structures

May 6, 2022 by Tom Nardi 14 Comments

Mylar has a lot of useful properties, and as such as see it pop up pretty often, not just in DIY projects but in our day-to-day lives. But until today, we’ve never seen a piece of Mylar jump up and try to get our attention. But that’s precisely the promise offered by ElectriPop, a fascinating project from Carnegie Mellon University’s Future Interfaces Group.

The core principle at work here is fairly simple. When electrostatically charged, a strip of Mylar can be made to lift up vertically into the air. Cut that strip down the center, and the two sides will repel each other and produce a “Y” shape. By expanding on that concept with enough carefully placed cuts, it’s possible to create surprisingly complex three dimensional shapes that pop up once a charge is applied. A certain degree of motion can even be introduced by adjusting the input power. The video after the break offers several examples of this principle in action: such as a 3D flower that either stands up tall or wilts in relation to an external source of data, or an avatar that flails its arms wildly to get the user’s attention.

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Photo of the spectrophotometer in question, with a screenshot of the decoding software on the right

Exporting Data From Old Gear Through LCD Sniffing

May 5, 2022 by Arya Voronova 27 Comments

[Jure Spiler] was at a flea market and got himself a spectrophotometer — a device that measures absorbance and transmittance of light at different wavelengths. This particular model seems to be about 25 years old, and it’s controlled by a built-in keyboard and uses a graphical LCD to display collected data. That might have been acceptable when it was made, but it wasn’t enough for [Jure]. Since he wanted to plot the spectrophotometry data and be able to save it into a CSV file, hacking ensued.

He decided to tap into the the display communication lines. This 128×64 graphical display, PC-1206B, uses a 8-bit interface, so with a 16-channel logic analyzer, he could see the data being sent to the display. He even wrote decoder software – taking CSV files from the logic analyzer and using primitive optical recognition on the decoded pixels to determine the digits being shown, and drawing a nice wavelength to absorbance graph. From there, he set out to make a standalone device sniffing the data bus and creating a stream of data he could send to a computer for storage and processing.

[Jure] stumbled into a roadblock, however, when he tried to use an Arduino for this task. Even using a sped-up GPIO library (as opposed to notoriously inefficient digitalRead), he couldn’t get a readout frequency higher than 80 KHz – with the required IO readout rate deemed as 1 MHz, something else would be called for. We do wonder if something like RP2040 with its PIO machinery would be better for making such captures.

At that point, however, he found out that there’s undocumented serial output on one of the pins of the spectrophotometer’s expansion port, and is currently investigating that, having shelved the LCD sniffing direction. Nevertheless, this serves as yet another example for us, for those times when an LCD connection is all that we can make use of.

We’ve seen hackers sniff LCD interfaces to get data from reflow ovens, take screenshots from Game Boys and even equip them with HDMI and VGA ports afterwards. With a skill like this, you can even give a new life to a vintage calculator with a decayed display! Got an LCD-equipped device but unsure about which specific controller it uses? We’ve talked about that!

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