Building A Motion Capture Suit On The Cheap

Motion capture is a technology used in many films, particularly the animated variety. It makes giving characters realistic movements a cinch, as they’re all based on those of a real person. [Checkered Bug] worked with a middle school group who were looking to get started, so he whipped up a capable rig on a budget.

The rig is based around a chest unit that connects out to several satellite units placed at points on the body. Each unit contains a Bosch IMU which is used to measure the acceleration and rotation of the user’s various body parts. The data is fed back to an Arduino Mega, where it’s then passed to a PC running Blender. Motion sequences can be recorded live in Blender, or saved to an SD card and imported later. Files are available on Github for those keen to recreate the project.

It’s a tidy setup that does good motion capture on a low budget. Such a rig would have been inordinately expensive back in the day, but can now be whipped up for just a few hundred dollars. We’ve seen other motion capture systems before, too. Video after the break.

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Giant Bearing Is At The Heart Of A Camera Mount

We bet you have all some cool part in your bin that is just gnawing at you to build something cool. That doodad, possibly from a garage sale, surplus store, or clearance rack deserves a project fitting of its near-infinite potential. [isaac879] finally marries a giant ball bearing with his passion for photography in the form of a pan-tilt camera mount for his Canon DSLR. The problem with tossing your golden-ticket part into a project is that not everyone has a MacGuffin, or a brand new one might be bank-breakingly expensive, so he does us a favor and makes a drop-in replacement that you can print and fill with 6mm brass bbs. This sort of thing is why we love hackers.

The camera mount has the features we expect to see in a robust stepper mount, such as infinite spinning, time delay, and an Xbox controller interface. Inside the base is the industrial bearing or its plastic replica, and that wide base won’t be tipping over anytime soon. Gearing all around is of the herringbone style, of the type you find in classroom pencil sharpeners because they transfer power smoothly. Speaking of things going smoothly, we enjoyed his assembly montage where every part fits together perfectly and there is not a naughty word to be uttered. Just like real life.

If you like homemade bearings, check out this slew bearing that looks like it was made with Perler beads, and we have a self-aligning camera tripod mount for the photography buffs.

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Dyeing Fabric To Create Sensors

Fabrics with electrical functionality have been around for several years, but are very rarely used in mainstream clothing. The fabrics are very expensive and the supply can be unreliable. Frustrated by this, [Counter Chemists] developed PolySense, simple open-source technology to make any fibrous material into a conductive material that can be used to sense pressure, stretch, capacitive touch, humidity, or temperature.

PolySense uses a process called in-situ polymerization, effectively dying a fabric to become piezoelectric. This is done by first soaking the fabric in a mixture of water and the organic compound pyrrole, and then adding iron chloride to trigger a reaction. The polymerization process that takes place wraps the individual fibers of the fabric in conductive polymer chains.

Instead of just uniformly coating a fabric, various masking techniques can be used to dye patterns onto the fabric for various use cases. The video after the break shows a range of these applications, including using polymerized gloves and leggings for motion capture, a zipper that acts like a linear potentiometer, and touch-sensitive fabric. The project page lists sources for the required chemicals in both Europe and the US, and we look forward to seeing what other applications the community can come up with.

The project is very well documented, with a number of scientific papers covering all the details. [Counter Chemists] will also be presenting PolySense at the 2020 Virtual Maker Faire.

This technology can also be used to make a fabric piano with a lot less effort. On the more mechanical side of things, you can also 3D print on pre-stretched fabric to make it pop into 3D shapes.

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Hackaday Links: March 15, 2020

Just a few weeks ago in the Links article, we ran a story about Tanner Electronics, the Dallas-area surplus store that was a mainstay of the hacker and maker scene in the area. At the time, Tanner’s owners were actively looking for a new, downsized space to move into, and they were optimistic that they’d be able to find something. But it appears not to be, as we got word this week from James Tanner that the store would be shutting its doors after 40 years in business. We’re sad to see anyone who’s supported the hardware hacking scene be unable to make a go of it, especially after four decades of service. But as we pointed out in “The Death of Surplus”, the center of gravity of electronics manufacturing has shifted dramatically in that time, and that’s changed the surplus market forever. We wish the Tanner’s the best of luck, and ask those in the area to stop by and perhaps help them sell off some of their inventory before they close the doors on May 31.

Feel like getting your inner Gollum on video but don’t know where to begin? Open source motion capture might be the place to start, and Chordata will soon be here to help. We saw Chordata as an entry in the 2018 Hackaday Prize; they’ve come a long way since then and are just about to open up their Kickstarter. Check out the video for an overview of what Chordata can do.

Another big name in the open-source movement has been forced out of the organization he co-founded. Eric S. Raymond, author of The Cathedral and the Bazaar and co-founder and former president of the Open Source Initiative has been removed from mailing lists and banned from communicating with the group. Raymond, known simply as ESR, reports that this was in response to “being too rhetorically forceful” in his dissent from proposed changes to OSD, the core documents that OSI uses to determine if software is truly open source. Nobody seems to be saying much about the behavior that started the fracas.

COVID-19, the respiratory disease caused by the newly emerged SARS-CoV-2 virus, has been spreading across the globe, causing panic and claiming lives. It’s not without its second-order effects either, of course, as everything from global supply chains to conferences and meetings have been disrupted. And now, coronavirus can be blamed for delaying the ESA/Russian joint ExoMars mission. The mission is to include a Russian-built surface platform for meteorological and biochemical surveys, plus the ESA’s Rosalind Franklin rover. Program scientists are no longer able to travel and meet with their counterparts to sort out issues, severely crimping productivity and forcing the delay. Social distancing and working from home can only take you so far, especially when you’re trying to get to Mars. We wonder if NASA’s Perseverance will suffer a similar fate.

Speaking of social distancing, if you’ve already decided to lock the doors and hunker down to wait out COVID-19, you’ll need something to keep you from going stir crazy. One suggestion: learn a new skill, like PCB design. TeachMePCB is offering a free rigid PCB design course starting March 28. If you’re a newbie, or even if you’ve had some ad hoc design experience, this could be a great way to productively while away some time. And if that doesn’t work for you, check out Bartosz Ciechanowski’s Gears page. It’s an interactive lesson on why gears look like they do, and the math behind power transmission. Ever wonder why gear teeth have an involute shape? Bartosz will fix you up.

Stay safe out there, everyone. And wash those hands!

Hackaday Prize China Finalists Announced

In the time since the Hackaday Prize was first run it has nurtured an astonishing array of projects from around the world, and brought to the fore some truly exceptional winners that have demonstrated world-changing possibilities. This year it has been extended to a new frontier with the launch of the Hackaday Prize China (Chinese language, here’s a Google Translate link), allowing engineers, makers, and inventors from that country to join the fun. We’re pleased to announce the finalists, from which a winner will be announced in Shenzhen, China on November 23rd. If you’re in Shenzen area, you’re invited to attend the award ceremony!

All six of these final project entries have been translated into English to help share information about projects across the language barrier. On the left sidebar of each project page you can find a link back to the original Chinese language project entry. Each presents a fascinating look into what people in our global community can produce when they live at the source of the component supply chain. Among them are a healthy cross-section of projects which we’ll visit in no particular order. Let’s dig in and see what these are all about!

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Simple Sensor Provides Detailed Motion Capture For VR Hands

Consider the complexity of the appendages sitting at the end of your arms. The human hands contain over a quarter of the entire complement of bones in the body, use dozens of muscles both in the hand itself and extending up the forearm, and are capable of almost infinite variance in the movements they can create. They are exquisite machines.

And yet when it comes to virtual reality, most simulations treat the hands like inert blobs. That may be partly due to their complexity; doing motion capture from so many joints can be computationally challenging. But this pressure-sensitive hand motion capture rig aims to change that. The product of an undergraduate project by [Leslie], [Hunter], and [Matthew], the idea was to provide an economical and effective way to capture gestures for virtual reality simulators, which generally focus on capturing large motions from the whole body.

The sensor consists of a sandwich of polyurethane foam with strain gauge sensors embedded within. The user slips his or her hand into the foam and rests the fingers on the sensors. A Teensy and twenty lines of code translate finger motions within the sandwich into five axes of joystick movement, which is then sent to Unreal Engine, where finger motions were translated to a 3D-model of a hand to play a VR game of “Rock, Paper, Scissors.”

[Leslie] and her colleagues have a way to go on this; testers complained that the flat hand posture was unnatural, and that the foam heated things up quickly. Maybe something more along the lines of these gesture-capturing gloves would work?

One-Legged Jumping Robot Shows That Control Is Everything

Robots that can jump have been seen before, but a robot that jumps all the time is a little different. Salto-1P is a one-legged jumping robot at UC Berkeley, and back in 2017 it demonstrated the ability to hop continuously with enough control to keep itself balanced. Since then it has been taught some new tricks; having moved beyond basic stability it can now jump around and upon things with an impressive degree of control.

Key to doing this is the ability to plant its single foot exactly where it wants, which allows for more complex behaviors such as hopping onto and across different objects. [Justin Yim] shows this off in the video embedded below, which demonstrates the Salto-1P bouncing around in a remarkably controlled fashion, even on non-ideal things like canted surfaces. Two small propellers allow the robot to twist in midair, but all the motive force comes from the single leg.

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