LED Matrix Watch Is The Smart Watch We Didn’t Know We Wanted

[Mile] put together this stunning LED matrix watch, on which the stars of this show are the 256 monochrome 0603 LEDs arranged in a grid on its face. The matrix is only 1.4in in the diagonal and is driven by a combination of an LED driver and some shift registers. The brain is an ATmega328p. We appreciate the extra effort taken to add a USB to UART adapter so the mega can be programmed over USB. It also contains all the necessary circuitry to charge and maintain the lithium battery inside safely.

Input into the device is done with a hall effect sensor which keeps the build from having any moving parts. The body is a combination of 3D printed parts and really fetching brass details connecting to the band.

If it weren’t over the top enough the build even has an ambient light sensor so the display can dim or brighten depending. We bet [Mile] is pretty proud to wear this on their wrist.

A Self-Healing, Stretchable Electronic Skin

In a report published by Science Advances, a research team from the United States and Korea revealed a strain-sensitive, stretchable, and autonomous self-healing semiconductor film. In other words, they’ve created an electronic skin that’s capable of self-regulation. Time to cue the ending track from Ex Machina? Not quite.

Apart from the inevitable long timeline it will take to see the material in production, there are still challenges to improve sensing for active semiconductors. The methods used by the team – notably using a dynamically cross-linked blend of polymer semiconductor and self-healing elastomer – have created a film with a gauge factor of 5.75×10^5 at full strain. At room temperature, even with fracture strains, the material demonstrated self healing.

The technique mimics the self healing properties of human skin, accelerating the development of biomedical devices and soft robots. While active-matrix transistor array-based sensors can provide signals that reduce crosstalk between individual pixels in electronic skin, embedding these rigid sensors and transistors into stretchable systems causes mechanical mismatch between rigid and soft components. A strain-sensing transistor simplifies the process of fabrication, while also improving mechanical conformability and the lifetime of the electronic skin.

The synthetic skin was also shown to operate within a medically safe voltage and to be waterproof, which will prevent malfunctions when placed in contact with ionic human sweat.

[Thanks Qes for the tip!]

Building An Engine With An A/C Compressor

Air conditioning compressors aren’t exactly a mainstay of the average hacker’s junk box. Typically, they’re either fitted to a car to do their original job, or they’re on the bench getting refurbished. However, with the right mods, it’s possible to turn one into a functioning internal combustion engine.

The build starts by disassembling the compressor, which contains three double-sided pistons. The housing is drilled with ports to allow gas to flow into and out of the cylinders, as well as to transfer from one side of the piston to the other. Acrylic end plates are fitted to the assembly. One end acts as an intake manifold, delivering air and fuel to the cylinders. The other side acts as the cylinder head, mounting the sparkplugs. Everything is then connected with acrylic tubing and a small square section of acrylic is turned into a carburetor to supply the air-fuel mix. Ignition is handled by coils triggered by the movement of the flywheel.

After an initial failure due to the acrylic manifold cracking, a stronger part is fabricated, and the engine bursts into life. The acrylic end caps give a great view of the combustion process in action. We’d love to see the a dyno graph on how much power and torque the unit puts out, or to see it hooked up to a bicycle or cart.

We’ve seen others attempt their own engine builds, too. If you’ve got an unconventional engine build of your own, be sure to let us know. Video after the break.

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Start Your Day With The Mountain That Rises

Like many of us, [Zach Archer] enjoys the comfort of his darkened room so much that he has trouble getting up and facing the day. To make things a little easier for himself, he decided to put together a custom alarm clock that would fill his mornings with the glorious glow of LEDs; and since he finds the mountains an inspirational sight he decided to wrap the whole thing up in a 3D printed enclosure that resembles snow capped peaks.

But even Bob Ross himself couldn’t have imagined a snowy mountain range that featured an integrated e-ink screen. The big 4.2″ panel is connected to a custom designed PCB by [romkey], which was graciously donated for this project. An ESP32 runs the show, providing a convenient web interface to control not only the clock, but various aspects of the mountain’s internal LEDs such as fade in time and total duration.

[Zach] says he originally printed the mountains in PLA, but the heat generated by the LEDs eventually started to cause things to warp. Switching over to translucent PETG not only solved the heat problem, but made for a very effective LED diffuser. Rather than complex animation patterns, he’s found that smoothly transitioning between different shades of blue and green seems to work best for him in the mornings.

This isn’t the first time we’ve seen somebody use LEDs to get them out of bed in the morning, but we do appreciate the aesthetic that [Zach] has achieved here between the design of the mountains and the impressive artwork on the e-ink display. Then again, we’re also quite partial to this version that looks like a warp core, so our tastes do run the gamut.

Sara Adkins Is Jamming Out With Machines

Asking machines to make music by themselves is kind of a strange notion. They’re machines, after all. They don’t feel happy or hurt, and as far as we know, they don’t long for the affections of other machines. Humans like to think of music as being a strictly human thing, a passionate undertaking so nuanced and emotion-based that a machine could never begin to understand the feeling that goes into the process of making music, or even the simple enjoyment of it.

The idea of humans and machines having a jam session together is even stranger. But oddly enough, the principles of the jam session may be exactly what machines need to begin to understand musical expression. As Sara Adkins explains in her enlightening 2019 Hackaday Superconference talk, Creating with the Machine, humans and machines have a lot to learn from each other.

To a human musician, a machine’s speed and accuracy are enviable. So is its ability to make instant transitions between notes and chords. Humans are slow to learn these transitions and have to practice going back and forth repeatedly to build muscle memory. If the machine were capable, it would likely envy the human in terms of passionate performance and musical expression.

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The Story Of A Secret Underground Parisian Society

Deep in the heart of Paris, a series of underground tunnels snakes across the city. They cross into unkept public spaces from centuries ago that have since vanished from collective memory – abandoned basements, catacombs, and subways hundreds of miles apart.

Only a few groups still traverse these subterranean streets. One that came into public view a few years ago, Les UX (Urban eXperiment), has since claimed several refurbished developments, including restoring the long neglected Pantheon clock and building an underground cinema, complete with a bar and restaurant.

While the streets of Paris are tame during the day, at night is when Les UX really comes alive. A typical night might involve hiding in the shadows away from potential authorities roaming the streets, descending into the tunnels through a grate in the road, and carrying materials to an agreed upon drop off location. Other nights might involve wedging and climbing over pipes and ladders, following the routes into the basements of buildings left unguarded.
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[Ben Krasnow] Builds A Mass Spectrometer

One of the features that made Scientific American magazine great was a column called “The Amateur Scientist.” Every month, readers were treated to experiments that could be done at home, or some scientific apparatus that could be built on the cheap. Luckily, [Ben Krasnow]’s fans remember the series and urged him to tackle a build from it: a DIY mass spectrometer. (Video, embedded below the break.)

[Ben] just released the video below showing early experiments with a copper tube contraption that was five months in the making; it turns out that analytical particle physics isn’t as easy as it sounds. The idea behind mas spectrometry is to ionize a sample, accelerate the ions as they pass through a magnetic field, and measure the deflection of the particles as a function of their mass-to-charge ratio. But as [Ben] discovered, the details of turning a simple principle into a working instrument are extremely non-trivial.

His rig uses filaments extracted from carefully crushed incandescent lamps to ionize samples of potassium iodide chloride; applied to the filament and dried, the salt solution is ionized when the filament is heated. The stream of ions is accelerated by a high-voltage field and streamed through a narrow slit formed by two razor blades. A detector sits orthogonal to the emitter across a powerful magnetic field, with a high-gain trans-impedance amplifier connected. With old analog meters and big variacs, the whole thing has a great mad scientist vibe to it that reminds us a bit of his one-component interferometer setup.

[Ben]’s data from the potassium sample agreed with expected results, and the instrument is almost sensitive enough to discern the difference between two different isotopes of potassium. He promises upgrades to the mass spec in the future, including perhaps laser ionization of the samples. We’re looking forward to that.

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