Comparing AliExpress Vs LCSC-Sourced MOSFETs

August 24, 2024 by Maya Posch 26 Comments

The fake AliExpress-sourced IRFP460 MOSFETs (Credit: Learn Electronics Repair, YouTube)

These days, it’s super-easy to jump onto the World Wide Web to find purported replacement parts using nothing but the part identifier, whether it’s from a reputable source like Digikey or Mouser or from more general digital fleamarkets like eBay and AliExpress. It’s hardly a secret that many of the parts you can buy online via fleamarkets are not genuine. That is, the printed details on the package do not match the actual die inside. After AliExpress-sourced MOSFETs blew in a power supply repair by [Learn Electronics Repair], he first tried to give the MOSFETs the benefit of the doubt. Using an incandescent lightbulb as a current limiter, he analyzed the entire PSU circuit before putting the blame on the MOSFETs (IRFP460) and ordering new ones from LCSC.

Buying from a distributor instead of a marketplace means you can be sure the parts are from the manufacturer. This means that when a part says it is a MOSFET with specific parameters, it almost certainly is. A quick component tester session showed the gate threshold of the LCSC-sourced MOSFETs to be around 3.36V, while that of the AliExpress ‘IRFP460’ parts was a hair above 1.8V, giving a solid clue that whatever is inside the AliExpress-sourced MOSFETs is not what the package says it should be.

Unsurprisingly, after fitting the PSU with the two LCSC-sourced MOSFETs, there was no more magic smoke, and the PSU now works. The lesson here is to be careful buying parts of unknown provenance unless you like magic smoke and chasing weird bugs.

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A man in glasses and a black sweatshirt sits in front of an orange and black computer screen just below eye level at the table in front of him. His keyboard sits on the table below. He appears to be in a park as there are trees and grass in the background.

Flying Lotus Is A Framework-Powered Portable All-in-One Computer

August 24, 2024 by Navarre Bartz 12 Comments

One of the things that we love about the modern era of computing is the increasing ease by which you can roll your own custom computer, as seen with the cyberdeck phenomenon. The Flying Lotus is another awesome build in this vein.

Built around the Framework ecosystem, this device was built to suit the very specific use case of its designer, [Carlos Aldana]. He found himself traveling a lot and that the ergonomics of a laptop left a lot to be desired, especially when in the air. Add to it the fact that he has trouble typing on typical laptop keyboards for any length of time, and you can see how an ergonomic keyboard plus a laptop just doesn’t really work on a tray table.

The Flying Lotus takes the screen, modular ports, and mainboard of a Framework laptop and puts them into a single computing block that can be hung from the clever tabs at the top or mounted on a stand that puts the screen at a more ergonomically ideal height from the work surface. [Aldana] describes it as an “iMac that’s portable.” Since it doesn’t have an integrated keyboard, you can run it with whatever keyboard you like from super duper ergo to a teeny game controller sized unit.

We’ve talked about why we like Framework so much before, and if you’d like another take on a modern portable computer, how about this portable Mac mini?

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Compact Driver Powers Steppers With USB-C PD

August 24, 2024 by Dan Maloney 12 Comments

NEMA-17 steppers are (almost) a dime a dozen. They’re everywhere, they’re well-known to hackers and makers, and yet they’re still a bit hard to integrate into projects. That’s because the motor alone isn’t much use, and by the time you find or build a driver and integrate it with a microcontroller, you’ve probably expended more effort than you will on the rest of the project. This USB-C PD stepper driver aims to change that.

What caught our eye about [Josh Rogan]’s PD Stepper is his effort to make this a product rather than just a project. The driver is based on a TMC2209 for silent operation and a lot of torque thanks to the power delivery capabilities of USB-C PD. The PCB is very nicely designed and has an AS5600 rotary magnetic encoder for closed-loop operation. There’s also an ESP32-S3 on-board, so WiFi and Bluetooth operation are possible — perfect for integration into Home Assistant via ESPHome.

[Josh]’s mechanical design is top-notch, too, with a machined aluminum spacer that fits on the back of a NEMA-17 motor perfectly and acts as a heat spreader. A machined polycarbonate cover protects the PCB and makes a very neat presentation. [Josh] has kits available, or you can roll your own with the provided build files.

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A Journey Into Unexpected Serial Ports

August 24, 2024 by Jenny List 17 Comments

Through all the generations of computing devices from the era of the teleprinter to the present day, there’s one interface that’s remained universal. Even though its usefulness as an everyday port has decreased in the face of much faster competition, it’s fair to say that everything has a serial port on board somewhere. Even with that ubiquity though, there’s still some scope for variation.

Older ports and those that are still exposed via a D socket are in most case the so-called RS-232, a higher voltage port, while your microcontroller debug port will be so-called TTL (transistor-transistor logic), operating at logic level. That’s not quite always the case though, as [Terin Stock] found out with an older Garmin GPS unit.

Pleasingly for a three decade old device, given a fresh set of batteries it worked. The time was wrong, but after some fiddling and a Windows 98 machine spun up it applied a Garmin update from 1999 that fixed it. When hooked up to a Flipper Zero though, and after a mild panic about voltage levels, the serial port appeared to deliver garbage. There followed some investigation, with an interesting conclusion that TTL serial is usually the inverse of RS-232 serial, The Garmin had the RS-232 polarity with TTL levels, allowing it to work with many PC serial ports. A quick application of an inverter fixed the problem, and now Garmin and Flipper talk happily.

Intuitive Explanation Of Arithmetic, Geometric & Harmonic Mean

August 24, 2024 by Maya Posch 8 Comments

The simple definition of a mean is that of a numeric quantity which represents the center of a collection of numbers. Here the trick lies in defining the exact type of numeric collection, as beyond the arithmetic mean (AM for short, the sum of all values divided by their number) there are many more, with the other two classical Pythagorean means being the geometric mean (GM) and harmonic mean (HM).

The question that many start off with, is what the GM and AM are and why you’d want to use them, which is why [W.D.] wrote a blog post on that topic that they figure should be somewhat intuitive relative to digging through search results, or consulting the Wikipedia entries.

Compared to the AM, the GM uses the product of the values rather than the sum, which makes it a good fit for e.g. changes in a percentage data set. One thing that [W.D] argues for is to use logarithms to grasp the GM, as this makes it more obvious and closer to taking the AM. Finally, the HM is useful for something like the average speed across multiple trips, and is perhaps the easiest to grasp.

Ultimately, the Pythagorean means and their non-Pythagorean brethren are useful for things like data analysis and statistics, where using the right mean can reveal interesting data, much like how other types using something like the median can make a lot more sense. The latter obviously mostly in the hazy field of statistics.

No matter what approach works for you to make these concepts ‘click’, they’re all very useful things to comprehend, as much of every day life revolves around them, including concepts like ‘mean time to failure’ for parts.

Top image: Cycles of sunspots for the last 400 years as an example data set to apply statistical interpretations to. (Credit: Robert A. Rohde, CC BY-SA 3.0)

A Game Of Snake On A LEGO Mechanical Computer

August 23, 2024 by Dan Maloney 6 Comments

Really, [OzzieGerff] had us at “LEGO.” But then he took it to another place entirely and built a completely mechanical, nearly 100% LEGO version of Snake. And it’s just as cool as it sounds.

Mind you, it’s a little hard to grok how this whole contraption works, which has been in the works for a while, but we’ll try to summarize as best we can. The most important aspect of this build is that there are no electronics at all — everything is done with mechanical linkages, with some Technics pneumatic components and a couple of electric motors to provide the oomph. The three main components are the input section, which consists of a two-axis joystick, a tail buffer, which keeps track of the length of the snake’s tail as gameplay progresses, and the largest component, the 16×16 display.

The joystick translates user inputs into pneumatic signals which pass through a mechanical filtering unit that prevents the head of the snake from doubling back on itself. The filtered inputs then pass into the screen reader, a complex device that probes the status of a given pixel on the display and determines the status of the snake’s head. If it touches a snake pixel, the game’s over. Hitting a blank pixel moves the head of the snake by one and takes one pixel off the end, while a food pixel extends the snake’s length.

Keeping track of the length of the snake is the job of the buffer, which uses Technics tank tracks and levers. Setting a one is done by flipping the lever to one side as it passes under the write head; a read head further down the track senses which way the lever is flipped and translates it into a pneumatic signal. The buffer has four channels, one for each possible direction the snake’s head could be moving. The signals drive a screen writer, which moves a pyramidal follower across a series of push-rods that flip the corresponding pixel on the display to show the proper icon. Simplicity itself? No, but the video below will make things a lot clearer.

It doesn’t look like [Ozzie] is quite done with this game, as he doesn’t show any actual gameplay yet. We’d love to see and hear that — we suspect it’ll make quite a racket. We’ll be keeping an eye out for this one, but while we wait, check out this rope braiding machine or watch Lego break steel.

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You Can Get A Precision Instrument-Guided Landing Even In Antarctica

August 23, 2024 by Lewin Day 8 Comments

Traditional airports spend big money to install instrument landing systems (ILS) to guide planes in safely. In places like Antarctica, though, it’s simply not possible to permanently install a massive antenna array for localization, particularly with all the ice shifting about on the regular. As covered by Flightradar24, the solution to this is to use a transponder landing system (TLS) instead.

A TLS tracks planes by using multilateration—basically, transponder signals are picked up by multiple antennas and the time delays are used to figure out the position of the aircraft. It then sends the guidance signals a plane would normally expect to receive from an ILS transmitter array, for horizontal and vertical guidance. These signals appear to the plane to be coming from antennas located as per a typical ILS array, with the TLS able to generate signals from ‘virtual emanation points” as needed. This allows the TLS to generate different landing approaches to suit different planes and conditions. From the pilot and aircraft side, it’s all perfectly transparent.

In Antarctica’s McMurdo station, landings are handled by a TLS system that barely takes up more space than a single shipping crate. The system can be set up in just a few hours, unlike a traditional ILS which takes significant installation work spanning weeks or months at best. At the moment, though, the landing strip at McMurdo is stable enough that the system only needs periodic realignment every three years or so.

You might assume that if you’re approaching Antarctica by plane, everything would be on manual. However, the creature comforts of modern airports are available even at one of the the most southerly airports on Earth!