Trying A New Radial Impeller Design For Quadcopters

September 21, 2026 by Maya Posch 19 Comments

Even if the world has already settled on plain old propellers as the way to make quadcopter drones fly, this doesn’t mean that you cannot give other designs a shake to see what kind of flying performance they result in. For example impeller designs that depart radically from standard propellers – themselves a sub-category of axial impellers – and go radically radial instead as in this design by [quadmovr] with accompanying demonstration video.

This is itself a remix of a design by [Baba] to make it fit the target 1750KV T-mount motor. As for whether this is a design that you want to slap on your own quadcopter, the obvious disadvantage is that it’s much heavier than regular propellers.

Weighing [quadmovr]’s drone without battery pack and with these 3D-printed PETG impellers shows them to weigh 189 grams. This compares to 141 grams with the standard three-bladed propellers, or a hefty 12.8 gram weight penalty per impeller. Naturally this translates into less flying time, so what are the advantages?

The noise profile of the impeller design is definitely more pleasant, and much like novice quadcopters with the protective ring around the propellers these impellers should be more robust. On the other hand increased mass adds to inertia, and there is a lot more surface area with the air to add drag, so despite the absolutely sick moves that [quadmovr] pulls off with both impeller configurations in the video one has to admit that regular three-blade propellers do have the edge here.

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DIY Router On X86 E-Waste: OpenWrt And OPNsense

September 21, 2026 by Maya Posch 23 Comments

In previous installments of this series we looked at how creating a DIY router using an e-waste-level PC has changed over the years, before attempting to boot OpenWrt for x86 on it. After an initial SD card booting failure on one system, another system with a newer mainboard – an Intel Board D2500CC – was used which happily booted OpenWrt from an SD card inserted into a USB card reader.

Unfortunately, OpenWrt didn’t see any usable Ethernet interfaces despite having no less than four Intel Ethernet controllers and two hooked up to active networks. After recently getting back to the project, I found out why both onboard Intel 82574L Ethernet controllers didn’t show up in OpenWrt: the drivers for the Intel 82574L controllers are in the e1000e driver package, while only the e1000 package is present in the provided x86 image. This issue persists in the ‘generic’ image profile to this day.

Yet rather than diving head-first into building my own image that includes the kmod-e1000e package, I decided to give OPNsense a shake first.

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Searching For Dark Matter With A Levitating Magnet

September 21, 2026 by Maya Posch 31 Comments

Much of science is performed through inference, with the readings on instruments, a flash of light in heavy water, or the results of parsing through terabytes of sensor data after a particle accelerator collision either backing up a proposed scenario or weakening its foundations.

In the case of so-called dark matter, this is even more relevant, as we are talking about a proposed form of matter whose most pertinent feature is that it doesn’t interact with anything else except through gravity. This is where the wiggling of a levitating magnet may be the key to detecting it.

In this experimental setup by Rice University and Dutch researchers at the Leiden Institute, a tiny permanent magnet the size of a grain of sand is levitated above a superconductor, surrounded by highly sensitive detectors that should be able to spot even minuscule movements. So far, they have collected a month’s worth of data, with no conclusive results yet.

Even if they don’t detect any ‘knocks’ on this tiny levitating magnet, it will still help refine existing models of what dark matter’s properties might be. For the next phase of this research, they’ll add more of these sensors, which will also make it easier to distinguish background noise from any unusual readings.

We’ve previously talked about [Vera Ruben]’s contributions to the hunt for dark matter and the mysteries that prompted the idea that it might exist.

Making A Copper-Oxide Photodetector From Scratch

September 20, 2026 by Maya Posch 5 Comments

Photodetectors come in a wide variety of constructions and materials, with the Cu₂O-based photodetector that [Mad Scientist Creations] demonstrates in a recent video being a good example of a photodetector that can be created at home using nothing but some copper and a heat source.

Of the two copper elements in a salt water cell, one element is heated to the point where a copper oxide layer forms, specifically Cu₂O, which acts as a semiconductor and provides the photosensitive layer. Even a fairly crude sensor created with a regular gas stove produces enough of a current that it can be used in a simple light detection circuit.

Although copper-oxide photodetectors may seem quaint, they are getting a lot of interest as they feature a very narrow bandgap at 1.2 eV. In a 2019 study by [Hyeon-Joo Song] et al. as published in Scientific Reports such a sensor is enhanced with an optimized grain structure that improves its performance, with much higher sensitivity and faster response times.

As demonstrated by [Andrzej Kwiatkowski] et al. in a 2024 paper in Solar Energy Materials and Solar Cells these copper-oxide sensors can also be used for gas detectors, though they used advanced gas deposition to produce the thin films instead of sticking a bit of copper tape into a natural gas flame.

Even if DIY copper-oxide sensors aren’t quite as exciting as what one can do with access to a well-equipped (semiconductor) lab, it’s still a pretty accessible material that lends itself for easy experimentation.

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Teardown And Repair Of An Insoma Water Timer

September 19, 2026 by Maya Posch 5 Comments

Water timers are nifty devices that can water the lawn at set times or keep that vegetable garden from turning into a dustbowl. When [electronupdate] timer refused to output water on any of its three outlets, he did the right thing. Instead of angrily checking the warranty on the sodding thing, he tore it apart to attempt a repair.

As expected, the design of these devices is quite straightforward. Three solenoids control whether an outlet is open or closed. A control board also handles the user controls and display.

There was no obvious sign of damage, and the PCB was potted in a white substance that should have kept out any moisture. A quick check with a battery revealed that the three solenoids also worked just fine, so the cause likely was somewhere on the — potted — PCB.

These solenoids are rated for 6VDC and take about 20 ms to act, but on an oscilloscope capture it was plain to see that the board was only putting out around 2V. This wasn’t enough to drive the solenoid, raising the question of what had gone wrong on the controller board and setting the stage for some fun epoxy potting compound scraping.

A good bit of elbow grease revealed the control ICs, the H-bridges that drive the solenoids, and the rest of the circuitry, including a power boost circuit with a big electrolytic capacitor. The latter had a bit of suspicious liquid near its base, which turned out to be the culprit. Perhaps the most annoying thing here is that this electrolytic capacitor had the temerity to fail after only four months of use, but at least it was an easy enough fix.

If we had been in there, we might have been tempted to avoid many future battery changes. Impractical, but we wonder if anyone ever built a water timer with a water clock?

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Using Azo Photoisomerization To Alter Semiconductor Film Properties

September 19, 2026 by Maya Posch 2 Comments

Generally semiconductor devices like transistors have fixed properties, but using an azobenzene (Azo) compound it’s possible to optically alter these properties by exposing them to UV light. This is demonstrated in a recent paper by [Jaehoon Ji] et al., as published in Science Advances, with accompanying coverage by Princeton University.

Building on previous research on e.g. flakes of MoS₂ with photochromic Azo molecules, a functional semiconductor device was created. This uses a transition metal dichalcogenide (TMD) monolayer combined with the Azo compound, with the latter altering the electrical and optical properties of the structure.

In both n- and p-type FET semiconductors it was demonstrated using visible and UV light that this can alter the carrier densities in the material, effectively altering the FET’s behavior.

While this is of course just a proof of concept, it does show that by using (Azo) molecules that can respond to certain electromagnetic radiation frequencies, electric fields, temperature, etc. semiconductor devices can be created whose behavior dynamically changes with these factors. This could potentially provide new ways to make programmable circuits and sensors.

Making A Digital Music Player For Cassette Decks

September 18, 2026 by Maya Posch 35 Comments

In the cross-over between the era of tapes into that of MP3s, you’d see quite a few of those special cassette tapes that were actually digital music players inside. Some simply provided a 3.5 mm input, while others were complete MP3 players or Bluetooth receivers that just happened to also output to the magnetic read head of a cassette player. Recently [Jonathan Rowny] decided to make his own version of the latter.

Although getting the actual audio signal into the read head is easy enough – requiring little more than its equivalent being used as a write head on the cassette side – actually interfacing with the player’s mechanisms like auto-stop, reverse and so on requires the use of some gearing that detect motion on what would be the tape spools, as well as transfer the motion from the take-up spool to the other spool so that features like the auto-stop mechanism don’t get triggered.

A lot of inspiration here can be found in e.g. the videos made by [Clint] of [Lazy Game Reviews] who looked at a number of examples – including their internals – over the years, with various levels of functionality. For this particular implementation an ESP32-S3 module is used for the brains, along with a microSD card reader for music and a PCM5102 I2S audio codec to create the analog audio signal.

The gears were printed using an SLA printer and seem to work all right. Unfortunately he didn’t realize the importance of the capstan as the mechanism that actually transports the tape, so its motion was not measured as is done in the better cassette adapters. This will likely be corrected in a future iteration, however.

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