A Brief Look Inside A Homebrew Digital Sampler From 1979

While we generally prefer to bring our readers as much information about a project as possible, sometimes we just have to go with what we see. That generally happens with new projects and work in progress, but it can also happen with old projects. Sometimes very old indeed, as is the case with this digital sampling unit for analog oscilloscopes, circa 1979.

We’ve got precious little to go on with this one other than the bit of eye candy in the video tour below and its description. Luckily, we’ve had a few private conversations with its maker, [Mitsuru Yamada], over the years, enough to piece together a little of the back story here — with apologies for any wrong assumptions, of course.

Built when he was only 19, this sampler was an attempt to build something that couldn’t be bought, at least not for a reasonable price. With no inexpensive monolithic analog-to-digital converters on the market, he decided to roll his own. A few years back he recreated the core of that with his all-discrete successive approximation ADC.

The sampler shown below has an 8-bit SAR ADC using discrete CMOS logic and enough NMOS memory to store 256 samples. You can see the ADC and memory cards in the homebrew card cage made from aluminum angle stock. The front panel has a ton of controls and sports a wide-range attenuator, DC offset, and trigger circuit with both manual and automatic settings.

It’s an impressive build, especially for a 19-year-old with presumably limited resources. We’ve reached out to [Yamada-san] in the hope that he’ll be able to provide more details on what’s under the hood and if this still works after all these years. We’ll pass along whatever we get, but in the meantime, enjoy.

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Credit: Xinmei Liu

The US Surgeon General’s Case For A Warning Label On Social Media

The term ‘Social Media’ may give off a benign vibe, suggesting that it’s a friendly place where everyone is welcome to be themselves, yet reality has borne out that it is anything but. This is the reason why the US Surgeon General [Dr. Vivek H. Murthy] is pleading for a health warning label on social media platforms. Much like with warnings on tobacco products, it’s not expected that such a measure would make social media safe for children and adolescents, but would remind them and their parents about the risks of these platforms.

While this may sound dire for what is at its core about social interactions, there is a growing body of evidence to support the notion that social media can negatively impact mental health. A 2020 systematic review article in Cureus by [Fazida Karim] and colleagues found anxiety and depression to be the most notable negative psychological health outcomes. A 2023 editorial in BMC Psychology by [Ágnes Zsila] and [Marc Eric S. Reyes] concurs with this notion, while contrasting these cons of social media with the pros, such as giving individuals an online community where they feel that they belong.

Ultimately, it’s important to realize that social media isn’t the end-all, be-all of online social interactions. There are still many dedicated forums, IRC channels and newsgroups far away from the prying eyes and social pressure  of social media to act out a personality. Having more awareness of how social interactions affect oneself and/or one’s children is definitely essential, even if we’re unlikely to return to the ‘never give out your real name’ days of  the pre-2000s Internet.

A rectangular box with a purple section sandwiched between two red sections sits on a black tabletop. The end of the box is open. Black and red wires run out of the back of the box to a breadboard.

Improving Wind Turbine Testing With A Better Air Source

When comparing the efficiency of different wind turbine blade designs, [AdamEnt] found using a hair dryer wasn’t the best tool for the job. Enter his new 3D-printed wind tunnel.

After several prototypes, [AdamEnt] decided on a design that exploits slicer infill to create a flow straightener without having to do any tedious modeling of a lattice. Combined with a box on both ends of the straightener to constrain the flow, he has a more controllable air source with laminar instead of turbulent flow for testing his wind turbines.

The BLDC motor driving the air is attached to a toroidal blade of MIT fame. We get a little bit of the math behind calculating wind turbine efficiency and see a quick test of a blade placed next to the outlet of the air source at the end of the video.

If you’re planning on building your own wind tunnel, we’ve covered a few. We’ve even seen one that goes up to Mach 20, although that probably wouldn’t be useful for wind turbine design!

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Harmonic Table Keyboard Brings Old Idea Back To Life

If you missed the introduction of the Axis-49 and Axis-64 keyboards by C-Thru Music, you’re definitely not alone. At the time it was a new musical instrument that was based on the harmonic table, but it launched during the Great Recession and due to its nontraditional nature and poor timing, the company went out of business. But the harmonic table layout has a number advantages for musicians over other keyboard layouts, so [Ben] has brought his own version of the unique instrument to life in his latest project.

Called the Midihex, the keyboard has a number of improvements over the version from C-Thru Music, most obviously its much larger 98 playable keys and five function keys. The keys themselves are similar to Cherry MX keys but which use Hall-effect sensors. This style of key allows the device to send continuous key position information to the host computer, and since this is a MIDI instrument, this capability allows it to support a MIDI protocol called MIDI Polyphonic Expression (MPE) which allows each note to be more finely controlled by the musician than a standard MIDI instrument. The PCB is powered by a Teensy 4.1 at the core.

For any musicians that haven’t tried out a harmonic table before, an instrument like this might be worth trying out. The layout provides easier chord and scale patterns, and for beginner musicians it can have a much shallower learning curve than other types of instruments. If you can’t find an original Axis-49 or Axis-64 anywhere to try out, though, we actually posted a teardown of one way back in 2009 when the company was still producing instruments.

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PostmarketOS Now Boots On Over 250 Devices

Every year, as consumers gobble up the latest Android devices, more old, but perfectly serviceable, units end up collecting dust in drawers. Or worse, they end up getting tossed in the trash. One of the most promising tools we have to help keep these older devices useful is postmarketOS, a full-fledged Linux distribution that provides a flexible and up-to-date software environment on devices that might otherwise be stuck with some old and unsupported version of Google’s mobile operating system.

As of the latest update on the postmarketOS blog, the team has announced an exciting milestone: over 250 devices can now boot the stable release of the OS.

Now to be clear, not all devices will be fully functional. In fact, the blog post clarifies that some of them only barely boot. But it’s progress, and now that these semi-supported devices aren’t hidden behind a development version of the OS, it means more folks will be able to put them to use.

For example, if you want to turn your old smartphone into a low-energy headless webserver, it doesn’t really matter if its display, touchscreen, or speakers are supported. You just need it to boot into Linux and fire up an SSH server so you can get in and start working.

But support for new devices is just one of the additions in this new v24.06 release. The blog post also points out several notable software upgrades, including the move to the 6.x branch of KDE Plasma Mobile. This brings with it a long list of improvements and changes, including a rewritten homescreen with enhanced customization options. If you prefer a more minimal GUI, don’t worry. This new release also updates Sxmo, which provides a menu-driven interface for both touch screens and hardware controls.

Among the newly supported devices is a generic x86_64 image that should work on a wide array of PCs. While obviously there’s no shortage of Linux distros you could run on your old computer, being able to install postmarketOS on it is definitely helpful for development purposes. There’s also a new Tegra ARMv7 target which brings a number of new devices into the fold, such as the Google Nexus 7, and Microsoft Surface RT.

Looking to run postmarketOS on your own hardware? The best way to start is to check the Devices page and see how many of those old gadgets you’ve got collecting dust in a drawer are compatible.

The Solar System Is Weirder Than You Think

When I was a kid, the solar system was simple. There were nine planets and they all orbited in more-or-less circles around the sun. This same sun-and-a-handful-of-planets scheme repeated itself again and again throughout our galaxy, and these galaxies make up the universe. It’s a great story that’s easy to wrap your mind around, and of course it’s a great first approximation, except maybe that “nine planets” thing, which was just a fluke that we’ll examine shortly.

What’s happened since, however, is that telescopes have gotten significantly better, and many more bodies of all sorts have been discovered in the solar system which is awesome. But as a casual astronomy observer, I’ve given up hope of holding on to a simple mental model. The solar system is just too weird.

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Magic Cane Is The Secret Behind Lightsaber

Everyone has a lightsaber or two lying around the house, but not everyone has a lightsaber that extends and retracts automatically. And that’s because, in the real world, it’s not an easy design challenge. [HeroTech]’s solution for the mechanism is simple and relies on an old magician’s trick: the appearing cane. (Video, embedded below.)

An appearing cane is a tightly coiled up spring steel sheet that springs, violently, to its full length when a pin is released, but they can’t retract while the audience is looking. This is fine for magic tricks, but a lightsaber has to be able to turn off again. Here, an LED strip does double duty as source of glow but also as the cable that extends and retracts the appearing cane spring. A motor and spool to wind up the LED strip takes care of the rest.

There are still a number of to-dos in this early stage prototype, and the one mentioned in the video is a tall order. Since the strip doesn’t illuminate out the sides, the lightsaber has two good viewing angles, and two bad ones. The plan is to rotate the LED strip quickly inside the sheath: an approach that was oddly enough used in the original movie prop, as demonstrated in this documentary. Doing this reliably in an already packed handle is going to be a challenge.

If you’re thinking you’ve seen a magic-cane lightsaber before, well, maybe you saw this video. And if you want a light saber with real lasers, check out this build that brings its own fog machine. Take that, Darth Vader!

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