2025-04-03 13:00:33
There seems to be nothing a 555 can’t do. We’ve seen it before, but [electronzapdotcom] reminds us you can use a 555 and a few parts to make a reasonable touch switch. The circuit lives on a breadboard, as shown in the video below.
The circuit uses some very large resistors so that noise from your body can overcome the logic level on the trigger and threshold inputs. You can easily adapt this idea if you need a simple touch switch. Though we imagine this circuit wouldn’t work well if you were in a quiet environment. We suspect 50 or 60 Hz hum is coupling through your finger and triggering the pins, but it could be a different effect.
How reliable is it? Beats us. The circuit is a bistable, so essentially your finger pumps a signal into a flip-flop. This is old trick, but could be useful. Of course, if you really need a touch switch, you have plenty of options. You can get little modules. Or, directly measure skin resistance.
2025-04-03 10:00:16
The plethora of smart home devices available today deliver all manner of opportunities, but it’s fair to say that interfacing with them is more often done in the browser or an app than in the terminal. WattWise from [Naveen Kulandaivelu] is a tool which changes all that, it’s a command-line interface (CLI) for power monitoring smart plugs.
Written in Python, the tool can talk either directly to TP-Link branded smart plugs, or via Home Assistant. It tracks the power consumption with a simple graph, but the exciting part lies in how it can be used to throttle the CPU of a computer in order to use power at the points in the day when it is cheapest. You can find the code in a GitHub repository.
We like the idea of using smart plugs as instruments, even if they may not be the most accurate of measurement tools. It takes them even further beyond the simple functionality and walled-garden interfaces provided by their manufacturers, which in our view can only be a good thing.
Meanwhile, for further reading we’ve looked at smart plugs in detail in the past.
2025-04-03 07:00:16
Somewhere in the universe, there’s a place that lists every x86 operating system from scratch. Not just some bootloaders, or just a kernel stub, but documentation to build a fully functional, interrupt-handling, multitasking-capable OS. [Erik Helin and Adam Renberg] did just that by documenting every step in The Little Book About OS Development.
This is not your typical dry academic textbook. It’s a hands-on, step-by-step guide aimed at hackers, tinkerers, and developers who want to demystify kernel programming. The book walks you through setting up your environment, bootstrapping your OS, handling interrupts, implementing virtual memory, and even tackling system calls and multitasking. It provides just enough detail to get you started but leaves room for exploration – because, let’s be honest, half the fun is in figuring things out yourself.
Completeness and structure are two things that make this book stand out. Other OS dev guides may give you snippets and leave you to assemble the puzzle yourself. This book documents the entire process, including common pitfalls. If you’ve ever been lost in the weeds of segmentation, paging, or serial I/O, this is the map you need. You can read it online or fetch it as a single 75-page long PDF.
Mockup photo source: Matthieu Dixte
2025-04-03 04:00:59
Macro pads are handy for opening up your favorite programs or executing commonly used keyboard shortcuts. But why stop there?
That’s what [Jeroen Brinkman] must have been thinking while creating the Programmer’s Macro Pad. Based on the Arduino Pro Micro, this hand-wired pad is unique in that a single press of any of its 16 keys can virtually “type” out multiple lines of text. In this case, it’s a capability that’s being used to prevent the user from having to manually enter in commonly used functions, declarations, and conditional statements.
For example, in the current firmware, pressing the “func” key will type out a boilerplate C function:
int () { //
;
return 0;
}; // f
It will also enter in the appropriate commands to put the cursor where it needs to be so you can actually enter in the function name. The other keys such as “array” and “if” work the same way, saving the user from having to enter (and potentially, even remember) the correct syntax.
The firmware is kept as simple as possible, meaning that the functionality of each key is currently hardcoded. Some kind of tool that would let you add or change macros without having to manually edit the source code and flash it back to the Arduino would be nice…but hey, it is a Programmers Macro Pad, after all.
Looking to speed up your own day-to-day computer usage? We’ve covered a lot of macro pads over the years, we’re confident at least a few of them should catch your eye.
2025-04-03 02:30:38
This week, Jonathan Bennett chats with Bashonly about yt-dlp, the audio/video downloader that carries the torch from youtube-dl! Why is this a hard problem, and what does the future hold for this swiss-army knife of video downloading? Watch to find out!
Did you know you can watch the live recording of the show right on our YouTube Channel? Have someone you’d like us to interview? Let us know, or contact the guest and have them contact us! Take a look at the schedule here.
Direct Download in DRM-free MP3.
If you’d rather read along, here’s the transcript for this week’s episode.
Theme music: “Newer Wave” Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
2025-04-03 01:02:15
Tattoos. Body paint. Henna. All these are popular kinds of body art with varying histories and cultural connotations, many going back centuries or even longer. They all have something in common, though—they all change how the body reflects light back to the viewer. What if, instead, body art could shine a light of its very own?
This is the precise topic which [Katherine Connell] came to discuss at the 2024 Hackaday Supercon. Her talk concerns rethinking body art with the use of light emitting diodes—and is both thoroughly modern and aesthetically compelling. Beyond that, it’s an engineering development story with liquid metal and cutting-edge batteries that you simply don’t want to miss!
The inspiration behind this project was simple. [Katherine] grew up in the 80s, and being exposed to that neon-soaked era gave her a desire to glow-in-the-dark. However, she didn’t want to get into any hardcore body modification—hence, she pursued a non-invasive stick-on solution.
As you might imagine, creating these wasn’t trivial. They need to stick to the skin for long periods of time without causing irritation, while also being lightweight and slim enough to be practical to wear. Indeed, to that end, Sprite Lights are less than 1.5 mm thick—an impressive engineering feat.
Her first attempts involved creating a synthetic skin-like material using latex, with LEDs stuck underneath. However, this wasn’t a particularly desirable solution. Latex allergies are relatively common, and producing the designs took a lot of careful hand-soldering and manual work. It was also difficult to attach the latex to the skin, and to color match it with the wearer to make it look right.
From there, [Katherine] experimented with 3D-printing thin films with transparent PLA, with LEDs underneath. This was a much quicker way to work, but still didn’t attach well to the skin and had some aesthetic flaws. Another 3D-printing attempt saw [Katherine] create molds to produce transparent silicone films with LEDs embedded underneath, but this again proved very labor intensive and it’s difficult to get silicone to stick to anything, including humans. [Katherine] even tried experimenting with Galinstan, a very off-beat metallic alloy, to make circuits inside flexible silicone. She created viable stretchable circuits but they were not very robust, particularly since the Galinstan tends to melt at body temperature.
Having developed decent flexible circuits that could light up, power was next on the agenda. Desiring to create stick-on devices with an ultra-thin form factor, there was no room to include a traditional battery, so [Katherine] had to figure out how to power Sprite Lights effectively. She found flexible batteries from a company called Zinergy that could deliver 3V and 20 mAh. She was able to specify a custom flat round design, with the company able to make them just 0.7mm thick and 55 mm round. They use a compound similar to regular AA batteries, which is screen printed onto one layer of plastic and sealed with another layer on top. The batteries have the benefit of being safe to place on skin, with no risk of explosion or chemical exposure, even if they happen to be punctured or cut while worn. Perhaps the only drawback is that they’re non-rechargeable—they’re safe, but single-use.
Armed with her new batteries, [Katherine] developed her concept further. She stepped up to using commercially-available flex PCBs produced by JLCPCB, in place of her homebrewed concepts used previously. She combined these with the flexible Zinergy batteries underneath, and custom-made die-cut stickers from MakeStickers on top. This gave her an art layer, an LED circuit layer, and a battery layer underneath, with a hypoallergenic medical tape used as the final layer to stick the assembly to the skin. An intermediate fabric tape layer is included to connect the battery’s contacts to the flex PCB, which is populated with LEDs. By leaving a paper layer on the fabric tape between the contacts, this allows the Sprite Light to remain off until it’s ready to be used. The combination comes in under 1.5 mm thick.
ED NOTE: Grabbed some pictures from the SpriteLights website.
Ultimately, Sprite Lights are a super-cool piece of body art. But beyond that, [Katherine] told us the great engineering story behind these astounding self-glowing stickers. As her fine example demonstrates, you can do really cool things if you just keep working at it and teach yourself the right skills along the way!
