DIY Strontium Aluminate Glows In The Dark

[Maurycyz] points out right up front: several of the reagents used are very corrosive and can produce toxic gasses. We weren’t sure if they were trying to dissuade us not to replicate it or encourage us to do so. The project in question is making strontium aluminate which, by the way, glows in the dark.

The material grows strongly for hours and, despite the dangers of making it, it doesn’t require anything very exotic. As [Maurycyz] points out, oxygen and aluminum are everywhere. Strontium sounds uncommon, but apparently, it is used in ceramics.

For the chemists among us, there’s an explanation of how to make it by decomposing soluble nitrate salts. For the rest of us, the steps are to make aluminum hydroxide using potassium alum, a food preservative, and sodium hydroxide. Then, it is mixed with nitric acid, strontium carbonate, europium, and dysprosium. Those last elements determine the color of the glow.

A drying step removes the acid, followed by dissolving with urea and water. The heat of the reaction wasn’t enough to form the final product, but it took time with an oxy-propane torch to form blobs of strontium aluminate. The product may not have been pure, because it didn’t glow for hours like commercial preparations. But it did manage to glow for a few minutes after light exposure.

We try to limit our chemistry to less toxic substances, although ferric chloride can make a mess. You could probably track down the impurities with a gas chromatograph. What we really want is a glow-in-the-dark car antenna.

Time-of-Flight Sensors: How Do They Work?

With the right conditions, this tiny sensor can measure 12 meters

If you need to measure a distance, it is tempting to reach for the ubiquitous ultrasonic module like an HC-SR04. These work well, and they are reasonably easy to use. However, they aren’t without their problems. So maybe try an IR time of flight sensor. These also work well, are reasonably easy to use, and have a different set of problems. I recently had a project where I needed such a sensor, and I picked up a TF-MiniS, which is a popular IR distance sensor. They aren’t very expensive, and they work serial or I2C. So how did it do?

The unit itself is tiny and has good specifications. You can fit the 42 x 15 x 16 mm module anywhere. It only weighs about five grams — as the manufacturer points out, less than two ping-pong balls. It needs 5 V but communicates using 3.3 V, so integration isn’t much of a problem.

At first glance, the range is impressive. You can read things as close as 10 cm and as far away as 12 m. I found this was a bit optimistic, though. Although the product sometimes gets the name of LiDAR, it doesn’t use a laser. It just uses an IR LED and some fancy optics.

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Robotics Class Is Open

If you are like us, you probably just spin up your own code for a lot of simple projects. But that’s wasteful if you are trying to do anything serious. Take a robot, for example. Are you using ROS (Robot Operating System)? If not — or even if you are — check out [Janne Karttunene] and the University of Eastern Finland’s open-source course Robotics and ROS 2 Essentials.

The material is on GitHub. Rather than paraphrase, here’s the description from the course itself:

This course is designed to give you hands-on experience with the basics of robotics using ROS 2 and Gazebo simulation. The exercises focus on the Andino robot from Ekumen and are structured to gradually introduce you to ROS 2 and Docker.

No prior experience with ROS 2 or Docker is needed, and since everything runs through Docker, you won’t need to install ROS 2 on your system beforehand. Along the way, you’ll learn essential concepts like autonomous navigation and mapping for mobile robots. All the practical coding exercises are done in Python.

Topics include SLAM, autonomous navigation, odometry, and path planning. It looks like it will be a valuable resource for anyone interested in robotics or anything else you might do with ROS.

If you want a quick introduction to ROS, we can help. We’ve seen a number of cool ROS projects over the years.

Forgotten Internet: UUCP

What’s Forgotten Internet? It is the story of parts of the Internet — or Internet precursors — that you might have forgotten about or maybe you missed out on them. This time, we’re looking at Unix-to-Unix Copy, more commonly called UUCP. Developed in the late 1970s, UUCP was a solution for sending messages between systems that were not always connected together. It could also allow remote users to execute commands. By 1979, it was part of the 7th Edition of Unix.

Ken Thompson and Dennis Ritchie may have used UUCP on a PDP-11 like this one. (Photo via Computer History Museum/Gwen Bell)

Operation was simple. Each computer in a UUCP network had a list of neighbor systems. Don’t forget, they weren’t connected, so instead of an IP address, each system had the other’s phone number to connect to a dial up modem. You also needed a login name and password. Almost certainly, by the way, those modems operated at 300 baud or less.

If a computer could dial out, when someone wanted to send something or do a remote execution, the UUCP system would call a neighboring computer. However, some systems couldn’t dial out, so it was also possible for a neighbor to call in and poll to see if there was anything you needed to do. Files would go from one system to another using a variety of protocols.

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No Ham License? Listen Anyway In Your Browser

Full disclosure: ham radio isn’t for everyone, and there are many different facets to it. What appeals to one person might bore another to death. One area of ham radio that has changed a lot in the last few years is more or less local and typically mobile operation on VHF or UHF. Not long ago, hams used HTs (walky-talkies or handi-talkies) or mobile radios via repeaters to talk to each other and — the golden prize back then — make phone calls from their cars. Cell phones have made that much less interesting, but there is still an active community of operators talking on repeaters. However, the traffic has gone digital, the Internet is involved, and people with inexpensive, low-powered radios can talk to each other across the globe. This is nothing new, of course. However, having digital services means that operators with special interests can congregate in what amounts to radio chat rooms organized by region or topic.

There’s a long history of people listening to ham radio conversations with shortwave radios, SDRs, and scanners. But with so much activity now carried on the Internet, you can listen in using nothing more than your web browser or a phone app. I’ll show you how. If you get interested enough, it is easy enough to get your license. You don’t need any Morse code anymore, and a simple Technician class license in the United States is all you need to get going.

A Quick DMR Primer

There are several digital ham networks around and like real networks, you can have different physical transport layers and then build on top of that. For the purposes of this post, I’m going to focus on DMR (digital mobile radio) on the Brandmeister network which is very large and popular ham network. You won’t need a license nor will you need to sign up for anything as long as you are content to just listen.

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Head To Head: Servos Vs Steppers

You have a project that needs something to move. Should you use a stepper motor or a servo motor? [Matthias] has an opinion, and you can hear his thoughts in the video below. One tip we’ll take away from the video: when working with motors, shoot some high-frame-rate video and slow it down to see what’s really happening.

The initial tests looked fine at normal speed. But increasing the frame rate and decreasing the playback speed showed some very interesting things like how much each motor was overshooting. The ability to control this sort of thing is a key differentiator for these kinds of motors.

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Gaming Table Has Lights, Action

We couldn’t decide if [‘s] Dungeons and Dragons gaming table was a woodworking project with some electronics or an electronics project with some woodworking. Either way, it looks like a lot of fun.

Some of the features are just for atmosphere. For example, the game master can set mood lighting. Presets can have a particular light configuration for, say, the woods or a cave.

But the table can also be a game changer since the game runner can send private messages to one or more players. Imagine a message saying, “You feel strange and suddenly attack your own team without any warning.”

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