Misc Hacks

4137 Articles

Simulated Newton’s Cradle Makes A Flashy Desk Toy

June 1, 2019 by No comments

Newton’s Cradle was once upon a time, a popular desk toy in offices around the world. For [TecnoProfesor], however, it wasn’t quite flashy enough. Instead, they built a simulated version with flashing LEDs. As you do.

Rather than relying on the basic principles of the cradle to make it work, this relies on two servo motors to move the balls on the ends, with the ones in the middle remaining stationary. Each ball is fitted with an RGB LED, which flashes with the simulated “motion” of the cradle. By using ping pong balls, the light from the LEDs is nicely diffused. The frame is built from wooden dowels, metal rods, and acrylic.

It’s a project that is sure to confuse at first glance, but it’s a great way to learn basic microcontroller skills like interfacing with LEDs and servomotors. We’d love to see a version that works like a real Newton’s Cradle, flashing the LEDs as they are hit by their neighbours. We’ve even seen them automated, for the truly lazy among us.  Alternatively, one could go completely ridiculous and have such a device tweet on every hit, though you might run afoul of the API’s spam restrictions. If you give it a go, drop us a line.

Ferrofluid Display Fuels The Fun, And The Procrastination

May 28, 2019 by 14 Comments

When deadlines loom and your future is on the line, do what top college students through the ages have always done: procrastinate! [Simen] and [Amund] did that in grand style by starting a YouTube channel, delightfully and aptly named “Applied Procrastination”, wherein they plan to avoid their responsibilities as long as possible in favor of making a large-scale ferrofluidic display panel. (Video, embedded below.)

We suppose we should encourage them to hit the books, but honestly they look like they’re having much more fun and learning more than they would in class. The idea isn’t new; we’ve seen ferrofluid clocks before, after all. [Amund] and [Simen] have grander plans for their display, but they’re wisely starting small with basic experiments. They had an early great idea to use a double-pane window as a tank for their display, but coatings on the inside of the glass and the aluminum frame conspired to cloud the display. They also did some tests to make sure they can control 252 electromagnets safely. They did manage to get a small test display working, but really the bulk of the video is just them playing with magnets and ferrofluid. And again, we’re OK with that.

It looks like this is going to be an interesting project, with hopefully regular updates to the channel now that summer break is upon us. Unless they find something else to do, of course.

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For Better Photogrammetry, Just Add A Donut

May 14, 2019 by 19 Comments

If you don’t have access to a 3D scanner, you can get a lot done with photogrammetry. Basically, you take a bunch of pictures of an object from different angles, and then stitch them together with software to create a 3D model. For best results, you need consistent, diffuse lighting, an unchanging background, and a steady camera.

Industrial designer [Eric Strebel] recently made an Intro to Photogrammetry video wherein he circled an object taking photos with his bare hands. One commenter suggested a different method: build a donut-shaped turntable that circles the object, which sits on a stationary platform. Attach the camera to the donut, counterbalance the weight, and Bob’s your proverbial uncle. [Eric] thought it was a brilliant idea (because it is), and he built a proof of concept. This is that video.

[Eric] can move the camera up and down the arc of the boom to get all the Z-positions he wants. The platform has a mark every 10° and there’s a pointer in the platform to line them up against for consistent camera positioning. He was pleasantly surprised by the results, which we agree are outstanding.

We always learn a lot from [Eric]’s videos, and this one’s no exception. Case in point: he makes a cardboard mock-up by laying out the pieces, and uses that to make a pattern for the recycled plywood and melamine version. In the photogrammetry video, he covers spray paint techniques to make objects reflect as little light as possible so the details don’t get lost.

If you prefer to rotate your objects, get an Arduino out and automate the spin.

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Supercapacitors Propel Rocket To The Skies

May 7, 2019 by 33 Comments

OK, so this isn’t really a rocket. In the strictest definition, rockets are vehicles or projectiles that propel themselves through jettisoning mass, usually through the combustion of fuel. But with electric motors getting stronger and stronger, folks are building craft that look a lot more like rockets than airplanes. [Tom Stanton] is one such person (Youtube link, embedded below).

We’ve seen “electric rocket” builds before, but where others have used lithium batteries, [Tom] has used supercapacitors instead. Six supercaps are installed in a 3D printed mount, and supply power to a 500 W brushless outrunner motor which gives the rocket the thrust to climb into the sky.

In testing, [Tom] estimates the rocket was able to reach an altitude of approximately 60 m, or 200 ft. That’s not particularly astounding, but it does prove that supercaps can run a high current load in a real world situation. Additionally, their fast recharge rate allows [Tom] to make a repeat flights in just about the time it takes to repack the parachute. Video after the break.

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Cold Plasma Torch Produces A Cleansing Flame That Never Consumes

April 28, 2019 by 20 Comments

It’s basically a lightsaber. Except smaller. And with an invisible blade. And cold to the touch. But other than that, this homebrew cold plasma torch (YouTube, embedded below) is just like the Jedi’s choice in elegant weaponry.

Perhaps we shouldn’t kid [Justin] given how hard he worked on this project – seventeen prototypes before hitting on the version seen in the video below – but he himself notes the underwhelming appearance of the torch without the benefit of long-exposure photography. That doesn’t detract from how cool this build is, pun intended. As [Justin] explains, cold plasma or non-equilibrium plasma is an ionized stream of gas where the electron temperature is much hotter than the temperature of the heavier, more thermally conductive species in the stream. It’s pretty common stuff, seen commercially in everything from mercury vapor lamps to microbial sterilization.

It’s the latter use that piqued [Justin]’s interest and resulted in a solid year of prototyping before dialing in a design using a flyback transformer to delivery the high voltage to a stream of argon flowing inside a capillary tube. The quartz tube acts as a dielectric that keeps electrons from escaping and allows argon to be ionized and wafted gently from the tube before it can reach thermal equilibrium. The result is a faint blue glowing flame that’s barely above room temperature but still has all the reactive properties of a plasma. The video shows all the details of construction and shows the torch in action.

Hats off to [Justin] for sticking with a difficult build and coming through it with an interesting and useful device. We’ve no doubt he’ll put it to good use in his DIY biohacking lab in the coming months.

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Electromechanical YouTube Sub Counter Trades Clicks For Clacks

April 28, 2019 by 11 Comments

Acquiring a new YouTube subscriber is a blessed event that deserves far more fanfare than a phone notification. But maybe blinkenlights don’t really do it for you anymore, or you simply prefer to be soothed sonically rather than visually. Well, what could be more satisfying than the crisp clack of an electromechanical 7-segment display? Six of them, of course. These things look great, they sound great, and once they’re set, they don’t need power to stay that way.

These displays switch between black and white by reversing current flow through their electromagnets, so [Zack] turned to the H-bridge in order to use them with DC. One H-bridge for each segment of six displays adds up fast, though. To get around this, [Zack] tied one pole of each electromagnet together for a common signal input, and used the other pole to control each segment individually. Then, he was able to tie all the A segments together, all the B segments, and so on, and only needs 13 H-bridges to do it all.

There was just one thing [Zack] didn’t count on. Once he got the board soldered up and running, the displays started acting funny. The low impedance of the coils was causing them to influence each other over the common path, so he added diode arrays to keep them in line.

[Zack]’s using an ESP32 to get the 411 through the Google API, and four octal serial switches to drive the displays. Even more satisfying than all those clacks is the displays’ operational economy baked into [Zack]’s code—as they count up, any segments common to the first digit and the next digit remain on. Increment your way past the break to check out the build video.

Not focused on numbers, but still want to celebrate each new sub? Try a dancing robot or a Tetris twist.

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Making Microfluidics Simpler With Shrinky Dinks

April 23, 2019 by 6 Comments

It’s as if the go-to analogy these days for anything technical is, “It’s like a series of tubes.” Explanations thus based work better for some things than others, and even when the comparison is apt from a physics standpoint it often breaks down in the details. With microfluidics, the analogy is perfect because it literally is a series of tubes, which properly arranged and filled with liquids or gasses can perform some of the same control functions that electronics can, and some that it can’t.

But exploring microfluidics can be tough, what with the need to machine tiny passages for fluids to flow. Luckily, [Justin] has turned the process into child’s play with these microfluidic elements made from Shrinky Dinks. For those unfamiliar with this product, which was advertised incessantly on Saturday morning cartoon shows, Shrinky Dinks are just sheets of polystyrene film that can be decorated with markers. When placed in a low oven, the film shrinks about three times in length and width while expanding to about nine times its pre-shrunk thickness. [Justin] capitalized on this by CNC machining fine grooves into the film which become deeper after shrinking. Microfluidics circuits can be built up from multiple layers. The video below shows a mixer and a simple cell sorter, as well as a Tesla valve, which is a little like a diode.

We find [Justin]’s Shrinky Dink microfluidics intriguing and can’t wait to see what kind of useful devices he comes up with. He’s got a lot going on, though, from spider-powered beer to desktop radio telescopes. And we wonder how this technique might help with his CNC-machined microstrip bandpass filters.

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