Author: Al Williams

4377 Articles

Hackaday Podcast Episode 312: Heart Attacks, The Speed Of Light, And Self-balancing

March 14, 2025 by 7 Comments

Elliot does the podcast on the road to Supercon Europe, and Al is in the mood for math and nostalgia this week. Listen in and find out what they were reading on Hackaday this week.

The guys talked about the ESP-32 non-backdoor and battery fires. Then it was on to the hacks.

Self-balancing robots and satellite imaging were the appetizers, but soon they moved on to Kinect cameras in the modern day. Think you can’t travel at the speed of light? Turns out that maybe you already are.

Did you know there was a chatbot in 1957? Well, sort of. For the can’t miss stories: watches monitor your heart and what does the number e really mean?

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!

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You Know Pi, But Do You Really Know E?

March 14, 2025 by 29 Comments

Pi Day is here! We bet that you know that famous constant to a few decimal points, and you could probably explain what it really means: the ratio of a circle’s circumference to its diameter. But what about the constant e? Sure, you might know it is a transcendental number around 2.72 or so. You probably know it is the base used for natural logarithms. But what does it mean?

The poor number probably needed a better agent. After all, pi is a fun name, easy to remember, with a distinctive Greek letter and lots of pun potential. On the other hand, e is just a letter. Sometimes it is known as Euler’s number, but Leonhard Euler was so prolific that there is also Euler’s constant and a set of Euler numbers, none of which are the same thing. Sometimes, you hear it called Napier’s constant, and it is known that Jacob Bernoulli discovered the number, too. So, even the history of this number is confusing.

But back to math, the number e is the base rate of growth for any continually growing process. That didn’t help? Well, consider that many things grow or decay through growth. For example, a bacteria culture might double every 72 hours. Or a radioactive sample might decay a certain amount per century. Continue reading “You Know Pi, But Do You Really Know E?” →

Linux Fu: Use The Source (Command), Luke

March 13, 2025 by 12 Comments

You can argue if bash is a good programming language or not, but you can’t argue that it is a programming language. However, there are a few oddities about it that make it different from most other languages you probably know. For one thing, variables are dynamically scoped. Second, you can easily change variables in an upper scope. This leads to a problem when you want to do something like reset your path:

#!/bin/bash
#: This does NOT work
PATH=/usr/bin:/bin

Well, actually, it does work; it just doesn’t work the way you imagine it might. The key is to realize that when you execute our script (say, resetpath), a new copy of bash runs. It inherits all the variables from your shell. Now the script sets PATH for the new copy of bash. Anything else you run in that script will see your change. But when the script exits, the new copy of bash is gone and the old copy sees the same old PATH it always did.

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Hacking A Rotary Phone

March 13, 2025 by 15 Comments

[Yaymukund] made an interesting observation. Old-style rotary phones were made to last and made for service. Why? Because you didn’t own them, the phone company did. There was no advantage for them for you to need a service call or a new phone. Of course, many of these old phones are still hanging around like the GPO 746 that appears in the post.

What do you do with an old rotary phone? In this case, you make it play a random tune whenever someone picks up the handset. As you might expect, you don’t need much of the original phone to do this. In particular, you need the handset receiver and the switch hook. We’d have liked to read the dial to select a tune, but perhaps that could be in version two.

All the components wire back to a D92732 circuit board. Finding the right wires was a bit finicky, but eventually, a Teensy, a battery pack, and an audio breakout board were in place. The rest is mostly trivial.

[Yaymukund] spent about £300, but over half of that was on tools most Hackaday readers will already have. The phone itself was £65. You can use these phones as a basis for many projects. Even if you want to go mobile.

What’s Wrong With This Antenna Tuner?

March 10, 2025 by 16 Comments

[Tech Minds] built one of those cheap automatic antenna tuners you see everywhere — this one scaled up to 350 watt capability. The kit is mostly built, but you do have to add the connectors and a few other stray bits. You can see how he did it in the video below.

What was very interesting, however, was that it wasn’t able to do a very good job tuning a wire antenna across the ham bands, and he asks for your help on what he should try to make things better.

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Freeing Windows

March 10, 2025 by 63 Comments

There have been several attempts to make an unencumbered version of Windows. ReactOS is perhaps the best-known. You could also argue that Wine and its progeny, while not operating systems in the strictest sense of the word, might be the most successful. Joining the fray is Free95, a GPL-3.0 system that, currently, can run simple Windows programs. The developer promises to push to even higher compatibility.

As you might expect, the GitHub site is calling for contributors. There will be a lot to do. The src subdirectory has a number of files, but when you consider the sheer volume of stuff crammed into Windows, it is just a minimal start.

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You Are Already Traveling At The Speed Of Light

March 10, 2025 by 40 Comments

Science fiction authors and readers dream of travelling at the speed of light, but Einstein tells us we can’t. You might think that’s an arbitrary rule, but [FloatHeadPhysics] shows a different way to think about it. Based on a book he’s been reading, “Relativity Visualized,” he provides a graphic argument for relativity that you can see in the video below.

The argument starts off by explaining how a three-dimensional object might appear in a two-dimensional world. In this world, everything is climbing in the hidden height dimension at the exact same speed.

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