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While vacuum electronic devices have largely been superseded over much of consumer electronics, there’s one place where they can still be found for now.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!

Continue reading “Powering A Cavity Magnetron, From A Battery” →

A Handheld Hackintosh, But So Much More

December 3, 2023 by Jenny List 2 Comments

As handheld computing has solidified alongside everything else into the mobile phone, it’s sad that the once promising idea of a general purpose machine in the palm of the hand has taken a turn into the dumbed-down walled-garden offered by smartphone vendors. There was a time when it seemed that a real computer might be a common miniaturized accessory, but while it’s not really come to pass, at least [iketsj] has taken a stab at it. His handheld Hackintosh runs MacOS on a miniature scale, and looks rather nice.

At its heart is the LattePanda Alpha x86 single board computer, with a small custom expansion board for a couple of buttons, a USB hub, a small keyboard, and a display. These parts are all mounted to a baseboard with metal stand-offs, and the power is sourced from a single USB-C socket at the bottom edge. What makes it more extraordinary is that it’s not the first handheld Hackintosh from this maker, the previous one being significantly bigger.

On one hand then, this is home-built PC like any other, assembled from off-the-shelf-parts. But on the other it’s far from normal, for despite its simplicity it forms a very usable small form factor device. The Akruvia Una keyboard uses tactile switches so maybe it’s not the machine to type your thesis on, but other than that it makes a great little machine for MacOS, Linux, or Windows. We like it, and we think you will too when you see the video below the break.

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Honey, I Ate The Camera

December 2, 2023 by Jenny List 17 Comments

We like cameras here at Hackaday. We like them a lot. But until now that liking has never extended to liking their taste. A build from [Dmitri Tcherbadji] could change all that though, and he’s created a working Fuji Instax Square camera made from gingerbread.

To look at, it’s a straightforward box camera, albeit one made from sheets of gingerbread stuck together with what looks like icing. The film rests in an off-the-shelf development unit but the rest is edible, including unexpectedly the lens which is made of sugar glass. The photos it returns are definitely somewhat cloudy, but that it works at all is a significant feat.

While it’s an unconventional choice it’s clear that gingerbread, or at least a baked material similar to it, could become a useful tool in a maker’s arsenal. In this case it’s light-proof, but were instantly curious about how well a moulded piece of dough might hold its shape when baked. He reports the gingerbread expanding in the oven, however we’re guessing that tuning the quantity of raising agent could help.

Home-made cameras have featured here many times, but Instax seems to pop up most often as a hacked in replacement for obsolete Polaroid packs.

The Sunspots Are Coming (Again)

December 1, 2023 by Jenny List 5 Comments

There are a bunch of ways to estimate the age of a radio amateur, by the letters in their callsign, by their preferred choice of homebrewing technology, or sometimes by their operating style. One that perhaps doesn’t immediately come to mind is to count how many solar cycles they remember, and since the current cycle 25 is my fourth I guess I’ve seen a few. Cycle 25 is so far shaping up to be quite an active one especially of late, which popular media are describing as bombarding us with flares from a “sunspot archipelago” and the more measured tones of spaceweather.com giving us warning of X-class flares heading in our direction, today!

Jean-Claude Roy, VP, Hydro Quebec — We wouldn’t be this guy for anything. From CBC’s coverage of the 1989 power outage.

As the technology for solar observation has increased in sophistication and the Internet has allowed anyone to follow the events above us as they unfold, the awareness of solar phenomena has shifted away from the relatively small numbers of astronomers and radio amateurs who would once have been eagerly awaiting a solar cycle to a wider audience. Ever since a particularly severe event in March 1989 during cycle 22 caused disruptions including the blackout of a significant part of Canada it’s been a periodic topic of mild doom in slow news moments. But what lies behind the reports of solar activity? Perhaps it’s time to take a look.

The solar cycle refers to the 11-year period of solar activity from a maximum of observed sunspots through a minimum to a new maximum. The sunspots are the visible evidence of the solar magnetic field changing its polarity, and appear as darker areas where there is a greater strength of magnetic flux in the sun’s photosphere. We refer to solar cycles by number with solar cycle 1 occurring in 1755 because that year represents the earliest cycle which can be found in modern astronomical observation data, but previous cycles have been deduced over millennia through dendrochronology, sediment analysis, isotope observations, and other methods. Continue reading “The Sunspots Are Coming (Again)” →

A Few New Car Owners Will Join The 48V Future

December 1, 2023 by Jenny List 135 Comments

Leaving aside all the annoying hype surrounding Tesla’s Cybertruck, there’s a little technical detail which might be of more interest to readers than the automotive behemoth itself. It’s one of very few vehicles on the road to eschew 12 volt electrics for not 24 volt, but 48 volt. This has been one of those automotive innovations promised as just around the corner for many years, and it seems finally we’ll see it in practice.

The reason that there’s nothing new in the prospect of moving on from 12 volt electrics has been brewing for decades now. A typical car has plenty of motorized gadgets from seat adjusters to sunroofs, as well as at least one heated windscreen or other surface. These devices take a lot of power, and at the lower voltage require significant current to operate. The 48 volt system will require much less in the way of copper to get the power where it’s needed, so the surprise is that we’ve not yet seen it in run-of-the-mill vehicles from the likes of Ford or Volkswagen.

What we’re guessing is that other manufacturers will be watching from the sidelines as to whether 48 volt electrics cause any problems for the Tesla, and it’s not impossible we could see it becoming the new hotness. There are many choice words we could say relating to the hype around Tesla and its supposed level of innovation, but it could be that this time they’ve really been first with something the whole industry will go for. If so we should rejoice, because it’s likely to push down the prices of 48 volt lithium-ion packs.

Header image: Mliu92, CC BY-SA 3.0.

The Minimum Required For A Film Camera

November 30, 2023 by Jenny List 13 Comments

Film cameras can be complex and exquisitely-crafted masterpieces of analogue technology. But at their very simplest they need be little more than a light-proof box with a piece of film at the back of it, and some kind of lens or pinhole with a shutter. [ChickenCrimpy] adds the most basic of 35 mm cartridge to create what he calls the Minimum Viable Camera. It’s a half-frame 35 mm pinhole film camera with the simplest possible construction.

It can be built from almost any flat light-proof 3 mm thick stock, though something that you can run through a laser cutter is probably ideal. Once snapped together to make to box-like structure, tape is added along the joins for light-proofing. The film is reeled from a full 35 mm cartridge to an empty one, and cranked back frame-by-frame by means of a wooden key that engages with the spindle.

There’s no lens, instead this is a pinhole camera, and the shutter is a piece of the stock held on the front of the camera with bolts and butterfly nuts. Taking a photo is as simple as pointing the device at the subject and lifting the shutter away for a few seconds. There’s a video overview for the project which we’ve placed below the break.

It’s true that this camera needs a moment in the darkroom to load, but we like its extreme simplicity and the ethereal and grainy pictures it produces. If you fancy an introduction to 35 mm photography you could definitely do worse.

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Noise Cancelling Isn’t As Easy As You’d Think

November 28, 2023 by Jenny List 14 Comments

On the face of it, producing a set of noise cancelling headphones should be a relatively straightforward project. But as [Pete Lewis] found out, things are not always as they seem. The result is a deep dive into microphone specifications, through which most of us could probably learn something.

Noise cancelling headphones have a set of microphones which provide anti-phase noise through an amplifier to the ‘phones, thus in theory cancelling out the external noise. Since [Pete] is a musician this pair would have to be capable of operating at high noise levels, so he checked the spec for his microphone and with an acoustic overload point at 124 dB for a 115 environment he was ready to go.

Unfortunately these ‘phones showed distortion, which brings us back to the acoustic overload point. This is the sound level at which the microphone has 10% distortion, which is a very high figure, and certainly meant there was enough distortion to be audible at the lower level. After a search for a higher spec microphone and a move to a digital codec-based solution with an ESP32 he eventually cracks it though, leading to an inexpensive set of noise cancelling headphones for high-noise environments.

If distortion interests you, it’s a subject we’ve visited in the past.

Header image: fir0002, GFDL 1.2.