GymCam Knows Exactly What You’ve Been Doing In The Gym

Getting exact statistics on one’s physical activities at the gym, is not an easy feat. While most people these days are familiar with or even regularly use one of those motion-based trackers on their wrist, there’s a big question as to their accuracy. After all, it’s all based on the motions of just one’s wrist, which as we know leads to amusing results in the tracker app when one does things like waving or clapping one’s hands, and cannot track leg exercises at the gym.

To get around the issue of limited sensor data, researchers at Carnegie Mellon University (Pittsburgh, USA) developed a system based around a camera and machine vision algorithms. While other camera solutions that attempt this suffer from occlusion while trying to track individual people as accurately as possible, this new system instead doesn’t try to track people’s joints, but merely motion at specific exercise machines by looking for repetitive motion in the scene.

The basic concept is that repetitive motion usually indicates forms of exercise, and that no two people at the same type of machine will ever be fully in sync with their motions, so that merely a handful of pixels suffice to track motion at that machine by a single person. This also negates many privacy issues, as the resolution doesn’t have to be high enough to see faces or track joints with any degree of accuracy.

In experiments at the university’s gym, the accuracy of their system over 5 days and 42 hours of video. Detecting exercise activities in the scene was with a 99.6% accuracy, disambiguating between simultaneous activities was 84.6% accurate, while recognizing exercise types was 93.6% accurate. Ultimately repetition counts for specific exercises were within 1.7 counts.

Maybe an extended version of this would be a flying drone capturing one’s outside activities, giving one finally that 100% accurate exercise account while jogging?

Thanks to [Qes] for sending this one in!

Scratch Built Media Player Channels 1980s Design

No, you aren’t looking at a 30 year old Teac graphic equalizer that somebody modified. The MWA-002 Network Music Player created by [GuzziGuy] is built entirely from new components, and easily ranks up there with some of the most gorgeous pieces of homebrew audio gear we’ve ever seen. Combining modular hardware with modern manufacturing techniques, this 1980s inspired build is a testament to how far we’ve come in terms of what’s possible for the dedicated hacker and maker.

The enclosure, though it looks all the world like a repurposed piece of vintage hardware, was built with the help of a CNC router. It’s constructed from pieces of solid oak, plywood, and veneered MDF that have all been meticulously routed out and cut. Even the front panel text was engraved with the CNC and then filled in with black paint to make the letters pop.

Internally, the MWA-002 is powered by a Raspberry Pi 3 running Mopidy to play both local tracks and streaming audio. Not satisfied with the Pi’s built-in capabilities, [GuzziGuy] is using a Behringer UCA202 to produce CD-quality audio, which is then fed into a TPA3116 amplifier. In turn, the output from the amplifier is terminated in a set of female jacks on the player. Just like the stereo equipment of yore, this player is designed to be connected to a larger audio system and doesn’t have any internal speakers.

The primary display is a 256×64 Futaba GP1212A02A FVD which has that era-appropriate glow while still delivering modern features. [GuzziGuy] says it was more difficult to interface with this I2C display than the LCDs he used in the past due to the lack of available libraries, but we think the final product is proof it was worth the effort. He bought both the VFD spectrum analyzer and LED VU meter as turn-key modules, but the center equalizer controls are completely custom; with dual MCP3008 ADCs to read the state of the sliders and the Linux Audio Developer’s Simple Plugin API (LADSPA) to tweak the Pi’s audio output accordingly.

We’re no strangers to beautiful pieces of audio gear here at Hackaday, but generally speaking, most projects involve modernizing or augmenting an existing device. While those projects are to be admired, the engineering that goes into creating something of this caliber from modular components and raw building materials is really an accomplishment on a whole different level.

Atomic Pi Gets A 3D-Printed Mac Makeover

The Atomic Pi is a pretty impressive piece of kit for the price, but it’s not exactly a turn-key kind of product. Even to a greater extent than what you might normally expect with a “dev” board like this, the user is responsible for putting together the rest of the pieces required to actually utilize it. But with this design by [Renri Nakano], you can turn the Atomic Pi into something that’s dangerously close to being a practical computer, and a trendy one at that.

Inspired by the 2019 Apple Mac Pro “Cheese Grater”, this 3D printable enclosure for the Atomic Pi is equal parts form and function. It integrates the necessary power supply to get things up and running without the need for the official breakout board or power module, which is good, since at the time of this writing they don’t seem to be available anyway. Plus it has a cool looking power button, so that’s got to count for something.

There’s also an integrated USB hub to give the Atomic Pi a bit more expandability, and a short HDMI extension cable that puts a video port on the back of the case. [Renri] even thought to leave an opening so you could run the wires for your wireless antennas.

At this point, we’ve seen several projects that mimic the unique case design of the 2019 Mac Pro. The level commitment ranges from recreating the design in CAD and milling it out of aluminum to just sticking a Raspberry Pi inside of a literal cheese grater from the kitchen. Naturally we enjoy a well executed Internet meme as much as the next hacker, but all the same, we were glad to see [Renri] put in the effort to make sure this case was more than just a pretty face.

[Thanks to baldpower for the tip.]

Walking Arm Trebuchet Is Different, But Effective

For many of us, our first encounter with the famous trebuchet was Age of Empires II, or perhaps a documentary on historical siege engines. However, many people continue to pursue builds of their very own, exploring designs new and old. The walking arm trebuchet is a good example, which uses an unconventional design to great effect.

The design eschews a rigid frame, instead consisting of simply an arm and a triangular leg assembly. The arm is held upside down, and is launched by allowing the trebuchet to collapse forward to rest on the triangular leg. The triangular leg is fitted with spikes which dig into the ground, and the arm then pivots around, launching the projectile. The design is reportedly quite efficient, similar to a floating arm trebuchet, with a very simple design. Performance was so good, it netted a clean sweep of the 2018 Vermont Pumpkin Chuckin’ festival.

There’s a wide variety of ways to go about building a trebuchet, and we’ve featured some before. You can even instrument your payloads to quantify performance. Video after the break.

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Even Joke Torpedoes Are Pretty Hard To Get Right

It’s rare that makers get involved in out-and-out munition production. It’s dangerous, and usually frowned upon by local authorities. That said, it can be fun to experiment around, and [Ivan] does just that, attempting to launch a 3D-printed torpedo from a kayak. The build may have been done as a marketing exercise, but it raises some interesting questions about naval engineering.

The first revision consists of a 3D-printed hull, containing a rubber-band powered propeller. A soda bottle filled with compressed air is then used as a warhead, fitted with a contact fuse to release its charge on impact. Unfortunately, initial tests were underwhelming, with the rubber band mechanism failing to provide any real forward propulsion.

A trip back to the drawing board was due, and the design was revived with a brushless motor powerplant instead. This allowed the torpedo to trawl, albeit slowly, through the water. It also proved that the compressed air “warhead” could successfully discharge, albeit with less of a bang, more of a whimper.

The build, while undertaken for the sake of fun, does highlight some of the engineering challenges inherent in building a working torpedo. There were issues with buoyancy, as well as providing the torpedo with enough power to move quickly in the water. On top of this, the matter of guidance is also an important one. We’d love to know how the Hackaday commentariat would go about solving these issues when undertaking their own build – let us know down below. We’ve seen others tackle similar builds before, too. Video after the break.

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Subaru Coils Make A Great HV Power Source

High-voltage experimenters are a unique breed. They’re particularly adept at scrounging for parts in all kinds of places, and identifying how to put all manner of components to use in the service of the almighty arc. [Jay] is one such inventor, and recently came across a useful device from Subaru.

The device in question is an ignition coil from the Subaru Outback. It consists of a pair of high-voltage transformers, connected together, in a wasted-spark setup to run four-cylinder engines. Having sourced the part from a friend, [Jay] realised that with some modification, it would make a great high-voltage power source. The first job was to figure out how to remove the internal electronics that drive the transformers. In this case, it was a simple job of hacking off a chunk of the case, removing the interfering hardware. With this done, it’s possible to directly access the transformer connections.

In [Jay]’s experiments, the device is run in an anti-parallel configuration, to produce higher than normal voltages at the output. In various tests, it’s demonstrated running from both a classic 555 circuit, as well as a ZVS driver. For future projects, [Jay] intends to use this setup to drive a large voltage multiplier, also noting it can be used with Tesla coils and plasma balls with the right additional hardware.

While [Jay] doesn’t include any specific model numbers, reports are that these coils are readily available in a variety of 1990s and 2000s Subaru vehicles. Others have used similar hardware to create high voltage projects, too – this stun gun is a great example. Video after the break.

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AI Makes Hyperbolic Brain Hats A Reality

It isn’t often that the world of Hackaday intersects with the world of crafting, which is perhaps a shame because many of the skills and techniques of the two have significant overlap. Crochet for instance has rarely featured here, but that is about to change with [Janelle Shane]’s HAT3000 neural network trained to produce crochet hat patterns.

Taking the GPT-2 neural network trained on Internet text  and further training it with a stack of crochet hat patterns, she was able to generate AI-designed hats which her friends on the Ravelry yarn forum set to crochet into real hats. It’s a follow-up to a previous knitting-based project, and instead of producing the hats you might expect it goes into flights of fancy. Some are visibly hat-like while others turn into avant-garde creations that defy any attempt to match them to real heads. A whole genre of hyperbolic progressions of crochet rows produce hats with organic folds that begin to resemble brains, and tax both the stamina of the person doing the crochet and their supply of yarn.

Perhaps most amusingly the neural network retains the ability to produce text, but when it does so it now inevitably steers the subject back to crochet hats. A Harry Potter sentence spawns a passage of something she aptly describes as “terrible crochet-themed erotica“, and such is the influence of the crochet patterns that this purple prose can even include enough crochet instructions to make them crochetable. It would be fascinating to see whether a similar model trained with G-code from Thingiverse would produce printable designs, what would an AI make with Benchy for example?

We’ve been entertained by [Janelle]’s AI work before, both naming tomato varieties, and creating pie recipes.

Thanks [Laura] for the tip.