2026-03-15 04:00:08
It’s Pi Day, and while we know that many of you celebrate privately, those that take a moment to put aside their contemplation of all things circular and join us on this mathematically-significant day will likely know the name [Cristiano Monteiro]. Since 2022 he’s made it a yearly tradition to put together a themed project every March 14th, and he’s just put the finishing touches on the 2026 edition.
Generally, [Cristiano] sends in some interesting hardware device that visualizes the calculation of pi, but this year he surprised us a bit by delivering a software project. His Orbital Pi Simulator allows you to see what would happen to an orbiting spacecraft if it’s navigation system suddenly believed the value of pi was something different.
In broad strokes, we can imagine what would happen. If you plug in something significantly higher than 3.14, the orbit becomes elliptical to the point that the craft can fly off into deep space. Drop the value down, and the orbit will intersect with the Earth — a guaranteed recipe for a bad time.
The Kerbal Space Program players in the audience will no doubt point out that a spacecraft in a stable orbit would more or less stay on that same trajectory indefinitely and not need to manually adjust its velocity in the first place. Further, they would argue that said spacecraft suddenly firing its thrusters retrograde because a flipped bit in its computer resulted in the value of pi suddenly being 1.2 isn’t very realistic. Those people would be correct, but they would also be no fun at parties.
Fans of math and/or circles will no doubt be interested in the previous devices [Cristiano] has built to mark this date. Last year he put together a robotic hand that counted out pi with its 3D printed fingers, and in 2024 he used the Pepper’s Ghost illusion to great effect. For those wondering, not everything he does is pi-related. The portable GPS time server he sent out way in 2021 was a particularly slick piece of hardware.
2026-03-15 01:00:45
Cooking with charcoal is a fairly common human activity, as much as others have come to prefer fuels like propane and propane accessories for their outdoor, summertime grilling. Although it’s made from wood, it has properties that make it much more useful for cooking — including burning at a higher temperature and with more consistent burn rates. It can also be used as a fuel for generating heat and electricity, but since it’s not typically found lying around in the forest it has to be produced, which [Greenhill Forge] has demonstrated his charcoal production system in one of his latest videos.
The process for creating charcoal is fairly simple. All that needs to happen is for wood to be heated beyond a certain temperature in the absence of oxygen. At this point it will off-gas the water stored in it as well as some of the volatile organic compounds, and what’s left behind is a flammable carbon residue. Those volatile organics are flammable as well, though, so [Greenhill Forge] uses them to heat the wood in a self-sustaining reaction. First, a metal retort is constructed from a metal ammo box, with a pipe extending from the side and then underneath the box. A few holes are drilled in this part, and the apparatus is mounted above a small fire on a metal stand. With the fire lit the wood begins heating, and as it heats these compounds exit the pipe and ignite, adding further fuel to the fire. Eventually the small fire will go out, allowing the retort to heat itself on the gasses released from the wood alone.
To generate the hot water, [Greenhill Forge] has taken an extra step and enclosed the retort in a double walled metal cylinder. Inside the cylinder is a copper tube packed in sand, which harvests the waste heat from the charcoal production for hot water. In his test runs, the water in a large drum was heated to the point that the tubing he used for the test began to melt, so it is certainly working better than he expected.
After the retort cools, [Greenhill Forge] uses the charcoal in another process that generates about a days’ worth of electricity and hot water. It’s part of a complete off-grid system that’s fairly carbon neutral, since trees are an abundant renewable resource compared to fossil fuels. Heating with wood directly is still common in many cold areas around the world, with the one major downside being the labor required to keep the stove running. But we’ve seen at least one project which solves this problem as well.
2026-03-14 22:00:41
On the podcast, [Tom] and I were talking about the new generation of smartphones which are, at least in terms of RAM and CPU speed, on par with a decent laptop computer. If so, why not just add on a screen, keyboard, and mouse and use it as your daily driver? That was the question posed by [ETA Prime] in a video essay and attempt to do so.
Our consensus was that it’s the Android operating system holding it back. Some of the applications you might want to run just aren’t there, and on the open side of the world, even more are missing. Is the platform usable if you can’t get the software you need to get your work done?
But that’s just the computer-as-a-tool side of the equation. The other thing a computer is, at least to many of our kind of folk, is a playground. It’s a machine for experimenting with, and for having fun just messing around. Android has become way too polished to have fun, and recent changes on the Google side of things actively prevent you from installing arbitrary software. The hardware is similarly too slimmed-down to allow for experimentation.
Looking back, these have been the same stumbling blocks for the last decade. In 2018, I was wondering aloud why we as a community don’t hack on cell phones, and the answer then was the same as it is now – the software is not friendly to our kind. You can write phone apps, and I have tried to do so, but it’s just not fun.
The polar opposites of the smartphone-as-computer are no strangers in our community. I’m thinking of the Linux single-board computers, or even something like a Steam Deck, all of which are significantly less powerful spec-wise than a flagship cell phone, but which are in many ways much more suitable for hacking. Why? Because they make it easy to do the things that we like to do. They’re designed to be fun computers, and so we use them.
So for me, a smartphone isn’t a computer, but oddly enough it’s not because of the hardware. It’s because what I want out of a computer is more than Turing completeness. What I want is the fun and the freedom of computering.
2026-03-14 19:00:23
[My Engines] has been doing some sterling work on Stirling engines for some years now. Their thermoacoustic engine is now finally far enough along to open-source, so the magic of collaboration can speed technological advancement.
You’ve probably heard of Stirling Engines, but what’s this “thermoacoustic” business? Hot sound? Well, that’s the translation, and it’s not a bad starting point for understanding what’s going on: the engine converts heat into high-amplitude sound waves — that is, waves of pressure — which means the engine itself has no moving parts. Well, almost. Obviously moving parts are required to get power out. In [My Engines] case he’s using a piston and linear generator, but otherwise it makes for a very simple, very reliable engine that can be fueled by any available source of heat. Say like burning methane from [My Engines]’s home biogas plant.
[My Engines] promises more videos to help you understand the construction in a way his previous videos might not detail, and has put 3D models and drawings at a public Google Drive. There’s also a Discord you can join, because apparently that’s the only way to communicate about projects these days.
The whole build is very much within range of a home maker, though there’s a lot more to it than the toy Stirling engines you may have made out of tin cans back in the day. If you want to play with thermoacoustics but [My Engines]’s design seems like a little much to get started with, you can make a demonstrator with some steel wool and a test tube. Be careful, though: model engines can be an addictive hobby.
2026-03-14 16:00:29
The physicist William Shockley is perhaps today best known for three things: his role in the invention of the transistor, his calamitous management of Shockley Semiconductor which led to a mass defection of employees and precipitated the birth of the Silicon Valley we know, and his later descent into promoting eugenics. This was not the sum of his work though, and [David Prutchi] has been experimenting with a now-mostly-forgotten device that bears the Shockley name (PDF), after finding one used in an early heart pacemaker circuit. His findings are both comprehensive and fascinating.
The Shockley diode, or 4-layer diode as it later became known, is as its name suggests a two terminal device with a 4-layer NPNP structure. It can be modeled as a pair of complementary transistors in parallel with a reverse biased diode, and the avalanche breakdown characteristics of that diode when a particular voltage is applied to it provide the impetus to turn on the two transistors. This makes it a voltage controlled switch, that activates when the voltage across it reaches that value.
The PDF linked above goes into the Shockley diode applications, and in them we find a range of relaxation oscillators, switches, and logic circuits. The oscillators in particular could be made with the barest minimum of components, important in a time when each semiconductor device could be very expensive. It may have faded into obscurity as it was superseded by more versatile 4-layer devices such as the PUJT or silicon-controlled switch and then integrated circuits, but he makes the point that its thyristor cousin is still very much with us.
This appears to be the first time we’ve featured a 4-layer diode, but we’ve certainly covered the genesis of the transistor in the past.
2026-03-14 13:00:24
Although the Apple II range of computers were based around the 6502 processor, they could still run x86 software using expansion cards that were effectively self-contained computers. This way an Apple IIe owner, for example, could install an Intel 8088-based AD8088 co-processor card by ALF Products and run CP/M-86 as well as MS-DOS. Unfortunately, as [Seth Kushniryk] discovered while digging into this MS-DOS option, there don’t seem to be any remaining copies of the accompanying MS-DOS 2.0 software.
The obvious response to this is of course to try and port it once again, which [Seth] did. So far he got it to boot, though it’s not quite ready for prime-time yet. Although the AD8088 card is fairly self-contained, it still has to talk with the Apple IIe system, which poses some challenges. To help with the porting he’s using the MS-DOS 2.0 OEM Adaptation Kit that was released along with the sources a while back.
The Apple II has to first load the basic MS-DOS files into the 8088’s RAM before handing over control, which works now along with the basic functionality. Before [Seth] releases the port to the public he still wants to fix a number of issues, in particular the clock. ProDOS on the Apple IIe encodes the year differently than MS-DOS, so that the latter’s clock is off by a few years, and the console driver is still not quite as robust as [Seth] would like it to be.
Beyond this there is also working with the other cards in the Apple II2 system, including the Super Serial Card, and working with the ProDOS filesystem.
