[MindYourDecisions] presents a Babylonian tablet dating back to around 1800 BC that shows that the hypotenuse of a unit square is the square root of two or 1.41421. How did they know that? We don’t know for sure how they computed it, but experts think it is the same as the ancient Greek method written down by Hero. It is a specialized form of the Newton method. You can follow along and learn how it works in the video below.
The method is simple. You guess the answer first, then you compute the difference and use that to adjust your estimate. You keep repeating the process until the error becomes small enough for your purposes.
[Folaefolc] was craving a new keyboard build a few weeks ago and got inspired by the humble 3.5″ floppy disk. So much so that he decided to make a split keyboard with each half having the exact footprint of a floppy — 90 mm x 94 mm. And you know the PCBs have floppy details silkscreened on the back. Just check out the gallery.
Image via [Folaefolc] via redditThis bad boy uses a pair of Liatris microcontrollers, which are made by splitkb and are designed to be drop-in replacements for Pro Micros and an alternative to the RP2040.
The other fun part of this build is that [Folaefolc] used RJ9 connectors to join the halves instead of something like TRRS.
Most RC planes follow a simple control scheme: elevators for pitch, rudder for yaw, and ailerons for roll. This one-to-one mapping keeps things straightforward, and fewer actuators means less weight. But nature has other ideas. Birds achieve flight control through complex, coordinated movements where different body parts can affect multiple degrees of freedom simultaneously. Now, researchers at EPFL have brought this biological approach to robotics with the LisEagle, a drone featuring morphing wings and tail that demonstrate remarkable stability.
All the actuators!
The LisEagle packs seven different actuation methods alongside its nose-mounted motor. Three of these control the bird-like wingtips and spreading tail, while the remaining actuators handle more conventional controls: independently twisting wing bases (similar to ailerons) and a tail assembly that combines elevator and rudder functions in its vertical stabilizer.
Testing took place in controlled indoor conditions, with the maintaining position in front of an open wind tunnel. Optical position tracking provided closed-loop feedback and power was provided via a tether to minimize weight. A PID flight controller orchestrated all seven actuators in concert, achieving impressive stability even when faced with induced turbulence or being poked with a stick. In a demonstration of redundancy, the researchers deliberately disabled the twisting wing mechanisms, and the aircraft maintained control using just its wingtips and tail.
The team went further, employing Bayesian optimization to find the most efficient actuator combinations. This revealed potential energy savings of up to 11%, with optimal configurations varying based on airspeed as lift requirements changed.
While research into the flight mechanisms of bees, bats and birds might not immediately translate to practical applications, it deepens our understanding of flight control principles. Don’t be surprised if morphing wings become a more common sight in future aircraft designs.
Earlier this year [Skyhawkson] got ahold of an Apollo-era printed circuit board which he believes was used in a NASA test stand. He took high quality photos of both sides of the board and superimposed them atop each other. After digging into a few obsolete parts from the 1960s, he was able to trace out the connections. I ran across the project just after making schematics for the Supercon badge and petal matrix. Being on a roll, I decided to take [Skyhawkson]’s work as a starting point and create KiCad schematics. Hopefully we can figure out what this circuit board does along the way.
It is hard to imagine that there was a time when having a keyboard and screen readily available was a real problem for people who wanted to experiment with computers. In the 1970s, if you wanted a terminal, you might well have built a [Don Lancaster] “TV Typewriter” and the companion “low cost keyboard.” [Artem Kalinchuk] wanted to recreate this historic keyboard and, you know what? He did! Take a look at the video below.
The first task was to create a PCB from the old artwork from Radio Electronics magazine. [Artem] did the hard work but discovered that the original board expected a very specific kind of key. So, he created a variant that takes modern MX keyboard switches, which is nice. He does sell the PCBs, but you can also find the design files on GitHub.
What if GPS had existed in 1565? No satellites or microelectronics, sure—but let’s play along. Imagine the bustling streets of Antwerp, where merchants navigated the sprawling city with woodcut maps. Or sailors plotting Atlantic crossings with accuracy unheard of for the time. This whimsical intersection of history and tech was recently featured in a blog post by [Jan Adriaenssens], and comes alive with Bert Spaan’s Allmaps Here: a delightful web app that overlays your GPS location onto georeferenced historical maps.
Take Antwerp’s 1565 city map by Virgilius Bononiensis, a massive 120×265 cm woodcut. With Allmaps Here, you’re a pink dot navigating this masterpiece. Plantin-Moretus Museum? Nailed it. Kasteelpleinstraat? A shadow of the old citadel it bordered. Let’s not forget how life might’ve been back then. A merchant could’ve avoided morning traffic and collapsing bridges en route to the market, while a farmer relocating his herd could’ve found fertile pastures minus the swamp detour.
Unlike today’s turn-by-turn navigation, a 16th-century GPS might have been all about survival: avoiding bandit-prone roads, timing tides for river crossings, or tracking stars as backup. Imagine explorers fine-tuning their Atlantic crossings with trade winds mapped to the mile. Georeferenced maps like these let us re-imagine the practical genius of our ancestors while enjoying a modern hack on a centuries-old problem.
[Kevin] doesn’t stock zener diodes anymore. Why? Because for everything he used to use zeners, he now uses TL431 bandgap voltage references. These look like zener diodes but have an extra terminal. That extra terminal allows you to set the threshold to any value you want (within specifications, of course). Have a look at the video below for an introduction to these devices and a practical circuit on a breadboard.
Inside, there’s a voltage reference, an op-amp, and a transistor, so these are tiny 3-terminal ICs. The chip powers itself from the load, so there are no separate power supply pins.
