A DIY Pulse Tube Cryocooler In The Quest For Home-Made Liquid Nitrogen

January 1, 2023 by Maya Posch 5 Comments

What if you have a need for liquid nitrogen, but you do not wish to simply order it from a local supplier? In that case you can build your very own pulse tube cryocooler, as [Hyperspace Pirate] is in the process of doing over at YouTube. You can catch part 1 using a linear motor and part 2 using a reciprocating piston-based version also after the break. Although still very much a work-in-progress, the second version of the cryocooler managed to reduce the temperature to a chilly -75°C.

The pulse tube cryocooler is one of many types of systems used for creating a cooling effect. Commercially available refrigerators and freezers tend to use Rankine cycle coolers due to their low cost and effectiveness at (relatively) warmer temperatures. For cryogenic temperatures, Stirling engines are commonly used, although they find some use in refrigeration as well. All three share common elements, but they differ in their efficiency over a larger temperature range.

In this video series, the viewer is taken through the physics behind these coolers and the bottlenecks which prevent them from simply cooling down to zero Kelvin. Despite the deceptive simplicity of pulse tube cryocoolers — with just a single piston, a regenerator mesh, and some tubing — making them work well is an exercise in patience. We’re definitely looking forward to the future videos in this series as it develops.

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Iron Nitrides: Powerful Magnets Without The Rare Earth Elements

September 1, 2022 by Dan Maloney 39 Comments

Since their relatively recent appearance on the commercial scene, rare-earth magnets have made quite a splash in the public imagination. The amount of magnetic energy packed into these tiny, shiny objects has led to technological leaps that weren’t possible before they came along, like the vibration motors in cell phones, or the tiny speakers in earbuds and hearing aids. And that’s not to mention the motors in electric vehicles and the generators in wind turbines, along with countless medical, military, and scientific uses.

These advances come at a cost, though, as the rare earth elements needed to make them are getting harder to come by. It’s not that rare earth elements like neodymium are all that rare geologically; rather, deposits are unevenly distributed, making it easy for the metals to become pawns in a neverending geopolitical chess game. What’s more, extracting them from their ores is a tricky business in an era of increased sensitivity to environmental considerations.

Luckily, there’s more than one way to make a magnet, and it may soon be possible to build permanent magnets as strong as neodymium magnets, but without any rare earth metals. In fact, the only thing needed to make them is iron and nitrogen, plus an understanding of crystal structure and some engineering ingenuity.

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A Nitrogen Soldering Iron Review

April 14, 2022 by Al Williams 30 Comments

If you’ve ever welded, you know that some welders blow a shield gas over the work for different reasons. For example, you often use a gas to displace oxygen from the area and avoid oxidation. You can also solder using a nitrogen shield. This allows higher temperatures and a reduction of flux required in the solder. Wave soldering often uses nitrogen, and JBC offers a soldering iron that can employ nitrogen shield gas. [SDG Electronics] puts that iron through its paces in the video below.

As you might expect, this isn’t a $50 soldering iron. The price for the iron is just under $1,000 and that doesn’t include the power supply or the nitrogen source. The nitrogen generator that converts compressed air into nitrogen is particularly expensive so [SDG] just used a cylinder of gas.

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The Astronomical Promises Of The Fisher Space Pen

September 23, 2021 by Kristina Panos 57 Comments

We’ve all heard of the Fisher Space Pen. Heck, there’s even an episode of Seinfeld that focuses on this fountain of ink, which is supposed to be ready for action no matter what you throw at it. The legend of the Fisher Space Pen says that it can and will write from any angle, in extreme temperatures, underwater, and most importantly, in zero gravity. While this technology is a definite prerequisite for astronauts in space, it has a long list of practical Earthbound applications as well (though it would be nice if it also wrote on any substrate).

You’ve probably heard the main myth of the Fisher Space Pen, which is that NASA spent millions to develop it, followed quickly by the accompanying joke that the Russian cosmonauts simply used pencils. The truth is, NASA had already tried pencils and decided that graphite particles were too much of an issue because they would potentially clog the instruments, like bags of ruffled potato chips and unsecured ant farms.

A Space-Worthy Instrument Indeed

Usually, it’s government agencies that advance technology, and then it trickles down to the consumer market at some point. But NASA didn’t develop the Space Pen. No government agency did. Paul Fisher of the Fisher Pen Company privately spent most of the 1960s working on a pressurized pen that didn’t require gravity in the hopes of getting NASA’s attention and business. It worked, and NASA motivated him to keep going until he was successful.

An original Fisher Space Pen AG-7 atop the Apollo 11 flight plan. — The pen that went to the moon. Image via Sebastien Billard

Then they tested the hell out of it in all possible positions, exposed it to extreme temperatures between -50 °F and 400 °F (-45 °C to 204 °C), and wrote legible laundry lists in atmospheres ranging from pure oxygen to a total vacuum. So, how does this marvel of engineering work?

The Fisher Space Pen’s ink cartridge is pressurized to 45 PSI with nitrogen, which keeps oxygen out in the same manner as potato chip bags. Inside is a particularly viscous, gel-like ink that turns to liquid when it meets up with friction from the precision-fit tungsten carbide ballpoint.

Between the viscosity and the precision fit of the ballpoint, the pen shouldn’t ever leak, but as you’ll see in the video below, (spoiler alert!) snapping an original Space Pen cartridge results in a quick flood of thick ooze as the ink is forced out by the nitrogen.

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Clever Gas Mixer Gets Just The Right Blend For Homebrew Laser Tubes

April 28, 2021 by Dan Maloney 11 Comments

[Lucas] over at Cranktown City on YouTube has been very busy lately, but despite current appearances, his latest project is not a welder. Rather, he built a very clever gas mixer for filling his homemade CO2 laser tubes, which only looks like a welding machine. (Video, embedded below.)

We’ve been following [Lucas] on his journey to build a laser cutter from scratch — really from scratch, as he built his own laser tube rather than rely on something off-the-shelf. Getting the right mix of gas to fill the tube has been a bit of a pain, though, since he was using a party balloon to collect carbon dioxide, helium, and nitrogen at measuring the diameter of the ballon after each addition to determine the volumetric ratio of each. His attempt at automating the process centers around a so-called AirShim, which is basically a flat inflatable bag made of sturdy material that’s used by contractors to pry, wedge, lift, and shim using air pressure.

[Lucas]’ first idea was to measure the volume of gas in the bag using displacement of water and some photosensors, but that proved both impractical and unnecessary. It turned out to be far easier to sense when the bag is filled with a simple microswitch; each filling yields a fixed volume of gas, making it easy to figure out how much of each gas has been dispensed. An Arduino controls the pump, which is a reclaimed fridge compressor, monitors the limit switch and controls the solenoid valves, and calculates the volume of gas dispensed.

Judging by the video below, the mixer works pretty well, and we’re impressed by its simplicity. We’d never seriously thought about building our own laser tube before, but seeing [Lucas] have at it makes it seem quite approachable. We’re looking forward to watching his laser project come together.

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Scratch-Built CO2 Laser Tube Kicks Off A Laser Cutter Build

March 31, 2021 by Dan Maloney 30 Comments

When we see a CO₂ laser cutter build around these parts, chances are pretty good that the focus will be on the mechatronics end, and that the actual laser will be purchased. So when we see a laser cutter project that starts with scratch-building the laser tube, we take notice.

[Cranktown City]’s build style is refreshingly informal, but there’s a lot going on with this build that’s worth looking at — although it’s perhaps best to ignore the sourcing of glass tubing by cutting the ends off of an old fluorescent tube; there’s no mention of what became of the mercury vapor or liquid therein, but we’ll just assume it was disposed of safely. We’ll further assume that stealing nitrogen for the lasing gas mix from car tires was just prank, but we did like the rough-and-ready volumetric method for estimating the gas mix.

The video below shows the whole process of building and testing the tube. Initial tests were disappointing, but with a lot of tweaking and the addition of a much bigger neon sign transformer to power the tube, the familiar bluish-purple plasma made an appearance. Further fiddling with the mirrors revealed the least little bit of laser output — nowhere near enough to start cutting, but certainly on the path to the ultimate goal of building a laser cutter.

We appreciate [Cranktown City]’s unique approach to his builds; you may recall his abuse-powered drill bit index that we recently covered. We’re interested to see where this laser build goes, and we’ll be sure to keep you posted.

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A Simple But Effective High-Flow Oxygen Concentrator From Hardware Store Parts

March 24, 2021 by Dan Maloney 76 Comments

To say that a lot has happened in the year since the COVID-19 pandemic started is an understatement of epic proportions, so much so that it may be hard to remember how the hardware hacking community responded during those early days, with mass-produced PPE, homebrew ventilators and the like. But we don’t recall seeing too many attempts to build something like this DIY oxygen concentrator during that initial build-out phase.

Given the simplicity and efficacy of the design, dubbed OxiKit, it seems strange that we didn’t see more of these devices. OxiKit uses zeolite, a porous mineral that can be used as a molecular sieve. The tiny beads are packed into columns made from hardware store PVC pipes and fittings and connected to an oil-less air compressor through some solenoid-controlled pneumatic valves. After being cooled in a coil of copper pipe, the compressed air is forced through one zeolite column, which preferentially retains the nitrogen while letting the oxygen pass through. The oxygen stream is split, with part going into a buffer tank and part going into the outlet of the second zeolite column, where it forces the adsorbed nitrogen to be released. An Arduino controls the valves that alternate the gas flow back and forth, resulting in 15 liters per minute of 96% pure oxygen.

OxiKit isn’t optimized as a commercial oxygen concentrator is, so it’s not particularly quiet. But it’s a heck of a lot cheaper than a commercial unit, and an easy build for most hackers. OxiKit’s designs are all open source, but they do sell kits and some of the harder-to-source parts and supplies, like the zeolite. We’d be tempted to build something like this just because the technology is so neat; having a source of high-flow oxygen available isn’t a bad idea, either.