3D Printed DIN Rail Mount Is Attractive

February 11, 2024 by 8 Comments

DIN rails aren’t very common in hobby projects, although you do see them occasionally. But in some industries, they are everywhere. The rail is just a piece of aluminum or steel with slots to hold it to a wall or bulkhead. There are two small lips that equipment like circuit breakers, power supplies, or controllers can attach easily. A common 3D printing project is a way to mount something like a printer controller to DIN rails. [NotLikeALeafOnThe Wind] shows a different take on it: a magnetic holder that temporarily attaches a rail to a ferrous surface.

Of course, mounting the rail is only half the equation. After that, you still need things to mount on the rail. Luckily, there’s no shortage of designs for DIN mounts for many common boards and modules.

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Running UNIX On A Nintendo Entertainment System

February 11, 2024 by 19 Comments

Who wouldn’t want to run a UNIX-like operating system on their NES or Famicom? Although there’s arguably no practical reason for doing so, [decrazyo] has cobbled together a working port of Little Unix (LUnix), which was originally written for the Commodore 64 and 128 by [Daniel Dallmann]. The impetus for this project was initially curiosity, but when [decrazyo] saw that someone had already written a UNIX-like OS for the 6502 processor, it seemed apparent that the NES was too similar to the C64 to not port it.

Much of this is relatively straightforward, as the 6502 MPU in the C64 is nearly identical to the Ricoh 2A03 in the NES, with the latter missing the binary-coded decimal support, which is not a crucial feature. The only significant roadblock was the lack of RAM in the NES. The console has a mere 2 KB of RAM and 2 KB of VRAM, which made it look anemic even next to the C64. Here, a Japan-only accessory came to the rescue: the Famicom Disk System (FDS), which is a proprietary floppy disk-based system that slots into the bottom of the Famicom and was used for games as well as storing saves back in the day.

By using a Famicom with FDS, it was possible to gain an additional 32 kB provided by the FDS, making the userspace utilities available in the shell. The fruits of this labor work well enough that he could also pop it up on an EverDrive cartridge that supports FDS ROMs and boot it up on an unmodified NES. Whether this is cooler than the NES-OS, which we covered previously, is up for debate.

Incidentally, [Maciej Witkowiak] seems to have resumed development on LUnix, with a new release in 2023, so maybe UNIX-on-6502 may see a revival after a few decades of little happening.

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Analog Engineer’s Pocket Reference Needs A Big Pocket

February 10, 2024 by 24 Comments

We always admire when companies produce useful tools or documentation that aren’t specific to their products. For example, consider LTSpice. Sure, it has the company’s models baked in. But there’s no reason you can’t use it for anything. Thanks! We were interested to see Texas Instrument’s fifth edition of the “Analog Engineer’s Pocket Reference” is still freely available. While we aren’t sure a book with nearly 200 pages in it is a “pocket reference,” we do think you’ll enjoy it, even if you don’t want to use TI’s offerings. This book has been around for 50 years, but it is updated periodically, and this version is the fifth iteration.

The book has several sections ranging from conversion between units and color codes to amplifier noise calculations and understanding ADC settling times. Want to know more about PCB microstrips? Page 85.

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Pimp My Pot Redux, Now Cheaper And Even Better

February 10, 2024 by 10 Comments

If there’s one thing we like around here more than seeing an improved version of a project we’ve already covered, it’s when the improvements make the original project cheaper. In the case of this LED ring light for pots and encoders, not only is it cheaper than its predecessors, it’s better looking and easier to integrate into your projects.

Right from its start, [upir]’s “Pimp My Pot” project has been all about bringing some zazzle to rotary controls. Knobs with a pointer and a scale on the panel are okay — especially when they go to eleven — but more lights mean more fun. The fun comes at a price, though; the previous version of “PMP” used an off-the-shelf LED ring light with a unit cost of about $10. Not the end of the world, perhaps, but prohibitive, and besides, where’s the fun in just buying a component specifically made for rotary control indication?

The new version shown in the video below is pin-compatible with the driver board [upir] used for the previous version, which is based on the MAX7219 display driver. Modifying the previous board to accommodate 32 white 0402 LEDs over a 270° arc was no mean feat. [upir] covers both creating the schematic and the PCB layout in some detail, providing his usual trove of tool-chain tips for minimizing the amount of manual work needed.

Wisely, [upir] chose to get his boards assembled by the vendor; getting all those LEDs to line up perfectly is a job best left to the robots. While the board is designed for use with pots that mount on either side, we much prefer mounting the pot’s shaft through the board, as it keeps the LEDs closer to the knob. The final price per board works out to about $6.30 in quantities of ten and falls to a trivial $1.70 each for lots of 1,000. Pretty sweet savings on a pretty sweet-looking build.

This is a cool use of a ring of LEDs, but if you prefer the finger kind, you can make that, too. You can do it the easy way or the hard way.

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Wooden Desk Lamp Uses Unusual Dimmer

February 10, 2024 by 11 Comments

One of the problems with laser cutting projects is that while they look good, they often look like they were laser cut. [Timber Rough] has a wooden desk lamp that not only looks good but has one of the most unusual dimming features we’ve seen.

One thing that stands out is the lamp is made of different kinds of wood, and that helps. But the dimmer is a magnet and Hall effect sensor that levitates. It is hard to explain, but a quick look at the video below will clarify it.

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Pi 5 And SDR Team Up For A Digital Scanner You Can Actually Afford

February 10, 2024 by 29 Comments

Listening to police and fire calls used to be a pretty simple proposition: buy a scanner, punch in some frequencies — or if you’re old enough, buy the right crystals — and you’re off to the races. It was a pretty cheap and easy hobby, all things considered. But progress marches on, and with it came things like trunking radio and digital modulation, requiring ever more sophisticated scanners, often commanding eye-watering prices.

Having had enough of that, [Top DNG] decided to roll his own digital trunking scanner on the cheap. The first video below is a brief intro to the receiver based on the combination of an RTL-SDR dongle and a Raspberry Pi 5. The Pi is set up in headless mode and runs sdrtrunk, which monitors the control channels and frequency channels of trunking radio systems, as well as decoding the P25 digital modulation — as long as it’s not encrypted; don’t even get us started on that pet peeve. The receiver also sports a small HDMI touchscreen display, and everything can be powered over USB, so it should be pretty portable. The best part? Everything can be had for about $250, considerably cheaper than the $600 or so needed to get into a purpose-built digital trunking scanner — we’re looking at our Bearcat BCD996P2 right now and shedding a few tears.

The second video below has complete details and a walkthrough of a build, from start to finish. [Top DNG] notes that sdrtrunk runs the Pi pretty hard, so a heat sink and fan are a must. We’d probably go with an enclosure too, just to keep the SBC safe. A better antenna is a good idea, too, although it seems like [Top DNG] is in the thick of things in Los Angeles, where LAPD radio towers abound. The setup could probably support multiple SDR dongles, opening up a host of possibilities. It might even be nice to team this up with a Boondock Echo. We’ve had deep dives into trunking before if you want more details.

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The Usage Of Embedded Linux In Spacecraft

February 10, 2024 by 46 Comments

As the first part of a series, [George Emad] takes us through a few examples of the Linux operating system being used in spacecraft. These range from SpaceX’s Dragon capsule to everyone’s favorite Martian helicopter. An interesting aspect is that the freshest Linux kernel isn’t necessarily onboard, as stability is far more important than having the latest whizzbang features. This is why SpaceX uses Linux kernel 3.2 (with real-time patches) on the primary flight computers of both Dragon and its rockets (Falcon 9 and Starship).

SpaceX’s flight computers use the typical triple redundancy setup, with three independent dual-core processors running the exact same calculations and a different Linux instance on each of its cores, and the result being compared afterwards. If any result doesn’t match that of the others, it is dropped. This approach also allows SpaceX to use fairly off-the-shelf (OTS) x86 computing hardware, with the flight software written in C++.

NASA’s efforts are similar, with Ingenuity in particular heavily using OTS parts, along with NASA’s open source, C++-based F’ (F Prime) framework. The chopper also uses some version of the Linux kernel on a Snapdragon 801 SoC, which as we have seen over the past 72 flights works very well.

Which is not to say using Linux is a no-brainer when it comes to use in avionics and similar critical applications. There is a lot of code in the monolithic Linux kernel that requires you to customize it for a specific task, especially if it’s on a resource-constrained platform. Linux isn’t particularly good at hard real-time applications either, but using it does provide access to a wealth of software and documentation — something that needs to be weighed up against the project’s needs.