Breadboard for vacuum tubes

This Board Helps You Prototype Circuits With Tubes

September 14, 2025 by 11 Comments

There you are at the surplus store, staring into the bin of faded orange, yellow, red, and black, boxes–a treasure trove of vintage vacuum tubes—dreaming about building a tube amp for your guitar or a phonograph preamp for your DIY hi-fi sound system. But, if you are not already in possession of a vintage, purpose-built tube testing device, how would you test them to know whether they are working properly? How would you test out your designs before committing to them? Or maybe your goal is simply to play around and learn more about how tubes work.

One approach is to build yourself a breadboard for tubes, like [MarceloG19] has done. Working mostly with what was laying around, [MarceloG19] built a shallow metal box to serve as a platform for a variety of tube sockets and screw terminals. Connecting the terminals to the socket leads beneath the outer surface of the box made for a tidy and firm base on which to connect other components. The built-in on/off switch, fuse and power socket are a nice touch.

[MarceloG19’s] inaugural design is a simple Class A amplifier, tested with a sine wave and recorded music. Then it’s on to some manual curve tracing, to test a tube that turns out to be fairly worn-out but serviceable for certain use cases.

If you’re dipping your toes into tube-based electronics, you’re going to want a piece of equipment like this prototyping board and [MarceloG19’s] documentation and discussion are a good read to help get you started.

Once you have your board ready, it’s time to move on to building a stereo amplifier , a tube-based headphone preamp, or take things in a different direction with this CRT-driven audio amplifier.

Reverse-Engineering The Milwaukee M18 Diagnostics Protocol

September 14, 2025 by 15 Comments

As is regrettably typical in the cordless tool world, Milwaukee’s M18 batteries are highly proprietary. Consequently, this makes them a welcome target for reverse-engineering of their interfaces and protocols. Most recently the full diagnostic command set for M18 battery packs were reverse-engineered by [ToolScientist] and others, allowing anyone to check useful things like individual cell voltages and a range of statistics without having to crack open the battery case.

These results follow on our previous coverage back in 2023, when the basic interface and poorly checksummed protocol was being explored. At the time basic battery management system (BMS) information could be obtained this way, but now the range of known commands has been massively expanded. This mostly involved just brute-forcing responses from a gaggle of battery pack BMSes.

Interpreting the responses was the next challenge, with responses like cell voltage being deciphered so far, but serial number and the like being harder to determine. As explained in the video below, there are many gotchas that make analyzing these packs significantly harder, such as some reads only working properly if the battery is on a charger, or after an initial read.

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From Paper To Pixels: A DIY Digital Barograph

September 14, 2025 by 6 Comments

A barograph is a device that graphs a barometer’s readings over time, revealing trends that can predict whether stormy weather is approaching or sunny skies are on the way. This DIY Digital Barograph, created by [mircmk], offers a modern twist on a classic technology.

Dating back to the mid-1700s, barographs have traditionally used an aneroid cell to move a scribe across paper that advances with time, graphing pressure trends. However, this method has its shortcomings: you must replace the paper once it runs through its time range, and mechanical components require regular maintenance.

[mircmk]’s DIY Digital Barograph ditches paper and aneroids for a sleek 128×64 LCD display that shows measurements from a BME280 pressure sensor. Powered by an ESP32 microcontroller — the code for which is available on the project page — the device checks the sensor upon boot and features external buttons to cycle through readings from the current moment, the last hour, or three hours ago. Unlike traditional barographs that only track pressure, the BME280 also measures temperature and humidity, which are displayed on the screen for a more complete environmental snapshot.

Head over to the project’s Hackaday.io page for more details and to start building your own. Thanks to [mircmk] for sharing this project! We’re excited to see what you come up with next. If you’re inspired, check out other weather display projects we’ve featured.

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3D Modeling With Paper As An Alternative To 3D Printing

September 13, 2025 by 30 Comments
Manual arrangement of the parts in Pepakura Designer. (Credit: Arvin Podder)
Manual arrangement of the parts in Pepakura Designer. (Credit: Arvin Podder)

Although these days it would seem that everyone and their pets are running 3D printers to churn out all the models and gadgets that their hearts desire, a more traditional approach to creating physical 3D models is in the form of paper models. These use designs printed on paper sheets that are cut out and assembled using basic glue, but creating these designs is much easier these days, as [Arvin Poddar] demonstrates in a recent article.

The cool part about making these paper models is that you create them from any regular 3D mesh, with any STL or similar file from your favorite 3D printer model site like Printables or Thingiverse being fair game, though [Arvin] notes that reducing mesh faces can be trickier than modelling from scratch. In this case he created the SR-71 model from scratch in Blender, featuring 732 triangles. What the right number of faces is depends on the target paper type and your assembly skills.

Following mesh modelling step is mesh unfolding into a 2D shape, which is where you have a few software options, like the paid-for-but-full-featured Pepakura Designer demonstrated, as well as the ‘Paper Model’ exporter for Blender.

Beyond the software used to create the SR-71 model in the article, the only tools you really need are a color printer, paper, scissor,s and suitable glue. Of course you are always free to use fancier tools than these to print and cut, but the bar here is pretty low for the assembly. Although making functional parts isn’t the goal here, there is a lot to be said for paper models for pure display pieces and to get children interested in 3D modelling.

Aussie Researchers Say They Can Bring The Iron Age To Mars

September 13, 2025 by 42 Comments
It’s not martian regolith, bu it’s the closest chemical match available to the dirt in Gale Crater. (Image: Swinburne University)

Every school child can tell you these days that Mars is red because it’s rusty. The silicate rock of the martian crust and regolith is very rich in iron oxide. Now Australian researchers at CSIRO and Swinburn University claim they know how to break that iron loose.

In-situ Resource Utilization (IRSU) is a big deal in space exploration, with good reason. Every kilogram of resources you get on site is one you don’t have to fight the tyranny of the rocket equation for. Iron might not be something you’d ever be able to haul from Earth to the next planet over, but when you can make it on site? You can build like a Victoria is still queen and it’s time to flex on the French.

The key to the process seems to be simple pyrolysis: they describe putting dirt that is geochemically analogous to martian regolith into a furnace, and heating to 1000 °C under Martian atmospheric conditions to get iron metal. At 1400 °C, they were getting iron-silicon alloys– likely the stuff steelmakers call ferrosilicon, which isn’t something you’d build a crystal palace with.

It’s not clear how economical piling red dust into a thousand-degree furnace would be on Mars– that’s certainly not going to cut it on Earth– but compared to launch costs from Earth, it’s not unimaginable that martian dirt could be considered ore.

The schematic on the left and the assembled circuit on the right.

How To Make A Simple MOSFET Tester

September 13, 2025 by 22 Comments

Over on YouTube our hacker [VIP Love Secretary] shows us how to make a simple MOSFET tester.

This is a really neat, useful, elegant, and simple hack, but the video is kind of terrible. We found that the voice-over constantly saying “right?” and “look!” seriously drove us to distraction. But this is a circuit which you should know about so maybe do what we did and watch the video with subtitles on and audio off.

To use this circuit you install the MOSFET you want to test and then press with your finger the spare leg of each of two diodes; in the final build there are some metal touch pads attached to the diodes to facilitate this. One diode will turn the MOSFET off, the other diode will turn the MOSFET on, and the LED will show you which is which.

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Send Images To Your Terminal With Rich Pixels

September 13, 2025 by 10 Comments

[darrenburns]’ Rich Pixels is a library for sending colorful images to a terminal. Give it an image, and it’ll dump it to your terminal in full color. While it also supports ASCII art, the cool part is how it makes it so easy to display an arbitrary image — a pixel-art rendition of it, anyway — in a terminal window.

How it does this is by cleverly representing two lines of pixels in the source image with a single terminal row of characters. Each vertical pixel pair is represented by a single Unicode ▄ (U+2584 “lower half block”) character. The trick is to set the background color of the half-block to the upper pixel’s RGB value, and the foreground color of the half-block to the lower pixel’s RGB. By doing this, a single half block character represents two vertically-stacked pixels. The only gotcha is that Rich Pixels doesn’t resize the source image; if one’s source image is 600 pixels wide, one’s terminal is going to receive 600 U+2584 characters per line to render the Rich Pixels version.

[Simon WIllison] took things a step further and made show_image.py, which works the same except it resizes the source image to fit one’s terminal first. This makes it much more flexible and intuitive.

The code is here on [Simon]’s tools GitHub, a repository for software tools he finds useful, like the Incomplete JSON Pretty Printer.