Fidget-Spinning Robot Out-Uselesses Other Useless Machines

When the [Director of Legal Evil] at Louisville’s LVL1 Hackerspace decided to demonstrate the uselessness of a 3D printer by printing a fidget spinner, another member at the space’s Tuesday meeting rose to the challenge and built a machine that whose sole purpose is to spin fidget spinners.

[Gary Flispart] used an Arduino clone and what appears to be a motor driver in conjunction with a stepper motor. The motor moves a belt that turns a series of metal scraps serving as a four-bar linkage. The linkage moves the dowel that turns the spinner and then gets out of the way so it doesn’t inhibit the toy’s rotation. The Digital Fidget Digit, as [Gary] calls it, looks like it was built out of scrap metal and random pieces of wood in the glorious tradition of hackerspace projects.

We at Hackaday love crazy projects that come out of hackerspaces, like the iris porthole at i3Detroit, another space’s ultimate fume extractor, and LVL1’s doomcano.

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Hackaday Prize Entry: 3D Printed Linear Actuator Does 2kg+

The rabbit hole of features and clever hacks in [chiprobot]’s NEMA17 3D Printed Linear Actuator is pretty deep. Not only can it lift 2kg+ of mass easily, it is mostly 3D printed, and uses commonplace hardware like a NEMA 17 stepper motor and a RAMPS board for motion control.

The main 3D printed leadscrew uses a plug-and-socket design so that the assembly can be extended easily to any length desired without needing to print the leadscrew as a single piece. The tip of the actuator even integrates a force sensor made from conductive foam, which changes resistance as it is compressed, allowing the actuator some degree of feedback. The force sensor is made from a 3M foam earplug which has been saturated with a conductive ink. [chiprobot] doesn’t go into many details about his specific method, but using conductive foam as a force sensor is a fairly well-known and effective hack. To top it all off, [chiprobot] added a web GUI served over WiFi with an ESP32. Watch the whole thing in action in the video embedded below.

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Hackaday Prize Entry: Modular Stepper Control

Stepper motors are a great solution for accurate motion control. You’ll see them on many 3D printer designs since they can precisely move each axis. Steppers find uses in many robotics projects since they provide high torque at low speeds.

Since steppers are used commonly used for multi-axis control systems, it’s nice to be able to wire multiple motors back to a single controller. We’ve seen a few stepper control modules in the past that take care of the control details and accept commands over SPI, I2C, and UART. The AnanasStepper 2.0 is a new stepper controller that uses CAN bus for communication, and an entry into the 2017 Hackaday Prize.

A CAN bus has some benefits in this application. Multiple motors can be connected to one controller via a single bus. At low bit rates, it can work on kilometer long busses. The wiring is simple and cheap: two wires twisted together with no shielding requirements. It’s also designed to be reliable in high noise environments such as cars and trucks.

The project aims to implement an API that will allow control from many types of controllers including Arduino, Linux CNC, several 3D printer controllers, and desktop operating systems. With a few AnanasSteppers one of these controllers, you’d be all set up for moving things on multiple axes.

Landscape to Portrait at the Click of a Mouse

Modern 16:9 aspect ratio monitors may be great for watching a widescreen movie on Netflix, but for most PDFs, Word documents, and certain web pages, landscape just won’t do. But if you’re not writing the next great American novel and aren’t willing to commit to portrait mode, don’t — build an auto-rotating monitor to switch your aspect ratio on the fly.

Like many of us, [Bob] finds certain content less than suitable for the cinematic format that’s become the standard for monitors. His fix is simple in concept, but a little challenging to engineer. Using a lazy susan as a giant bearing, [Bob] built a swivel that can be powered by a NEMA 23 stepper and a 3D-printed sector of a ring gear. Due to the narrow clearance between the top and bottom of the lazy susan, [Bob] had to do considerable finagling to get through holes for the mounting hardware located, but in the end the whole thing worked great.

Our only quibble would be welding galvanized pipe for the stand, which always gives us the willies. But we will admit the tube notching turned out great with just a paper template. We doubt it would have been much better if he used an amped-up plasma-powered tubing notcher.

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Linear Clock Slows the Fugit of the Tempus

We feature a lot of clocks here on Hackaday, and lately most of them seem to be Nixie clocks. Not that there’s anything wrong with that, but every once in a while it’s nice to see something different. And this electromechanical rack and pinion clock is certainly different.

[JON-A-TRON] calls his clock a “perpetual clock,” perhaps in a nod to perpetual calendars. But in our opinion, all clocks are perpetual, so we’ll stick with “linear clock.” Whatever you call it, it’s pretty neat. The hour and minute indicators are laser cut and engraved plywood, each riding on a rack and pinion. Two steppers advance each rack incrementally, so the resolution of the clock is five minutes. [JON-A-TRON] hints that this was a design decision, in part to slow the perceived pace of time, an idea we can get behind. But as a practical matter, it greatly simplified the gear train; it would have taken a horologist like [Chris] at ClickSpring to figure out how to gear this with only one prime mover.

In the end, we really like the look of this clock, and the selection of materials adds to the aesthetic. And if you’re going to do a Nixie clock build, do us a favor and at least make it levitate.

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Walter is the Slickest Retro-Futuristic Robot Arm

[Jochen Alt] is on a roll. We just covered his ball-balancing robot, Paul, only to find his phenomenal six-DOF robot arm in full retro style. Its name is “Walter” and it’s done up in DDR style (the former East Germany), in painted, 3D-printed plastic. The full design and build documents are an absolutely amazing resource if you’re into robot arm or legs.

In particular, the sections on trajectory planning and kinematics are fantastic. If you’re interested in robot motion planning by Bezier curves, you know where to go. (We’ve always wanted a Bezier-curve 3D printer slicer, but that’s another story.) The construction is also top-notch here, and the attention to detail that went into this arm is phenomenal. It’s all done with stepper motors and geared belts, which allow each of Walter’s joints to be driven by a motor that’s one joint further upstream than would be the case if it were designed with servos. [Jochen] even went so far as to expose the belt in some places to show off the gearing. Walter is worth checking out.

Even if you’ll never build such a fancy robot arm, you should read through the docs just to appreciate all of the thought and work that went into this very refined and simple-from-the-outside design. If you’d like to start out on the simple side of the spectrum, check out these robot arms made of office supplies or a desk lamp. Once you’re ready for your second arm project this short list, some of which [Jochen] mention in his writeup, should get you up and grasping. And do check out his balancing bot, Paul.

Unique Planetary Gearbox can be Custom Printed for Steppers

Stepper motors are a staple in all sorts of projects, but it’s often the case that a gearbox is needed, especially for applications like the linear drives in CNC machines and 3D printers. In those mechanisms, a high-torque, low backlash gearbox might be just the thing, and a 3D printable split planetary harmonic drive for the popular NEMA 17 motors would be even better.

Right up front, we’ll say that we’re skeptical that any plastic gearbox can stay as backlash free as [SirekSBurom] claims his creation is. But we can see the benefits of the design, and it has some nice features. First off, of course, is that it’s entirely 3D printed, except for a few screws. That it mates perfectly with a NEMA 17 motor is a really nice feature, too, and with the design up on Thingiverse it shouldn’t be too tough to scale it up and down accordingly. The videos below show you the theory: the stepper drives a sun gear with two planet gears orbiting, each of which engages a fixed ring of 56 teeth, and an output ring of 58 teeth. Each revolution of the planets around the fixed ring rotates the output ring by one tooth, leading to almost 100:1 reduction.

We think the ‘harmonic’ designation on this gearbox is a little of a misnomer, since the defining feature of a harmonic drive seems to be the periodic deformation of a flex spline, as we saw in this 3D-printed strain wave gear. But we see the resemblance to a harmonic drive, and we’ll admit this beastie is a little hard to hang a name tag on. Whatever you call it, it’s pretty cool and could be a handy tool for all kinds of builds.

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