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Hackaday Links: October 3, 2021

It’s one thing to speculate about what’s happening with the Mars helicopter Ingenuity, but it’s another to get an insider’s view on recent flight problems. As we previously reported, Ingenuity is starting to face a significant challenge, as a seasonal atmospheric pressure drop on Mars threatens to make the already rarefied air too thin to generate useful lift. Mission controllers tested the chopper at higher rotor speeds, and while that worked, later attempts to fly using that higher speed resulted in an abort. The article, written by one of the NASA/JPL engineers, is a deep dive into the problem, which occurred when Ingenuity sensed excessive wiggle in two of the servos controlling the rotor swashplate. The thought is that accumulated wear in the servos and linkages might be causing the problem; after all, Ingenuity has made thirteen flights so far, greatly exceeding the five flights originally programmed for it. Here’s hoping they can adapt and keep the helicopter flying, but whatever they do, it’ll have to wait a few weeks until Mars completes its conjunction and pops back out from behind the Sun.

With all the attention understandably paid to the recent 20th anniversary of the 9/11 terror attacks, it’s easy to forget that barely a month after that day, a series of what appeared to be follow-on attacks started: the Anthrax Attacks. Members of Congress and media outlets were targeted via the mail with highly refined anthrax spores, leading to the deaths of five people, with dozens more injured and exposed to anthrax. IEEE Spectrum has an interesting article that goes into some of the technology that was rapidly deployed in an attempt to sanitize the mail, including electron beam and X-ray irradiation to kill any spores. The article also points out how this wasn’t the first time people were afraid of the mail; outbreaks of yellow fever in 1899 led to fumigation of the mail with sulfur, after perforating it with a wicked-looking paddle.

Attention PCB-design newbies — now’s your chance to learn the entire PCB design process from the ground up, with the guidance of industry professionals. TeachMePCB is back again this year, offering to teach you everything you need to know about properly laying out a PCB design in pretty much any EDA software you want. The course requires a two- to five-hour commitment every week for two months, after which you’ll have designed a PCB for a macropad using a Raspberry Pi Pico. The course facilitator is Mark Hughes from Royal Circuits, who did a great Hack Chat with us last year on PCB finishes. This seems like a great way to get up to speed on PCB design, so if you’re interested, act soon — 460 people are already signed up, and the deadline is October 10.

Some of us really love factory tours, no matter what the factory is making. All the better when the factory makes cool electronics stuff, and better still when it’s our friends at Adafruit showing us around their New York City digs. True, it’s a virtual tour, but it has pretty much become a virtual world over the last couple of years, and it’s still a great look inside the Adafruit factory. Hackaday got an in-person tour back in 2015, but we didn’t know their building used to be a Westinghouse radio factory. In fact, the whole area was once part of the famed “Radio Row” that every major city seemed to have from the 1920s to the 1960s. It’s good to get a look inside a real manufacturing operation, especially one that’s right in the heart of a city.

And finally, those with a fear of heights might want to avoid watching this fascinating film on the change-out of a TV transmitter antenna. The tower is over 1,500′ (450 m) tall, lofting an aging antenna over the flat Florida terrain. Most of the footage comes from body-mounted cameras on the riggers working the job, including the one very brave soul who climbed up the partially unbolted antenna to connect it to the Sikorsky S64 Skycrane helicopter. It’s a strange combination of a carefully planned and slowly executed ballet, punctuated by moments of frenetic activity and sheer terror. The mishap when releasing the load line after the new antenna was placed could easily have swept the whole rigging crew off the antenna, but luckily nobody was injured.

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Laser Theremin Turns Your Hand Swooshes Into Music

In a world where smartphones have commoditized precision MEMS Sensors, the stage is set to reimagine clusters of these sensors as something totally different. That’s exactly what [chronopoulos] did, taking four proximity sensors and turning them into a custom gesture input sensor for sound generation. The result is Quadrant, a repurposable human-interface device that proves to be well-posed at detecting hand gestures and turning them into music.

At its core, Quadrant is a human interface device built around an STM32F0 and four VL6180X time-of-flight proximity sensors. The idea is to stream the measured distance data over as fast as possible from the device side and then transform it into musical interactions on the PC side. Computing distance takes some time, though, so [chronopoulos] does a pipelined read of the array to stream the data into the PC over USB at a respectable 30 Hz.

With the data collected on the PC side, there’s a spread of interactions that are possible. Want a laser harp? No problem, as [chronopoulos] shows how you can “pluck” the virtual strings. How about an orientation sensor? Simply spread your hand over the array and change the angle. Finally, four sensors will also let you detect sweeping gestures that pass over the array, like the swoosh of your hand from one side to the other. To get a sense of these interactions, jump to the video demos at the 2:15 mark after the break.

If you’re curious to dig into the project’s inner workings, [chronopoulos] has kindly put the firmware, schematics, and layout files on Github with a generous MIT License. He’s even released a companion paper [PDF] that details the math behind detecting these gestures. And finally, if you just want to cut to the chase and make music of your own, you can actually snag this one on Tindie too.

MEMs sensors are living a great second life outside our phones these days, and this project is another testament to the richness they offer for new project ideas. For more MEMs-sensor-based projects, have a look at this self-balancing robot and magic wand.

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Forget Digital Computing, You Need An Analog Computer

The analog computer of decades-gone-by is something many of us younger engineers never got the chance to experience first hand. It’s pretty much a case of reading about them on these fine pages or perhaps looking at a piece of one behind glass in one of the more interesting museums out there. But now, there is another option, (THAT) The Analog Thing. Developed by Berlin-based Analog computer-on-chip specialist Anabrid, THAT is an Open Source analog computer you can build yourself (eventually) or buy from them fully assembled. At least, that’s their plan.

From the 1970s onwards, digital computers became powerful enough to replace analog computers in pretty much every area, and with the increased accuracy this brought, the old analog beasts became obsolete overnight. Now, there seems to be a move to shift back a little, with hybridized analog-digital approaches looking good for some applications, especially where precision is not paramount. After all, that pile of fatty grey matter between your ears is essentially a big analog computer, and that’s pretty good at problem solving.

Looking over the project Wiki there are a few application examples and some explanatory notes. Schematics are shown, albeit only images for now. We can’t find the PCB files either, but the assembly instructions show many bodge wires, so we guess they’re re-spinning the PCB to apply fixes before releasing them properly. This is clearly work-in-progress and as they say on the main site, their focus is on chips for hybrid analog-digital computing, with a focus on energy-efficient approximate methods. With that in mind, we can forgive that the community-focused learning tools are still being worked on. All that said, this is still a very interesting project, and definitely would be a Christmas present this scribe would be more than happy to unwrap.

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Supercapacitor E-Bike With DIY Motor

Supercapacitor technology often looks like a revolutionary energy storage technology on the surface, but the actual performance numbers can be rather uninspiring. However, for rapid and repeated charge and discharge cycles, supercaps are hard to beat. [Tom Stanton] wanted to see if supercaps have any practical use on e-bikes, and built a DIY electric motor in the process.

One of the problems with supercaps is the rapid voltage drop during discharge compared to batteries, which can limit the amount of usable energy. In an attempt to get around the voltage limitation, [Tom] built his own axial flux motor for the bike, using 3D printed formers for the coils and an aluminum rotor with embedded magnets. He expected torque to be severely limited, so he also machined a large sprocket for the rear wheel. He built a capacitor bank using six 2.7V 400F supercaps, only equivalent to the capacity of a single AA cell. Although it worked, the total range was only around 100 m at low speed. When he hooked the motor up to a conventional battery, he did find that it was quite usable, if a bit underpowered.

The controller for the DIY motor was not capable of doing regenerative braking, so he fitted the capacitors to another e-bike that does have regenerative braking. Using this feature, he was able to reclaim some power while slowing down or going downhill. Since this type of charging cycling is what supercaps are suited for, it worked, but not nearly to the level of being practical.

[Tom]’s projects are a popular feature here on Hackaday, and he has also experimented with supercaps in RC “rockets” and a flywheel for energy storage on the same bike.

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What Goes Into A High Voltage Diode?

When we use an electronic component, we have some idea of what goes on inside it. We know that inside a transistor there’s a little piece of semiconductor with a junction made from differently doped regions etched into it, and in a capacitor, there will be metalized plates on the surface of some kind of dielectric. Reverse engineering has given us extensive die photography of integrated circuits, but there remain a few component mysteries to be uncovered. One is laid bare by [WizardTim], as he cross-sections a 20KV high-voltage diode.

A conventional low-voltage silicon diode has a forward voltage drop of about 0.7V and a relatively low maximum reverse voltage, for example with the 1N4001 rectifier it’s 50V.  For the higher-spec 1N4007, the reverse voltage rating is 700V. This diode has a 25KV reverse voltage, and a clue to its construction comes in its quoted 45V forward voltage. Sure enough, when mounted in resin and carefully sanded and polished flat it reveals its interior as a stack of diodes in series to increase the reverse voltage at the expense of forward voltage.

Revealing the inner workings of an unusual component is fascinating, and the lapping technique used is definitely worth a look. It’s something we’ve seen before, for example in reducing CPU thickness for increased performance.

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Some Pleasing Experiments In 8-Bit Video Cards

These days, supply chain factors and high demand have made it incredibly difficult to lay one’s hands on a GPU. However, if you’re into older computers, you might find it hard to source old-school video cards too. Fear not, for [Dave’s Dev Lab] has been cooking up some experiments with a goal of eventually producing a new 8-bit ISA video card from scratch.

The long term goal is to recreate the original design of early IBM hardware, namely, the MDA and CGA video cards of decades past. The experiments center around the venerable Motorola 6845 which was widely used in computers in the 1980s. However, [Dave] intends to make them suitable for outputting to modern screens using typical VGA and DVI outputs, as well as those expected by modern TFT LCDs.

Thus far, [Dave] has achieved successful VGA output in a 40×35 text mode. With an 8×16 font, and the display running at 640×480 resolution at 60 Hz, everything hums along nicely. Similar experiments with a modern 480×272 LCD display have also worked well.

There’s a long way to go before [Dave’s] hardware is playing Commander Keen, but it’s great to see such effort being put into the platform. It could yet serve as a great upgrade for those wishing to use their vintage IBM metal without having to source a tired old CGA monitor.

We’ve seen similar work before too, with the Graphics Gremlin from [Tube Time] achieving a similar task. If you’ve been brewing up your own ISA hardware at home, do drop us a line.

A 3D-printed mini laser engraver made from DVD-RW drive motors.

Mini Laser Engraver Could Carve Out A Place On Your Desk

Got a couple of old DVD-RW drives lying around, just collecting dust? Of course you do. If not, you likely know where to find a pair so you can build this totally adorable and fully dangerous laser engraver for your desk. Check out the complete build video after the break.

[Smart Tronix] doesn’t just tell you to salvage the stepper motors out of the drives — they show you how it’s done and even take the time to explain in writing what stepper motors are and why you would want to use them in this project, which is a remix of [maggie_shah]’s design over on Thingiverse. As you might expect, the two steppers are wired up to an Arduino Uno through a CNC shield with a pair of A4988 motor drivers. These form the two axes of movement — the 250mW laser is attached to x, and the platform moves back and forth on the y axis. We’d love to have one of these to mess around with. Nothing that fits on that platform would be safe! Just don’t forget the proper laser blocking safety glasses!

Need something much bigger that won’t take up a lot of space? Roll up your sleeves and build a SCARA arm to hold your laser.

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