Robotic Ball Bouncer Uses Machine Vision To Stay On Target

March 5, 2020 by Dan Maloney 20 Comments

When we first caught a glimpse of this ball juggling platform, we were instantly hooked by its appearance. With its machined metal linkages and clear polycarbonate platform, its got an irresistibly industrial look. But as fetching as it may appear, it’s even cooler in action.

You may recognize the name [T-Kuhn] as well as sense the roots of the “Octo-Bouncer” from his previous juggling robot. That earlier version was especially impressive because it used microphones to listen to the pings and pongs of the ball bouncing off the platform and determine its location. This version went the optical feedback route, using a camera mounted under the platform to track the ball using OpenCV on a Windows machine. The platform linkages are made from 150 pieces of CNC’d aluminum, with each arm powered by a NEMA 17 stepper with a planetary gearbox. Motion control is via a Teensy, chosen for its blazing-fast clock speed which makes for smoother acceleration and deceleration profiles. Watch it in action from multiple angles in the video below.

Hats off to [T-Kuhn] for an excellent build and a mesmerizing device to watch. Both his jugglers do an excellent job of keeping the ball under control; his robotic ball-flinger is designed to throw the ball to the same spot every time.

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Single Bolt Transformed Into A Work Of Art

March 1, 2020 by Dan Maloney 24 Comments

Every once in a while, this job helps you to discover something new and completely fascinating that has little to do with hacking but is worth sharing nonetheless. Turning a single brass bolt into a beautiful Cupid’s bow is certainly one of those times.

Watching [Pablo Cimadevila] work in the video below is a real treat, on par with a Clickspring build for craftsmanship and production values. His goal is to use a largish brass bolt as the sole source of material for a charming little objet d’art, which he achieves mainly with the use of simple hand tools. The stave of the bow is cut from the flattened shank of the bolt with a jeweler’s saw, with the bolt head left as a display stand. The offcuts are melted down and drawn out into wire for both the bowstring and the shaft of the arrow, a process that’s fascinating in its own right. The heart-shaped arrowhead and the faces of the bolt head are bedazzled with rubies; the technique [Pablo] uses to create settings for the stones is worth the price of admission alone. The complete video below is well worth a watch, but if you don’t have the twelve minutes to spare, a condensed GIF is available.

[Pablo]’s artistry reminds us a bit of this not-quite-one-bolt combination lock. We love the constraint of sourcing all a project’s materials from a single object, and we really appreciate the craftsmanship that goes into builds like these.

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Gravity-Defying Water Droplet Fountain Gets An Upgrade

February 25, 2020 by Rich Hawkes 2 Comments

When we last saw [isaac879]’s levitating RGB time fountain, it was made of wood which meant that it would absorb water and didn’t really show off the effect very well. His new version solves this problem with an acrylic case, new PCB and an updated circuit.

Like the original, this project drops water past strobing RGB LEDs creating an illusion of levitating, undulating colored water droplets. The pump at the top creates the droplets, but the timing has a tendency to drift over time. He thus implemented a PID controller to manage the pump’s drip rate, which was done by having the droplets pass by an infrared diode connected to an ATTiny85. The ’85 used the diode and PWM to control the pump motor speed and communicated to the Arduino over I2C.

The video shown below shows the whole process of designing and building the new time fountain. Everything from circuit and PCB design to 3D printing to assembly is shown along with narration describing what’s going on in case you want to build one yourself. If you do, all the files and components required are listed in the info section of the video.

There’s more that [isaac879] wants to do to improve the time fountain, but V2 looks great. It’s sleeker and smaller than the original and solves some of the design issues of the first. For more inspiration, check out some of the other levitating water fountain projects that have been posted over the years.

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LoRa Tutorials For The DIY Masses

February 25, 2020 by Inderpreet Singh 21 Comments

LoRa is the go-to tech for low power, long range wireless sensor networks. Designing with off-the-shelf modules can be a boon or a bane depending on the documentation and support. Luckily, [Renzo] has prepared a set of tutorials to get you started.

In his seven part series of write-ups, [Renzo] starts by connecting the E32 module from AliExpress to an Arduino as well as an ESP8266 to demonstrate essential communications. Then he discusses the configuration options and the library he created to make like a bit easier. Following that is a series of posts discussing transmission types as well as power saving methods including sleep modes and wake-on-radio.

The information will be extremely handy for someone starting off with the SX1276/SX1278 Wireless Modules which are relatively inexpensive as opposed to more standardized development kits. We love the abundance of fritzing diagrams, arduino code and helper library and hope someone will build on it. You can get the library from Github for your tinkering pleasure.

If you are looking for ideas for this newly discovered skill, have a look at LoRa Enabled Mailbox as well as Electric Fence Monitoring with The Things Network for a bit of IoT action.

Origami Butterfly: A Flex PCB Adventure Unfolds

February 24, 2020 by Kristina Panos 3 Comments

Flexible circuits have been around longer than you might expect, although they only recently rounded the bend and bounced into the hobbyist’s toolbox. When Boldport fanatic [Laura Lindzey] found out about them, her immediate dream project was to make an origami butterfly that does something cool, though she wasn’t sure what.

The idea she landed on is this: when the butterfly alights on a power-providing flower, it draws electrical nectar through its diode legs and lights up the LEDs on its wings. As long as one leg touches a ground petal and another touches a VIN petal, there will be light.

Though the idea may be simple, it’s the execution that’s mind-bending. After meticulous planning and a lot of paper prototyping, she sent off the gerbers and got version one back. The circuit worked, but assembly was tedious — not what you want when you’re trying to stay friendly with the other people in your PCB exchange club.

We imagine that hard creases are probably not what the flexible PCB purveyors have in mind, but this origami butterfly is an awesome exercise in what can be done with flexible PCBs. Not only that, it’s a great insight into some design rules where almost none exist, learned through firsthand experience. Every technology can benefit from trailblazers like [Laura].

If you want to do some flexible prototyping at home, just print your own pliable PCBs.

This Mallet Has Backwards Dovetails… That’s Impossible!

February 22, 2020 by Mike Szczys 14 Comments

Dovetails are a wedge-shaped joint found in woodworking. The wedge makes for strong joinery because a force that tries to pull it apart also increases the friction on the joint. This mallet has dovetails on either side that keep the head from flying off, but there’s also a through tenon in the center. This is an impossible joint as there’s no way to slide the mallet head onto the handle. The two pieces of wood must have grown that way!

As with everything, there’s a trick here, let it scratch your brain for a while before reading on… if you can guess how it’s done it’ll be very satisfying when you confirm your theory. Both the trick of the impossible mallet and the superb hand joinery are shown off in this video from the [Third Coast Craftsman].

The trick comes in the form of internal voids hidden from view once the two pieces of the mallet have been assembled. The through tenon is exactly as you’d expect: a straight tenon slides into a straight mortise in the mallet. The dovetails to either side of the handle and the pockets they mate with in the mallet head are not at all what you’d expect. The edges of the dovetail have been chamfered at 45 degrees so you can’t pull them to the outside of the mallet as you slide them into place. The opposite is the actual trick. Each of the dovetails bends inward until a ramp at the very end of the mallet pocket pushes it back into place.

Underside of mallet head shows “ramp” detail

Tenons clamped during assembly

The impossible mallet isn’t a new concept and stands as a formidable challenge for any accomplished woodworker. The images above are of [Jim Guilford’s] impossible mallet. Here the trick is fully exposed, showing the dovetail tenons of the handle clamped together as it is driven into place. Two things are striking here; the joints cannot be tested and must be perfect before assembly, and there is a real chance the tenons will break or the mallet head will split apart from the force of assembly. This project will test your courage as much as it will your patience.

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Wearable Cone Of Silence Protects You From Prying Ears

February 17, 2020 by Dan Maloney 36 Comments

Careful, the walls have ears. Or more specifically, the smart speaker on the table has ears, as does the phone in your pocket, the fitness band on your wrist, possibly the TV, the fridge, the toaster, and maybe even the toilet. Oh, and your car is listening to you too. Probably.

How does one fight this profusion of listening devices? Perhaps this wearable smart device audio jammer will do the trick. The idea is that the MEMS microphones that surround us are all vulnerable to jamming by ultrasonic waves, due to the fact that they have a non-linear response to ultrasonic signals. The upshot of that is when a MEMS hears ultrasound, it creates a broadband signal in the audible part of the spectrum. That creates a staticky noise that effectively drowns out any other sounds the microphone might be picking up.

By why a wearable? Granted, [Yuxin Chin] and colleagues from the University of Chicago have perhaps stretched the definition of that term a tad with their prototype, but it turns out that moving the jammer around does a better job of blocking sounds than a static jammer does. The bracelet jammer is studded with ultrasonic transducers that emit overlapping fields and result in zones of constructive and destructive interference; the wearer’s movements vary the location of the dead spots that result, improving jamming efficacy. Their paper (PDF link) goes into deeper detail, and a GitHub repository has everything you need to roll your own.

We saw something a bit like this before, but that build used white noise for masking, and was affixed to the smart speaker. We’re intrigued by a wearable, especially since they’ve shown it to be effective under clothing. And the effect of ultrasound on MEMS microphones is really interesting.

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