Flexible Actuators Spring Into Action

Most experiments in flexible robot actuators are based around pneumatics, but [Ayato Kanada] and [Tomoaki Mashimo] has been working on using a coiled spring as the moving component of a linear actuator. Named the flexible ultrasonic motor (FUSM), [Yunosuke Sato] built on top of their work and assembled a pair of FUSM into a closed-loop actuator with motion control in two dimensions.

A single FUSM is pretty interesting by itself, its coiled spring is the only mechanical moving part. An earlier paper published by [Kanada] and [Mashimo] laid out how to push the spring through a hole in a metal block acting as the stator of this motor. Piezoelectric devices attached to that block minutely distorts it in a controlled manner resulting in linear motion of the spring.

For closed-loop feedback, electrical resistance from the free end of the spring to the stator block can be measured and converted to linear distance to within a few millimeters. However, the acting end of the spring might be deformed via stretching or bending, which made calculating its actual position difficult. Accounting for such deformation is a future topic for this group of researchers.

This work was presented at IROS2020 which like many other conferences this year, moved online and became IROS On-Demand. After a no-cost online registration we can watch the 12-minute recorded presentation on this project or any other at the conference. The video includes gems such as an exaggerated animation of stator block deformation to illustrate how a FUSM works, and an example of the position calculation challenge where the intended circular motion actually resulted in an oval.

Speaking of conferences that have moved online, we have our own Hackaday Remoticon coming up soon!

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A Linear Stencil Clock Built For Quiet Operation

We around the Hackaday shop never get tired of seeing new ways to mark the passage of time. Hackers come up with all manner of interesting timekeeping modalities using every imaginable material and method of moving the mechanism once per whatever minimum time unit the hacker chooses to mark.

But honestly, there are only so many ways to make a clock, and while we’re bound to see some repeats, it’s still nice to go over old ground with a fresh approach. Take this linear sliding stencil clock for instance. [Luuk Esselbrugge] has included some cool design elements that bear a closer look. The video below shows that the display is made up of four separate stepper motors, each driving a vertical stencil via a rack-and-pinion mechanism. There a simple microswitch for homing the display, and a Neopixel for lighting things up.

The video below shows that the stencils move very, very slowly; [Luuk] says that this is to keep the steppers as quiet as possible. Still, this means that some time changes take more than a minute to accomplish, which is a minor problem. The Neopixel also doesn’t quite light up just one digit, which should be a pretty easy fix for version 2. Still, even with these issues, we like the stately movements of this clock, and appreciate [Luuk]’s attempts to make it easier to live with.

Don’t let the number of clocks you see on these pages dissuade you from trying something new, or from putting your twist on an old design. Start with fridge magnets, an old oscilloscope, or even a bevy of steel balls, and let your imagination run wild. Just make sure to tell us all about it when you’re done.

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Linear Clock Ratchets Up The Action

On the face of it, making a clock that displays the time by moving a pointer along a linear scale shouldn’t be too hard. After all, steppers and linear drives should do the job in a jiffy. Throw an Arduino in and Bob’s your uncle, right?

Wrong. At least that’s not the way [Leo Fernekes] decided to build this unique ratcheting linear clock, a brilliant decision that made the project anything but run-of-the-mill. The idea has been kicking around in [Leo]’s head for years, and there it stayed until inspiration came in the unlikely form of [This Old Tony], one of our favorite YouTube machinists. [Old Tony] did a video on the simple genius of latching mechanisms, like the ones in retractable pens, and that served as an “A-ha!” moment for [Leo]. For a ratchet, he used a strip of bandsaw blade oriented so the teeth point upward. A complex bit of spring steel, bent to engage with the blade’s teeth, forms a pawl to keep the pointer moving upward until it reaches the top.

[Leo] decided early on that this would be an impulse clock, like the type used in schools and factories. He used a servo to jog a strip of tape upward once each minute; the tape is engaged by jaws that drag the pointer along with it, moving the pawl up the ratchet by one tooth and lifting the pointer one minute closer to the top. The pointer releases at the top and falls back to start the cycle over; to arrest its freefall, [Leo] had the genius idea of attaching magnets and using eddy currents induced in the aluminum frame for the job. Finished off with a 3D-printed Art Deco scale, the clock is a unique timepiece that’s anything but boring.

We really appreciate [Leo]’s unique and creative take on projects, and his range. Check out his everlasting continuity tester and his phage-like sentry gun for some neat build details.

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Mini CNC Mill Goes Horizontal To Reuse CD Drives

Here at Hackaday, we pride ourselves on bringing you the freshest of hacks, preferably as soon as we find out about them. Thanks to the sheer volume of cool hacks out there, though, we do miss one occasionally, like this e-waste horizontal CNC mill that we just found out about.

Aptly called the “CDCNC” thanks to its reliance on cast-off CD drive mechanisms for its running gear, [Paul McClay]’s creation is a great case study on what you can do without buying almost any new parts. It’s also an object lesson in not getting caught in standard design paradigms. Where most CNC mills mount the spindle vertically, [Paul] tilted the whole thing 90 degrees so the spindle lies on its side. Moving it back and forth on a pair of CD drive mechanisms is far easier than fighting gravity for control, and as a bonus the X- and Y-axes have minimal loading too. The video below shows the mill in action, and it’s easy to see how the horizontal arrangement really helps make this junk bin build into something special.

We think [Paul] did a great job of thinking around the problem with this build, and we’re glad he took the time to tip us off. Apparently it was the upcoming CNC on the Desktop Hack Chat that moved him to let us know about this build. Here’s hoping he drops by for the chat and shares his experience with us.

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Linear Track Makes Plasma Cuts Neat And Simple

No microcontroller, no display, and not even an LED in sight. That’s how [Made in Poland] decided to roll with this motorized linear plasma cutter, and despite the simplicity it really gets the job done when there’s metal to be cut.

Plasma cutting makes slicing and dicing heavy stock a quick job, but it’s easy to go off course with the torch or to vary the speed and end up with a poor edge. This tool takes the shakes out of the equation with a completely homebrew linear slide fabricated from square tubing. A carriage to hold the plasma cutter torch moves on a length of threaded rod chucked into the remains of an old cordless drill. The original clutch of the drill removes the need for limit switches when the carriage hits either end of the slide, which we thought was a great touch. Simple speed and direction controls are provided, as is a connection in parallel with the torch’s trigger. One nice feature of the carriage is the ability to swivel the torch at an angle, making V-groove welds in thick stock a snap. No need for a complicated bed with sacrificial supports and a water bath, either — just hang the stock over the edge of a table and let the sparks fall where they may.

Simple is better sometimes, but a CNC plasma table may still be your heart’s desire. We understand.

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Simple Camera Slider Adds A Dimension Or Two To Your Shots

Camera sliders are a popular build, and properly executed they can make for impressive shots for both time-lapse sequences or real-time action. But they seem best suited for long shots, as dollying a camera in a straight line just moves subjects close to the camera through the frame.

This slider with both pan and tilt axes can make moving close-ups a lot easier. With his extremely detailed build log, [Dejan Nedalkovski] shows how he went about building his with only the simplest of materials and tools. The linear rail is simply a couple of pieces of copper pipe supported by an MDF frame. The camera trolley rides the rails on common skateboard bearings and is driven by a NEMA-17 stepper, as are the pan and tilt axes. [Dejan] also provided a barn-door style pivot to tilt the camera relative to the rails, allowing the camera to slide up and down an inclined plane for really interesting shots. The controller uses an Arduino and a joystick to drive the camera manually, or the rig can be programmed to move smoothly between preset points.

This is a step beyond a simple slider and feels a little more like full-blown motion control. We’ve got a feeling some pretty dramatic shots would be possible with such a rig, and the fact that it’s a simple build is just icing on the cake.

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Hybrid Lab Power Supply From Broken Audio Amp

The lab power supply is an essential part of any respectable electronics workbench. However, the cost of buying a unit that has all the features required can be eye-wateringly high for such a seemingly simple device. [The Post Apocalyptic Inventor] has showed us how to build a quality bench power supply from the guts of an old audio amplifier.

We’ve covered our fair share of DIY power supplies here at Hackaday, and despite this one being a year old, it goes the extra mile for a number of reasons. Firstly, many of the expensive and key components are salvaged from a faulty audio amp: the transformer, large heatsink and chassis, as well as miscellaneous capacitors, pots, power resistors and relays. Secondly, this power supply is a hybrid. As well as two outputs from off-the-shelf buck and boost converters, there is also a linear supply. The efficiency of the switching supplies is great for general purpose work, but having a low-ripple linear output on tap for testing RF and audio projects is really handy.

The addition of the linear regulator is covered in a second video, and it’s impressively technically comprehensive. [TPAI] does a great job of explaining the function of all the parts which comprise his linear supply, and builds it up manually from discrete components. To monitor the voltage and current on the front panel, two vintage dial voltmeters are used, after one is converted to an ammeter. It’s these small auxiliary hacks which make this project stand out – another example is the rewiring of the transformer secondary and bridge rectifier to obtain a 38V rail rated for twice the original current.

The Chinese DC-DC switching converters at the heart of this build are pretty popular these days, in fact we’re even seeing open source firmware being developed for them. If you want to find out more about how they operate on a basic level, here’s how a buck converter works, and also the science behind boost converters.

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