Bot Makes Etch A Sketch Art In One Continuous Line

Introduced in 1960 for the princely sum of $2.99 ($25.00 today), Etch A Sketch was to become a standard issue item for the Baby Boomers’ toy box. As enchanting as the toy seems, it’s hard to see why it had staying power: it was hard for young fingers to twirl the knobs, diagonal lines and smooth curves required a concert pianist’s fine motor control, and whatever drawings we managed to make were erased at the slightest jostle of the tablet.

Intent on righting these wrongs, [Sunny Balasubramanian] not only motorized an Etch A Sketch, but he’s also given it a mind of its own in a way. For those unfamiliar with the toy, it’s basically a manual X-Y plotter that drags a stylus across the underside of a glass screen, scraping off a silver powder clinging to the glass to make dark lines. Replacing the knobs with steppers is straightforward, of course, but driving them is the trick. [Sunny] hooked his up to a Raspberry Pi and wrote some Python code to drive them. The Pi also accepts input image files and processes them for rendering through the plotter, first doing Canny edge detection in OpenCV, then plotting a single path through the largest collection of connected pixels in the image. From there it’s just a matter of spinning the motors to create surprisingly detailed images. Check out the short video below to see it in action.

It’s hardly the first automatic Etch A Sketch we’ve seen – here’s one that automates everything including the shake to erase the drawing. That one cheats a little though, in that it rasters across the screen like a CRT. We really like how this one just does a single path. Pretty clever.

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Automated Turntable For 3D Scanning

Those just starting out in 3D printing often believe that their next major purchase after the printer will be a 3D scanner. If you’re going to get something that can print a three dimensional model, why not get something that can create said models from real-world objects? But the reality is that only a small percentage ever follow through with buying the scanner; primarily because they are notoriously expensive, but also because the scanned models often require a lot of cleanup work to be usable anyway.

While this project by [Travis Antoniello] won’t make it any easier to utilize scanned 3D models, it definitely makes them cheaper to acquire. So at least that’s half the battle. Consisting primarily of a stepper motor, an Arduino, and a EasyDriver controller, this is a project you might be able to assemble from the parts bin. Assuming you’ve got a pretty decent camera in there, anyway…

The general idea is to place a platform on the stepper motor, and have the Arduino rotate it 10 degrees at a time in front of a camera on a tripod. The camera is triggered by an IR LED on one of the Arduino’s digital pins, so that it takes a picture each time the platform rotates. There are configurable values to give the object time to settle down after rotation, and a delay to give the camera time to take the picture and get ready for the next one.

Once all the pictures have been taken, they are loaded into special software to perform what’s known as photogrammetry. By compiling all of the images together, the software is able to generate a fairly accurate 3D image. It might not have the resolution to make a 1:1 copy of a broken part, but it can help shave some modeling time when working with complex objects.

We’ve previously covered the use of photogrammetry to design 3D printed accessories, as well as a slightly different take on an automated turntable a few years ago. The process is still not too common, but the barriers to giving it a try on your own are at least getting lower.

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Custom Split-Flap Display Is a Unique Way to Show the Weather

There’s little doubt about the charms of a split-flap display. Watching a display build up a clear, legible message by flipping cards can be mesmerizing, whether on a retro clock radio from the 70s or as part of a big arrival and departure display at an airport or train station. But a weather station with a split-flap display? That’s something you don’t see often.

We usually see projects using split-flap units harvested from some kind of commercial display, but [gabbapeople] decided to go custom and build these displays from the ground up. The frame and mechanicals for each display are made from laser-cut acrylic, as are the flip-card halves. Each cell can display a full alphanumeric character set on 36 cards, with each display driven by its own stepper. An Arduino fetches current conditions from a weather API and translates the description of the weather into a four-character code. The codes shown in the video below seem a little cryptic, but the abbreviation list posted with the project makes things a bit clearer. Bonus points if you can figure out what “HMOO” is without looking at the list.

We like the look and feel of this, but we wonder if split-flap icons might be a neat way to display weather too. It seems like it would be easy enough to do with [gabbapeople]’s detailed instructions. Or you could always look at one of the many other custom split-flap displays we’ve featured for more inspiration.

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Semi-automated Winder Spins Rotors for Motors

What’s your secret evil plan? Are you looking for world domination by building a machine that can truly replicate itself? Or are you just tired of winding motor rotors and other coils by hand? Either way, this automated coil winder is something you’re probably going to need.

We jest in part, but it’s true that closing the loop on self-replicating machines means being able to make things like motors. And for either brushed or brushless motors, that means turning spools of wire into coils of some sort. [Mr Innovative]’s winder uses a 3D-printed tube to spin magnet wire around a rotor core. A stepper motor turns the spinner arm a specified number of times, pausing at the end so the operator can move the wire to make room for the next loop. The rotor then spins to the next position on its own stepper motor, and the winding continues. That manual step needs attention to make this a fully automated system, and we think the tension of the wire needs to be addressed so the windings are a bit tighter. But it’s still a nice start, and it gives us some ideas for related coil-winding projects.

Of course, not every motor needs wound coils. After all, brushless PCB motors with etched coils are a thing.

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Light Painting Animations Directly From Blender

Light painting: there’s something that never gets old about waving lights around in a long exposure photo. Whilst most light paintings are single shots, some artists painstakingly create frame-by-frame animations. This is pretty hard to do when moving a light around by hand: it’s mostly guesswork, as it’s difficult to see the results of your efforts until after the photo has been taken. But what if you could make the patterns really precise? What if you could model them in 3D?

[Josh Sheldon] has done just that, by creating a process which allows animations formed in Blender to be traced out in 3D as light paintings. An animation is created in Blender then each frame is automatically exported and traced out by an RGB LED on a 3D gantry. This project is the culmination of a lot of software, electronic and mechanical work, all coming together under tight tolerances, and [Josh]’s skill really shines.

The first step was to export the animations out of Blender. Thanks to its open source nature, Python Blender add-ons were written to create light paths and convert them into an efficient sequence that could be executed by the hardware. To accommodate smooth sliding camera movements during the animation, a motion controller add-on was also written.

The gantry which carried the main LED was hand-made. We’d have been tempted to buy a 3D printer and hack it for this purpose, but [Josh] did a fantastic job on the mechanical build, gaining a solidly constructed gantry with a large range. The driver electronics were also slickly executed, with custom rack-mount units created to integrate with the DragonFrame controller used for the animation.

The video ends on a call to action: due to moving out, [Josh] was unable to continue the project but has done much of the necessary legwork. We’d love to see this project continued, and it has been documented for anyone who wishes to do so. If you want to check out more of [Josh]’s work, we’ve previously written about that time he made an automatic hole puncher for music box spools.

Thanks for the tip, [Nick].

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Hackaday Links: July 29, 2018

Another holy scroll for the Church of Robotron. PoC || GTFO is a semi-annual journal of hardware exploitation, and something you must read. About a year ago, No Starch Press released the first Bible of PoC || GTFO, and now it’s time for a new testament. PoC || GTFO Volume 2 is out now, covering Elegies of the Second Crypt War to Stones from the Ivory Tower, Only as Ballast. It’s still Bible-shaped, with a leatherette cover and gilt edges.

KiCad version 5 is out, and you know what that means: It’s time to start on version 6. To that end, CERN has opened up the floodgates where youyes, you can donate to KiCad development. The team is looking for 600 hours of development and 30,000 Swiss Francs or about that many US Dollars. As of this writing (last Wednesday), more than 200 people have donated, at an average donation per person of about 80 CHF.

Oh good, this is finally over. Qualcomm will not be buying NXP. Previously, Reuters reported Qualcomm would purchase the other semiconductor manufacturer for $38 Billion, the largest semiconductor deal ever. There were earlier rumors of an acquisition. The deal was struck down by Chinese regulators, and speculation rages that this is a reaction to the US/China trade war. Qualcomm now has to pay NXP $2 Billion in fees, which they could use to dig out some of the unobtanium Motorola datasheets locked away in a file cabinet.

The uStepper (or μStepper, whatever) is a neat little add-on to standard NEMA stepper motors. It bolts to the back and gives you the ability to control a stepper over a standard serial bus, with a built-in encoder. Now there’s a new Kickstarter for an improved version that uses the Trinamic TMC2208 ‘silent’ motor driver. That Kickstarter is just a draft now, but if you’re planning a 3D printer build, this could be what you’re waiting for.

An MRI-Safe 3D Printed Pneumatic Stepper Motor

You will no doubt have seen those videos where MRI machines suck up all sorts of metallic objects with hilariously disastrous results. The magnetic field in one of these machines can easily pull in metal objects from across the room, exerting a force of several hundred pounds on any ferrous object unlucky enough to wander too close. As you can probably imagine, designing mechanical devices that can operate in such an intense magnetic field is exceptionally difficult.

But this fully 3D printed pneumatic stepper motor designed by [Foad Sojoodi Farimani] might one day change that. The PneuAct, which he presented at the recent International Conference on Robotics and Automation (ICRA) in Brisbane, Australia, manages to run at up to 850 RPM with full position control using bursts of air rather than electronic pulses. Made entirely of plastic and without any electronic components, the PneuAct can not only operate in intense magnetic fields but also areas with flammable gases where sparks could potentially cause an explosion.

We often say that a design is “fully” 3D printable, even though it might require screws or other bits of hardware. But in the case of the PneuAct, it’s truly all printed. It has to be, or else the whole thing would be ripped apart when it got to close to the MRI machine. Each and every piece of the motor is printed in ABS, and can be used without any additional machining or cleanup. No lubrication is required, and [Foad] mentions that the whole thing is so cheap that it can be disposable. Which is a huge advantage in medical environments where contamination could be a concern.

Design-wise the PneuAct is essentially an expanded version of the 3D printed air motors we’ve seen previously, but it would be fair to say that none has ever been studied so closely before.

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