Author: Al Williams

4265 Articles

Models Of Wave Propagation

July 28, 2025 by 7 Comments

[Stoppi] always has interesting blog posts and videos, even when we don’t understand all the German in them. The latest? Computer simulation of wave propagation (Google Translate link), which, if nothing else, makes pretty pictures that work in any language. Check out the video below.

Luckily, most browsers will translate for you these days, or you can use a website. We’ve seen waves modeled with springs before, but between the explanations and the accompanying Turbo Pascal source code, this is worth checking out.

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Learn Computing? Head For MonTana!

July 28, 2025 by 10 Comments

We’ve often thought that it must be harder than ever to learn about computers. Every year, there’s more to learn, so instead of making the gentle slope from college mainframe, to Commodore 64, to IBM PC, to NVidia supercomputer, you have to start at the end. But, really, you don’t. You can always emulate computers from simpler times, and even if you don’t need to, it can be a lot of fun.

That’s the idea behind the MonTana mini-computer. It combines “…ideas from the PDP-11, MIPS, Scott CPU, Game Boy, and JVM to make a relatively simple 16-bit computer…”

The computer runs on Java, so you can try it nearly anywhere. The console is accessed through a web browser and displays views of memory, registers, and even something that resembles a Game Boy screen. You’ll need to use assembly language until you write your own high-level language (we’d suggest Forth). There is, however, a simple operating system, MTOS.

This is clearly made for use in a classroom, and we’d love to teach a class around a computer like this. The whole thing reminds us of a 16-bit computer like the PDP-11 where everything is a two-byte word. There are only 4K bytes of memory (so 2K words). However, you can accomplish a great deal in that limited space. Thanks to the MTOS API, you don’t have to worry about writing text to the screen and other trivia.

It looks like fun. Let us know what you’ll use it for. If you want to go down a level, try CARDIAC. Or skip ahead a little, and teach kids QBasic.

A History Of Pong

July 28, 2025 by 8 Comments

Today, creating a ground-breaking video game is akin to making a movie. You need a story, graphic artists, music, and more. But until the middle of the 20th century, there were no video games. While several games can claim to be the “first” electronic or video game, one is cemented in our collective memory as the first one we’d heard of: Pong.

The truth is, Pong wasn’t the first video game. We suspect that many people might have had the idea, but Ralph Baer is most associated with inventing a practical video game. As a young engineer in 1951, he tried to convince his company to invest in games that you could play on your TV set. They didn’t like the idea, but Ralph would remember the concept and act on it over a decade later.

But was it really the first time anyone had thought of it? Perhaps not. Thomas Goldsmith Jr. and Estle Ray Mann filed a patent in 1947 for a game that simulated launching missiles at targets with an oscilloscope display. The box took eight tubes and, being an oscilloscope, was a vector graphic device. The targets were physical dots on a screen overlay. These “amusement devices” were very expensive, and they only produced handmade prototypes.

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Signal Injector Might Still Be Handy

July 26, 2025 by 1 Comment

Repairing radios was easier when radios were simple. There were typically two strategies. You could use a signal tracer (an amplifier) to listen at the volume control. If you heard something, the problem was after the volume control. If you didn’t, then the problem was something earlier in the signal path. Then you find a point halfway again, and probe again. No signal tracer? You can also inject a signal. If you hear it, the problem is before the volume. If not, it is after. But where do you get the signal to inject? [Learn Electronics Repair] sets out to make a small one in a recent video you can see below.

Both signal tracers and injectors were once ubiquitous pieces of equipment when better options were expensive. However, these days, you can substitute an oscilloscope for a signal tracer and a signal generator for an injector. Still, it is a fun project, and a small dedicated instrument can be handy if you repair a lot of radios.

The origin of this project was from an earlier signal injector design and a bet with a friend about making a small version. They are both working on their designs and want people to submit their own designs for a little ad hoc contest.

We always preferred a signal tracer since it is more passive. Those were typically just audio amplifiers with an optional diode in the input to demodulate RF. A computer amplified speaker and a diode can do the job, as can an LM386. Or, you can build something complex, if you prefer.

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Read QR Codes On The Cheap

July 26, 2025 by 15 Comments

Adding a camera to a project used to be a chore, but modern camera modules make it simple. But what if you want to read QR codes? [James Bowman] noticed a $7 module that claims to read QR codes so he decided to try one out.

The module seems well thought out. There’s a camera, of course. A Qwiic connector makes hooking up easy. An LED blinks blue when you have power and green when a QR code shows up.

Reading a QR code was simple in Python using the I2CDriver library. There are two possible problems: first, if the QR code contains a large amount of data, you may exceed the I2C limit of 254 bytes. Second, despite claiming a 110-degree field of view, [James’] testing showed the QR code has to be almost dead center of the camera for the system to work.

What really interested us, though, was the fact that the device is simply a camera with an RP2040 and little else. For $7, we might grab one to use as a platform for other imaging projects. Or maybe we will read some QR codes. We’d better pick up a few. Then again, maybe we can just do it by hand.

Hackaday Podcast Episode 330: Hover Turtles, Dull Designs, And K’nex Computers

July 25, 2025 by 1 Comment

What did you miss on Hackaday last week? Hackaday’s Elliot Williams and Al Williams are ready to catch you up on this week’s podcast. First, though, the guys go off on vibe coding and talk about a daring space repair around Jupiter.

Then it is off to the hacks, including paste extruding egg shells, bespoke multimeters, and an 8-bit mechanical computer made from a construction toy set.

For can’t miss articles, you’ll hear about boring industrial design in modern cell phones and a deep dive into how fresh fruit makes it to your table in the middle of the winter.

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!

The DRM-free MP3 was stored in a public refrigerated warehouse to ensure freshness. Why not download it and add it to your collection?

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Not Repairing An Old Tape Recorder

July 24, 2025 by 13 Comments

When you think of a tape recorder, you might think of a cassette tape. However, [Michael Simpson] has an old Star-Lite small reel-to-reel tape machine. It isn’t a repair so much as a rework to make it work better. These cheap machines were never the best, although a $19 tape player back then was a luxury.

Part of the problem is that the design of the tape player wasn’t all that good to begin with. The motor runs off two C cells in parallel. When these were new in the 1960s, that would have meant conventional carbon-zinc batteries, so the voltage would have varied wildly. That didn’t matter, though, because the drive was directly to the tape reel, so the speed also varied based on how much tape was left on the reel.

The amplifier has four transistors. [Michael] decided to replace the capacitors on the unit. He noticed, too, that the volume control is in line with the microphone when recording, so even though the recording was supposedly in need of repair, it turned out to be simply a case of the volume control being turned down. Pretty impressive for a six-decade-old piece of consumer electronics.

The capacitor change-out was simple enough. Some cleaning and lubing was also in order. Did it help? You’ll have to listen and decide for yourself.

So, no real repair was in the works, but it is an interesting look back at an iconic piece of consumer tech. Tape recorders like this were an early form of social media. No kidding. If you’d rather not buy a tape recorder, you could roll your own.

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