Drop-In Switch Mode Regulators

March 31, 2024 by 29 Comments

Perhaps the simplest way to regulate a DC voltage is using a voltage divider and/or an active device like a Zener diode. Besides simplicity, they have the additional advantage of not being particularly noisy, but with a major caveat: they are terribly inefficient. To solve this problem a switching regulator can be used instead, but that generally increases complexity and noise. With careful design, though, a switching regulator can be constructed to almost completely replicate a linear regulator like this drop-in TO3 replacement. (Google Translate from German)

While the replacement regulator was built by [Mr. Floppy], the units are being put to the test in the linked video below by [root42]. The major problem these solve compared to other switching regulators is the suppression of ripple, which is a high-frequency artifact that appears on the DC voltage. Reducing ripple in this situation involved designing low-inductance circuit traces on the PCB as well as implementing a number of EMI filters on both input and output. The final result is an efficient voltage supply for retrocomputers which has a ripple lower than their oscilloscopes can measure without special tools.

[root42] is not only testing these, but the linked video also has him using the modules to repair a Commodore 1541 which originally had the linear TO3 voltage regulators. It’s definitely a non-trivial task to build a switching power supply that meets the requirements of sensitive electronics like these. Switch mode power supplies aren’t new ideas, either, and surprisingly pre-date the first commercially-available transistor although modern ones like these are much less expensive to build.

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Modular Vacuum Table Custom-Fits The Parts

March 31, 2024 by 3 Comments

[enhydra] needed to modify a bunch of side inserts from some cheap ABS enclosures, and to save time and effort, he created a simple vacuum table with swappable inserts to precisely fit the parts. Suction is provided by a shop vacuum (plugged in near the bottom in the photo above) and it worked very well! Sealing and gaskets weren’t even required.

A vacuum table provides a way to hold workpieces flat and secure while a CNC machine does its thing, and because no clamps are involved, it can really speed up repetitive work. [enhydra]’s solution combines a vacuum table with a jig that ensures every rectangular piece is held exactly where the machine expects it to be, making the whole process of modifying multiple units significantly more efficient.

The whole thing — vacuum table and modular top — was straightforward to CNC cut out of what looks like particle board and worked as-is, no added gaskets or seals required, making this a very economical solution.

Vacuum tables can be pretty versatile and applied in more than one way, so keep that in mind the next time you’re wondering how best to approach a workshop problem. We’ve seen a well-engineered table used to speed up PCB milling, and we’ve also seen a DIY vacuum table combined with a heat gun and plastic plates from the dollar store make a bare-bones thermoforming rig.

A Threat Level Monitor For Everyone

March 31, 2024 by 25 Comments

A TV news pundit might on any given evening in 2024 look at the viewers and gravely announce that we are living in uncertain times. Those of us who’ve been around for a bit longer than we’d like to admit would see that, scratch our heads, and ask “Have we ever not lived in uncertain times?” If all this uncertainty is getting to you though, you can now reassure yourself as [Ian Williams] has, with a threat level monitor which displays the UK’s current level of projected fear threat level.

The build is fairly straightforward in hardware terms, with a Raspberry Pi Zero and a Pimoroni e-paper display pHAT. The software grabs the current level of doom from in this case the UK government’s website with a nifty bit of Python code, and turns it into an easy to read alert level bar.

So if you’re genuinely worried that the sky might fall upon your head you can now gain reassurance from a small piece of electronic hardware. If you feel things are really going south though, how about converting your basement into a fallout shelter?

Playing Chess Against Your Printer, With PostScript

March 30, 2024 by 9 Comments

Can you play chess against your printer? The answer will soon be yes, and it’s thanks to [Nicolas Seriot]’s PSChess. It’s a chess engine implemented in PostScript, of all things. It’s entirely working except for one last hurdle, but more on that in a moment.

What’s it like to play PSChess? Currently, one uses a PostScript interpreter (such as GhostScript) to run it, much like one would use the Python interpreter to run Python code. The user inputs moves by typing in commands like d2d4 (representing a piece’s source coordinate and a destination coordinate on the 2D board). Then the program makes a move, and outputs an updated board state to both the console and a PDF document. Then it’s the user’s turn again, and so on until somebody loses.

The chess parts are all working, but there’s one last feature in progress. The final step of the project is to enable PSChess to be run directly on a printer instead of using GhostScript as the interpreter. Intrigued? You can find the code at the project’s GitHub repository.

So why PostScript? While it is a Turing-complete stack-based interpreted language, it was never intended to be used directly by humans. There are no meaningful development tools to speak of. Nevertheless, [Nicolas] finds PostScript an appealing tool for programming projects and provides tips and techniques for like-minded folks. One of the appeals is working within constraints to solve a problem, just like implementing a chess engine in only 4k, or draw poker in 10 lines of BASIC.

Using Electroadhesion To Reversibly Adhere Metals And Graphite To Hydrogels And Tissues

March 30, 2024 by 6 Comments

The usual way to get biological tissues and materials like gels and metals to stick together is using sutures, adhesives or both. Although this generally works, it’s far from ideal, with adhesives forming a barrier layer between tissues and the hard or impossible to undo nature of these methods. A viable alternative might be electroadhesion using cation and anion pairs, which uses low-voltage DC to firmly attach the two sides, with polarity reversal loosening the connection with no permanent effects. This is what a group of researchers have been investigating for a few years now, with the most recent paper on the topic called Reversibly Sticking Metals and Graphite to Hydrogels and Tissues by [Wenhao Xu] and colleagues published this year in ACS Central Science.

This follows on the 2021 study published in Nature Communications by [Leah K. Borden] and colleagues titled Reversible electroadhesion of hydrogels to animal tissues for suture-less repair of cuts or tears. In this study a cationic hydrogel (quaternized dimethyl aminoethyl methacrylate, QDM) was reversibly bonded to bovine aorta and other tissues, with said tissues functioning as the anionic element. Despite demonstrated functionality, the exact mechanism which made the application of 3-10 VDC (80 – 125 mA) for under a minute (10+ seconds) cause both sides to bond so tightly, and reversibly, is still unknown. This is where the recent study provides a mechanism and expands the applications.

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A Single Transistor Solid State Tesla Coil

March 30, 2024 by 10 Comments

Tesla coils are one of those builds that capture the interest of almost anybody passing by. For the naïve constructor, they look simple enough, but they can be finicky beasts—beasts that can bite if not treated with respect. [Mirko Pavleski] has some experience with them and shares it with us over on Hackaday.io. One of the first big improvements of this build style is the shift from the originally used spark gap commutator to that of a direct AC drive via a MOSFET oscillator. This improves the primary drive power for its size and eliminates that noisy spark gap. That’s one less source of broadband RF noise and the audible racket these produce.

A hand holding a secondary coil for a Tesla coil build
You can buy ready-wound secondary coils from the usual CN suppliers

The primary side of a Tesla coil is usually a handful of turns of thick wire to handle the current without melting. This build runs at two or three amps, giving a primary power of around 150 Watts. However, this is quite a small unit; with larger ones, the power is much higher, and the resulting discharge sparks much longer. On the secondary side, the air-coupled coil is formed from 520 turns of much thinner wire since it doesn’t need to convey so much current. That’s the thing with transformers with large turns ratios — the secondary voltage will be much higher, and the current will be correspondingly much lower. The idea with Tesla coils is that the secondary circuit forms a resonant circuit with the ‘top load’, usually some hollow metal can. This forms an LC circuit with a corresponding resonant frequency dependent on the secondary inductance values, the object’s capacitance and anything else connected. The primary circuit is designed to resonate at this same frequency to give maximum power coupling across the air gap. Changing either circuit can spoil this balance unless there is a feedback circuit to keep it in check. This could be with a sense coil, a local antenna or something more direct, like in this case.

To ensure the primary circuit doesn’t melt, it needs to be able to drive a reasonable current at this frequency, often in the low MHz range. This leads to a common difficulty: ensuring the switching transistor and rectifying diode are fast enough at the required current level with enough margin. [Mirko] points out several components that can achieve the operating frequency of around 1.7 MHz, which his top load configuration indicates.

For a bit more info on building these fascinating devices, you could check out our earlier coverage, like this useful guide. Of course, simple can be best. How about a design with just three components?

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A Practical Guide To Understanding How Radios Work

March 30, 2024 by 9 Comments

How may radios do you own? Forget the AM/FM, GMRS/FRS radios you listen to or communicate with. We’re talking about the multiple radios and antennas in your phone, your TV, your car, your garage door opener, every computing device you own- you get the idea. It’s doubtful that you can accurately count them even in your own home. But what principles of the electromagnetic spectrum allow radio to work, and how do antenna design, modulation, and mixing affect it? [Michał Zalewski] aka [lcamtuf] aims to inform you with his excellent article Radios, how do they work?

A simple illustration compares a capacitor to a dipole antenna.
A simple illustration compares a capacitor to a dipole antenna.

For those of you with a penchant for difficult maths, there’s some good old formulae published in the article that’ll help you understand the physics of radio. For the rest of us, there are a plethora of fantastic illustrations showing some of the less obvious principals, such as why a longer diploe is more directional than a shorter dipole.

The article opens with a thought experiment, explaining how two dipole antennas are like capacitors, but then also explains how they are different, and why a 1/4 wave dipole saves the day. Of course it doesn’t stop there. [lcamtuf]’s animations show the action of a sine wave on a 1/4 wave dipole, bringing a nearly imaginary concept right into the real world, helping us visualize one of the most basic concepts of radio.

Now that you’re got a basic understanding of how radios work, why not Listen to Jupiter with your own homebrew receiver?