A ZX Spectrum with a Microdrive emulator plugged into its expansion port

A Modern Replacement For The ZX Spectrum’s Odd Tape Storage System

July 29, 2023 by Robin Kearey 44 Comments

Unless you were lucky enough to be able to afford a floppy disk drive, you probably used cassette tapes to store programs and data if you used pretty much any home computer in the 1980s. ZX Spectrum users, however, had another option in the form of the Microdrive. This was a rather unusual continuous-loop mini-tape cartridge that could store around 100 kB and load it at lightning speed, all at a much lower price point than a floppy drive. The low price came at the cost of poor durability however, and after four decades it’s becoming harder and harder to find cartridges that work reliably. [Derek Fountain] therefore set out to make a modern Microdrive emulator that stores data on SD cards.

Several projects already exist to replace Microdrives, but they typically also need the ZX Interface 1, a serial/network expansion module that’s becoming equally hard to find. Hence [Derek]’s choice to make his emulator a completely standalone system that directly plugs into the Spectrum’s expansion port.

The system is housed in a 3D-printed enclosure that holds two PCBs. Three Raspberry Pi Picos run the show inside: one to hold the ZX Interface 1’s ROM image and interface with the Spectrum’s bus, another to simulate the Microdrive, and a third to run the user interface and communicate with the SD card. The user can choose between eight tape images stored in .MDR format by using two pushbuttons and a rotary encoder, with a small OLED display showing the machine’s configuration.

While you might think that three dual-core 133 MHz ARM CPUs would run circles around the Spectrum’s Z80, it actually took quite a bit of work to get everyting running properly in real time. The 3.5 MHz bus clock rate gave the second Pico precious little time to fetch the required bytes out of its flash memory. Its RAM was fast enough for that, but too small to hold all eight tape images at the same time. In the end, [Derek] settled on using a separate 8 MB SPI DRAM chip that could easily keep up the data rate, with the Pi just using its GPIO ports to shuttle the data around.

All source code and extensive documentation are available on Derek’s excellent blog post and GitHub page. Be sure to also check out [Jenny]’s detailed review and teardown if you’d like to know more about the weird and wonderful Microdrive system.

Thanks for the tip, [Andrew]! Continue reading “A Modern Replacement For The ZX Spectrum’s Odd Tape Storage System” →

Fiber-Infused Ink Allows 3D-Printed Heart Muscle To Beat

July 29, 2023 by Maya Posch 7 Comments

Illustration from Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013.

What makes a body’s organs into what they are is more than just a grouping of specialized cells. They also need to be oriented and attached to each other and scaffolding in order to create structures which can effectively perform the desired function. A good example here is the heart, which requires a large number of muscle cells to contract in unison in order for the heart component (like a ventricle) to effectively pump blood. This complication is what has so far complicated efforts to 3D print complex tissues and entire organs, but recently researchers have demonstrated a way to 3D print heart muscle which can contract when stimulated similarly to a human heart’s ventricle.

At the center of this technique lies a hydrogel that is infused with gelatin fibers. Using a previously developed Rotary Jet-Spinning technology that was reported on in 2016, a sheet of spun fibers was produced that were then cut up into micrometer-sized fibers which were dispersed into the hydrogel. After printing the desired structure – taking into account the fiber alignment – it was found that the cardiomyocytes (the cells responsible for carrying the contractile signal in the heart muscle) align along the thus laid out pattern, ultimately creating a cardiac muscle capable of organized contraction.

These findings come after many years of research into the topic, with e.g. Zihan Wang and colleagues in a 2021 paper reporting on the challenges remaining with 3D printing cardiac tissue, yet also the massive opportunities that this could provide. Although entire heart replacements (via therapeutic cloning with the patient’s own cells) might become possible too, more immediate applications would involve replacements for damaged cardiac muscle and other large structures of the heart.

Mechanical Pencil Solder Feeder Hack

July 29, 2023 by Chris Lott 29 Comments

Want a better way to feed solder, but want to do it on the quick and cheap? Well [ptkrf] has a solution for you in an old instructables post we stumbled upon recently. You might have, or can inexpensively buy, a mechanical pencil which has the feeder button on the side rather than on top, as usual. With the pencil in hand, [ptkrf] shows you the simple procedure for modifying the pencil into a solder feeder. You might need to experiment with different size pencils and solders to get a perfect match. Common mechanical pencils come in sizes to accommodate 0.5, 0.7, and 0.9 mm leads, but there are bigger and smaller ones available. Perhaps one of those really large drafting lead holders could be repurposed as a solder dispenser for the bigger jobs.

We discussed a 3D printed solder feeder a few days ago, but if you don’t have one, this may be a good way to go. Thanks to [iliis] for sending in this tip.

Automate Your Pin Header Chopping Chores Away

July 29, 2023 by Dan Maloney 7 Comments

In most cases, cutting pin headers is a pretty simple job to tackle with a pair of cutters or even your bare fingers. But if you’re doing a lot of it, like for kitting up lots of projects for customers, then you might want to look at something like this automatic pin header cutter.

Even if you don’t need to follow [Mr. Innovative]’s lead on this, it’s worth taking a look at the video below, which has a couple of cool ideas that are probably applicable to other automation projects, especially those where lots of small parts are handled. Processing begins with a hopper that holds a stack of header strips over what we’d call a “reverse guillotine,” consisting of a spring-loaded plunger riding on a cam. A header strip is pushed out of the hopper to expose the specified number of terminals, the cam rotates and raises the plunger, and the correct length header is snapped off.

For our money, the neatest part of this build is the feed mechanism for the hopper. Rather than anything complicated like a rack-and-pinion, [Mr. Innovative] opted for a pusher made from a stiff yet flexible strip of plastic, which is forced along the bottom of the hopper by a pair of stepper-driven drive rollers. The plastic pusher is stored rolled up in a spiral fixture so it doesn’t take up much room.

Overall, it’s a simple and largely effective design. [Mr. Innovative] does express a little dissatisfaction with some aspects of the build, though; it looks like the stack of header strips needs a little weight on top of it to keep them feeding properly, and we notice a couple of iterations of the cutting mechanism in the video. The cut headers do seem to either fly off into the stratosphere or stay attached to each other, which could lead to jamming problems.

But still, it’s a solid design and reminds us of some other projects by [Mr. Innovative], like this SMD tape slicer or a CNC gear cutter.

Continue reading “Automate Your Pin Header Chopping Chores Away” →

Voyager Command Glitch Causes Unplanned Pause In Communications

July 29, 2023 by Dan Maloney 31 Comments

Important safety tip: When you’re sending commands to the second-most-distant space probe ever launched, make really, really sure that what you send isn’t going to cause any problems.

According to NASA, that’s just what happened to Voyager 2 last week, when uplinked commands unexpectedly shifted the 46-year-old spacecraft’s orientation by just a couple of degrees. Of course, at a distance of nearly 20 billion kilometers, even fractions of a degree can make a huge difference, especially since the spacecraft’s high-gain antenna (HGA) is set up for very narrow beamwidths; 2.3° on the S-band channel, and a razor-thin 0.5° on the X-band side. That means that communications between the spacecraft and the Canberra Deep Space Communication Complex — the only station capable of talking to Voyager 2 now that it has dipped so far below the plane of the ecliptic — are on pause until the spacecraft is reoriented.

Luckily, NASA considered this as a possibility and built safety routines into Voyager‘s program that will hopefully get it back on track. The program uses the onboard star tracker to get a fix on the bright star Canopus, and from there figures out which way the spacecraft needs to move to get pointed back at Earth. The contingency program runs automatically several times a year, just in case something like this happens.

That’s the good news; the bad news is that the program won’t run again until October 15. While that’s really not that far away, mission controllers will no doubt find it an agonizingly long time to be incommunicado. And while NASA is outwardly confident that communications will be restored, there’s no way to be sure until we actually get to October and see what happens. Fingers crossed.

The Right Benchmark For GPT

July 29, 2023 by Elliot Williams 41 Comments

Dan Maloney wanted to design a part for 3D printing. OpenSCAD is a coding language for generating 3D objects. ChatGPT can write code. What could possibly go wrong? You should go read his article because it’s enlightening and hilarious, but the punchline is that it ran afoul of syntax errors, but also gave him enough of a foothold that he could teach himself enough OpenSCAD to get the project done anyway. As with many people who have asked the AI to create some code, Dan finds that it’s not as good as asking someone who knows what they’re doing, but that it’s also better than nothing.

And this is where I start grumbling. When you type your desires into the word-follower machine, your alternative isn’t nothing. Your alternative is to fire up a search engine instead and type “openscad tutorial”. That, for nearly any human endeavor, will get you a few good guides, written by humans who are probably expert in the subject in question, and which are aimed at teaching you the thing that you want to learn. It doesn’t get better than that. You’ll be up and running with your design in no time.

Indeed, if you think about the relevant source material that the LLM was trained on, it’s exactly these tutorials. It can’t possibly do better than the best of them, although the resulting average tutorial might be better than the worst you’ll find. (Some have speculated on what happens when the entire Internet is filled with these generated texts – what will future AIs learn from?)

In Dan’s case, though, he didn’t necessarily want to learn OpenSCAD – he just wanted the latch designed. But in the end, he had to learn enough OpenSCAD to get the AI code compiling without error. He spent an hour learning OpenSCAD and now he’s good to go on his next project too.

So the next time you hear someone say that they got an answer back from a large language model that wasn’t perfect, but it was “better than nothing”, think critically if “nothing” is really the right benchmark.

Do you really want to learn nothing? Do you really have no resources to get started with? I would claim that we have the most amazing set of tutorial resources the world has ever known at our fingertips. Compared to the ability to teach millions of humans to achieve their own goals, that makes the LLM party tricks look kinda weak, in my opinion.

The Right Equipment Makes A Difference For Digital Oscilloscope Music

July 29, 2023 by Dan Maloney 4 Comments

We all love our cheap digital oscilloscopes, and with good reason. But if there’s one place where analog scopes still shine, it’s anywhere you need X-Y mode. Digitally sampling the inputs and mapping them on the screen as discrete points just isn’t the same as steering an electron beam around a CRT, making X-Y mode work on digital scopes — at least the affordable ones — somewhat lacking.

Thankfully, nobody told [Mark Hughes] that his digital scope would make a lousy X-Y display, so he just plunged ahead and figured out how to make it work anyway. The results are actually pretty good, but it took some doing. His setup begins with OsciStudio, an application built to take 3D shapes and animations and turn them into oscilloscope music. The output from that is piped to a USB sound card; [Mark] used a PreSonus Studio 26c, an adapter with DC-coupled inputs, which he found to be critical to getting good images. Also important was a USB isolator and good-quality cables, which greatly reduced jitter and made the image much more stable.

DC-coupled

AC-coupled

Displaying the image was as easy as connecting the left and right outputs from the sound card to the two scope inputs — [Mark] used a Keysight EDUX1052G — and setting it to X-Y mode. It took a fair amount of fiddling to get as far as he did, but we think the results speak for themselves. As for the sounds made by these images, he says it’s a bit like a hung sound card when a computer blue-screens. So, yeah — not exactly musical, but still an interesting way to have some fun with your digital scope.