BNCs For An Old Instrument

October 27, 2024 by Jenny List 5 Comments

Back in the summer our eye was caught by [Jazzy Jane]’s new signal generator, or perhaps we should say her new-to-her signal generator. It’s an Advance E1 from around 1950, and it was particularly interesting from here because it matches the model on the shelf above this bench. She’s back with a new video on the E1, allowing us a further look inside it as she replaces a dead capacitor, gets its audio oscillator working, and upgrades its sockets.

Treating us to a further peek inside the unit, first up is a leaky capacitor. Then a knotty question for old tech enthusiasts, to upgrade or not? The ancient co-ax connectors are out of place on a modern bench, so does originality matter enough to give it a set of BNC sockets? We’d tend to agree; just because we have some adapters for the unit here doesn’t mean it’s convenient. Following on from that is a period variable frequency audio mod which has failed, so out that comes and a little fault-finding is required to get the wiring of the audio transformer.

These instruments are not by any means compact, but they do have the advantage of being exceptionally well-built and above all cheap. We hope readers appreciate videos like the one below the break, and that you’re encouraged not to be scared of diving in to older items like this one to fix them. Meanwhile the first installment is here.

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DIY Eye And Face Tracking For The Valve Index VR Headset

May 19, 2024 by Donald Papp 10 Comments

The Valve Index VR headset has been around for a few years now. It doesn’t come with eye or face tracking, but that didn’t stop inspired folks like [Physics-Dude] from adding DIY solutions in elegant and effective ways using a combination of hardware, open software, and 3D printable parts.

The whole assembly integrates tightly, thanks in part to the “frunk” designed into the Index for exactly this kind of thing.

This project leverages the EyeTrackVR project (and optionally, Project Babble for mouth tracking) which both have great applications particularly in social VR spaces.

These are open-source, self-contained and modular solutions intended for a variety of hardware platforms. Of course, every millimeter and gram tends to count when it’s something that gets worn on one’s head, so [Physics-Dude] tailored a solution specifically for the Valve Index. His project makes great use of the platform’s hacker-friendly hardware design.

[Physics-Dude] also makes excellent use of a certain widely-available “gumstick” style USB hub as an important part of his build. Combined with with the front-mounted USB port on the Index, it results in an extremely compact and tightly integrated solution that looks great. While it can be risky to rely on a particular off-the-shelf item in a build, doing so absolutely has its place here.

The documentation is fantastic, including welcome guidance on cable routing and step-by-step instructions. If you’ve been interested in adding eye tracking to a project, be sure to give it a look. Already have eye tracking in a project of your own? Tell us all about it!

Small, Quiet Air Compressor Puts 3D-Printed Parts To Best Use

April 11, 2024 by Dan Maloney 14 Comments

When the only tool you’ve got is a hammer, every problem starts to look like a nail. Similarly, while a 3D printer is a fantastic tool to have, it can make you think it’s possible to build all the things with printed parts. Knowing when to print ’em and when to machine ’em is important, a lesson that [Diffraction Limited] has taken to heart with this semi-printed silent air compressor.

The key to this compressor’s quiet operation is a combination of its small overall size. its relatively low output, and its strategic use of plastic components, which tend to dampen vibrations. The body of the compressor and the piston arms are the largest 3D-printed parts; the design calls for keeping printed parts in compression for longer life, while the parts of the load path in tension travel through fasteners and other non-printed parts. The piston design is interesting — rather than being attached to connecting rods via wrist pins, the machined Delrin pistons are solidly attached to the piston arms. This means they have to swivel within the cylinders, which are made from short pieces of metal tubing, with piston seals designed to move up and down in grooves on the pistons to allow air to move past them. The valve bodies atop each cylinder are salvaged from another compressor.

When powered by a NEMA23-frame BLDC motor via a belt drive, the compressor is remarkably quiet; not quite silent perhaps, but still impressively smooth, and capable of 150 PSI at low speeds. And as a bonus, the split crankcase makes it easy to open up and service, or just show off how it works. We’ve seen a variety of 3D-printed compressors, from screw-type to Wankel, but this one really takes the prize for fit and finish. Continue reading “Small, Quiet Air Compressor Puts 3D-Printed Parts To Best Use” →

Electrospinning Artificial Heart Valves

March 29, 2024 by Dan Maloney 10 Comments

When you think about additive manufacturing, thoughts naturally turn to that hot-glue squirting CNC machine sitting on your bench and squeezing whatever plastic doodad you need. But 3D printing isn’t the only way to build polymer structures, as [Riley] shows us with this fascinating attempt to create electrospun heart valves.

Now, you may never have heard of electrospinning, but we’ll venture a guess that as soon as you see what it entails, you’ll have a “Why didn’t I think of that?” moment. As [Riley] explains, electrospinning uses an electric field to build structures from fine threads of liquid polymer solution — he uses polycaprolactone (PCL), a biodegradable polyester we’ve seen used in other medical applications, which he dissolves in acetone. He loads it into a syringe, attaches the positive terminal of a high-voltage power supply to the hypodermic needle, and the negative terminal to a sheet of aluminum foil. The charge turns the PCL droplets into fine threads that accumulate on the foil; once the solvent flashes off, what’s left is a gossamer layer of non-woven plastic fabric.

To explore the uses of this material, [Riley] chose to make an artificial heart valve. This required a 3D-printed framework with three prongs, painted with conductive paint. He tried a few variations on the design before settling on a two-piece armature affixed to a rotating shaft. The PCL accumulates on the form, creating a one-piece structure that can be gingerly slipped off thanks to a little silicon grease used as a release agent.

The results are pretty impressive. The structure bears a strong resemblance to an artificial tricuspid heart valve, with three delicate leaves suspended between the upright prongs. It’s just a proof of concept, of course, but it’s a great demonstration of the potential of electrospinning, as well as an eye-opening look at what else additive manufacturing has to offer.

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How A Steam Bug Once Deleted All Of Someone’s User Data

January 20, 2024 by Maya Posch 14 Comments

In a retrospective, [Kevin Fang] takes us back to 2015, when on the Steam for Linux issue tracker [keyvin] opened an issue to report that starting the Steam client after moving the Steam folder had just wiped all of his user data, including his backup drive mounted under /media. According to [keyvin], he moved the standard ~/.local/share/steam to a drive mounted under /media and symlinked ~/.local/share/steam to this new location on the external drive. He then tried starting Steam, which failed, before Steam crashed and tried reinstalling itself. That’s when [keyvin] realized that Steam had apparently recursively deleted everything owned by his user from the root folder.

The infamous Valve code that made Linux users sad.

In the issue thread, user [doofy] got hit by the same bug when trying to directly start the ~/.local/share/steam/steam.sh script with debugging enabled. He then was the first to point out the rm -rf in that steam.sh script, but since this particular line is in a function only called when Steam tries to remove and reinstall itself to ‘fix’ a botched start, how did this happen? Ultimately it seems to be because of the STEAMROOT variable being set to an empty string, and another unset variable triggering the reset_steam() function, leading to the demise of all the user data.

Since then Valve has presumably fixed the issue, as no further users have filed tickets, but it’s concerning that a similar issue seems to still exist on Windows. Whether or not the original Linux issue has been fixed, it shows clearly how one should always check return values and perhaps, just maybe, never do an automated rm -rf or equivalent.

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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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Building A Giant Vacuum Tube Smart Lamp

May 19, 2023 by Lewin Day 12 Comments

Vacuum tubes are pretty, which is why they’re often showcased externally on exquisitely-expensive home Hi-Fi hardware. But if you just want to gaze at their beauty without making any noise, why not build this vacuum tube lamp from [Noel Törjék] instead?

[Noel] got into some creative reuse with this build, with the main body consisting of a bell jar and wooden bowls. The internal structure is then created from jar lids, wire, metal sheeting, steel rods, and galvanized wire mesh. Simple modelling techniques are used to assemble the internal parts of the “valve,” including the grid and the electrodes and so on. As for light, [Noel] employed a ZigBee LED driver that he could control over his smart home setup via a Philips Hue bridge.

The final result looks like an extra-large tube. Anyone who knows what it is will spot that it’s not a real one, but they’re also exactly the audience that will appreciate it for what it is. Everyone else will probably just think you’ve taken an interest in strange art-deco replica lighthouses. It’s not the first time we’ve seen replica valves around these parts, though, and we’re sure it won’t be the last!