Author: Dan Maloney

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Hackaday Links: December 8, 2024

December 8, 2024 by 14 Comments

For some reason, we never tire of stories highlighting critical infrastructure that’s running outdated software, and all the better if it’s running on outdated hardware. So when we learned that part of the San Francisco transit system still runs on 5-1/4″ floppies, we sat up and took notice. The article is a bit stingy with the technical details, but the gist is that the Automatic Train Control System was installed in the Market Street subway station in 1998 and uses three floppy drives to load DOS and the associated custom software. If memory serves, MS-DOS as a standalone OS was pretty much done by about 1995 — Windows 95, right? — so the system was either obsolete before it was even installed, or the 1998 instance was an upgrade of an earlier system. Either way, the San Francisco Municipal Transportation Agency (SFMTA) says that the 1998 system due to be replaced originally had a 25-year lifespan, so they’re more or less on schedule. Replacement won’t be cheap, though; Hitachi Rail, the same outfit that builds systems that control things like the bullet train in Japan, is doing the job for the low, low price of $212 million.

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Liquid Metal Ion Thrusters Aren’t Easy

December 7, 2024 by 10 Comments

What do scanning electron microscopes and satellites have in common? On the face of things, not much, but after seeing [Zachary Tong]’s latest video on liquid metal ion thrusters, we see that they seem to have a lot more in common than we’d initially thought.

As you’d expect with such a project, there were a lot of false starts and dead ends. [Zach] started with a porous-emitter array design, which uses a sintered glass plate with an array of tiny cones machined into it. The cones are coated in a liquid metal — [Zach] used Galinstan, an alloy of gallium, indium, and tin — and an high voltage is applied between the liquid metal and an extraction electrode. Ideally, the intense electric field causes the metal to ionize at the ultra-sharp tips of the cones and fling off toward the extraction electrode and into the vacuum beyond, generating thrust.

Getting that working was very difficult, enough so that [Zach] gave up and switched to a slot thruster design. This was easier to machine, but alas, no easier to make work. The main problem was taming the high-voltage end of things, which seemed to find more ways to produce unwanted arcs than the desired thrust. This prompted a switch to a capillary emitter design, which uses a fine glass capillary tube to contain the liquid metal. This showed far more promise and allowed [Zach] to infer a thrust by measuring the tiny current created by the ejected ions. At 11.8 μN, it’s not much, but it’s something, and that’s the thing with ion thrusters — over time, they’re very efficient.

To be sure, [Zach]’s efforts here didn’t result in a practical ion thruster, but that wasn’t the point. We suspect the idea here was to explore the real-world applications for his interests in topics like electron beam lithography and microfabrication, and in that, we think he did a bang-up job with this project.

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3D Printed Caliper Extensions Make Hole Measurement Easier

December 6, 2024 by 21 Comments

If there’s anything more frustrating than mounting holes that don’t line up with the thing you’re mounting, we don’t know what it could be. You measure as carefully as possible, you drill the holes, and yet at least one hole ends up being just out of place. Sometimes you can fudge it, but other times you’ve got to start over again. It’s maddening.

Getting solid measurements of the distance between holes would help, which is where these neat snap-on attachments for digital calipers come in. [Chris Long] came up with the 3D printed tools to make this common shop task a little easier, and they look promising. The extensions have cone-shaped tips that align perfectly with the inside edge of the caliper jaws, which lines the jaws up with the center of each hole. You read the center-to-center distance directly off the caliper display, easy peasy.

Of course, there’s also the old machinist’s trick (last item) about zeroing out the calipers after reading the diameter of one of the holes and then measuring the outside-to-outside distance between the two holes. That works great when you’ve got plenty of clearance, but the shorter inside jaws might make measuring something like a populated PCB with this method tricky. For the price of a little filament and some print time, these might be just the tool to get you out of a bind.

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Hacked Ultrasonic Sensors Let You See With Sound

December 6, 2024 by 13 Comments

If you want to play with radar — and who could blame you — you can pretty easily get your hands on something like the automotive radar sensors used for collision avoidance and lane detection. But the “R” in radar still stands for “Radio,” and RF projects are always fraught, especially at microwave frequencies. What’s the radar enthusiast to do?

While it’s not radar, subbing in ultrasonic sensors is how [Dzl] built this sonar imaging system using a lot of radar principles. Initial experiments centered around the ubiquitous dual-transducer ultrasonic modules used in all sorts of ranging and detection project, with some slight modifications to tap into the received audio signal rather than just using the digital output of the sensor. An ESP32 and a 24-bit ADC were used to capture the echo signal, and a series of filters were implemented in code to clean up the audio and quantify the returns. [Dzl] also added a downsampling routine to bring the transmitted pings and resultant echoes down in the human-audible range; they sound more like honks than pings, but it’s still pretty cool.

To make the simple range sensor more radar-like, [Dzl] needed to narrow the beamwidth of the sensor and make the whole thing steerable. That required a switch to an automotive backup sensor, which uses a single transducer, and a 3D printed parabolic dish reflector that looks very much like a satellite TV dish. With this assembly stuck on a stepper motor to swivel it back and forth, [Dzl] was able to get pretty good images showing clear reflections of objects in the lab.

If you want to start seeing with sound, [Dzl]’s write-up has all the details you’ll need. If real radar is still your thing, though, we’ve got something for that too.

Thanks to [Vanessa] for the tip.

Non-Planar Fuzzy Skin Textures Improved, Plus A Paint-On Interface

December 6, 2024 by 3 Comments

If you’ve wanted to get in on the “fuzzy skin” action with 3D printing but held off because you didn’t want to fiddle with slicer post-processing, you need to check out the paint-on fuzzy skin generator detailed in the video below.

For those who haven’t had the pleasure, fuzzy skin is a texture that can be applied to the outer layers of a 3D print to add a little visual interest and make layer lines a little less obvious. Most slicers have it as an option, but limit the wiggling action of the print head needed to achieve it to the XY plane. Recently, [TenTech] released post-processing scripts for three popular slicers that enable non-planar fuzzy skin by wiggling the print head in the Z-axis, allowing you to texture upward-facing surfaces.

The first half of the video below goes through [TenTech]’s updates to that work that resulted in a single script that can be used with any of the slicers. That’s a pretty neat trick by itself, but not content to rest on his laurels, he decided to make applying a fuzzy skin texture to any aspect of a print easier through a WYSIWYG tool. All you have to do is open the slicer’s multi-material view and paint the areas of the print you want fuzzed. The demo print in the video is a hand grip with fuzzy skin applied to the surfaces that the fingers and palm will touch, along with a little bit on the top for good measure. The print looks fantastic with the texture, and we can see all sorts of possibilities for something like this.

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Exercise Wheel Tracker Confirms Suspicions About Cats

December 5, 2024 by 23 Comments

What do cats get up to in the 30 minutes or so a day that they’re awake? Being jerks, at least in our experience. But like many hackers, [Brent] wanted to quantify the activity of his cat, and this instrumented cat exercise wheel was the result.

To pull this off, [Brent] used what he had on hand, which was an M5Stack ESP32 module, a magnetic reed switch, and of course, the cat exercise wheel [Luna] seemed to be in the habit of using at about 4:00 AM daily. The wheel was adorned with a couple of neodymium magnets to trip the reed switch twice per revolution, with the pulse stream measured on one of the GPIOs. The code does a little debouncing of the switch and calculates the cat’s time and distance stats, uploading the data to OpenSearch for analysis and visualization. [Brent] kindly includes the code and the OpenSearch setup in case you want to duplicate this project.

As for results, they’re pretty consistent with what we’ve seen with similar cat-tracking efforts. A histogram of [Luna]’s activity shows that she does indeed hop on the wheel at oh-dark-thirty every day, no doubt in an effort to assassinate [Brent] via sleep deprivation. There’s also another burst of “zoomies” around 6:00 PM. But the rest of the day? Pretty much sleeping.

Gas Gauge Upgrade Keeps VW Restoration Classy

December 4, 2024 by 45 Comments

Getting every detail perfectly right is often the goal in automotive restorations, and some people will go to amazing lengths to make sure the car looks and acts just like it did when it rolled off the dealer’s lot all those decades ago. That ethos can be pushed a little too far, though, especially with practical matters like knowing how much gas is left in the tank. Get that wrong and you’ll be walking.

Unwilling to risk that cruel fate with his restoration of 1978 Volkswagen Bus, [Pegork] came up with a replacement fuel gauge that looks identical to the original meter, but actually works. The gas gauges on ’60s and ’70s VWs were notoriously finicky, and when they bothered to work at all they were often wildly inaccurate. The problem was usually not with the sender unit in the tank, but the gauge in the dash, which used a bimetallic strip heated by a small coil of wire to deflect a needle. [Pegor]’s “SmoothBus” modification replaces the mechanical movement with a micro servo to move the needle. The variable voltage coming back from the fuel sender is scaled through a voltage divider and read by an analog input on an ATtiny85, which does a little algorithmic smoothing to make sure the needle doesn’t jump around too much. A really nice addition is an LED low fuel indicator, a feature that would have saved us many walks to the gas station back in our VW days. Except for the extra light, the restored gauge looks completely stock, and it works far better than the original.

Hats off to [Pregor] for this fantastic restomod. As we’ve noted before, classic VWs are perhaps the most hackable of cars, and we applaud any effort to keep these quirky cars going.