Got Junk? Then Build This Scrappy TEA Laser

March 13, 2025 by Dan Maloney 24 Comments

A piece of glass, some bits of tinfoil, a sheet of plastic, a couple of razor blades, and a few assorted bits and bobs are all it takes to build this TEA nitrogen laser. Oh, and a 5,000-volt flyback supply with enough amperage to stop your heart. You’ll need that too.

Seriously, if you choose to follow [MultiverseCurator] ‘s example and build this laser, you’ll want to take the proper precautions. A transversely excited atmospheric laser is simple in concept, but there are plenty of ways for them to go wrong. Unlike the gas lasers used in laser cutters, there’s no enclosed resonator cavity or mirrors. Rather, the excitation takes place across a narrow gap between two electrodes, using atmospheric nitrogen as the lasing medium. This results in hard UV emissions, which means you can’t see them with the naked eye. Add to that the spark gap creating extremely loud discharges as the laser operates, and hazards abound. Proceed with caution.

Construction starts with a flat glass plate and a pair of large capacitors made from aluminum foil plates separated by a plastic dielectric. The razor blades are connected across the capacitors, separated by a narrow gap, with an inductor made from magnet wire in parallel. A spark gap made from nuts and bolts goes in series, and the whole assembly gets connected to a high-voltage power supply — [Multiverse] used a ZVS driver and a CRT flyback transformer with an eight-megohm resistor in series. The video below has all the build details.

It’ll take a little fiddling to get it lasing, and you’ll need something phosphorescent to see the UV light — a scrap of copy paper should do. But the results are pretty amazing for something made from scrap. If you want to take the design to the next level, you’ll want to check out [Les Wright]’s TEA laser build.

Continue reading “Got Junk? Then Build This Scrappy TEA Laser” →

Low-Cost Cryocooler Pumps Out Cheap DIY Liquid Nitrogen

July 15, 2024 by Dan Maloney 18 Comments

A word of caution if you’re planning to try this cryocooler method for making liquid nitrogen: not only does it involve toxic and flammable gasses and pressures high enough to turn the works into a bomb, but you’re likely to deplete your rent account with money you’ll shell out for all the copper tubing and fittings. You’ve been warned.

In theory, making liquid nitrogen should be as easy as getting something cold enough that nitrogen in the air condenses. The “cold enough” part is the trick, and it’s where [Hyperspace Pirate]’s cryocooler expertise comes into play. His setup uses recycled compressors from cast-off air conditioners and relies on a mixed-gas Joule-Thomson cycle. He plays with several mixtures of propane, ethylene, methane, argon, and nitrogen, with the best results coming from argon and propane in a 70:30 percent ratio. A regenerative counterflow heat exchanger, where the cooled expanding gas flows over the incoming compressed gas to cool it, does most of the heavy lifting here, and is bolstered by a separate compressor that pre-cools the gas mixture to about -30°C before it enters the regenerative system.

There’s also a third compressor system that pre-cools the nitrogen process gas, which is currently supplied by a tank but will eventually be pulled right from thin air by a pressure swing adsorption system — basically an oxygen concentrator where you keep the nitrogen instead of the oxygen. There are a ton of complications in the finished system, including doodads like oil separators and needle valves to control the flow of liquid nitrogen, plus an Arduino to monitor and control the cycle. It works well enough to produce fun amounts of LN₂ on the cheap — about a quarter of the cost of commercially made stuff — with the promise of efficiency gains to come.

It does need to be said that there’s ample room for peril here, especially containing high pressures within copper plumbing. Confidence in one’s brazing skills is a must here, as is proper hydro testing of components. That said, [Hyperspace Pirate] has done some interesting work here, not least of which is keeping expenses for the cryocooler to a minimum.

Continue reading “Low-Cost Cryocooler Pumps Out Cheap DIY Liquid Nitrogen” →

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.

Continue reading “A DIY Pulse Tube Cryocooler In The Quest For Home-Made Liquid Nitrogen” →

Iron Nitrides: Powerful Magnets Without The Rare Earth Elements

September 1, 2022 by Dan Maloney 41 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.

Continue reading “Iron Nitrides: Powerful Magnets Without The Rare Earth Elements” →

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.

Continue reading “A Nitrogen Soldering Iron Review” →

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.

Continue reading “The Astronomical Promises Of The Fisher Space Pen” →

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.

Continue reading “Clever Gas Mixer Gets Just The Right Blend For Homebrew Laser Tubes” →