Voltage Divider? Filter? It’s Both!

July 10, 2025 by Al Williams 3 Comments

When we do textbook analysis, we tend to ignore the real-world concerns for the sake of learning. So, a typical theoretical voltage divider is simply two resistors. But if you examine a low-pass RC filter, you’ll see a single resistor and a capacitor. What if you combine them? That’s what [Old Hack EE] did in a recent video, and you can check it out below.

It helps if you are familiar with Thevenin equivalents and, of course, Ohm’s Law. There’s also a bit of algebra, but nothing too complicated. The example design has a lossy filter at 100 Hz.

Of course, RC filters are easy to understand if you think of them as voltage dividers with a frequency-variable resistance, which is what the math is basically saying. The load impedance, in this case, is R2 in parallel with Xc at a given frequency.

He mentions that you might find a circuit like this in a power supply. However, it is also common to see this circuit wherever a divider drives a load with capacitance or even parasitic capacitance in cables or circuit boards.

We’ve discussed Thevenin equivalence modeling before. If you want really good filters, you are probably going to need op-amps.

Continue reading “Voltage Divider? Filter? It’s Both!” →

Personal Reflections On Immutable Linux

July 10, 2025 by Tyler August 51 Comments

Immutable distributions are slowly spreading across the Linux world– but should you care? Are they hacker friendly? What does “immutable” mean, anyway?

Immutable means “not subject or susceptible to change” according to Merriam-Webster, which is not 100% accurate in this context, but it’s close enough and the name is there so we’re stuck with it. Immutable distributions are subject to change, it’s just that how you change them is quite a bit different than bog-standard Linux. Will this matter to you? Read on to find out! (Or, if you know the answers already, read on to find out how angry you should be in the comments section.) Continue reading “Personal Reflections On Immutable Linux” →

A black and white illustration of people with headphones or microphones and floating empty speech bubbles. They appear happy and engaged with each other in a pleasant, park-like environment. In the foreground, on top of a wall, various anthropomorphized big tech logos like Apple, Amazon, and Google spy down on the people with binoculars like hunters assessing their prey. The text reads, "But like any good thing on the internet, there's a big tech monopoly trying to ruin it."

Long Live RSS!

July 10, 2025 by Navarre Bartz 34 Comments

While we know that many of you are reading Hackaday via our Really Simple Syndication (RSS) feed, we suspect that most people on the street wouldn’t know that it underlies a lot of the modern internet. [A. McNamee] and [A. Service] have created an illustrated history of RSS that proudly proclaims RSS is (not) dead (yet)!

While tens of millions of users used Google Reader before it was shut down, social media and search companies have tried to squeeze independent blogs and websites for an increasingly large part of their revenue, making it more and more difficult to exist outside the walled gardens of Facebook, Apple, Google, etc. Despite those of you that remember, RSS has been mostly forgotten.

RSS has been the backbone of the podcast industry, however, quietly serving feeds to millions of users everywhere with few of them aware that an open protocol from the 90s was serving up their content. As with every other corner of the internet where money could be made, corporate raiders have come to scoop up creators and skim the profits for themselves. Spotify has been the most egregious actor here, but the usual suspects of Apple, Google, and Amazon are also making plays to enclose the podcast commons.

If you’d like to learn more about how big tech is sucking the life out of the internet (and possibly how to reverse the enshittification) check out Cory Doctorow’s keynote from our very own Supercon.

Ask Hackaday: Are You Wearing 3D Printed Shoes?

July 10, 2025 by Al Williams 50 Comments

We love 3D printing. We’ll print brackets, brackets for brackets, and brackets to hold other brackets in place. Perhaps even a guilty-pleasure Benchy. But 3D printed shoes? That’s where we start to have questions.

Every few months, someone announces a new line of 3D-printed footwear. Do you really want your next pair of sneakers to come out of a nozzle? Most of the shoes are either limited editions or fail to become very popular.

First World Problem

You might be thinking, “Really? Is this a problem that 3D printing is uniquely situated to solve?” You might assume that this is just some funny designs on some of the 3D model download sites. But no. Adidas, Nike, and Puma have shoes that are at least partially 3D printed. We have to ask why.

We are pretty happy with our shoes just the way that they are. But we will admit, if you insist on getting a perfect fitting shoe, maybe having a scan of your foot and a custom or semi-custom shoe printed is a good idea. Zellerfield lets you scan your feet with your phone, for example. [Stefan] at CNC Kitchen had a look at those in a recent video. The company is also in many partnerships, so when you hear that Hugo Boss, Mallet London, and Sean Watherspoon have a 3D-printed shoe, it might actually be their design from Zellerfield.

Continue reading “Ask Hackaday: Are You Wearing 3D Printed Shoes?” →

An Emulated Stroll Down Macintosh Memory Lane

July 10, 2025 by Tyler August 6 Comments

If you’re into Macs, you’ll always remember your first. Maybe it was the revolutionary classic of 1984 fame, perhaps it was the adorable G3 iMac in 1998, or even a shiny OS X machine in the 21st century. Whichever it is, you’ll find it emulated in [Marcin Wichary]’s essay “Frame of preference: A history of Mac settings, 1984–2004” — an exploration of the control panel and its history.

Image of PowerBook showing the MacOS 8.0 desktop. — That’s not a photograph, it’s an emulator. (At least on the page. Here, it’s a screenshot.)

[Marcin] is a UI designer as well as an engineer and tech historian, and his UI chops come out in full force, commenting and critiquing Curputino’s coercions. The writing is excellent, as you’d expect from the man who wrote the book on keyboards, and it provides a fascinating look at the world of retrocomputing through the eyes of a designer. That design-focused outlook is very apropos for Apple in particular. (And NeXT, of course, because you can’t tell the story of Apple without it.)

There are ten emulators on the page, provided by [Mihai Parparita] of Infinite Mac. It’s like a virtual museum with a particularly knowledgeable tour guide — and it’s a blast, getting to feel hands-on, the design changes being discussed. There’s a certain amount of gamification, with each system having suggested tasks and a completion score when you finish reading. There are even Easter eggs.

This is everything we wish the modern web was like: the passionate deep-dives of personal sites on the Old Web, but enhanced and enabled by modern technology. If you’re missing those vintage Mac days and don’t want to explore them in browser, you can 3D print your own full-size replica, or a doll-sized picoMac.

Generatively-Designed Aerospike Test Fired

July 10, 2025 by Navarre Bartz 28 Comments

The aerospike engine holds great promise for spaceflight, but for various reasons, has remained slightly out of reach for decades. But thanks to Leap 71, the technology has moved one step closer to a spacecraft near you with the test fire of their generatively-designed, 3D printed aerospike.

We reported on the original design process of the engine, but at the time it hadn’t been given a chance to burn its liquid oxygen and kerosene fuel. The special sauce was the application of a computational physics model to tackle the complex issue of keeping the engine components cool enough to function while directing 3,500˚C exhaust around the eponymous spike.

Printed via a powder bed process out of CuCrZr, cleaned, heat treated, and then prepped by the University of Sheffield’s Race 2 Space Team, the rocket produced 5,000 Newtons (1,100 lbf) of thrust during its test fire. For comparison, VentureStar, the ill-fated aerospike single stage to orbit project from the 1990s, was projected to produce more than 1,917 kilonewtons (431,000 lbf) from each of its seven RS-2200 engines. Leap 71 obviously has some scaling up to do before this can propel any crewed spacecraft.

If you want to build your own aerospike or 3D printed rocket nozzles we encourage you to read, understand, and follow all relevant safety guidelines when handling your rockets. It is rocket science, after all!

Solder Smarts: Hands-Free Fume Extractor Hack

July 9, 2025 by Matt Varian 8 Comments

[Ryan] purchased a large fume extractor designed to sit on the floor below the work area and pull solder fumes down into its filtering elements. The only drawback to this new filter was that its controls were located near his feet. Rather than kicking at his new equipment, he devised a way to automate it.

By adding a Wemos D1 Mini microcontroller running ESPHome, a relay board, and a small AC-to-DC transformer, [Ryan] can now control the single push button used to cycle through speed settings wirelessly. Including the small transformer inside was a clever touch, as it allows the unit to require only a single power cable while keeping all the newfound smarts hidden inside.

The relay controls the button in parallel, so the physical button still works. Now that the extractor is integrated with Home Assistant, he can automate it. The fan can be controlled via his phone, but even better, he automated it to turn on by monitoring the power draw on the smart outlet his soldering iron is plugged into. When he turns on his iron, the fume extractor automatically kicks in.

Check out some other great automations we’ve featured that take over mundane tasks.