Used Facemasks Turned Into Rapid Antigen Tests With Injection Molding

March 24, 2022 by Dan Maloney 15 Comments

Here’s a little eye-opener for you: next time you’re taking a walk, cast your eyes to the ground for a bit and see how far you can go without spotting a carelessly discarded face mask. In our experience, it’s no more than a block or two, especially if you live near a school. Masks and other disposal artifacts of the COVID-19 pandemic have turned into a menace, and uncounted billions of the things will be clogging up landfills, waterways, and byways for decades to come.

Unless they can be recycled into something useful, of course, like the plastic cases used for rapid antigen tests. This comes to us by way of [Ric Real] from the Design and Manufacturing Futures lab at the University of Bristol in the UK. If any of this sounds or looks familiar, refer back to October when the same team presented a method for turning old masks into 3D printer filament. The current work is an extension of that, but feeds the polypropylene pellets recovered from the old masks into a desktop injection molding machine.

The injection molding machine is fitted with 3D-printed molds for the shells of lateral flow devices (LFD) used for COVID-19 rapid antigen testing. The mold tooling was designed in Fusion 360 and printed on an Elegoo Mars MSLA printer using a high-strength, temperature-resistant resin. The molds stood up to the manual injection molding process pretty well, making good-quality parts in the familiar blue and white colors of the starting material. It’s obviously a proof of concept, but it’s good to see someone putting some thought into what we can do with the megatonnes of plastic waste generated by the pandemic response.

Linux Fu: Simple Pipes

March 16, 2022 by Al Williams 15 Comments

In the old days, you had a computer and it did one thing at a time. Literally. You would load your cards or punch tape or whatever and push a button. The computer would read your program, execute it, and spit out the results. Then it would go back to sleep until you fed it some more input.

The problem is computers — especially then — were expensive. And for a typical program, the computer is spending a lot of time waiting for things like the next punched card to show up or the magnetic tape to get to the right position. In those cases, the computer was figuratively tapping its foot waiting for the next event.

Someone smart realized that the computer could be working on something else while it was waiting, so you should feed more than one program in at a time. When program A is waiting for some I/O operation, program B could make some progress. Of course, if program A didn’t do any I/O then program B starved, so we invented preemptive multitasking. In that scheme, program A runs until it can’t run anymore or until a preset time limit occurs, whichever comes first. If time expires, the program is forced to sleep a bit so program B (and other programs) get their turn. This is how virtually all modern computers outside of tiny embedded systems work.

But there is a difference. Most computers now have multiple CPUs and special ways to quickly switch tasks. The desktop I’m writing this on has 12 CPUs and each one can act like two CPUs. So the computer can run up to 12 programs at one time and have 12 more that can replace any of the active 12 very quickly. Of course, the operating system can also flip programs on and off that stack of 24, so you can run a lot more than that, but the switch between the main 12 and the backup 12 is extremely fast.

So the case is stronger than ever for writing your solution using more than one program. There are a lot of benefits. For example, I once took over a program that did a lot of calculations and then spent hours printing out results. I spun off the printing to separate jobs on different printers and cut like 80% of the run time — which was nearly a day when I got started. But even outside of performance, process isolation is like the ultimate encapsulation. Things you do in program A shouldn’t be able to affect program B. Just like we isolate code in modules and objects, we can go further and isolate them in processes.

Doubled-Edged Sword

But that’s also a problem. Presumably, if you want to have two programs cooperate, they need to affect each other in some way. You could just use a file to talk between them but that’s notoriously inefficient. So operating systems like Linux provide IPC — interprocess communications. Just like you make some parts of an object public, you can expose certain things in your program to other programs.

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A Sinclair ZX81 Clone Still Has The Power To Fascinate

March 15, 2022 by Jenny List 26 Comments

The golden age of 8-bit computing brought us pixelated graphics in bright colours, accompanied of course by chiptune music. This aesthetic is strong enough to define a collective image of a generation’s youth, even if the 1980s reality had much more of the tired 1970s leftovers about it. The truth was that not all popular 8-bit machines had colour, sound, or good graphics, and among these limited-capability machines was Sir Clive Sinclair’s ZX81. With a Z80, 1k of RAM, a membrane keyboard, and not much else, it helped set the stage for the hugely popular ZX Spectrum which followed it. The fun’s not over though, as [Augusto Baffa] demonstrates with his modern recreation of a machine that can switch between the ’81 and its less-popular ZX80 predecessor.

Rather than a Eurocard-sized mainboard and membrane keypad, this clone copies the ZX80 with a full-sized mainboard the front of which carries the keyboard contacts. It also eschews the ULA found in the ’81 for discrete TTL. It’s based upon the venerable Grant Searle design for a homebuilt Sinclair computer, and all of the files for this version can be found in a GitHub repository.

There is a lot to be said for the ZX81 as a model for retrocomputer experimentation, because of its extreme simplicity. It may have been no great shakes in the computing department compared to many of its competitors, but it remains possibly one of the easiest of the bunch whose operation to completely understand. Also we like it for that paltry 1k of memory, teaching kids about memory constraints is a good thing in our book.

We’ve featured the diminutive ZX more than once, including a couple of years ago in our April Fools coverage.

Hackaday Podcast 159: Zombie Killer Or Rug Maker, 3D Printed Rims, 1950s Drum Machines, And Batteries On Wheels

March 11, 2022 by Tom Nardi No comments

Join Hackaday Editor-in-Chief Elliot Williams and Managing Editor Tom Nardi as they look back on the best hacks and stories of the previous week. There’s plenty in the news to talk about, though between faulty altimeters and the ongoing conflict in Ukraine, it isn’t exactly of the positive variety. But things brighten up quickly as discussion moves on to 3D printed car wheels, a fantastically complex drum machine from 1958, a unique take on the seven-segment flip display, and a meticulously designed (and documented) coffee machine upgrade. Somewhere in there a guy also recreates a rare German anti-air rocket launcher from WWII, but it’s all in the name of history. We’ll also tackle two very different forms of electric propulsion, from the massive wheeled batteries popping up in garages and driveways all over the world to high-efficiency thrusters for deep space missions.

Direct Download (~60 MB)

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

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Review: DevTerm Linux Handheld Has Retro-Future Vibe

March 2, 2022 by Donald Papp 32 Comments

It’s not every day that an open-source, portable Linux handheld computer gets announced, so I couldn’t resist placing an order for the DevTerm by ClockworkPi back when we first learned about the stylish little terminal, which includes a 1280 x 480 screen (double-wide VGA) and a modular little thermal printer.

Of course, the global semiconductor shortage combined with shipping slowdowns led to delays, but things did ultimately come together for the project. I’ve always been a sucker for small-format machines, especially ones that come as a well-designed kit, and that means I can tell you all about what it was like to put it together and turn it on. There’s a lot to look at, so let’s get started.

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Finding Lo-fi In All The Strange Places

February 23, 2022 by Matthew Carlson 12 Comments

If you haven’t heard any lo-fi music yet, it stands for low-fidelity music. Lofi music today is characterized by audio imperfections such as cable noise or tape hiss. To get a pleasantly warm imperfect sound, many artists turn to vintage equipment. [HAINBACH] found an excellent instrument, the obsolete classroom tool known as magnetic card audio recorders.

The basic mechanism of the device is that it reads and writes to the two tracks on the quarter-inch tape fed through it. One track is meant for the teacher and one track is meant for the student. Originally designed to assist language learners, we can see why it would be an ideal source of good lo-fi samples. The microphone and speaker need to be high quality to hear the nuances of the example sentence. [HAINBACH] also admires the general tone and timbre of the device as opposed to just using a cassette recorder.

The tape in question is glued to little plastic cards. With some modification, you can run the card backward, create a loop, or stitch sections together. With multiple machines, you can run the card from one machine directly into another. They were made by several companies and can be found relatively cheap on online auction houses. While we can’t credit [HAINBACH] for coming up with the idea as it was featured in the movie Baby Driver, it’s still an example of an awesome hack.

Magnetic tape has long been a fascination of musical instruments. This Crudman, which is a modern-day interpretation of the much older Mellotron from 1963, is a great example of that.

Video after the break.

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PlottyBot: A DrawBot That Plots A Lot

February 7, 2022 by Michael Shaub 15 Comments

Fire up those 3D printers because if you’re like us, you’ll want your own PlottyBot. Still, have a pile of “thank you notes” to write from recent winter holiday gift exchanges? Hoping to hand letter invitations to a wedding or other significant event? Need some new art to adorn your lock-down shelter or shop? It sounds like [Ben] could help you with that.

Besides being a handsomely designed desktop DrawBot, this project from [Ben] looks to have some solid software to run it, a community of makers who have tested the waters, and very detailed build instructions. Those include everything from a BOM with links for ordering parts to animated GIF assembly for the trickier steps.

If you’d like to graduate from “handwritten” cards and letters to something poster-sized are customization tips for expanded X and Y dimensions. As we’ve included in other recent articles, one caveat to mention is the current scarcity of the Raspberry Pi Zeros that PlottyBots require. But if you have one on hand or think you’ll be able to source one by the time you’ve 3D printed all the parts, it might just be the perfect time to add another bot to your family. As a heads up, this project is self-hosted on a solar-powered server, so maybe take turns reading the complete build log.

A nice bonus if you need help drawing something suitably complex to require a robot’s help, [Ben] also created MandalGaba which looks like an awesome online tool for drawings like the ones shown above.