Crisp Clean Shortcuts

People always tell us that their favorite part about using a computer is mashing out the exact same key sequences over and over, day in, day out. Then, there are people like [Benni] who would rather make a microcontroller do the repetitive work at the touch of a stylish USB peripheral. Those people who enjoy the extra typing also seem to love adding new proprietary software to their computer all the time, but they are out of luck again because this dial acts as a keyboard and mouse so they can’t even install that bloated software when they work at a friend’s computer. Sorry folks, some of you are out of luck.

Rotary encoders as computer inputs are not new and commercial versions have been around for years, but they are niche enough to be awfully expensive to an end-user. The short BOM and immense versatility will make some people reconsider adding one to their own workstations. In the video below, screen images are rotated to get the right angle before drawing a line just like someone would do with a piece of paper. Another demonstration reminds of us XKCD by cycling through the undo and redo functions which gives you a reversible timeline of your work.

If you like your off-hand macro enabler to have more twists and buttons, we have you covered, or maybe you only want them some of the time.

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Mechanisms: Solenoids

Since humans first starting playing with electricity, we’ve proven ourselves pretty clever at finding ways to harness that power and turn it into motion. Electric motors of every type move the world, but they are far from the only way to put electricity into motion. When you want continuous rotation, a motor is the way to go. But for simpler on and off applications, where fine control of position is not critical, a solenoid is more like what you need. These electromagnetic devices are found everywhere and they’re next in our series on useful mechanisms.

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A Polar Coordinate CNC Plotter Even Descartes Could Love

Take apart a few old DVD drives, stitch them together with cable ties, add a pen and paper, and you’ve got a simple CNC plotter. They’re quick and easy projects that are fun, but they do tend to be a little on the “plug and chug” side. But a CNC plotter that uses polar coordinates? That takes a little more effort.

The vast majority of CNC projects, from simple two-axis plotters to big CNC routers, all tend to use Cartesian coordinate systems, where points on a plane are described by their distances from an origin point on two perpendicular axes. Everything is nice and square, measurements are straightforward, and the math is easy. [davidatfsg] decided to level up his CNC plotter a bit by choosing a polar coordinate system, with points described as a vector extending a certain distance from the origin at a specified angle. Most of the plotter is built from FischerTechnik parts, with a single linear axis intersecting the center point of a rotary drawing platform. Standard G-code is translated to polar coordinates by a Java applet before being sent to a custom Arduino controller to execute the moves. Check out the video below; it’s pretty mesmerizing to watch, and we can’t help but wonder how a polar 3D-printer would work out.

Have polar coordinates got you stumped? It can be a bit of an adjustment from Cartesian space for sure. It can be worth it, though, showing up in everything from cable plotters to POV fidget spinners and even to color space models.

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Rotary Electric Gun Might Not Put Your Eye Out, Kid

This one is clearly from the “it’s all fun and games until someone loses an eye” file, and it’s a bit of a departure from [Make It Extreme]’s usual focus on building tools for the shop. But what’s the point of having a well-equipped shop if you don’t build cool things, like this unique homebrew electric gun?

When we hear “electric gun” around here, we naturally think of the rail guns and coil guns we feature on a regular basis, which use stored electric charge to accelerate a projectile using electromagnetic forces. This gun is much simpler than that, using purely mechanical means to accelerate the projectiles. The heart of the unit is a machined aluminum spiral from an old scroll compressor, which uses interleaved orbiting spirals to compress gasses. This scroll was cut down to reduce its mass and fixed to a complex shaft assembly allowing it to spin up to tremendous speed with a powerful electric motor. A hopper feeds the marble-sized ammo into the eye of the scroll, which spits it out at high speed. Lacking a barrel, the gun can only spew rounds in the general direction of the target, but it makes up for inaccuracy with an impressive rate of fire — 100 rounds downrange in two seconds. It’s pretty powerful, too, judging by the divots in the sheet steel target in the video below.

Like all of [Make It Extreme]’s build, a lot of effort went into this, and it shows. Their other fun builds of dubious safety include these electromagnetic wall climbers and these “Go Go Gadget” legs.

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Roll Your Own Rotary Encoders

[miroslavus] hasn’t had much luck with rotary encoders. The parts he has tested from the usual sources have all been problematic either mechanically or electrically, resulting in poor performance in his projects. Even attempts to deal with the deficiencies in software didn’t help, so he did what any red-blooded hacker would do — he built his own rotary encoder from microswitches and 3D-printed parts.

[miroslavus]’s “encoder” isn’t a quadrature encoder in the classic sense. It has two switches and only one of them fires when it turns a given direction, one for clockwise and one for counterclockwise. The knob has a ratchet wheel on the underside that engages with a small trip lever, and carefully located microswitches are actuated repeatedly as the ratchet wheel moves the trip lever. The action is smooth but satisfyingly clicky. Personally, we’d forsake the 3D-printed baseplate in favor of a custom PCB with debouncing circuitry, and perhaps relocate the switches so they’re under the knob for a more compact form factor. That and the addition of another switch on the shaft’s axis to register knob pushes, and you’ve got a perfectly respectable input device for navigating menus.

We think this is great, but perhaps your project really needs a legitimate rotary encoder. In that case, you’ll want to catch up on basics like Gray codes.

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16-Cylinder Stirling Engine Gets a Tune Up

Tiny catapults, kinetic sculptures, a Newton’s Cradle — all kinds of nifty toys can adorn the desk of the executive in your life. On the high end of the scale, a 16-cylinder butane-powered Stirling engine makes a nice statement, but when it comes equipped with a propeller that looks ready for finger-chopping, some mods might be in order before bestowing the gift.

We don’t knock [JohnnyQ90] for buying a rotary Stirling engine from one of the usual sources rather than building, of course. With his micro Tesla turbine and various nitro-powered tools, he’s proven that he has the machining chops to scratch-build one of these engines. And it wasn’t just the digit dicing potential of the OEM engine that inspired him. There was a little too much slop in the bearings for his liking, so he machined a new bearing block and shaft extension. With a 3D-printed shroud, a small computer fan, and snappy brass nose cone, the engine started looking more like a small jet engine. And the addition of a pulley and a small generator gave the engine something interesting to do. What’s more, the increased airflow over the cold end of the engine boosted performance.

Need the basics of Stirling engines? Here’s a quick look at the 200-year history of these remarkable devices.

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Add Intuitiveness to OpenSCAD With Encoders

The first time I saw 3D modeling and 3D printing used practically was at a hack day event. We printed simple plastic struts to hold a couple of spring-loaded wires apart. Nothing revolutionary as far as parts go but it was the moment I realized the value of a printer.

Since then, I have used OpenSCAD because that is what I saw the first time but the intuitiveness of other programs led me to develop the OpenVectorKB which allowed the ubiquitous vectors in OpenSCAD to be changed at will while keeping the parametric qualities of the program, and even leveraging them.

All three values in a vector, X, Y, and Z, are modified by twisting encoder knobs. The device acts as a keyboard to

  1. select the relevant value
  2. replace it with an updated value
  3. refresh the display
  4. move the cursor back to the starting point

There is no software to install and it runs off a Teensy-LC so reprogramming it for other programs is possible in any program where rotary encoders may be useful. Additional modes include a mouse, arrow keys, Audacity editing controls, and VLC time searching.

Here’s an article in favor of OpenSCAD and here’s one against it. This article does a good job of explaining OpenSCAD.

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