OpenSCAD Handles The Math In 3D Printed Holder For Magnetic Spheres

August 28, 2018 by Donald Papp 35 Comments

3D printed holder mounted to bike wheel, fitting precisely 38 magnetic spheres around its perimeter. Tedious math? Not if you make OpenSCAD do it.

Off-the-shelf components are great; the world and our work simply wouldn’t be the same without. But one of the constraints is that one has to design around them, and that’s what led [Antonio Ospite] to create a parametric design in OpenSCAD for a 3D printed holder which snugly fits a number of magnetic spheres around its diameter.

If that sounds a bit esoteric, it will become much clearer in the context of [Antonio]’s earlier work in making a DIY rotary encoder out of a ring of magnetic spheres. He found that such a ring in front of two Hall effect sensors was low in cost, high in precision, and thanks to 3D printing it also had a lot of potential for customizing. But hampering easy design changes was the need for the spheres to fit snugly around whatever shape was chosen for the hardware, which meant constraints on the encoder diameter.

In this case, [Antonio] wished to create an encoder that could be attached to a bicycle wheel but needed to know what outer diameter would best fit a ring of magnetic balls perfectly, given that the balls were each 5 mm. OpenSCAD did the trick, yielding a design that fit the bike wheel and spokes while perfectly nestling 38 magnetic balls around the outside edge with a minimum of wasted space.

OpenSCAD is a CAD program that’s really more like a programming language than anything else. For those who are not familiar with it, [Brian Benchoff] walked through how to make a simple object in OpenSCAD, and [Elliot] has sung the praises of a few advanced functions. Now that this project makes DIY encoders easier, perhaps they could be used to add intuitive new controls to OpenSCAD itself.

Magnetic Spheres Line Up For Rotary Encoder Duty

June 5, 2018 by Dan Maloney 21 Comments

When it comes to rotary encoders, there are plenty of options. Most of them involve putting a credit card number into an online vendor’s website, though, and that’s sometimes just not in the cards. In that case building your own, like this encoder using magnetic spheres, is a pretty cool way to go too.

If he’d had less time to spare, we imagine [Antonio Ospite] would have gone for a commercial solution rather than building an encoder from scratch. Then again, he says his application had noise considerations, so maybe this was the best solution overall. He had some latching Hall effect sensors lying around, but lacked the ring magnet that is usually used with such sensors in magnetic encoders. But luckily, he had a mess of magnetic spheres, each 5 mm in diameter. Lined up in a circle around a knob made from a CD spindle, the spheres oriented themselves with alternating poles, which is just what the Hall sensors want to see. The sensors were arranged so the pulses are 90° apart, and can resolve 4.29° steps. Check out the video below to watch it work.

Small, cheap and effective are always good things. But magnets aren’t the only thing behind homebrew rotary encoders. A couple of microswitches might do in a pinch, or maybe even scrapped hard drives would suffice.

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Simple Decoder Serves As Solo Ham’s Test Buddy

March 31, 2018 by Dan Maloney 11 Comments

For a hobby that’s ostensibly all about reaching out to touch someone, ham radio can often be a lonely activity. Lots of hams build and experiment with radio gear much more than they’re actually on the air, improving their equipment iteratively. The build-test-tweak-repeat cycle can get a little tedious, though, especially when you’re trying to assess signal strength and range and can’t find anyone to give you a report.

To close the loop on field testing, [WhiskeyTangoHotel] threw together a simple ham radio field confirmation unit that’s pretty slick. It relies on the fact that almost every ham radio designed for field use incorporates a DTMF encoder in the microphone or in the transceiver itself. Hams have used Touch Tones for in-band signaling control of their repeaters for decades, and even as newer digital control methods have been introduced, good old analog DTMF hangs in there. The device consists of a DTMF decoder attached to the headphone jack of a cheap handy talkie. When a DTMF tone is received, a NodeMCU connected to the decoder calls an IFTTT job to echo the key to [WTH]’s phone as an SMS message. That makes it easy to drive around and test whether his mobile rig is getting out. And since the receiver side is so portable, there’s a lot of flexibility in how tests can be arranged.

On the fence about ham as a hobby? We don’t blame you. But fun projects like this are the perfect excuse to go get licensed and start experimenting.

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High-Effort Streaming Remote For Low-Effort Bingeing

March 10, 2018 by Dan Maloney 7 Comments

There’s no limit to the amount of work some people will put into avoiding work. For instance, why bother to get up from your YouTube-induced vegetative state to adjust the volume when you can design and build a remote to do it for you?

Loath to interrupt his PC streaming binge sessions, [miroslavus] decided to take matters into his own hands. When a commercially available wireless keyboard proved simultaneously overkill for the job and comically non-ergonomic, he decided to build a custom streaming remote. His recent microswitch encoder is prominently featured and provides scrolling control for volume and menu functions, and dedicated buttons are provided for play controls. The device reconfigures at the click of a switch to support Netflix, which like YouTube is controlled by sending keystrokes to the PC through a matching receiver. It’s a really thoughtful design, and we’re sure the effort [miroslavus] put into this will be well worth the dozens of calories it’ll save in the coming years.

A 3D-printed DIY remote is neat, but don’t forget that printing can also save a dog-chewed remote and win the Repairs You Can Print contest.

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Roll Your Own Rotary Encoders

February 19, 2018 by Dan Maloney 36 Comments

[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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Scrap A Hard Drive, Build A Rotary Encoder

January 7, 2018 by Dan Maloney 26 Comments

There’s something to be said for the feel of controls. Whether it’s the satisfying snap of a high-quality switch or the buttery touch of the pots on an expensive amplifier, the tactile experience of the controls you interact with says a lot about a device.

[GreatScott!] knows this, and rather than put up with the bump and grind of a cheap rotary encoder, he decided to find an alternative. He ended up exploring hard drive motors as encoders, and while the results aren’t exactly high resolution, he may be onto something. Starting with a teardown of some old HDDs — save those magnets! — [Scott!] found that the motors fell into either the four-lead or three-lead categories. Knowing that HDD motors are brushless DC motors, he reasoned that the four-lead motors had their three windings in Wye configuration with the neutral point brought out to an external connection. A little oscilloscope work showed the expected three-phase output when the motor hub was turned, with the leading and lagging phases changing as the direction of rotation was switched. Hooked to an Arduino, the motor made a workable encoder, later improved by sending each phase through a comparator and using digital inputs rather than using the Nano’s ADCs.

It looks like [GreatScott!]’s current setup only responds to a full rotation of the makeshift encoder, but we’d bet resolution could be improved. Perhaps this previous post on turning BLDC motors into encoders will help.

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Add Intuitiveness To OpenSCAD With Encoders

November 1, 2017 by Brian McEvoy 44 Comments

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

select the relevant value
replace it with an updated value
refresh the display
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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