Author: Bryan Cockfield

1710 Articles

High Voltage Power Supply From USB

April 30, 2023 by 14 Comments

Those who work in different spaces may have different definitions of the term “high voltage”. For someone working on the GPIO pins of a Raspberry Pi it might be as little as 5 volts, someone working on a Tesla coil might consider that to be around 20 kV, and an electrical line worker might not reference something as HV until 115 kV. What we could perhaps all agree on, though, is that getting 300 volts out of a USB power supply is certainly a “high voltage” we wouldn’t normally expect to see in that kind of context, but [Aylo6061] needed just such a power supply and was eventually able to create one.

In this case, the high voltages will eventually be used for electrophoresis or electrowetting. But before getting there, [Aylo6061] has built one of the safest looking circuits we’ve seen in recent memory. Every high voltage part is hidden behind double insulation, and there is complete isolation between the high and low voltage sides thanks to a flyback converter. This has the benefit of a floating ground which reduces the risk of accidental shock. This does cause some challenges though, as voltage sensing on the high side is difficult while maintaining isolation, so some clever tricks were implemented to maintain the correct target output voltage.

The control circuitry is based around an RP2040 chip and is impressive in its own right, with USB isolation for the data lines as well. Additionally the project code can be found at its GitHub page. Thanks to a part shortage, [Aylo6061] dedicated an entire core of the microprocessor to decoding digital data from the high voltage sensor circuitry. For something with a little less refinement, less safety, and a much higher voltage output, though, take a look at this power supply which tops its output voltage around 30 kV.

Don’t Let The Baluns Float Over Your Head

April 29, 2023 by 5 Comments

Most ham radio operators will build an antenna of some sort when they first start listening or transmitting, whether it’s a simple dipole, a beam antenna like a Yagi, or even just a random wire vertical antenna. All of these will need to be connected feedline of some sort, and in the likely event you reach for some 50-ohm coax cable you’ll also need a balun to reduce noise or unwanted radiation. Don’t be afraid of extra expenses when getting into this hobby, though, as [W6NBC] demonstrates how to construct an “ugly balun” out of the coax wire itself (PDF).

The main purpose of a balun, a contraction of “balanced-unbalanced” is to convert an unbalanced transmission line to a balanced one. However, as [W6NBC] explains, this explanation obscures much of what baluns are actually doing. In reality, they take a three-wire system (the coax) and convert it to a two-wire system (the antenna), which keeps all of the electrical noise and current on the shield wire of the coax from interfering with the desirable RF on the interior of the coax.

This might seem somewhat confusing on the surface, as coax wires only have a center conductor and a shield wire, but thanks to the skin effect which drives currents to the outside of the conductor, the shield wire effectively becomes two conductors when taking into account its inner and outer surfaces. At these high frequencies the balun is acting as a choke which keeps these two high-frequency conductors separate from one another, and keeps all the noise on the outside of the shield wire and out of the transmitter or receiver.

Granted, the world of high-frequency radio circuits can get quite complex and counter-intuitive and, as we’ve shown before, can behave quite unexpectedly when compared to DC or even mains-frequency AC. But a proper understanding of baluns and other types of transformers and the ways they interact with RF can be a powerful tool to have. We’eve even seen other hams use specialty transformers like these to make antennas out of random lengths and shapes of wire.

Continue reading “Don’t Let The Baluns Float Over Your Head” →

Soldering Station Designed Around Batteries

April 28, 2023 by 19 Comments

Companies now are looking to secure revenue streams by sneakily locking customers into as many recurring services as possible. Subscription software, OS ecosystems, music streaming, and even food delivery companies all want to lock consumers in to these types of services. Battery-operated power tools are no different as there’s often a cycle of buying tools that fit one’s existing batteries, then buying replacement batteries, ad infinitum. As consumers we might prefer a more open standard but since this is not likely to happen any time soon, at least we can build our own tools that work with our power tool brand of choice like this battery-powered soldering station. Continue reading “Soldering Station Designed Around Batteries” →

Transistors That Grow On Trees

April 28, 2023 by 16 Comments

Modern technology is riddled with innovations that were initially inspired by the natural world. Velcro, bullet trains, airplanes, solar panels, and many other technologies took inspiration from nature to become what they are today. While some of these examples might seem like obvious places to look, scientists are peering into more unconventional locations for this transistor design which is both inspired by and made out of wood.

The first obvious hurdle to overcome with any electronics made out of wood is that wood isn’t particularly conductive, but then again a block of silicon needs some work before it reliably conducts electricity too. First, the lignin is removed from the wood by dissolving it in acetate, leaving behind mostly the cellulose structure. Then a conductive polymer is added to create a lattice structure of sorts using the wood cellulose as the structure. Within this structure, transistors can be constructed that function mostly the same as a conventional transistor might.

It might seem counterintuitive to use wood to build electronics like transistors, but this method might offer a number of advantages including sustainability, lower cost, recyclability, and physical flexibility. Wood can be worked in a number of ways once the lignin is removed, most notably when making paper, but removing the lignin can also make the wood relatively transparent as well which has a number of other potential uses.

Thanks to [Adrian] for the tip!

Using An Old Smartphone In Place Of A Raspberry Pi

April 27, 2023 by 63 Comments

The Raspberry Pi was a fairly revolutionary computing device when it came on the scene around a decade ago. Enough processing power to run a full Linux desktop and plenty of GPIO meant almost certain success. In the past year, though, they’ve run into some issues with their chip supplier and it’s been difficult to find new Pis, which has led to some looking for alternatives to these handy devices. [David] was hoping to build a music streaming server and built it on an old smartphone instead of the ubiquitous single-board computer.

Most smartphones are single-board computers though, and at least the Android devices are fully capable of running Linux just like the Pi. The only problem tends to be getting around the carrier or manufacturer restrictions like a locked bootloader or lack of root access. For [David]’s first try getting this to work, he tried to install Navidrome on a Samsung phone but had difficulties with the lack of memory and had to build the software somewhere else and then load it on the phone. It did work, but the stock operating system kept killing the process for consuming too much memory.

Without root access, [David] decided to try LineageOS, a version of Android which, among other benefits, is typically much more configurable than the stock version of Android that is shipped with smartphones. This allowed him to disable or uninstall anything not needed for his music server to free up enough memory. After some issues with transcoding the actual music files he planned on streaming, his music server was successfully up and running on a phone that would have otherwise been relegated to the junk drawer. The specific steps he took to get this working can be found on his GitHub page as well.

[David] also mentioned looking at PostmarketOS for this job which is certainly a viable option for some, but the Linux distribution for phones is only supported on a few devices. Another viable alternative for a project like this if no Raspberry Pis are available might be any of a number of Pine64 devices that might also be sitting around gathering dust, like the versatile Linux-based Pinephone.

The Goalie Mask, Reenvisioned

April 26, 2023 by 12 Comments

The goalie mask, at least the retro-styled fiberglass types from the 60s and 70s, hasn’t been used in hockey for about 50 years —  it’s instead made many more appearances in horror movies than on ice rinks. Since then, though, there’s been very little innovation surrounding the goalie mask even though there’s much more modern technology that could theoretically give them even greater visibility. [Surjan Singh] is hoping to use his engineering and hockey backgrounds to finally drive some improvements.

The “uncage” is based on Dyneema thread, a polyethylene fiber known for its strength and durability. It’s often used in applications that demand high strength with minimal weight, such as for sails or backpacking equipment. Using strands of Dyneema woven through a metal support structure is what gives this mask its high strength while also improving the visibility through it dramatically. [Surjan] has been prototyping this design extensively, as there were some issues with the fibers chafing on attachment points on the metal frame, but most of these issues have been ironed out or are being worked on currently.

In the meantime, [Surjan] has been looking for a professional-level goalie to help refine his design further and does seem to have some interest, but it doesn’t seem to have progressed past testing in the more controlled test environments yet. It’s not too far-fetched to imagine this as the future of goalie masks in professional hockey though since some innovation after 50 years of relative stagnation seems to be due. For something more accessible to those of us not currently playing in the NHL, though, you can wheel, snipe, and celly on this air hockey table instead.

Continue reading “The Goalie Mask, Reenvisioned” →

Build Your Own Bootable Emacs Environment

April 22, 2023 by 18 Comments

An old joke is that Emacs is a text editor with an operating system included, given that its extensibility and customization often goes far beyond traditional text editors. Part of its well-earned reputation comes from being built in Lisp which allows it to be expanded to do almost anything. Despite this in-joke in the community, though, you will still need an actual operating system to run it, but not much more than that.

This project uses User-Mode Linux (UML) as a foundation to load almost nothing other than an Emacs editor. UML is a virtualization technology that allows running multiple Linux kernel instances as separate virtual machines, so once the Linux environment is started and Emacs is compiled, the virtual machine can essentially boot straight into an Emacs environment. Some tools are needed outside of the Linux kernel like mount which allows the virtual file system to access the files needed to build Emacs, but as far as lightweight or minimalist Linux distributions go this one definitely gets at least an honorable mention.

While UML is virtualization software rather than a full-fledged Linux distribution, we would expect a similarly minimalist build could easily be done with something more hardware-based like Linux From Scratch. Emacs has been around for so long and had such a wide reach that it’s difficult to imagine a world without it. Even in more modern technology like browsers, knowing a little bit about Emacs can be an extremely powerful tool.