Generating Motion Via Nitinol Wires

December 2, 2023 by Lewin Day 13 Comments

Generally, when we’re looking to build something that moves we reach for motors, servos, or steppers — which ultimately are all just variations on the same concept. But there are other methods of locomotion available. As [Jamie Matthews] demonstrates, Nitinol wires can be another way to help get things moving.

Nitinol is a type of metal wire made of nickel and titanium that is also known as “memory wire”, because it can remember its former shape and transition back to it with a temperature change. [Jamie] uses this property to create a simple hand that is actuated by pieces of wire sourced from Amazon. This is actually a neat way to go, as it goes some way to mimicking how our own hands are moved by our tendons.

[Jamie] does a great job of explaining how to get started with Nitinol and how it works in a practical sense. We’ve seen it put to some wacky uses before, too, such as the basis for an airless tire.

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Tiny Speaker Busts Past Sound Limits With Ultrasound

November 27, 2023 by Donald Papp 15 Comments

Conventional speakers work by moving air around to create sound, but tiny speakers that use ultrasonic frequencies to create pressure and generate sound opens some new doors, especially in terms of maximum achievable volume.

A new design boasts being the first 140 dB, full-range MEMS speaker. But that kind of volume potential has less to do with delivering music at an ear-splitting volume and more to do with performing truly effective noise cancellation even in a small device like earbuds. Cancelling out the jackhammers of the world requires parts able to really deliver a punch, especially in low frequencies. That’s something that’s not so easy to do in a tiny form factor. The new device is the Cypress, from MEMS speaker manufacturer xMEMS and samples are aiming to ship in June 2024.

Combining ultrasonic waves to create audible sound is something we’ve seen show up in different ways, like using an array of transducers to focus sound like a laser beam. Another thing ultrasonics can do is cause sensors in complex electronics to become unhinged from reality and report false readings. Neato!

Turbocharge Your Transient Sensors With Math

November 25, 2023 by Julian Scheffers 19 Comments

If you’ve made a robot or played around with electronics before, you might have used a time-of-flight laser distance sensor before. More modern ones detect not just the first reflection, but analyze subsequent reflections, or reflections that come in from different angles, to infer even more about what they’re looking at. These transient sensors usually aren’t the most accurate thing in the world, but four people from the University of Wisconsin managed to get far more out of one using some clever math. (Video, embedded below.)

The transient sensors under investigation here sends out a pulse of light and records what it receives from nine angles in individual histograms. It then analyzes these histograms to make a rough estimate of the distance for each direction. But the sensor won’t tell us how it does so and it also isn’t very accurate. The team shows us how you can easily get a distance measurement that is more accurate and continues by showing how the nine distance estimates can even distinguish the geometry it’s looking, although to a limited extent. But they didn’t stop there: It can even detect the albedo of the material it’s looking at, which can be used to tell materials apart!

Overall, a great hack and we think this technology has potential – despite requiring more processing power. Continue reading “Turbocharge Your Transient Sensors With Math” →

A 3D Printed Grinder For Printed Lens Blanks

November 16, 2023 by Dan Maloney 20 Comments

When one thinks of applications for 3D printing, optical components don’t seem to be a good fit. With the possible exception of Fresnel lenses, FDM printing doesn’t seem up to the job of getting the smooth surfaces and precision dimensions needed to focus light. Resin printing might be a little closer to the mark, but there’s still a long way to go between a printed blank and a finished lens.

That gap is what [Fraens] aims to fill with this homebrew lens grinding machine. It uses the same basic methods used to grind and polish lenses for centuries, only with printed components and lens blanks. The machine itself consists of a motorized chuck for holding the lens blank, plus an articulated arm to hold the polishing tool. The tool arm has an eccentric drive that wobbles the polishing tool back and forth across the blank while it rotates in the chuck. Lens grinding requires a lot of water and abrasive, so a large bowl is provided to catch the swarf and keep the work area clean.

Lens blanks are printed to approximately their finished dimensions using clear resin in an SLA printer. [Fraens] spent a lot of time optimizing the printing geometry to minimize the number of print layers required. He found that a 30° angle between the lens and the resin pool worked best, resulting in the clearest blanks. To polish the rough blanks, a lapping tool is made from polymer modeling clay; after baking it dry, the tool can hold a variety of pads and polishing compounds. From there it’s just a matter of running the blank through a range of abrasives to get the desired final surface.

Are the lenses fantastic? Well, they’re probably not going to make it into fine optical equipment, but they’re a lot better than you might expect. Of course, there’s plenty of room for improvement; better resins might result in clearer blanks, and perhaps degassing the uncured resin under vacuum might help with bubbles. Skipping the printed blanks and going with CNC-machined acrylic might be worth a try, too.

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Lessons In Mass Production From An Atari Punk Console

November 16, 2023 by Dan Maloney 7 Comments

Sometimes the most interesting part of a project isn’t the widget itself, but what it teaches you about the manufacturing process. The story of the manufacturing scale-up of this Atari Punk Console and the lessons learned along the way is a perfect example of this.

Now, don’t get us wrong — we love Atari Punk Consoles. Anything with a couple of 555s that bleeps and bloops is OK in our books. But as [Adam Gulyas] tells the tale, the point of this project was less about the circuit than about the process of making a small batch of something. The APC was low-hanging fruit in that regard, and after a quick round of breadboarding to decide on component values, it was off to production. [Adam] was shooting for 20 units, each in a nice enclosure and a classy package. PCB assemblies were ordered, as were off-the-shelf plastic enclosures, which ended up needing a lot of tweaking. [Adam] designed custom labels for the cases, itself a fraught job; glossy label stock and button bezels apparently don’t mix.

After slogging through the assembly process, boxing the units for shipping was the next job. [Adam] sourced jewelry boxes just a bit bigger than the finished APCs, and rather than settle for tissue paper or packing peanuts, designed an insert to hold the units snugly. That involved a lot of trial and error and a little bit of origami-fu, and the results are pretty nice. His cost per unit came out to just a hair over $20 Canadian, including the packaging, which is actually pretty remarkable for such a short production run.

[Adam] includes a list of improvements for larger-scale runs, including ordering assembled PCBs, outsourcing the printing processes, and getting custom boxes made so no insert is needed. Any way you cut it, this production run came out great and teaches us all some important lessons.

Cheap Power Supplies With Fake Chips Might Not Be That Bad

November 10, 2023 by Dan Maloney 33 Comments

We all know the old maxim: if it’s too good to be true, it’s probably made with fake components. OK, maybe that’s not exactly how it goes, but in our world gone a little crazy, there’s good reason to be skeptical of pretty much everything you buy. And when you pay the equivalent of less than a buck for a DC-DC converter, you get what you pay for.

Or do you? It’s not so clear after watching [Denki Otaku]’s video on a bargain bag of buck converters he got from Amazon — ¥1,290 for a lot of ten, or $0.85 a piece. The thing that got [Denki]’s Spidey senses tingling is the chip around which these boards were built: the LM2596. These aren’t especially cheap chips; Mouser lists them for about $5.00 each in a reel of 500.

Initial testing showed the converters, which are rated at 3 to 42 VDC in and 1.25 to 35 VDC out, actually seem to do a decent job. At least with output voltage, which stays at the set point over a wide range of input voltages. The ripple voltage, though, is an astonishing 400 mV — almost 10% of the desired 5.0 V output. What’s more, the ripple frequency is 18 kHz, which is far below the 150 kHz oscillator that’s supposed to be in the LM2596. Other modules from the batch tested at 53 kHz ripple, so better, but still not good. There were more telltales of chip fakery, such as dodgy-looking lettering on the package, incorrect lead forming, and finger-scorching heat under the rated 3 A maximum load. Counterfeit? Almost definitely. Useless? Surprisingly, probably not. Depending on your application, these might do the job just fine, especially if you slap a bigger cap on the output to smooth that ripple and keep the draw low. And keep your fingers away, of course.

Worried that your chips are counterfeits? Here’s a field guide for fake chip spotters. And what do you do if you get something fake? A refund might just be possible.

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Flipped Transformer Powers Budget-Friendly Vacuum Tube Amp

November 7, 2023 by Dan Maloney 31 Comments

If you’ve ever wondered why something like a radio or a TV could command a hefty fraction of a family’s yearly income back in the day, a likely culprit is the collection of power transformers needed to run all those hungry, hungry tubes. Now fast-forward a half-century or more, and affordable, good-quality power transformers are still a problem, and often where modern retro projects go to die. Luckily, [Terry] at D-Lab Electronics has a few suggestions on budget-friendly transformers, and even shows off a nice three-tube audio amp using them.

The reason transformers were and still are expensive has a lot to do with materials. To build a transformer with enough oomph to run everything takes a lot of iron and copper, the latter of which is notoriously expensive these days. There’s also the problem of market demand; with most modern electronics favoring switched-mode power supplies, there’s just not a huge market for these big lunkers anymore, making for a supply and demand equation that’s not in the hobbyist’s favor.

Rather than shelling out $70 or more for something like a Hammond 269EX, [Terry]’s suggestion is to modify an isolation transformer, specifically the Triad N-68X. The transformer has a primary designed for either 120 or 230 volts, and a secondary that delivers 115 volts. Turn that around, though, and you can get 230 volts out from the typical North American mains supply — good enough for the plate supply on the little amp shown. That leaves the problem of powering the heaters for the tubes, which is usually the job of a second 6- or 12-volt winding on a power transformer. Luckily, the surplus market has a lot of little 6.3-volt transformers available on the cheap, so that shouldn’t be a problem.

We have to say that the amp [Terry] put these transformers to work in sounds pretty amazing — not a hint of hum. Good work, we say, but we hope he has a plan in case the vacuum tube shortage gets any worse.

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