Electrostatic Puck: Making An Electret

December 1, 2024 by 27 Comments

You might have heard of electrets being used in microphones, but do you know what they are? Electrets produce a semi-permanent static electric field, similar to how a magnet produces a magnetic field. The ones in microphones are very small, but in the video after the break [Jay Bowles] from Plasma Channel makes a big electret and demonstrates it’s effects.

Electrets have been around since the 1800s, and are usually produced by melting an insulating material and letting it solidify between two high-voltage electrodes. The original recipe used a mix of Carnauba wax, beeswax, and rosin, which is what [Jay] tried first. He built a simple electric field detector, which is just a battery, LED and FET, with an open-ended resistor on the FET’s gate.

[Jay] 3D printed a simple cylindrical mold and stuck aluminum foil to the outer surfaces to act as the electrodes. He used his custom 6000:1 voltage transformer to hold the electrodes at ~40 kV. The first attempt did not produce a working electret because the electrodes were not in contact with the wax, and kept arcing across, which causes the electric charge to drop off. Moving the aluminum electrodes the inner surfaces of the mold eventually produced an electret detectable out to 10 inches.

This was with the original wax recipe, but there are now much better materials available, like polyethylene. [Jay] heated a a block of it in the oven until it turned into a clear blob, and compressed it in a new mold with improved insulation. This produced significantly better results, with an electric field detectable out to 24 inches.

[Jay] also built an array of detectors in a 5×5 grid, which he used to help him visualize the size and shape of the field. He once pulled off a similar trick using a grid of neon bulbs.

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When Transistor Count Mattered

December 1, 2024 by 29 Comments

Many Hackaday readers have an interest in retro technology, but we are not the only group who scour the flea markets. Alongside us are the collectors, whose interest is as much cultural as it is technological, and who seek to preserve and amass as many interesting specimens as they can. From this world comes [colectornet], with a video that crosses the bridge between our two communities, examining the so-called transistor wars of the late 1950s and through the ’60s. Just as digital camera makers would with megapixels four or five decades later, makers of transistor radios would cram as many transistors as they could into their products in a game of one-upmanship.

A simple AM transistor radio can be made with surprisingly few components, but for a circuit with a reasonable performance they suggest six transistors to be the optimal number. If we think about it we come up with five and a diode, that’s one for the self-oscillating mixer, one for IF, an audio preamplifier, and two for the audio power amplifier, but it’s possible we’re not factoring in the relatively low gain of a 1950s transistor and they’d need that extra part. In the cut-throat world of late ’50s budget consumer electronics though, any marketing ploy was worth a go. As the price of transistors tumbled but their novelty remained undimmed, manufacturers started creating radios with superfluous extra transistors, even sometimes going as far as to fit transistors which served no purpose. Our curious minds wonder if they bought super-cheap out-of-spec parts to fill those footprints.

The video charts the transistor wars in detail, showing us a feast of tiny radios, and culminating in models which claim a barely credible sixteen transistors. In a time when far more capable radios use a fraction of the board space, the video below the break makes for a fascinating watch.

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A pair of hands hold two dark brown boards perpendicular two each other on a light brown benchtop. There are two light brown oval dowels in the end of one board that then project toward holes in the opposite board. Circular holes in the oval dowels are visible perpendicular to the second board, and will match up with holes in the board once pressed in. A cylindrical dowel is laying next to the joint and will be placed into the circular holes once assembled.

Creating A Signature Wood Joint

December 1, 2024 by 25 Comments

We really love when makers make their construction techniques evident in an aesthetically-pleasing way, and [Laura Kampf] has created a clever joint that reveals how a piece is made.

[Kampf] is a big fan of using her domino joiner, which is similar to biscuits or dowel joinery, but she didn’t love how it hid the construction of the joint. She first figured out an “off label” use of the joiner by running it from the outside of the joint to show the exposed domino from one end.

Building on the concept to show an interesting contrast on both sides of the joint, she drilled a hole perpendicular the domino and placed a dowel through it, creating a locking joint. The choice looks great once a finish is applied to really accentuate the contrast, and another bonus is that if glue is only applied to the dowel and domino, it becomes trivial to separate the joint if needed by drilling out the dowel.

If you’d like to see some other interesting ways to join wood, how about this laser-cut wedge tenon, soda bottle heat shrink, or this collection of CNC joints.

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Tailwheel Trainer Go-Cart To Avoid Wrecked Planes

December 1, 2024 by 16 Comments

Taildraggers remain a popular configuration for small aircraft, but they come with a significant risk during ground handling: ground loops. If the tail gets too far off course, it can swing around completely, often damaging or destroying aircraft if a wing hits the ground. Avoiding ground loops requires good rudder and brake control, and there currently isn’t a good way to learn it without getting into an actual aircraft. [Trent Palmer] is a pilot and who has been thinking about this problem for a few years, so he built a 3-wheeled electric go-cart to help pilots train their ground handling.

The cart is controlled exactly like a taildragger, with a pair of rudder pedals connected to the single steerable via cables, and springs to add some response delay. Independent hydraulic brakes on each main wheel, operated by toe pedals, further simulate the control on many aircraft. The main wheel are controlled with a throttle lever, with a differential to allow them to rotate at different speeds. The cart is unforgiving, and requires constant corrections with the pedals to keep it going straight.[Trent] had few pilot and non-pilot friends try out the cart, and even the experienced tailwheel pilots got into ground loop. It might be bit too sensitive, but everyone agreed that mastering this cart would significantly improve ground handling skills in actual aircraft.

Repairing a damaged aircraft can cost several thousand dollar, so a cheap training tool like this could prove invaluable flight schools and even individual pilots. [Trent] doesn’t have big plans for commercialization, but we wouldn’t be surprised if it goes that way.

Taildraggers are especially popular as bush planes, with many tracing their heritage from the humble Piper J-3 Cub. We’ve seen some extreme extreme modern bush planes, like [Mike Patey]’s Scrappy and Draco builds. Continue reading “Tailwheel Trainer Go-Cart To Avoid Wrecked Planes” →

8-Bit Computers Crunch Advanced Scientific Computations

December 1, 2024 by 37 Comments

Although largely relegated to retrocomputing enthusiasts and embedded systems or microcontrollers now, there was a time when there were no other computers available other than those with 8-bit processors. The late 70s and early 80s would have seen computers with processors like the Motorola 6800 or Intel 8080 as the top-of-the-line equipment and, while underpowered by modern standards, these machines can do quite a bit of useful work even today. Mathematician [Jean Michel Sellier] wanted to demonstrate this so he set up a Commodore 64 to study some concepts like simulating a quantum computer.

The computer programs he’s written to do this work are in BASIC, a common high-level language of the era designed for ease of use. To simulate the quantum computer he sets up a matrix-vector multiplication but simplifies it using conditional logic. Everything is shown using the LIST command so those with access to older hardware like this can follow along. From there this quantum computer even goes as far as demonstrating a quantum full adder.

There are a number of other videos on other topics available as well. For example, there’s an AmigaBasic program that simulates quantum wave packets and a QBasic program that helps visualize the statistical likelihood of finding an electron at various locations around a hydrogen nucleus. While not likely to displace any supercomputing platforms anytime soon, it’s a good look at how you don’t need a lot of computing power in all situations. And, if you need a refresher on some of these concepts, there’s an overview on how modern quantum computers work here.

A hand holds a small PCB with an edge connector over the exposed, mostly black components of an M4 Mac mini. The bottom cover is hanging by an FFC cable off to the left of the

Upgrading The M4 Mac Mini With More Storage

December 1, 2024 by 17 Comments

Apple’s in-house chips have some impressive specs, but user serviceability is something Apple left behind for consumer machines around a decade ago. Repair legend [dosdude1] shows us how the new M4 Mac mini can get a sizeable storage upgrade without paying the Apple tax.

The Mac mini is Apple’s least expensive machine, and in the old days you could swap a SATA drive for more storage and not pay the exorbitant prices that OEMs demand. Never one to turn down a walled garden, later Intel machines and now the ARM-based M-series chips soldered storage into the machine leaving an upgrade out of the hands of anyone without a hot air station.

Both the Mac Studio and Mac mini now have proprietary storage cards, and after some tinkering, [dosdude1] has successfully upgraded the storage on the base model M4 mini. While most people don’t casually reball NAND chips while chatting on a video, his previous work with others in the space to make a Mac Studio upgrade kit give us hope we’ll soon see economical storage upgrades that keep the Mac mini affordable.

We’ve previously covered the first time Apple tried to make its own processors, and some of their more recent attempts at repairability.

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Pushing 802.11ah To The Extreme With Drones

December 1, 2024 by 20 Comments

It might come as a surprise to some that IEEE, the Institute for Electrical and Electronics Engineers, does more than send out mailers asking people to renew their memberships. In fact, they also maintain various electrical standards across a wide range of disciplines, but perhaps the one most of us interact with the most is the 802.11 standard which outlines WiFi. There have been many revisions over the years to improve throughput but the 802.11ah standard actually looks at decreasing throughput in favor of extremely increased range. Just how far you can communicate using this standard seems to depend on how many drones you have.

802.11ah, otherwise known as Wi-Fi HaLow, operates in the sub-gigahertz range which is part of why it has the capability of operating over longer distances. But [Aaron] is extending that distance even further by adding a pair of T-Halow devices, one in client mode and the other in AP (access point) mode, on a drone. The signal then hops from one laptop to a drone, then out to another drone with a similar setup, and then finally down to a second laptop. In theory this “Dragon Bridge” could allow devices to communicate as far as the drone bridge will allow, and indeed [Aaron] has plans for future revisions to include more powerful hardware which will allow even greater distances to be reached.

While there were a few bugs to work out initially, eventually he was able to get almost two kilometers of distance across six devices and two drones. Something like this might be useful for a distributed network of IoT devices that are just outside the range of a normal access point. The Dragon Bridge borrowed its name from DragonOS, a Linux distribution built by [Aaron] with a wide assortment of software-defined radio tools available out of the box. He’s even put in on the Steam Deck to test out long-distance WiFi.

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