Powering A Cavity Magnetron, From A Battery

December 4, 2023 by Jenny List 47 Comments

While vacuum electronic devices have largely been superseded over much of consumer electronics, there’s one place where they can still be found for now. The cavity magnetron is a power RF oscillator device in which electrons are induced to move in a circular path through a tuned cavity, inducing a high-power RF field, and it lies at the heart of a domestic microwave oven. They usually need a high-voltage mains transformer and a rectifier to work, but [Hyperspace Pirate] has managed to make a solid-state power supply to power one from a 12 volt battery. Better still, he’s put the resulting combo in a Care Bears lunchbox. Take a look at the video below the break.

The video starts with a potted history of the magnetron before looking at the circuit of a typical oven, which uses a single diode and a capacitor in a simple voltage multiplier. The capacitor value is adjusted to lower the power output, and a pretty thorough job is done of characterising the circuit.

The low-voltage supply starts with an XVS inverter to make the high voltage via another multiplier, but the interesting part comes with the magnetron’s heater. It’s designed for 50 or 60Hz household electricity, but there it’s receiving 40 kHz and has an appreciable impedance. The addition of a capacitor soon restores it to a reasonable performance.

In case you noticed that the ZVS converter might be improved upon, take a look at a flyback converter. Meanwhile, we should probably echo the safety message in the video that playing with magnetrons and their associated transformers can be a nasty way to die. Please take care out there!

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Retrotechtacular: The Story Of Turpentine

December 4, 2023 by Dan Maloney 33 Comments

If someone in 2023 has ever had much call to use turpentine, chances are good it was something to do with paint or other wood finishes, like varnish. Natural turpentine is the traditional solvent of choice for oil paints, which have decreased in popularity with the rise of easy-to-clean polymer-based paints and coating. Oh sure, there are still those who prefer oil paint, especially for trim work — it lays up so nice — but by and large, turpentine seems like a relic from days gone by, like goose grease and castor oil.

It wasn’t always so, though. Turpentine used to be a very big deal indeed, as shown by this circa 1940 documentary on the turpentine harvesting and processing industry. Even then it was only a shadow of its former glory, when it was a vital part of a globe-spanning naval empire and a material of the utmost strategic importance. “Suwanee Pine” shows the methods used in the southern United States, where fast-growing pines offer up a resinous organic gloop in response to wounds in their bark. The process shown looks a lot like the harvesting process for natural latex, with slanting gashes or “catfaces” carved into the trunks of young trees, forming channels to guide the exudate down into a clay collecting cup.

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USB-C For Hackers: Program Your Own PSU

December 4, 2023 by Arya Voronova 20 Comments

Last time, I showed off a few ways you can convert an existing PSU to USB-C duty, and zoomed in on a particular way you can use to convert one of the ever-abundant 18 V – 20 V laptop PSUs to USB-C. All we have left is to write software for it, and I’ll explain how it works. There’s also that one cool USB-C secret I’ve found out, but you’ll have to read on to find out more.

From the last article, we have a board that has an RP2040 and FUSB302 combo on it, which takes a 20 V DC PSU input from a laptop brick, and can switch either 5 V, 20 V or 0 V to its USB-C socket using FETs. The USB-C communication firmware is simple enough, but there’s caveats, especially regarding safety. Let’s go through those!

The Code Logic

VBUS has to be non-powered by default – we only supply 5 V when the FUSB302 detects a 5.1 kΩ pulldown on one of the CC lines. After supplying 5 V, we send out PSU capability advertisements, of the kind that we’ve learned to parse in the Replying PD article – and whenever we get a Request, we have to switch to the requested profile, connecting the voltage rail requested to the FET. I opt to not do any current consumption control in this design, assuming a well-behaved device, but you theoretically should do that. It wouldn’t be hard to add a high-side current sensor, say, something from Analog Devices – I just don’t want to do that now, especially given that I’m already using two of the exposed ADC pins to do Lenovo/HP PSU capability detection instead, one is used up for VBUS measurement, and the fourth is used for VIN (20 V rail) measurement – that’s four ADCs, which is as much as the RP2040 has got. However, if I ever need more ADCs, I can add an analog mux like 4051 in the next version! Continue reading “USB-C For Hackers: Program Your Own PSU” →

The Hoarder’s Dilemma Hack Chat

December 4, 2023 by Dan Maloney 31 Comments

Join us on Wednesday, December 6 at noon Pacific for the The Hoarder’s Dilemma Hack Chat with Gabe Emerson!

There’s a lot to be said for the power of a well-stocked junk bin. It’s almost a magical thing, being able to dive into a random box and retrieve just the right part to perform a needful repair or to complete a project without the need to hit the web or hop in the car for a trip to the hardware store. For those who pride themselves on their resourcefulness, it can be a heady experience indeed.

But as with everything, such feats of fix-it come at a price. That little squirt of dopamine that comes from having just the right thing can make your monkey brain fixate on a simple equation: “More stuff is better stuff.” The higher and deeper your stash, the better your chances of having what you need, assuming you can find it, of course. This way lies madness, and perhaps an appearance on a reality TV show.

Is there a better way? It’s hard to say, but we figured it would be a good idea to loop in someone with a lot of experience collecting junk that somehow finds its way into some pretty cool projects. Gabe Emerson runs the popular and aptly named “saveitforparts” channel over on YouTube, and fancies himself an accomplished hoarder. We’d have to agree, given his recent 1,000-mile drive to pick up a used geodesic dome, or his ever-increasing collection of RV satellite dishes, which he somehow puts to good use. His junk collection is pretty epic; he even has a whole piece of property devoted to the larger pieces of his collection, like an entire monorail train. He seems uniquely qualified to discuss the “Hoarder’s Dilemma” and the painful process of deciding what stays and what goes.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, December 6 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

Another OmniBot 2000 Upgrade

December 4, 2023 by Al Williams No comments

There were many toy robots back in the 80s that were — frankly — underwhelming by today’s standards. Back then, any old thing that rolled around with some blinking lights would impress, but the bar is higher today. Then again, some of the basic components won’t really change. You still need wheels, motors, batteries, and all that. But the computers we can bring to bear today are much better. Maybe that’s why so many people, including [mcvella], decide to give these venerable toys like the OmniBot 2000 a facelift or, maybe a better analogy, a brain transplant.

In this particular case, the brain in question is a Raspberry Pi. The robot will also sport new sensors, motor controllers, and a webcam. There is also a new battery pack in play. The project doesn’t cover working with the single powered gripper arm. The left arm isn’t motorized. There is also a cassette tape deck you could probably make do something interesting. Of course, with a Raspberry Pi, you get wireless control, and the project uses Viam to define and control the robot’s motion.

There is some retro cool factor to using a robot like Ominbot. However, we might be more tempted to just build our own. With a 3D printer, a laser cutter, and a few motors, you could make something that would be about equivalent or better with little effort.

We have seen OmniBot conversions before, particularly over on Hackaday.io. Maybe someone will convert one over to steam power.

Italy Proposes Minimalist Lunar Outpost For Artemis

December 4, 2023 by Tom Nardi 26 Comments

When humanity first step foot on the Moon, they couldn’t stay around for very long. The Apollo program was limited by the technology of the era — given the incredible cost per kilogram to put a payload down on the lunar surface, it wasn’t feasible to bring down enough consumables for a lengthy stay. Even if they could have carried sufficient food and water to last more than a few days, the limiting factor would have become how long the crew could realistically remain cooped up in the tiny Lunar Excursion Module (LEM).

In comparison, the Artemis program is far more ambitious. NASA wants to establish a long-term, and perhaps even permanent, human presence on our nearest celestial neighbor. This will be made possible, at least in part, to the greatly reduced launch costs offered by current and near-future launch vehicles compared to legacy platforms like the Saturn V or Space Shuttle. But cheaper rides to space is only part of the equation. NASA will also be leaning heavily on the lessons learned during the International Space Program; namely, the advantages of modular design and international cooperation.

While NASA and their commercial partners will still end up providing the bulk of the hardware for the Artemis program, many modules and components are being provided by other countries. From the Orion’s European Service Module (ESM) to the Japanese life support systems to be installed on the Lunar Gateway Station, America won’t be going to the Moon alone this time.

The latest international contribution to the Artemis program comes from the Italian Space Agency (ASI), who have announced their intention to develop a lunar habitation module they’re calling the Multi-Purpose Habitat (MPH) in collaboration with Thales Alenia Space.

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This Laser-Cut One-Piece Wedge Tenon Locks Wood Joints Tight

December 4, 2023 by Dan Maloney 24 Comments

Woodworkers have always been very clever about making strong and attractive joints — think of the strength of a mortise and tenon, or the artistry of a well-made dovetail. These joints have been around for ages and can be executed with nothing more than chisels and a hand saw, plus a lot of practice, of course. But new tools bring new challenges and new opportunities in joinery, like this interesting “hammer joint” that can be made with a laser cutter.

This interesting joint comes to us from [Jiskar Schmitz], who designed it for quick, solid, joints without the need for glue or fasteners. It’s a variation on a wedged mortise and tenon joint, which strengthens the standard version of the joint by using a wedge to expand the tenon outward to make firm contact with the walls of the tenon.

The hammer joint takes advantage of the thin kerf of a laser cutter and its ability to make blind cuts to produce a tenon with a built-in wedge. The wedge is attached to a slot in the tenon by a couple of thin connectors and stands proud of the top of the tenon. The tenon is inserted into a through-hole mortise, and a firm hammer blow on the wedge breaks it free and drives it into the slot. This expands the tenon and locks it tightly into the mortise, creating a fairly bulletproof joint. The video below tells the tale.

While the hammer joint seems mainly aimed at birch plywood, [Jiskar] mentions testing it in other materials, such as bamboo, MDF, and even acrylic, although wood seems to be the best application. [Jiskar] also mentions a potential improvement: the addition of a ratchet and pawl shape between the wedge and the slot in the tenon, which might serve to lock the wedge down and prevent it from backing out.

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