Automatic Flag Waver Lets You Show Your Loyalty Without Getting Tired

October 16, 2022 by Robin Kearey 31 Comments

A flag is a great tool to show your loyalty to a country, a sports team or even a philosophical movement. But there’s not so much you can actually do with a flag: you can either hang it somewhere, or wave it around to attact others to your cause. [Mellow] found that waving quickly becomes tiresome, and decided to design a machine that automates this task for him.

Now there’s a bit more involved in designing a proper flag-waver than simply moving the flag back and forth. Ideally, the fabric should flow smoothly from side to side and show both sides equally, in the same way a human would do when waving a big flag around. After a bit of research [Mellow] decided on a design that generates a rather complex motion using just a single servo: the mast is tilted from left to right, while gravity ensures the flag rotates around its axis. It’s probably best demonstrated visually, as [Mellow] does in the video embedded below.

The flag-waving mechanism is designed in Fusion 360 and 3D printed using white filament. Inside a little square box is a Wemos D1 Mini, powered by a lithium battery scavenged from a vape pen, as well as a battery management system and a power switch. The servo sits on top of the box and holds the flag in a little socket that allows the mast to rotate freely. [Mellow] also went one step further and built a two-flag waver, which still uses only one servo but creates two opposite motions through a set of spur gears. Both waver types bring a lively atmosphere to their surroundings, and we can actually imagine them being useful in places like sports bars.

Automatic flag-wavers are still rare devices, and as far as we can tell this is only the second one we’ve seen, after this hat-mounted example. That is, if you don’t count the automatic “flag” on this mailbox.

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Sneeze Into Your Hand, Not Your Elbow With This Nose-Shaped Sanitizer Dispenser

July 9, 2022 by Dan Maloney 7 Comments

You’ve got to love a language like German, where not only is it possible for a word or two to stand in for a complex concept, but you don’t even need to speak the language to make a good guess at what it all means. Of course when your project is a giant nose that mock-sneezes sanitizer into your hands, it doesn’t really matter that you call it Der niesende Desinfektionsmittelspender. Humor based on bodily functions is, after all, the universal language.

Working knowledge of German or not, figuring out exactly what [Nina] is doing here isn’t too difficult. Judging by the video below and the build log, the idea is to detect the presence of a hand underneath the dispenser with a simple IR reflective sensor hooked to some kind of microcontroller — an ESP32 in this case. Audio clips of sneezes are stored on an SD card and played back through a small speaker, while a hobby servo pushes the button on an atomizer. It seems as if selecting the proper dispenser was the hardest thing about the project; [Nina] finally settled on a battery-operated mister that was just the right size to fit into the nose. Oh, didn’t we mention the giant, pink, 3D-printed nose that houses the whole thing? Sorry about that — it’s quite subtle and easy to miss.

Anyway, the whole project is a lot of fun and brought a genuine laugh when we saw it. It’s a clever way to poke gentle fun at the germaphobes who came up with other, less whimsical methods of dispensing hand sanitizer. But let’s face it, they ended up being proven pretty much on the mark about things.

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DIY Automated Printer Kerchunks Out Classic Embossed Labels

June 15, 2022 by Dan Maloney 28 Comments

For our money, the best label for pretty much any purpose is one of those embossed Dymo-style stick-on labels, the kind with the raised white letters. There’s just something about them — the raised letters just beg to be touched, their legibility is outstanding, they lend an unmatched retro feel to a project, and the experience of creating one with one of those manual kerchunkers is oddly satisfying.

But alas, those manual label makers aren’t what they used to be, as [Andrei Speridião] discovered when his fell apart in his hands. Rather than complain, he automated his label maker and turned it into a computer peripheral. Dubbed “E-TKT”, the DIY label printer takes the daisy-wheel embossing die from his defunct labeler and puts it under computer control. Rather than the ratchet mechanism of the original, a stepper motor advances the tape, another stepper rotates the wheel to the correct position, and a servo does the kerchunking duty. The process repeats until the label is complete and neatly cut off, ready to apply. An ESP32 runs the mechanism and serves up a web application to compose labels and control the printer. There’s also an OLED display and, of course, an embossed label. Video demo below.

We don’t care what [Bart Simpson] thinks, embossed labels are cool, and this makes them even cooler. And as [Andrei] points out, this is also a neat way around the nasty DRM trick that some companies are foisting on the label-making public. That alone is reason to cheer this project on — but we won’t complain about the beautiful photography and excellent documentation, either.

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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 47 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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