Author: Dan Maloney

3194 Articles

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 44 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.

Rolling Your Own Ball Screws

December 4, 2024 by 24 Comments

We’ve got mixed feelings about a new video from [AndysMachines] that details how he makes custom ball screws. On the one hand, there’s almost zero chance that we’ll ever have an opportunity to put this information to practical use. But on the other hand, the video gives a fantastic look at the inner workings and design considerations for ball screws, which is worth the price of admission alone

The story behind these ball screws is that [Andy] is apparently in cahoots with SkyNet and is building a T-800 Terminator of his own. Whatever, we don’t judge, but the build requires a short-throw linear drive mechanism that can be back-driven, specs that argue for a ball screw. [Andy] goes through the challenges of building such a thing, which mainly involve creating threads with a deep profile and wide pitch. The screw itself wasn’t too hard to cut, although there were some interesting practical details in the thread profile that we’d never heard of before.

The mating nut was another. Rather than try to cut deep internal threads, [Andy] took a sort of “open-face sandwich” approach, creating half-nuts in a single piece of brass using a CNC machine and a ball-nose mill. The threads were completed by cutting the two halves apart and bolting them together — very clever! [Andy] also showed how the balls recirculate in the nut through channels cut into one of the half-nuts.

Whether the results were worth the effort is up to [Andy], but we were just glad to be along for the ride. And if you want a little more detail on lead screws and ball screws, we’ve got just the article for that.

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Fail Of The Week: The SMD Crystal Radio That Wasn’t

December 3, 2024 by 18 Comments

The crystal radio is a time-honored build that sadly doesn’t get much traction anymore. Once a rite of passage for electronics hobbyists, the classic coil-on-an-oatmeal-carton and cat’s whisker design just isn’t that easy to pull off anymore, mainly because the BOM isn’t really something that you can just whistle up from DigiKey or Mouser.

Or is it? To push the crystal radio into the future a bit, [tsbrownie] tried to design a receiver around standard surface-mount inductors, and spoiler alert — it didn’t go so well. His starting point was a design using a hand-wound air-core coil, a germanium diode for a detector, and a variable capacitor that was probably scrapped from an old radio. The coil had three sections, so [tsbrownie] first estimated the inductance of each section and sourced some surface-mount inductors that were as close as possible to their values. This required putting standard value inductors in series and soldering taps into the correct places, but at best the SMD coil was only an approximation of the original air-core coil. Plugging the replacement coil into the crystal radio circuit was unsatisfying, to say the least. Only one AM station was heard, and then only barely. A few tweaks to the SMD coil improved the sensitivity of the receiver a bit, but still only brought in one very local station.

[tsbrownie] chalked up the failure to the lower efficiency of SMD inductors, but we’re not so sure about that. If memory serves, the windings in an SMD inductor are usually wrapped around a core that sits perpendicular to the PCB. If that’s true, then perhaps stacking the inductors rather than connecting them end-to-end would have worked better. We’d try that now if only we had one of those nice old variable caps. Still, hats off to [tsbrownie] for at least giving it a go.

Note: Right after we wrote this, a follow-up video popped up in our feed where [tsbrownie] tried exactly the modification we suggested, and it certainly improves performance, but in a weird way. The video is included below if you want to see the details.

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Torque Testing 3D Printed Screws

December 3, 2024 by 18 Comments

Unless you’ve got a shop with a well-stocked hardware bin, it’s a trip to the hardware store when you need a special screw. But [Sanford Prime] has a different approach: he prints his hardware, at least for non-critical applications. Just how much abuse these plastic screws can withstand was an open question, though, until he did a little torque testing to find out.

To run the experiments, [Sanford]’s first stop was Harbor Freight, where he procured their cheapest digital torque adapter. The test fixture was similarly expedient — just a piece of wood with a hole drilled in it and a wrench holding a nut. The screws were FDM printed in PLA, ten in total, each identical in diameter, length, and thread pitch, but with differing wall thicknesses and gyroid infill percentages. Each was threaded into the captive nut and torqued with a 3/8″ ratchet wrench, with indicated torque at fastener failure recorded.

Perhaps unsurprisingly, overall strength was pretty low, amounting to only 11 inch-pounds (1.24 Nm) at the low end. The thicker the walls and the greater the infill percentage, the stronger the screws tended to be. The failures were almost universally in the threaded part of the fastener, with the exception being at the junction between the head and the shank of one screw. Since the screws were all printed vertically with their heads down on the print bed, all the failures were along the plane of printing. This prompted a separate test with a screw printed horizontally, which survived to a relatively whopping 145 in-lb, which is twice what the best of the other test group could manage.

[Sanford Prime] is careful to note that this is a rough experiment, and the results need to be taken with a large pinch of salt. There are plenty of sources of variability, not least of which is the fact that most of the measured torques were below the specified lower calibrated range for the torque tester used. Still, it’s a useful demonstration of the capabilities of 3D-printed threaded fasteners, and their limitations.

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