The circuit, assembled on a purple PCB, with a large capacitor and a sizeable white resistor, wires soldered to holes in the PCB

Protect Your Drivers When The Motor Stalls

June 13, 2022 by Arya Voronova 46 Comments

[Mark Rehorst] tells us about a tragic incident involving an untimely demise of $200 worth of motor driving hardware, and shares a simple circuit so that we can prevent such tragedies in the future. His Arrakis sand table project has quite a few motors involved, and having forgotten to add limits into the software, he slammed a motor-driven mechanism into a well-fixed part of the table. The back EMF of the motor created a burst of energy, taking out the motor driver, the controller board, and the power supply.

With the postmortem done, he had to prevent this from happening again – preferably, in hardware. Based on a small appnote from Gecko Drives, he designed a simple PCB that shunts the motor with a high-power resistor, as soon as the current starts flowing into a direction it’s not supposed to flow into. He goes in depth about the way that the circuit works and the reasoning behind parts selection, as well as shows an LTSpice simulation and shares the PCB files. This was his first time designing PCBs in KiCad, and we believe he’s done a great job! This worklog is certainly worth reading if you’d like to understand how such circuits work and what goes into building one.

He dubs this a “bank account protection” circuit, and we can absolutely relate. It’s not just CNC tables that need such protections of course – we’ve seen a solution for small hacky makeshift electric vehicles, for instance. A motor’s generative properties aren’t always a problem, however – here’s just one example of a hacker trying to put them to good use.

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Pikul Servo Powered Falling Dominoes Pushing a Cube

Domino Row Goes With The Flow

May 30, 2022 by Michael Shaub 1 Comment

Around here, we’re always excited about a new actuator design. Linear actuators are particularly hard to make cheap, fast, and good, so it’s even better when something new that we can build ourselves slides onto the scene.

Researchers at U Penn’s Pikul Research Group took inspiration from the cascade of falling dominoes for an innovative take on linear motion. This article on IEEE Spectrum describes the similarity of the sequential tipping-over with the peristaltic motion of biological systems, including you, swallowing right now.

The motion propagation in falling dominoes, called a Soliton Wave, can be harnessed to push an object at the front of the wave, just like a surfer. See the videos after the break for examples of simple setups that any of us could recreate with laser-cut or 3D printed parts. Maybe you won’t be using them to help a robot swallow (a terrifying idea that the article suggests), but you might need a conveyor or a novel way to help a device crawl like a shrimp. The paper is behind a paywall on IEEE, though you readers likely see enough in the videos to get started, and we can’t wait to see where your dominoes will lead us next.

OpenCV Brings Pinch To Zoom Into The Real World

March 24, 2022 by Bryan Cockfield 11 Comments

Gesture controls arrived in the public consciousness a little over a decade ago as touchpads and touchscreens became more popular. The main limitation to gesture controls, a least as far as [Norbert] is concerned, is that they can only control objects in a virtual space. He was hoping to use gestures to control a real-world object instead, and created this device which uses gestures to control an actual picture.

In this unique augmented reality device, not only is the object being controlled in the real world but the gestures are being monitored there as well, thanks to a computer vision system watching his hand which is running OpenCV. The position data is fed into an algorithm which controls a physical picture mounted on a slender robotic arm. Now, when [Norbert] “pinches to zoom”, the servo attached to the picture physically brings it closer to or further from his field of view. He can also use other gestures to move the picture around.

While this gesture-controlled machine is certainly a proof-of-concept, there are plenty of other uses for gesture controls of real-world objects. Any robotics platform could benefit from an interface like this, or even something slightly more mundane like an office PowerPoint presentation. Opportunity abounds, but if you need a primer for OpenCV take a look at this build which tracks a hand in minute detail.

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RC Snowmobile Makes Tracks On Ice

February 18, 2022 by Bryan Cockfield 7 Comments

With all the futuristic technology currently at our disposal, it seems a little bizarre that most passenger vehicles are essentially the same thing that they were a century ago. Four wheels, a motor, and some seats would appear to be a difficult formula to beat. But in the 3D printing world where rapid prototyping is the name of the game, some unique vehicle designs have been pushed out especially in the RC world. One of the latest comes to us from [RCLifeOn] in the form of a single-wheeled RC snowmobile.

While not a traditional snowmobile with tracks, this one does share some similarities. It has one drive wheel in the back printed with TPR for flexibility and it also includes studs all along its entire circumference to give it better traction on ice. There are runners in the front made from old ice skates which the vehicle uses for steering, and it’s all tied together with an RC controller and some lithium batteries to handle steering and driving the electric motor.

There were some design flaws in the first iteration of this vehicle, including a very large turning radius, a gearing setup with an unnecessarily high torque, and a frame that was too flexible for the chain drive. [RCLifeOn] was also testing this on a lake which looked like it was just about to revert to a liquid state which made for some interesting video segments of him retrieving the stuck vehicle with a tree branch and string. All in all, we are hopeful for a second revision in the future when some of these issues are hammered out and this one-of-a-kind vehicle can really rip across the frozen wastes not unlike this other interesting snowmobile from a decade ago.

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A Solari Mechanical Digital Clock Hack With A Little Extra

February 14, 2022 by Dave Rowntree 7 Comments

[Alfredo Cortellini] was perusing an antique shop in Bologna, and came across a nice example of a late 1950s timepiece, in the shape of a Solari Cifra 5 slave clock, but as the shop owner warned, it could never tell the time by itself. That sounded like a challenge, and the resulting hack is a nice, respectful tweak of the internals to bring it into the modern era. Since the clock requires a single pulse-per-minute in order to track time, the simplest track often followed is to open the back, set the correct time manually by poking the appropriate levers, and then let an external circuit take over clocking it. [Alfredo] wanted autonomy, and came up with a solution to make the thing fully adjust itself automatically.

Electronics-wise, initial prototyping was performed with a Nucleo 32 dev board and a pile of modules, before moving to a custom PCB designed in Altium Designer. An STM32G031 runs the show, with a few push buttons and a SSD1306 OLED display forming the UI.

Using some strategically-placed magnets and hall effect sensors, the status of the internal mechanism could be determined. Minute advancements were effected by driving the clock’s 24V electromagnet with a DRV8871 motor driver IC, the power supply for which was generated from the USB supply via a TPS61041 boost converter. In order to synchronise the mechanism with the electronics, the unit could have been driven to advance a minute at a time, but since every hour would need sixty pulses, this could take a while given the limited speed at which that could be done reliably. The solution was to sneak in a crafty MG996R high-torque servo motor, which pushes on the hour-advancement lever, allowing the unit to be zeroed much faster. Sensing of the zero-hour position was done by monitoring the date-advance mechanism, that is not used in this model of clock. Once zeroed, the clock could then be advanced to the correct time and kept current. Firmware source, utililising FreeRTOS can be found on the project GItHub, with schematics and Fusion360 files on the Hackaday.IO project linked above.

If you were thinking you’ve seen these Solari soft-flap displays here before, you’d be quite correct, but if you’re not so much interested in marking the passage of time, but bending such devices to your other indication whims, we’ve got you covered also.

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No LEDs Required For This Servo-Controlled Larson Scanner

February 13, 2022 by Dan Maloney 31 Comments

All things considered, it’s pretty easy to get one LED is a strip to light up sequentially, and have it bounce back and forth. Turning that simple animation into a real Larson scanner, with smooth transitions and controlled fade-out, is another thing entirely. And forgetting the LEDs altogether and making a servo-operated Larson scanner is — well, let’s just call it an interesting lesson in hardware abstraction.

The Larson scanner, named after famed TV producer Glen A. Larson for his penchant for incorporating it into shows like Battlestar Galactica and Knight Rider, is actually hard to execute in hardware thanks to the fading tail that follows the lead pixel as it dances back and forth across the display. [Eric Gunnerson] decided to make this and other animation effects easier to achieve with Fade, a custom framework for LED animations that runs on an ESP32.

LED animations are fine, but what about servos? Could Fade be modified to support them? This turned out to be a fairly easy mod thanks to Fade’s architecture and [Eric]’s existing support for non-addressable LEDs via PWM signals. And it was even possible to support more than the 16 PWM channels on an ESP32by adding a UDP connection that puts multiple ESP32s under the control of a central microcontroller.

The video below shows [Eric]’s demo of servo support, with an eight-channel electromechanical Larson scanner. Each “pixel” is a painted ping pong ball swinging back and forth on a hobby servo, and the whole thing sounds just about as awful as you’d expect it to. If you squint just right, the effect looks pretty convincing, but that’s hardly the point. The real story here is [Eric]’s thoughtful architecture, which made the mods easier than starting from scratch.

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Forget Sudoku, Build Yourself A Minimalist Rubik’s Solver Robot

February 2, 2022 by Dave Rowntree 12 Comments

Some people like crossword puzzles, some are serious sudoku ninjas, but [Andrea Favero] likes to keep himself sharp, by learning coding and solving control problems, and that is something we can definitely relate to. When learning a new platform, it’s a very good idea to have a substantial project or goal in mind, and learn what is needed on the way there. [Andrea] chose to build an autonomous Rubik’s cube solver, and was kind enough to document exactly how how to do it, and we’re glad of it!

The result of the openCV processing chain

Working in python with OpenCV, [Andrea] uses the methodology by [Oussama Barkouki] to process each face image and convert it into a table of the colours of individual facelets. The basics of that, are first to convert the image to grayscale, then use a gaussian blur to denoise the image. Edges are identified using the canny algorithm, the result of which is then dilated and passed into a contour detector. The contours are sent into a cunning filter that identifies square contours, and those the wrong size are filtered off. What you’re left with are the outlines of the actual coloured facelets. Once you have a list of squares, these can be used to form image masks, and thence select the average colour from each square. The colour is then quantised and stored as a labelled colour from the standard Western Rubik’s cube colour scheme. Finally, once all face images are captured and facelets colours identified, the data are passed into a Rubik’s cube solving algorithm developed by [Hegbert Kociemba,] a guide to which is available on the speedsolving site. The result of the solving step is a sequence of descrambling moves, in the move notation developed by [David Singmaster]. Fascinating stuff, if you ask us! Continue reading “Forget Sudoku, Build Yourself A Minimalist Rubik’s Solver Robot” →