Challenge: Square A Voltage

July 1, 2025 by Al Williams 17 Comments

Your design task, should you decide to accept it: given an input voltage, square it. Ok, that’s too hard since squaring 8 volts would give you 64 volts, so let’s say the output should be 10% of the square, so 8 volts in would result in 6.4V. How do you do it? [Engineering Prof.] knows how and will show you what you can do in the video below.

The circuit uses two op amps and some transistors. However, the transistors are used in a way that depends on the temperature, so it is important to use a transistor array so they are matched and will all be at the same temperature.

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Phone Keyboard Reverse Engineered

June 30, 2025 by Al Williams 3 Comments

Who knows what you’ll find in a second-hand shop? [Zeal] found some old keyboards made to fit early Alcatel phones from the year 2000 or so. They looked good but, of course, had no documentation. He’s made two videos about his adventure, and you can see them below.

The connector was a cellphone-style phone jack that must carry power and some sort of serial data. Inside, there wasn’t much other than a major chip and a membrane keyboard. There were a few small support chips and components, too.

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Pi Networks The Smith Chart Way

June 26, 2025 by Al Williams 10 Comments

[Ralph] is excited about impedance matching, and why not? It is important to match the source and load impedance to get the most power out of a circuit. He’s got a whole series of videos about it. The latest? Matching using a PI network and the venerable Smith Chart.

We like that he makes each video self-contained. It does mean if you watch them all, you get some review, but that’s not a bad thing, really. He also does a great job of outlining simple concepts, such as what a complex conjugate is, that you might have forgotten.

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Rust Drives A Linux USB Device

June 26, 2025 by Al Williams 13 Comments

In theory, writing a Linux device driver shouldn’t be that hard, but it is harder than it looks. However, using libusb, you can easily deal with USB devices from user space, which, for many purposes, is fine. [Crescentrose] didn’t know anything about writing user-space USB drivers until they wrote one and documented it for us. Oh, the code is in Rust, for which there aren’t as many examples.

The device in question was a USB hub with some extra lights and gadgets. So the real issue, it seems to us, wasn’t the code, but figuring out the protocol and the USB stack. The post covers that, too, explaining configurations, interfaces, and endpoints.

There are other ancillary topics, too, like setting up udev. This lets you load things when a USB device (or something else) plugs in.

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Ceramic Printing Techniques For Plastic

June 25, 2025 by Al Williams No comments

[Claywoven] mostly prints with ceramics, although he does produce plastic inserts for functional parts in his designs. The ceramic parts have an interesting texture, and he wondered if the same techniques could work with plastics, too. It turns out it can, as you can see in the video below.

Ceramic printing, of course, doesn’t get solid right away, so the plastic can actually take more dramatic patterns than the ceramic. The workflow starts with Blender and winds up with a standard printer.

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The Tao Of Bespoke Electronics

June 25, 2025 by Al Williams 60 Comments

If you ever look at projects in an old magazine and compare them to today’s electronic projects, there’s at least one thing that will stand out. Most projects in “the old days” looked like something you built in your garage. Today, if you want to make something that rivals a commercial product, it isn’t nearly as big of a problem.

Dynamic diode tester from Popular Electronics (July 1970)

For example, consider the picture of this project from Popular Electronics in 1970. It actually looks pretty nice for a hobby project, but you’d never expect to see it on a store shelf.

Even worse, the amount of effort required to make it look even this good was probably more than you’d expect. The box was a standard case, and drilling holes in a panel would be about the same as it is today, but you were probably less likely to have a drill press in 1970.

But check out the lettering! This is a time before inkjet and laser printers. I’d guess these are probably “rub on” letters, although there are other options. Most projects that didn’t show up in magazines probably had Dymo embossed lettering tape or handwritten labels.

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Do You Need A Bench Meter?

June 24, 2025 by Al Williams 14 Comments

If you do anything with electronics or electricity, it is a good bet you have a multimeter. Even the cheapest meter today would have been an incredible piece of lab gear not long ago and, often, meters today are lighter and have more features than the old Radio Shack meters we grew up with. But then there are bench meters. [Learn Electronics Repair] reviews an OWON XDM1241 meter, and you have to wonder if it is better than just a decent handheld device. Check out the video below and see what you think.

Some of the advantage of a bench meter is just convenience. They stay in one place and often have a bigger display than a handheld. Of course, these days, the bench meter isn’t much better than a handheld anyway. In fact, one version of this meter even has a battery, if you want to carry it around.

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