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Hackaday Links: May 15, 2022

It may be blurry and blotchy, but it’s ours. The first images of the supermassive black hole at the center of the Milky Way galaxy were revealed this week, and they caused quite a stir. You may recall the first images of the supermassive black hole at the center of the M87 galaxy from a couple of years ago: spectacular images that captured exactly what all the theories said a black hole should look like, or more precisely, what the accretion disk and event horizon should look like, since black holes themselves aren’t much to look at. That black hole, dubbed M87*, is over 55 million light-years away, but is so huge and so active that it was relatively easy to image. The black hole at the center of our own galaxy, Sagittarius A*, is comparatively tiny — its event horizon would fit inside the orbit of Mercury — a much closer at only 26,000 light-years or so. But, our black hole is much less active and obscured by dust, so imaging it was far more difficult. It’s a stunning technical achievement, and the images are certainly worth checking out.

Another one from the “Why didn’t I think of that?” files — contactless haptic feedback using the mouth is now a thing. This comes from the Future Interfaces Group at Carnegie-Mellon and is intended to provide an alternative to what ends up being about the only practical haptic device for VR and AR applications — vibrations from off-balance motors. Instead, this uses an array of ultrasonic transducers positioned on a VR visor and directed at the user’s mouth. By properly driving the array, pressure waves can be directed at the lips, teeth, and tongue of the wearer, providing feedback for in-world events. The mock game demonstrated in the video below is a little creepy — not sure how many people enjoyed the feeling of cobwebs brushing against the face or the splatter of spider guts in the mouth. Still, it’s a pretty cool idea, and we’d like to see how far it can go.

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Computer Thing Might Be Garbage

[Tech Time Traveller] has a lot of voices in his head this week, and most of them are worried about his wife’s reaction to him buying other people’s garbage. We don’t blame him, though. He bought it from an estate sale and it was billed as a TV typewriter. The device looked completely homebrewed from somewhere around the late 1970s to the early 1980s. It contains a mess of components obviously hand-built in a combination of neat construction and messy wiring.

[Tech] videos most of his tests and exploration to get the thing working and tested. Given its age and construction, it worked surprisingly well, although it did take a little work to get it back to complete function. In fact, he bought the device three years ago and is finally getting around to finishing the project and putting together the video.

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Vicious Little Desktop Shredder Pulverizes Plastic Waste

We’ve all likely seen video of the enormous industrial shredders that eat engine blocks for lunch and spit out a stream of fine metal chips. The raw power of these metal-munching monsters is truly fearsome, and they appear to be the inspiration for SHREDII, the miniature plastic shredder for at-home recycling of plastic waste.

The fact that SHREDII isn’t all that large doesn’t make it any less dangerous, at least to things smaller and softer than engine blocks, like say fingers. The core of the shredder is a hexagonal axle carrying multiple laser-cut, sheet steel blades. The rotating blades are spaced out along the axle so they nest between a bed of stationary blades; rotating the common axle produces the shearing and cutting action needed to shred plastic.

On version one of the shredder, each blade had two hooked teeth, and the whole cutting head was made from relatively thick steel. When driven by a NEMA 34 stepper — an admittedly odd choice but it’s what they could get quickly — through a 50:1 planetary gearbox, the shredder certainly did the business. The shreds were a little too chunky, though, so version two used thinner steel for the blades and gave the rotary blades more teeth. The difference was substantial — much finer shreds that were suitable forĀ INJEKTO, their homebrew direct-feed injection molding machine.

There’s a lot to be said for closing the loop on plastics used in desktop manufacturing processes, and the team of SHREDII and INJEKTO stands to help the home gamer effectively reuse plastic waste. And while that’s all to the good, let’s face it — the oddly satisfying experience of watching a shredder like this chew through plastic like it isn’t even there is plenty of reason to build something like this.

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E-Paper Clock Displays Things In A Battery-Friendly Manner

Clock builds are a hacker staple, and many overflow with power-thirsty LEDs and network features. This build from [mattwach] takes quite the opposite approach, sipping away at its batteries thanks to an e-paper based design.

The build relies on a small Waveshare e-paper module which only requires power when the display is actually changing. When static, the display needs no electricity, and this helps save a great amount of power compared to OLED or LCD-based clocks.

An Atmega328p is the heart of the build, running off a 32.768 KHz clock crystal for a combination of precise timekeeping and low power draw. Time is ensured to be both precise and accurate thanks to a GPS module which allows the clock to sync to satellite time when powered up. It’s a common way to sync clocks to a high-quality time source. Most of the time, though, the GPS is kept powered down to save the 30-100 mA that the module typically draws when in use.

Other features include a temperature, humidity, and pressure sensor, with ambient pressure graphed over time. There’s also notification of sunrise and sunset times, along with the current phase of the moon. It’s all wrapped up in a case tastefully manufactured using 3D printed parts and some wooden CNC-cut panels for a nice rustic look.

With the e-paper display and the microcontroller configured for low-power operation, the clock will run for around 6 months on four AAA cells. Overall, it’s a nifty little clock that will provide the time, date, and other information without the need for an Internet connection. Video after the break.

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Upcycling A Flat Bed Scanner

[Piffpaffpoltrie] had a 20-year-old Acer flatbed scanner that they just couldn’t justify keeping. But it does seem a shame to throw away a working piece of gear. Instead, the old scanner became a light table. We’ll admit, as projects go, it isn’t the most technically sophisticated thing we’ve ever seen, but we do think it is a worthy way to upcycle something that would otherwise be filling up a landfill.

The scanner was old enough to have a CCFL light source inside. However, it was too small, so it came out along with many other components that may yet find use in another project. If you didn’t know , scanners are good sources for small stepper motors, straight rods, and first-surface mirrors.

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The Explosive Art Of Detonographs

The visual arts are a broad field, encompassing everything from the chiselling of marble sculptures to the creation of delicate landscapes in charcoal on paper. However, [Evelyn Rosenberg] has experimented with some altogether more radical techniques over the years, creating her explosively-formed detonographs.

The process of creating a detonograph starts with sketching out a design, and using it to create a plaster mold. The mold exists as a bas relief, upon which metal sheets are laid on top. Various different metals may be layered up to create varying effects, and other objects like leaves, branches, or lace may also be included in the stack up.

Rosenberg’s piece titled “Enchanted New Mexico.”

Then, the metal plate sitting atop the mold is covered with explosive powder. When this is detonated, it smashes everything together with great force. The metal sheet takes on the negative form of the bas relief mold, while also picking up imprints from any leaves or other objects included in the various layers. Dissimilar metals included in the stack-up may also weld together during this process.

With some post-processing like polishing and chemical treatments, the result is a beautiful metal artwork full of dimension and detail. It’s somewhat like an artistic take on the industrial process of explosive welding. Video after the break.

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Running ARM Chips On Algae Power

What’s the size of an AA battery and can run an ARM Cortex M0+ for six months? Well… probably an AA battery, but obviously, that wouldn’t be worth mentioning. But researchers at Cambridge have built a cell of blue-green algae that can do the job.

As you might expect, the algae need light, since they generate energy through photosynthesis. However, unlike conventional solar cells, the algae continue to produce energy in the dark at least for a while. Presumably, the algae store energy during the day and release it at night to survive naturally-occurring periods of darkness.

Generating power from photosynthesis isn’t a new idea since photosynthesis releases electrons. A typical cell has gold electrodes and a proton exchange membrane of some kind. You can see a video from Cambridge below about generating electricity from photosynthesis. Keep in mind, of course, that the Cortex M0+ is capable of very low power operation. Don’t look for that algae-powered spot welder anytime soon.

People tend to get fixated on electricity as energy, but there are other ways to harness photosynthesis. For example, we’ve seen algae fueling a chicken hole in the past. Not to mention we’ve seen algae used to power a robot in a novel and non-electrical way.

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