Testing Refrigerants And Capillary Tubes To Find Peak Performance

April 11, 2026 by Maya Posch 4 Comments

Heat lift graphs. (Credit: Hyperspace Pirate, YouTube)

Although vapor-compression refrigeration is a simple concept, there are still a lot of details in the implementation of such a system that determines exactly how efficient it is. After making a few of such systems, [Hyperspace Pirate] decided to sit down and create a testing system that allows for testing of many of these parameters.

Some of the major components that determine the coefficient of performance (COP) of a heat pump or similar system include the used refrigerant, as well as the capillary tube diameter or expansion valve design. For the testing in the video three refrigerants are used: R600 (N-Butane), R134a (tetrafluoroethene, AKA Freon) and R290 (propane), with R134a being decidedly illegal in places like the EU. The use of R600 instead of R600A is due to the former allowing for a lower pressure system, which is nice for low-power portable systems.

The test rig has the typical fresh-from-the-scrap-heap look that we’re used to and love from [Hyperspace Pirate], but does exactly what it says on the tin, and is easy for any DIY enthusiast to replicate. Which compressor to pick for a specific refrigerant is also covered in the video, along with oil type and more.

For basic systems you’d use a simple capillary tube, whereas an airconditioner or similarly more complex system would use an adjustable valve design. With the rig you can test the efficiency of different tube diameters, with three sizes available in this version. Unfortunately the electronic expansion valve (EEV) that was going to be used didn’t get a chance to shine due to unforeseen events.

With the R134a and butane a COP of 2.0 – 2.5 was achieved when taking power factor into account, which was reasonable considering a compressor was used that targets R134a. Regardless, if you have ever felt like repurposing that old compressor from a fridge or AC unit, this might be a fun afternoon project.

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Magnetic Levitation Using An Induction Cooktop

April 7, 2026 by Maya Posch 8 Comments

Adding another item on the list of things you probably shouldn’t be trying at home, we got [Brainiac75] giving magnetic levitation a shot using an unmodified induction cooktop and aluminium foil. Although not ferromagnetic, it turns out that aluminium can be made to do interesting things in the magnetic field created by the powerful electromagnet that underlies the induction principle.

Interestingly, although there’s a detection circuit in these units that should detect the presence of an appropriate (ferromagnetic) object, it appears that even a thin sheet of aluminium foil can completely deceive it. The effect is that of a force pushing the foil away from the cooktop’s surface, with foil areas that remain close enough to the ferrite bars on the electromagnet even heating up enough to begin melting the aluminium.

After a bit of fun with various shapes and types of aluminium objects, the video moves on to a scientific explanation of what’s going on. The surface resistivity of the foil is similar enough to ferromagnetic cookware that it fools the sensor, after which the skin effect of aluminium induces a current. This then does the typical Lorentz force things.

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A lead box with a small aperture sits on a desk. A ruler leads away from it. A small disk on a stand is held in front of the aperture.

Testing The Wave-Particle Duality With Gamma Rays

April 6, 2026 by Aaron Beckendorf 14 Comments

Everything on the electromagnetic spectrum has some properties of both waves and particles, but it’s difficult to imagine a radio wave, for example, behaving like a particle. The main evidence for a particle-like nature is quantization, the bundling of electromagnetic energy into discrete packets. One way around this is to theorize that quantization is due to the specific interaction between the electromagnetic field and matter, not intrinsic to the field itself. To investigate this theory, [Huygens Optics] conducted several experiments with gamma rays, including Compton scattering.

For these experiments, he used a Radiacode 110 X-ray and gamma ray detector, which uses a photodetector to detect radiation’s passage through a scintillation crystal. By summing the energy contained in the light emitted by one ray, it can measure the ray’s energy and, over time, create an energy spectrum. [Huygens Optics] used the americium capsule from an old smoke detector as a radiation source, and cast a lead enclosure to shield the Radiacode from most background radiation, with a small opening for measurements.

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Lab Gloves May Be Skewing Microplastics Data

April 6, 2026 by Maya Posch 16 Comments

The topic of micro- and nanoplastics (MNPs) has become increasingly prevalent over the past years, as amidst dismissal and panic, researchers attempt to distinguish just how much of a problem MNPs truly are. The most essential problem here is that we are still developing the tools to accurately measure the levels of MNP contamination. Recently, [Madeline E. Clough] et al. demonstrated in an article published in Analytical Methods how gloves worn in laboratory settings can create false positive MNP signals.

As we covered previously, detecting MNPs is tough due to the detection methods used, many of which rely on interpreting signals from methods like pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), with protocols for this and other methods still being worked on, particularly on how to filter out false positives.

The article by [Clough] demonstrates how dry contact of lab gloves on samples can deposit stearate salts – left over from their production, which are subsequently misidentified as being MNPs, specifically polyethylene (PE). These false positives occur with µ-Fourier transform infrared (µ-FTIR) spectroscopy and µ-Raman spectroscopy, but can occur with Py-GC-MS as well, as has been determined previously. Substances like the fatty lipids that are commonly found in the human body, and in particular the brain, will closely match the PE signature.

With these very common stearate salts now also a likely source of contamination with MNP measurements, it just becomes more obvious that it’s incredibly hard to make accurate assessments about any hazards of MNPs until we can determine their presence with any level of reliability.

Exposing A Radiation-Hardened 2.4 GHz Wi-Fi Receiver To 500 Kilograys

April 4, 2026 by Maya Posch 5 Comments

From outer space to down here on Earth, there are many places where ionizing radiation levels are high enough that they effectively bar access for humans, but also make life miserable for anything containing semiconductor technology. This is especially true for anything involving wireless communications, such as Wi-Fi. However, recently Japanese researchers have created a Wi-Fi chip that is claimed to be so radiation-hardened that it can be used even in gamma ray-rich environments, such as in the worst contaminated depths of the Fukushima Daiichi nuclear reactor.

The indicated dose exposure of 500 kilograys that the chip survived during testing is quite significant. A single gray (Gy) is the absorption of one joule of energy per kilogram of matter. In radiation therapy, a solid epithelial tumor can receive as much as 60 to 80 Gy in a single dose, for example.

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Addressing The Divisive Topic That Is Boiling Water

April 2, 2026 by Maya Posch 30 Comments

The topic of boiling water is apparently a rather divisive topic, with plenty of strong opinions to go around on what is safe and the most efficient way to go about it. Thus in a new video [Cahn] sought to address the many comments that came in after his previous testing of electric kettles on either 12 VDC or 240 VAC.

What’s interesting about this whole topic is that at its core the overall efficiency of boiling water is simply a matter of calculating the energy input minus energy losses, with the remaining energy going into the water.

As we can see in the video, using a higher battery voltage doesn’t really change the efficiency of a 12 VDC kettle, but the higher current draw does manage to melt a fuse that can’t take the heat — requiring a 20 amp fuse instead of the 15 A one.

One change that does make a difference is how it’s connected. Replacing the thin gauge wiring and the attached cigarette lighter plug on the 12 VDC kettle with beefier cable and an Anderson plug made things run cooler, resulting in an efficiency bump of about 10%. This cut the time required to get the water boiling by around 6 minutes.

Added to this test were an induction hob and an iso-butane-powered Jetboil, both of which scored rather unimpressively. For the induction option it’s obvious that a lot of energy is wasted by having the pan radiate it away from the water, while burning iso-butane loses energy through the exhaust gases. Ultimately what you pick to boil water with should thus be mostly determined by convenience rather than sheer physics.

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Watch An Electro-Permanent Magnet In Action

April 1, 2026 by Donald Papp 12 Comments

Electro-permanent magnets (EPMs) are pretty nifty concepts, and if you aren’t familiar with them, they are permanent magnets with the ability to be electrically switched on or off. Unlike an electromagnet — which maintains a magnetic field only while power is applied — an EPM can remain “on” even when power is removed. Want to see one work? There’s a video embedded below that shows one off, but if you’d like to know how they work, we have you covered.

Inside are two types of magnet, one of which is permanent and the other being a semi-hard magnet paired with an electromagnetic coil. A semi-hard magnet’s flux can be changed by exposing it to a strong enough magnetic field, and that’s the key to making it work.

When both magnets work together, the EPM is “on” and acts like a permanent magnet. To turn the EPM off, the polarity of the semi-hard magnet is flipped with a short and powerful electromagnetic pulse, after which the two magnets oppose one another and more or less cancel each other out. So rather than generating a magnetic field, an EPM more accurately reconfigures it.

As intriguing as EPMs are, we haven’t really seen one properly in action until it was brought to our attention that [Dave Jones] of EEVblog tried one out last year. He received a Zubax FluxGrip EPM, which is intended for drone and robotic applications and can hold up to 25 kg. Watch [Dave] fire it up in the video (link is cued up to the 7:30 mark), it’s pretty interesting to see one of these actually work.

EPMs are not prohibitively expensive but they are not exactly cheap, either. But if a switchable magnet sounds up your alley and you can’t afford an EPM, consider an alternative “switchable” magnet design that works by momentarily canceling out a permanent magnet with a paired electromagnet. Unlike an EPM, it’s not a permanent switch but it would be enough to drop a payload.

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