Kritik sah

When flying over the United States, Australia, and a few other vast and relatively empty parts of the world, strange circular formations can be spotted. These are typically center-pivot irrigation systems, an effective way to irrigate crops if efficient use of space is not too big of a priority. Keeping these massive machines in a straight line is an interesting engineering problem, though, and [rctestflight] built a miniature version of his that works on the same principle but mows his lawn instead . These systems work as semi-independent sections that are flexibly coupled at either end. The control scheme initially used here was to drive the outermost set of wheels at a constant speed, and then use limit switches at each coupling inside of that to drive inner sets of wheels once the outer set passes a setpoint. Eventually a potentiometer-based proportional controller was installed in place of the limit switches. With some other drivetrain issues sorted out it was on to building the ...

Continuing their reverse-engineering of Intel’s 8087 FPU, [Ken Shirriff] and friends took a look at one of the trigonometric functions , specifically FPTAN .  The most exciting part with such reverse-engineering is probably figuring out which algorithm was used in the implementation, while trying to determine the reasoning behind the final hardware design. If you’re running a simple MCU or MPU like the 6502 or Z80 without hardware functions you’d likely use an algorithm such as CORDIC or similar, as this requires only basic hardware features like addition, subtraction, bitshift, and look-up tables. One can also use polynomial approximation if there’s hardware support for a potential speed-up, or as is the case in the 8087, create a hybrid approach that targets speed and accuracy. In the article the exact implementation to get to 64 bits of accuracy is detailed, starting with the 16 bits calculated using CORDIC before switching to the Padé approximant techniqu...

Considering how important it is for everything from navigation to keeping clocks in sync, satellite navigation systems are surprisingly vulnerable to a variety of attacks, ranging from simple jamming to more sophisticated spoofing attacks. This may be changing, though, as Galileo, Europe’s GNSS, recently demonstrated its first cryptographically-secured position fix under spoofing conditions. Most GNSS systems, including GPS, have no verification measures to keep an adversary from transmitting a false signal at a higher power and hijacking a receiver; since GNSS signals are extremely weak by the time they reach the ground, this presents no great difficulty to a moderately well-equipped attacker. Galileo’s Signal Authentication System (SAS) aims to fix this. The Galileo ground station pre-selects signal spreading codes, which it then encrypts with a regularly-changing secret key and publishes. A receiver which anticipates needing a verified signal can then download these encrypted c...

As useful as steel and iron are to the modern world, their tendency to rust is a major downside. There’s a spectrum of ways to prevent it, from quickly slapping on a coat of paint on the easy side to alloying, chromizing, or physical vapor deposition at the extremely difficult or industrial-only end. For a middle ground accessible to the home shop, galvanizing is a go-to method of rust prevention that deposits a layer of zinc onto the metal instead, but even this generally involves the use of strong acids. This method, though, makes galvanizing accessible without any acids . (Spoiler alert: substitute strong bases.) Although the acids are omitted, the solution is caustic, so similar safety measures are still advised. The first step in the process is to dissolve sodium hydroxide into a container of distilled water. Metallic zinc can then be dissolved in the solution, with a bit of sugar and liquid soap to improve the finished quality of the coating. An electric current is applied ...

The introduction of the ATmega32U4 microcontroller, with its integrated USB controller, made a lot of hardware tasks much simpler than they were before. One of the arenas it revolutionized was custom keyboards, making it much easier to build not only standard mechanical keyboards, but keyboards of all kinds of shapes and layouts and custom macro keyboards as well. This trend has continued on for the better part of the past decade with other microcontrollers beyond the 32U4 now available as well, but this modular macro keypad takes it to a new level by keeping that simplicity but also keeping costs down. The suutari20, as it is called by its creator [Squalius] is able to achieve these aims by using 3.5 mm jacks commonly found in audio equipment. Each jack can support up to three keys, with the hub ultimately able to support 18 different keys. Those can include analog devices as well, such as volume knobs or jog controllers. The macro pad is powered by an RP2040 microcontroller from a ...

Everybody loves the Cheap Yellow Display (CYD) ESP32 dev boards, so why not treat yours to a little PDA? That’s right: turn it into a Portable Digital Assistant and relive the glory days of Palm with this project from [sau412]. For those readers who are too young to remember, a PDA was basically a phoneless and cameraless smart-phone, and devices running Palm Corporation’s Palm OS ruled the roost for most of the 90s and early 2000s. [sau412] hasn’t written an emulator or port of Palm OS; rather he’s created his own firmware for the ESP32-based CYD that is inspired by the PDAs of yore, and has many features you’d have expected back in the day. That includes a Gopher browser, to let you check out the undying alternative to the World Wide Web . There isn’t a general-purpose web browser, but there are RSS and Wikipedia readers, and what else do you need ? At least you won’t end up doomscrolling. There are also a passel of games and a BASIC inter...

PCB circuits are cool, but you know what is cooler? Terminator circuits that’s what! And what if the same material that makes Terminator circuits could also be used for smart heat sinks, flexible circuits, and self-healing material properties? Well, that is exactly what the lab at Virginia Tech’s VT MADE Lab has created, presented by Joel from [3DPrintingNerd] . So what does a Terminator circuit actually entail? Well, just like in Terminator 2, the circuits are made of liquid metal. Specifically, small drops of liquid metal alloy made of gallium and indium. These drops are contained within a matrix of PDMS polymer, which contains the magical liquid for conductivity, thermal and electrical . This makes a flexible and stretchy composite which can even self-repair when punctured or cut by bridging the Little “bubbles” of liquid alloy form a composite that will pop when applied over a threshold of force or puncture. broken circuit with the liquid alloy. Having a polymer matr...