Author: Donald Papp

1017 Articles

Sound And Water Make Weird Vibes In Microgravity

April 29, 2024 by 1 Comment

NASA astronaut [Don Pettit] shared a short video from an experiment he performed on the ISS back in 2012, demonstrating the effects of sound waves on water in space. Specifically, seeing what happens when a sphere of water surrounding an air bubble perched on a speaker cone is subjected to a variety of acoustic waves.

The result is visually striking patterns across different parts of the globe depending on what kind of sound waves were created. It’s a neat visual effect, and there’s more where that came from.

[Don] experimented with music as well as plain tones, and found that cello music had a particularly interesting effect on the setup. Little drops of water would break off from inside the sphere and start moving around the inside of the air bubble when cello music was played. You can see this in action as part of episode 160 from SmarterEveryDay (cued up to 7:51) which itself is about exploring the phenomenon of how water droplets can appear to act in an almost hydrophobic way.

This isn’t the first time water and sound collide in visually surprising ways. For example, check out the borderline optical illusion that comes from pouring water past a subwoofer emitting 24 Hz while the camera captures video at 24 frames per second.

Make 3D Scenes With A Holodeck-Like Voice Interface

April 29, 2024 by 4 Comments

The voice interface for the holodeck in Star Trek had users create objects by saying things like “create a table” and “now make it a metal table” and so forth, all with immediate feedback. This kind of interface may have been pure fantasy at the time of airing, but with the advent of AI and LLMs (large language models) this kind of natural language interface is coming together almost by itself.

A fun demonstration of that is [Dominic Pajak]’s demo project called VoxelAstra. This is a WebXR demo that works both in the Meta Quest 3 VR headset (just go to the demo page in the headset’s web browser) as well as on desktop.

The catch is that since the program uses OpenAI APIs on the back end, one must provide a working OpenAI API key. Otherwise, the demo won’t be able to do anything. Providing one’s API key to someone’s web page isn’t terribly good security practice, but there’s also the option of running the demo locally.

Either way, once the demo is up and running the user simply tells the system what to create. Just keep it simple. It’s a fun and educational demo more than anything and will try to do its work with primitive shapes like spheres, cubes, and cylinders. “Build a snowman” is suggested as a good starting point.

Intrigued by what you see and getting ideas of your own? WebXR can be a great way to give those ideas some life and looking at how someone else did something similar is a fine way to begin. Check out another of [Dominic]’s WebXR projects: a simulated BBC Micro, in VR.

Corral Some Zippy Blue Flames Into 3D Printed Troughs

April 28, 2024 by 18 Comments

[Steve Mould] came across an interesting little phenomenon of blue flames zipping around a circular track. This led to diving down a bit of a rabbit hole about excitable mediums, ultimately leading him to optimize the shapes and come up with some pretty wild variations which he shows off in a video (also embedded below.)

After figuring out that the moving flame depended on combustion of fuel vapor in an environment that didn’t allow for the whole surface to stay lit at once, [Steve] tried to optimize the design of 3d-printed channels and raceways to encourage this effect, and he came up with some pretty novel ones. The 3D models are here if you’d like to try them for yourself (we especially like the “figure eight” and “rays” models.)

The video is an excellent show & tell of everything [Steve] dove into, complete with plenty of demonstrations of harnessing this effect to create some nifty running flames. Check it out in the video below, and if unintuitive physical effects are your thing, don’t miss [Steve]’s peeling apart of the turntable paradox.

Continue reading “Corral Some Zippy Blue Flames Into 3D Printed Troughs” →

Train A GPT-2 LLM, Using Only Pure C Code

April 28, 2024 by 7 Comments

[Andrej Karpathy] recently released llm.c, a project that focuses on LLM training in pure C, once again showing that working with these tools isn’t necessarily reliant on sprawling development environments. GPT-2 may be older but is perfectly relevant, being the granddaddy of modern LLMs (large language models) with a clear heritage to more modern offerings.

LLMs are fantastically good at communicating despite not actually knowing what they are saying, and training them usually relies on PyTorch deep learning library, itself written in Python. llm.c takes a simpler approach by implementing the neural network training algorithm for GPT-2 directly. The result is highly focused and surprisingly short: about a thousand lines of C in a single file. It is a highly elegant process that does the same thing the bigger, clunkier methods accomplish. It can run entirely on a CPU, or it can take advantage of GPU acceleration, where available.

This isn’t the first time [Andrej Karpathy] has bent his considerable skills and understanding towards boiling down these sorts of concepts into bare-bones implementations. We previously covered a project of his that is the “hello world” of GPT, a tiny model that predicts the next bit in a given sequence and offers low-level insight into just how GPT (generative pre-trained transformer) models work.

Wine In Beverage Cans Had A Rotten Egg Problem, Until Now

April 27, 2024 by 70 Comments

Aluminum beverage cans are used for all kinds of drinks, but when it comes to wine there are some glitches. Chief among them is the fact that canned wine occasionally smelled like rotten eggs. Thankfully, researchers have figured out why that happens, and how to stop it. How was this determined? As the image above hints at, lots and lots of samples and testing.

What causes this, and why don’t other beverages have this problem? Testing revealed that the single most important factor was the presence of molecular sulfur dioxide (SO2), a compound commonly used in winemaking as an antioxidant and antimicrobial.

It turns out that the thin plastic lining on the inside of beverage cans doesn’t fully stop molecular SO2 from reacting with the surrounding aluminum, creating hydrogen sulfide (H2S) in the process. H2S has a very noticeable rotten egg smell, even in low concentrations.

Researchers discovered that if a canned beverage contained more than 0.5 ppm of molecular SO2, a noticeable increase in hydrogen sulfide was likely to be present within four to eight months. The problem is that since most wines aim for around 0.5 ppm of SO2, the average can on wine sitting on a shelf will have a problem sooner rather than later. The more SO2 in the wine (reds tend to contain less, whites more), the worse the problem.

Simply increasing the thickness of the plastic liner is an imperfect solution since it increases manufacturing costs as well as waste. So, researchers believe the right move is to use a more durable liner formulation combined with a lower SO2 concentration than winemakers are usually comfortable with. Unlike bottles, cans can be hermetically sealed which should offset the increased oxidation risk of using a lower concentration of SO2. The result should be wine as a canned beverage, with a shelf life of at least 8 months.

The research is published here and gives a great look at just how one approaches this kind of scientific problem, as well as highlighting just how interesting the humble aluminum beverage can really is.

Let The Solder Scroll Take Care Of Your Feed Needs

April 20, 2024 by 38 Comments

[Victor]’s nifty tool the Solder Scroll is a handheld device that lets one feed solder out simply by turning something a little like a scroll wheel. It looks like an intuitive and comfortable design that can adapt to a wide variety of solder thicknesses, and is entirely 3D printed.

One part we particularly like is the feed system. One rolls a wheel which feeds solder out using a mechanism a lot like extrusion gears in many 3D printer hot ends. Both wheels have ridged surfaces that grip and feed the solder; their gears mesh with one another so that moving one moves both in unison.

Solder feed tools like this have seen all kinds of interesting designs, because while the problem is the same for everyone, there are all kinds of different ways to go about addressing it. We love this one, and we have seen many other takes that range from a powered, glove-mounted unit to an extremely simple tool with no moving parts. We’ve even seen a method of hacking a mechanical pencil into a new role as a solder feeder.

DIY Quad-Motor Go-Kart Is A Thrilling Ride

April 18, 2024 by 29 Comments

[Peter Holderith] set out some time ago to build an electric go-kart. That by itself is not terribly unusual, but where his project diverts from the usual is in the fact that each of the four wheels has an integrated hub motor.

It might not look it, but each wheel has an integrated hub motor.

This kart project is a bit of a work in progress, with [Peter] previously building (then scrapping) a failed attempt at a cheap suspension system. But it’s completely operational with all four wheels able to deliver a monstrous amount of power despite being limited by the power supply (a battery pack salvaged from an Audi Q5 Hybrid).

The kart might not look it, but it weighs 177 pounds (80 kg) with the battery and motors accounting for nearly half of that. What is is like to drive? “Nothing short of thrilling,” says [Peter]. It’s got no suspension and is pretty bare bones, not to mention limited in power by the battery, but [Peter] finds it a satisfying drive that nevertheless delivers car-like cues in the driving experience. The build isn’t done, and [Peter] plans to see if more power is available by switching battery chemistries rather than add more battery weight.

Building and driving electric vehicles can be remarkably satisfying, and it’s an area in which hobbyists can meaningfully innovate. Self-balancing one-wheeled vehicles for example look like a ton of fun. Heck, researchers have discovered that even rats seem to enjoy driving just for the fun of it.