The (RF) Sniff Test

August 29, 2025 by Al Williams 12 Comments

Sometimes the old tricks are the best. [Kevin] learned an old trick about using a ‘scope to sniff RF noise and pays it forward by sharing it in a recent video. He uses an oscilloscope. But does he need some special probe setup? Nope. He quickly makes a little RF pickup probe, and if you have a ‘scope, we’re pretty sure you can make one in a few seconds, too.

Of course, you can get probes made for that, and there are advantages to using them. But the quick trick of quickly and non-destructively modifying the existing probe to pick up RF means you always have a way to make these measurements.

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Hackaday Podcast Episode 335: Beer, Toast, And Pi

August 29, 2025 by Al Williams 3 Comments

What happens when you listen in on Elliot Williams and Al Williams? You get a round up of the best of last week’s Hackaday posts, of course. The topics this week range from beer brewing to lightning protection, with a little bit of everything in between.

This week, many problems find solutions. Power drill battery dead? Your car doesn’t have a tire pressure monitor? Does your butter tear up your toast? You can find the answer to these problems, and more, on the Hackaday podcast.

For the can’t miss section, the guys are annoyed that Google wants to lock down their phones, and also talk about measuring liquid levels in outer space.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Or download in DRM-free MP3 without requiring developer registration.

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The (Data) Plot Thickens

August 28, 2025 by Al Williams 35 Comments

You’ve generated a ton of data. How do you analyze it and present it? Sure, you can use a spreadsheet. Or break out some programming tools. Or try LabPlot. Sure, it is sort of like a spreadsheet. But it does more. It has object management features, worksheets like a Juypter notebook, and a software development kit, in case it doesn’t do what you want out of the box.

The program is made to deal with very large data sets. There are tons of output options, including the usual line plots, histograms, and more exotic things like Q-Q plots. You can have hierarchies of spreadsheets (for example, a child spreadsheet can compute statistics about a parent spreadsheet). There are tons of regression analysis tools, likelihood estimation, and numerical integration and differentiation built in.

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Homebrew Tire Pressure Monitoring System

August 27, 2025 by Al Williams 53 Comments

When [upir] saw that you could buy tire valve stem caps that read pressure electronically, he decided to roll his own Tire Pressure Monitoring System (TPMS) like the one found on modern cars. An ESP32 and an OLED display read the pressure values. He didn’t have a car tire on his workbench though, so he had to improvise there.

Of course, a real TPMS sensor goes inside the tire, but screwing them on the valve stem is much easier to deal with. The sensors use Bluetooth Low Energy and take tiny batteries. In theory, you’re supposed to connect to them to your phone, although two different apps failed to find the sensors. Even a BLE scanner app wouldn’t pick them up. Turns out — and this makes sense — the sensors don’t send data if there’s no pressure on them, so as not to run down the batteries. Putting pressure on them made them pop up on the scanner.

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The Android Bluetooth Connection

August 27, 2025 by Al Williams 14 Comments

Suppose someone came to talk to you and said, “I need your help. I have a Raspberry Pi-based robot and I want to develop a custom Android app to control it.” If you are like me, you’ll think about having to get the Android developer tools updated, and you’ll wonder if you remember exactly how to sign a manifest. Not an appealing thought. Sure, you can buy things off the shelf that make it easier, but then it isn’t custom, and you have to accept how it works. But it turns out that for simple things, you can use an old Google Labs project that is, surprisingly, still active and works well: MIT’s App Inventor — which, unfortunately, should have the acronym AI, but I’ll just call it Inventor to avoid confusion.

What’s Inventor? It lives in your browser. You lay out a fake phone screen using drag and drop, much like you’d use QT Designer or Visual Basic. You can switch views and attach actions using a block language sort of like Scratch. You can debug in an emulator or on your live phone wirelessly. Then, when you are ready, you can drop an APK file ready for people to download. Do you prefer an iPhone? There’s some support for it, although that’s not as mature. In particular, it appears that you can’t easily share an iPhone app with others.

Is it perfect? No, there are some quirks. But it works well and, with a little patience, can make amazingly good apps. Are they as efficient as some handcrafted masterpiece? Probably not. Does it matter? Probably not. I think it gets a bad rep because of the colorful blocks. Surely it’s made for kids. Well, honestly, it is. But it does a fine job, and just like TinkerCad or Lego, it is simple enough for kids, but you can use it to do some pretty amazing things.

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Picture By Paper Tape

August 26, 2025 by Al Williams 14 Comments

The April 1926 issue of “Science and Invention” had a fascinating graphic. It explained, for the curious, how a photo of a rescue at sea could be in the New York papers almost immediately. It was the modern miracle of the wire photo. But how did the picture get from Plymouth, England, to New York so quickly? Today, that’s no big deal, but set your wayback machine to a century ago.

Of course, the answer is analog fax. But think about it. How would you create an analog fax machine in 1926? The graphic is quite telling. (Click on it to enlarge, you won’t be disappointed.)

If you are like us, when you first saw it you thought: “Oh, sure, paper tape.” But a little more reflection makes you realize that solves nothing. How do you actually scan the photo onto the paper tape, and how can you reconstitute it on the other side? The paper tape is clearly digital, right? How do you do an analog-to-digital converter in 1926? Continue reading “Picture By Paper Tape” →

The Shady School

August 25, 2025 by Al Williams 8 Comments

We can understand why shaderacademy.com chose that name over “the shady school,” but whatever they call it, if you are looking to brush up on graphics programming with GPUs, it might be just what you are looking for.

The website offers challenges that task you to draw various 2D and 3D graphics using code in your browser. Of course, this presupposes you have WebGPU enabled in your browser which means no Firefox or Safari. It looks like you can do some exercises without WebGPU, but the cool ones will need you to use a Chrome-style browser.

You can search by level of difficulty, so maybe start with “Intro” and try doing “the fragment shader.” You’ll notice they already provide some code for you along with a bit of explanation. It also shows you a picture of what you should draw and what you really drew. You get a percentage based on the matching. There’s also a visual diff that can show you what’s different about your picture from the reference picture.

We admit that one is pretty simple. Consider moving on to “Easy” with options like “two images blend,” for example. There are problems at every level of difficulty. Although there is a part for compute shaders, none seem to be available yet. Too bad, because that’s what we find most interesting. If you prefer a different approach, there are other tutorials out there.