TechyMagThings

We are fans of macro pads and especially homebrew ones. The Apna Dost project by [np_vishwakarma] ticks most of our boxes. In addition to a few buttons, there’s an encoder, an OLED display, and it runs QMK firmware. Plus, it looks good, too.

We like that the system uses an RP2040. It is possible you have everything you need to put one of these together right now. We would wish for a few more keys, but it wouldn’t be hard to add them, either.

Perhaps we would have laid it out so the OLED could more easily label the macro keys, but — again — you could do that easily if you wanted to build your own. We did like that encoder could serve multiple purposes.

It always ticks us off when cheap macro pads you buy don’t use QMK or some other reasonable firmware. This one does, though, so it should be very easy to modify and customize.

We converted an old conference badge to a QMK macro pad of sorts. If you want a real deep dive on a much larger macro pad, that’s out there, too.

When you think of a computer, you probably don’t think of a tube full of motors and mechanics. However, as [Our Own Devices] shows, the Bendix AN5841 API Computer, an air position indicator computer, is exactly that. Using mechanical integrators and data from other analog systems on an airplane to provide key flight data to a pilot. You can see the video below.

These devices were made for military aircraft, including the B-29. It is odd that speed data can be derived from a pump that balances pressures using a fan. The video does a good job of explaining exactly how that works.

The way engineers used mechanics to convert physical measurements into analog computations is nothing short of amazing. You have to wonder how you dream up this kind of stuff. Perhaps mechanical engineers wonder the same thing about electronics. But we sort of doubt it.

We are glad our computer doesn’t have any flexible shafts or rotating disks to do math. But we do love looking at ones that did. Some analog computers used voltages instead of mechanics. This video made us think of the M13A1 ballistic computer and, of course, the Norden.

Although in our imagination those scale models of cars certainly can drive and steer just like their full-scale counterparts, there’s something incredibly satisfying about watching them truly come to life. Here [diorama111] is an absolute master at the craft, with the most recent conversion of a 1:150 Toyota Probox car model once again demonstrating these skills with casual ease.

We previously covered such conversions, with another recent one in 2024 involving another 1:150 scale model. That particular one demonstrated driving around on scale model roads, which shows a good practical use of this conversion if you want to have e.g. a scale model town with cars that actually drive around.

In the video you can see how first the base of the scale model has a tiny 25 mAh Li-polymer battery installed, along with two motors, one for steering and one for driving using a rod-linkage system and a lead screw.

The tiny gears used were salvaged from mechanical watches, with photoreflectors keeping track of the driving and steering positions. Remote control is done by infrared, with a tiny SMD IR receiver module in the car, while charging and programming of the MCU is done via terminals installed on the bottom.

In the final part of the video the car is demonstrated driving around, with working head- and rear lights, as well as blinkers and stop lights, including the top rear one. In the video description links are provided to the various schematics and software on Google Drive for those who are feeling like a fun Sunday afternoon project.

Sometimes it’s useful to add extra mass to a 3D print, and [Joe Fedewa] shared a simple and effective technique that uses plaster of Paris. Rather than pause the print and insert hardware or weighted bits inside, he designed the base as hollow. Not in the sense of zero infill, but in the sense of modeling a cavity into the open bottom of the object.

After the print is complete, he mixes the dry plaster with water until it creates a thick but pourable mixture. Then the object gets turned upside-down and the cavity filled. In about an hour, it will have set up enough to be handled and worked.

Plaster of Paris has a good heft to it, but more importantly it can be made perfectly presentable thanks to being very friendly to post-processing. Any rough spots can be easily sanded and the whole bottom smoothed, so one doesn’t even need to cap it off. Completely cured plaster can be sealed with a clear coat for a more durable finish, if desired.

This basic concept has been used in other ways, such as reinforcing prints with concrete to yield parts solid enough to make tools out of. But using plaster of Paris not just to add mass, but specifically to create a presentable surface that doesn’t need covering up is a neat and highly economical adaptation of the idea.

Other methods of adding mass to a 3D print include inserting metal balls or chunky nuts, bolts, or other hardware, but this method doesn’t require pausing prints to insert things. Nor does it require sealing off or capping the print, messing with goopy epoxies or resins, or spending a lot of money — making it a good one to keep in mind in case it comes in handy someday.

An old algebra teacher used to say, “You have to take what you know and use it to get what you don’t know.” You might say the same thing about converting analog signals into digital. Computers know how to count and keep time. [Eric Explains] has a video purporting to explain “every type of analog-to-digital converter.” We aren’t sure he got every possible method, but there’s still a lot of information in the video, which you can see below.

From the flash ADC, using a ton of comparators to the successive approximation converter, which essentially plays a game of hi/lo, guessing the answer and figuring out if the real answer is higher or lower.

Those are pretty common, but the video also covers things like the Wilkinson ADC and other more exotic techniques. Each method, of course, has its advantages and disadvantages. For example, the flash ADC is fast, but requires a lot of components and power.

Sometimes, the method you use depends on how you are building. For example, you probably wouldn’t use a charge system on a breadboard since precision capacitors are finicky. But on an integrated circuit, capacitors made with photolithography may not be very precise, but the ratio between capacitors is super precise, making that a common technique in that domain.

Even if you never need to design your own converter, understanding the different architectures will let you make a better selection among alternatives. Then again, you can design your own. We’ve seen most of these architectures in past projects.

Recently [Bits und Bolts] stumbled over a pair of Dragon 3000 branded 3dfx Voodoo 2 cards in his unfixed cards pile, and decided that the best course of action was to not only fix them, but also run them in SLI for some sweet Unreal Tournament action. Naturally, these cards being in the broken cards pile meant that he first had to figure out why they were broken and fix all issues.

The advantage of having two identical Voodoo 2 cards is of course that any missing components, like some resistors on one card, could be referenced on the other card. Beyond that it was mostly a matter of reflowing clearly corroded pins on the ICs and replacing damaged resistors and resistor arrays before the first tests could be run.

Using the mojo utility it was easy enough to spot that there were still some lingering issues, with clear issues visible in 3D games as well. These were tracked down to a dodgy pin on one of the texture mapping units (TMUs) that needed some more reflowing, and a very sneaky resistor array that was cracked but not obviously so until prodded with a multimeter.

With both cards now making happy noises when individually tested, it was time to go full SLI, fire up the Pentium 2 system and enjoy the glory of 24 MB of VRAM at high resolutions in Unreal Tournament. Considering that the bloke who had sent in these cards had found them while cleaning up a shed, it’s quite amazing how little rework was needed to once again party like it’s 1999.

Unlike on Mars where for decades we have had dozens of orbital and ground-based platforms zipping and scurrying about to prod at every bit of emitted radiation, rock type and twitch of dust devils in its thin atmosphere, for other planets and their moons we have to do a lot more speculative interpretation of data. Such was the case with the presumed existence of water plumes on Jupiter’s moon Europa. These now appear to have been a statistical fluke, per research by [L. Roth] et al. in Astronomy & Astrophysics.

As succinctly summarized in the article on this by [Javier Barbuzano] of Sky and Telescope, the original 2013 finding of said water plumes by the same team was based on faint UV emissions from Europa’s southern hemisphere as captured by the Hubble Space Telescope. However, in more recent captures these emissions were not detected again, leading them to reexamine their original analysis of the 2013 data.

One of the main flaws was in the assumption of where Europe was located on Hubble’s 1,000 x 1,000 resolution detector, with the re-analysis showing that they were off by a couple of pixels. A second flaw was quite understandable as since 2013 we have learned that Europa has a thin hydrogen exosphere which interacts with the Sun’s UV radiation. The resulting scattering induces a UV glow which could be mistaken for UV radiation emanating from the moon’s surface.

Even with this one intriguing feature turning out to be a mirage, it doesn’t make Europa any less interesting as it’s still assumed to have vast liquid water oceans. Along with Uranus’ moon Miranda this makes it very worth it to experience more of the sights and sounds of these alien worlds, whether in person or via our robotic friends.