Author: Al Williams

4292 Articles

A Nuclear Physics Lab In Your Pocket

October 25, 2025 by 17 Comments

If you want to work with radioactive material, a cheap Geiger counter isn’t really what you want. According to [Project 326], you need a gamma ray spectrometer. The video below reviews the Radiacode 110. The channel has reviewed other Radiacode products, and they haven’t always been pleased with them, apparently. Is the 110 better?

The little spectrometer uses a scintillation crystal and performs a spectrogram on the result. It has a large library of materials so, at least for radioactive materials, you can point it at something and tell what kind of material you are dealing with and how radioactive it is.

While the smartphone app seems well done, the Windows application left something to be desired. Even still, it was able to identify several isotopes. The device can even pick up some alpha emitters that don’t directly register. However, it can identify some materials by different decomposition products. Unlike some earlier models, this device is supposed to be highly sensitive and high-resolution.

To confirm this, [Project 326] built a lead shielding structure and read a reference sample. Crunching some numbers confirmed that the claimed performance was accurate. It could even read very low-energy sources, though there were some limitations. The ergonomics of the device could be better, apparently, but it does deliver on performance.

Do you need a gamma ray spectrometer? We don’t know, but we suspect if you do, you don’t need us to tell you.

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What If Tinkercad Was Self-Hosted?

October 25, 2025 by 31 Comments

While we use a lot of CAD tools, many of us are fans of Tinkercad — especially for working with kids or just doing something quick. But many people dislike having to work across the Internet with their work stored on someone’s servers. We get it. So does [CommonWealthRobotics], which offers CaDoodle. It is nearly a total clone of Tinkercad but runs on Windows, Linux, Mac, or even Chrome OS.

Is it exactly Tinkercad? No, but that’s not always a bad thing. For example, CaDoodle can work with Blender, FreeCAD, OpenSCAD, and more. However, on the business end, it sure looks like the core functions of Tinkercad.

The program appears fairly new, so you have to make some allowances. For example, the Linux AppImage seems to have difficulty loading plugins (which it needs to import many of its file formats). In addition, on at least some systems, you have to resize the window after it starts, or it won’t respond. But, overall, it is pretty impressive. The Settings, by the way, has a checkbox for advanced features, and there are some other goodies there, too.

One reason we found this interesting is that we sometimes go into schools, and they don’t want us to have kids on the Internet. Of course, they don’t like us installing random software either, so you can pick your battles.

Tinkercad, of course, continues to add features. Not all of which you’d expect in a drawing package.

Relay Computer Knows The Sequence

October 25, 2025 by 11 Comments

When we first saw [DiPDoT’s] homebrew computer, we thought it was an Altair 8800. But, no. While it has a very familiar front panel, the working parts are all based on relays. While it isn’t finished, the machine can already do some simple calculations as you can see in the video below.

Turns out, the Altair front panel isn’t a coincidence. He wants to put the device in an Altair-style case. This limits him to two backplane cards, but he’s running out of space, so part of what he does in the video is redesign the backplanes.

We need to watch some more of these videos to figure out how he’s making his logic gates. A common approach is to wire AND gates as series relays and OR gates as parallel relays. However, there are some advantages to using relays as two-to-one multiplexers, which can create any logic gate you want.

If you just want to see the computer run, you can watch it generate a Fibonacci sequence around the 14:30 mark. Glorious sound from a beautiful bunch of relays. Not exactly a speed demon, mind you, but not half bad for a bunch of electromechanical relays.

There was a time when computers like this were state-of-the-art. In a way, we miss those days. But then again, in some ways, we don’t.

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Teaching Math With 3D Printers

October 25, 2025 by 10 Comments

We’ve often thought that 3D printers make excellent school projects. No matter what a student’s interests are: art, software, electronics, robotics, chemistry, or physics, there’s something for everyone. A recent blog post from [Prusa Research] shows how Johannes Kepler University is using 3D printing to teach math. You can see a video with Professor [Zsolt Lavicza] explaining their vision below.

Instead of relying on abstract 3D shapes projected on a 2D screen, GeoGebra, educational math software, creates shapes that you can produce on a 3D printer. Students can physically handle and observe these shapes in the real world instead of on a flat screen.

One example of how the 3D printer finds use in a math class is producing “Genius Square,” a multilevel tic-tac-toe game. You can find the model for that and other designs used in the classes, on Printables. Some prints are like puzzles where students assemble shapes from pieces.

Putting 3D printers in school isn’t a new idea, of course. However, machines have become much simpler to use in recent years, so maybe the time is now. If you can’t find money for printers in school, you can always teach robotics using some low-tech methods.

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Robot Phone Home…Or Else

October 24, 2025 by 64 Comments

We would have enjoyed [Harishankar’s] tear down of a robot vacuum cleaner, even if it didn’t have a savage twist at the end. Turns out, the company deliberately bricked his smart vacuum.

Like many of us, [Harishankar] is suspicious of devices beaming data back to their makers. He noted a new vacuum cleaner was pinging a few IP address, including one that was spitting out logging or telemetry data frequently. Of course, he had the ability to block the IP address which he did. End of story, right?

No. After a few days of working perfectly, the robot wouldn’t turn on. He returned it under warranty, but the company declared it worked fine. They returned it and, indeed, it was working. A few days later, it quit again. This started a cycle of returning the device where it would work, it would come home and work for a few days, then quit again.

You can probably guess where this is going, but to be fair, we gave you a big hint. The fact that it would work for days after blocking the IP address wouldn’t seem like a smoking gun in real time.

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Why Does The FCC Care About Computers?

October 23, 2025 by 18 Comments

Unless you are over a certain age, you probably take it for granted that electronic gadgets you buy have some FCC marking on them. But it wasn’t always true. [Ernie] submits that the FCC’s regulation of the computer industry was indirectly the result of the success of CB radio in that same time period.

Today, there is a high chance you don’t watch TV directly over the airwaves or even consume audio from a traditional radio station. Even if you do, the signal is increasingly likely to be digital. But only analog radio and TV were highly susceptible to interference. When a professional radio station or the power company interfered with you watching I Love Lucy, you could count on them to resolve it. Even ham radio operators, a small segment of the population, would, in general, graciously help you if their transmissions interfered with your equipment.

Never mind that, in many cases, it was the cheap TV or some other problem on the receiving end. Then there was another source of potential interference: CB radio. At first, you were about as likely to encounter a CB operator as a ham radio operator. But then in the 1970s, CB exploded, becoming a cultural phenomenon, and you can hear what a state it was in by watching the contemporary TV report in the video below.

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Tinkercad In Color

October 22, 2025 by 4 Comments

Tinkercad is famous for having lots of colors in the interface. But once you export an STL, that file is notoriously monochrome. If you are printing with a single color printer, no problems. But if you have a color printer, what do you do? [CHEP] shows some options, including a relatively new one, in the video below.

The simple way is to “paint” the STL inside your slicer. But as [CHEP] shows, that is a pain and also has some undesirable side effects. A better approach is to export each part (or, at least, each part of the same color) into separate STL files, which you can then import together in the slicer. You still have to paint, but you don’t have to select different faces, and the resulting coloring is more what you’d expect.

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