Fixing A 1990s LEGO Electric Train Speed Regulator

September 8, 2026 by No comments

Before LEGO train sets moved to battery-powered locomotives with plastic rails, all of them worked pretty much like any other train set of the era. This meant metal rails that the locomotive’s wheels would use to pick up power from and a central controller that would inject said power and also regulate the train’s speed and direction. The LEGO 2868b Electric Train Speed Regulator is one such example, and [Nonsense Wars] recently had one under the knife to repair it.

The single PCB inside is quite straightforward, with the 9-12 VAC supply input from an external power adapter, and a variable voltage regulator that sees its target voltage switched by a bank of resistors.

It are these resistors that the big yellow control switches between when you operate it, changing the output voltage and also output polarity you cross the midway point. Effectively this means that there is just one non-passive component on the PCB, in the form of the TO-220 package strapped to the big heatsink.

In this particular unit it was found to be a Fairchild KA317, which is for all intents and purposes here the same as an LM317T. One quick swap later and this controller was back in business like it was 1995.

Compared to the engineering crammed into a modern “smart brick”, things really have come quite a ways in the world of LEGO.

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Hackaday Europe 2026: Outdoors With Robots

September 8, 2026 by No comments

Erin Kennedy has been building robots for over a decade now, with a focus on smaller bots that interact with, or maybe even clean up, the outdoor environment. Still other bots are made to interact with people, and when the people are outside in the park, that’s where your robot needs to go.

Whatever the reason, Erin’s talk at Hackaday Europe 2026 is an invitation to take your projects out into the outdoors. But the great wide world outside of your lab is not necessarily the most friendly place for a little bot, and the other half of this talk is about practical design tips and lessons learned to help it survive. Continue reading “Hackaday Europe 2026: Outdoors With Robots” →

Disassembling A Mini Air Blower To Make RC Airplanes

September 8, 2026 by 13 Comments

As a certified RC airplane fan, the [RCMakerLab] on YouTube found themselves looking at one of those nifty mini air blowers that provide an alternative to a compressor and canned air for dusting and other high-volume, high-pressure air-related tasks.

Inside these quite affordable units is a ducted fan (EDF) that can produce fairly high levels of airflow to get to every last dust bunny hiding on a PCB or inside a keyboard, raising the question of whether you could use these to fly a model airplane with.

As can be seen in the torn down unit, there isn’t a lot to these air blowers, with the ESC bolted onto the EDF and only the speed regulator and on/off switch being external controls. This would make it very easy to integrate into an airplane, but leaves the question of whether it can generate enough thrust to make it worth the effort.

Using a custom rig, it was shown to generate up to 110 grams of thrust with a current of 16.5 A, which would at least go a long way to carrying its own battery pack. In order to create an airplane with it, probably two of these motors are needed. There’s also the potential of reducing weight by changing the ESC and such, making reusing these little EDFs from any discarded or broken mini air blowers at least worth a shot.

At the very least, it seems like it has a better shot of working than a plane powered by an electric leaf blower.

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A 1024 Byte Python Interpreter

September 8, 2026 by 4 Comments

Like many of us, [Austin] finds writing code satisfying — especially if it is challenging. His latest challenge: shoehorn something that looks like Python into 512 bytes. Ok, that didn’t work out, but would you believe 1024 bytes of source code?

The goal was to properly execute a fizzbuzz program using a decidedly Python-like syntax. Since he is only interpreting Python, some things were simplified. In addition, he tried hard to minimize things like whitespace and variable names. Still, there were other things to do, and he borrowed from tips for code golfing.

The resulting code is essentially illegible, but it handles integer variables and literals, assignment, arithmetic, many control structures, functions, and even print. Not bad for 1 K.

Despite being tiny, the parser does a lot, but it does cut corners. No bytecode, no syntax tree, and no error handling. Variables have to be a single lowercase letter. So, ok, it isn’t really Python. But it is something.

Naturally, this reminded us of the obfuscated C code contest. If you really want to go small, we appreciate small Forth.

Old IPad Keyboard Makes For A Modern Netbook

September 8, 2026 by 10 Comments

Netbooks were a class of tiny laptops which hit their peak over a decade ago, with the idea being that you could use the Internet and do your computing on the move with ease. Unfortunately manufacturers were scared of them eating their profits from bigger computers, and they were invariably built to a very disappointing spec. That doesn’t lessen the appeal of small form factor laptops though, and [bob-foss] is here with a simple hack to make one.

He’s taken a hinged keyboard case made for one of the previous generations of iPad Mini, and paired it with a high-end Lenovo gaming tablet by way of a 3D printed replacement for the original Apple-grabber. We said it was a simple hack and it is, but it’s no less elegant for that as the detail is what matters. This isn’t a mess-of-wires cyberdeck, instead it’s a machine you could pull out on a train and get some work done.

Meanwhile, if you’d like to take a wallow in what that netbook thing was all about, we took a look at the phenomenon back in 2020.

How Bats Prevent Doppler Acoustic Interference

September 7, 2026 by 9 Comments
https://commons.wikimedia.org/wiki/File:Bat(20070605).jpg
Lesser horseshoe bat. (Credit: Lylambda, Wikimedia)

As great as echolocation is, things can get rather messy once it’s not just you chirping away, but also hundreds of your buddies in roughly the same area. This is the scenario that the typical colonies of bats have to deal with. In a recent study by [Haruhito Matsumoto] et al. in Journal of Comparative Physiology they investigated how colonies of greater Japanese horseshoe bats deal with this issue.

Echolocation in animals can use a variety of methods, including frequency modulation (FM, varying the pitch) or constant frequency (CF), with both having their uses during hunting as well as obstacle avoidance. One big advantage of CF is that it can be used for Doppler shift, giving very precise information about location and velocity of objects in the environment, but if used in a busy colony the acoustic interference would effectively render them blind.

What researchers have found is that the CF component frequencies differ per bat colonies, with the mixing of wild-caught and resident horseshoe bats in this experiment showing them adjusting the dominant second harmonic (CF2) to match, with bats using a lower frequency CF2 adjusting it upwards. In this way frequency convergence is used as a strategy to avoid acoustic interference using a so-called ‘silent spectral window’.

As this spectral window for effective Doppler tracking is found above the CF2 frequency, it therefore makes sense that the bats at a lower CF2 harmonic would adjust their CF upwards to match that of their neighbors. Although more research is required to fully confirm these findings, it sheds some more light on the use of echolocation by these amazing flying mammals.

Kelvin–Helmholtz Instabilities Found To Drive Plasma Mixing On The Sun

September 7, 2026 by 3 Comments

As easy as the Sun is to observe, it’s simultaneously very hard to study due to how extreme the conditions are, even on the surface of a rather unassuming star. One of these study topics is the interaction between the Sun’s plasma and magnetic field, as this drives much of the dynamism of the Sun’s surface layer (i.e., the photosphere). Recent observations by the 4-meter solar telescope in Hawaii have now led to interesting new findings, as detailed in a paper in Nature by [David Kuridze] et al.

Despite popular portrayal, this photosphere is not a boiling liquid, but rather pockets of plasma at various temperatures. The plasma moves within the magnetic field and convective movements that create the ‘boiling’ pattern, which gives the illusion of a boiling liquid surface.

Within this photosphere, [Kuridze] et al. were able to observe Kelvin-Helmholtz instabilities, which are fluid instabilities caused by velocity shearing in either a continuous fluid or due to a velocity difference between two fluids. This is also observed in clouds in Earth’s atmosphere, where they cause the billowing effect, somewhat similar to watching a boiling liquid.

In a MURaM simulation (see heading image), these findings were confirmed, showing how these instabilities drive the transport of plasma in the Sun’s photosphere.