Why Do Rifa Capacitors Fail?

Anyone who works with older electronic equipment will before long learn to spot Rifa capacitors, a distinctive yellow-translucent component often used in mains filters, that is notorious for failures. It’s commonly thought to be due to their absorbing water, but based upon [Jerry Walker]’s long experience, he’s not so sure about that. Thus he’s taken a large stock of the parts and subjected them to tests in order to get to the bottom of the Rifa question once and for all.

What he was able to gather both from the parts he removed from older equipment and by applying AC and DC voltages to  test capacitors, was that those which had been used in DC applications had a much lower likelihood of exhibiting precursors to failure, and also a much longer time before failure when connected to AC mains.

Indeed, it’s only at the end of the video that he reveals one of the parts in front of him is an ex-DC part that’s been hooked up to the mains all the time without blowing up. It’s likely then that these capacitors didn’t perform tot heir spec only when used in AC applications. He still recommends replacing them wherever they are found and we’d completely agree with him, but it’s fascinating to have some light shed on these notorious parts.

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Building An Energy Sword Replica From Halo

A good many of us whiled away the hours of our youths playing Swords Only deathmatch in Halo 2. The Energy Sword, aka the Plasma Sword, was the star of the show, with its devastating glowing blades granting us scoreboard domination. [Arnov Sharma] has now built a quality replica of this science-fiction weapon.

The build starts with a 3D design drawn up in Fusion 360. The parts are then 3D printed, with opaque filament used for the handle and translucent PLA filament for the “blade”. Inside the blade elements are twenty WS2812B LEDs, creating the characteristic glow that made the Energy Sword so tantalizing to find in game. An ATtiny85 is charged with running the LEDs, with the aid of an IP5306 chip to act as a boost converter for the lithium-ion battery supplying the juice.

[Anton] admits that the sword was built for the sole purpose of beautifying his maker space. That’s something we can respect, because we’d love to have one hanging on the wall at home. We’ve featured some other fun gaming replicas before, too.

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A cat skull enclosed in a domed security camera enclosure with green LEDs illuminating the eye sockets, sitting on a table with other skulls and rocks.

Cat Skull For Internet Connection Divination

[Emily Velasco] has an internet provider that provides sub-par connectivity. Instead of repeatedly refreshing a browser tab to test if the network is up, [Emily] decided to create an internet status monitor by embedding indicator lights in a cat skull…for some reason.

The electronics are straightforward, with the complete parts list consisting of an Arduino Nano 33 IoT device connected to a pair of RGB LEDs and 50 Ohm resistors. The Nano attempts to connect to a known site (in this case, the Google landing page) every two seconds and sets the LEDs to green if it succeeds or red if it fails.

The cat skull is thankfully a replica, 3D printed by one of [Emily]’s Twitter acquaintances, and the whole project was housed in a domed security camera enclosure. [Emily] mounts the LEDs into the skull to create a “brain in a jar” effect.

The source is available on GitHub for those wanting to take a look. We’ve featured internet connectivity status indicators in the form of traffic lights here before, as well as various network status monitors and videoconferencing indicator lights.

Blender And OpenEMS Teamed Up Make Stunning Simulations

There’s tons of theory out there to explain the behavior of electronic circuits and electromagnetic waves. When it comes to visualization though, most of us have had to make do with our lecturer’s very finest blackboard scribbles, or some diagrams in a textbook. [Sam A] has been working on some glorious animated simulations, however, which show us various phenomena in a far more intuitive way.

The animations were created in Blender, the popular 3D animation software. As for the underlying simulation going on behind the scenes, this was created using the openEMS platform. [Sam] has used openEMS to run electromagnetic simulations of simple circuits via KiCAD. From there, it was a matter of finding a way to export the simulation results in a way that could be imported into Blender. This was achieved with Paraview software acting as a conduit, paired with a custom Python script.

The result is that [Sam] can produce visually pleasing electromagnetic simulations that are easy to understand. One needn’t imagine a RF signal’s behaviour in a theoretical coax cable with no termination, when one can simply see what happens in [Sam]’s animation. 

Simulation is a powerful tool which is often key to engineering workflows, as we’ve seen before.

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Modern Dance Or Full-Body Keyboard? Why Not Both!

If you felt in your heart that Hackaday was a place that would forever be free from projects that require extensive choreography to pull off, we’re sorry to disappoint you. Because you’re going to need a level of coordination and gross motor skills that most of us probably lack if you’re going to type with this full-body, semaphore-powered keyboard.

This is another one of [Fletcher Heisler]’s alternative inputs projects, in the vein of his face-operated coding keyboard. The idea there was to be able to code with facial gestures while cradling a sleeping baby; this project is quite a bit more expressive. Pretty much all you need to know about the technical side of the project can be gleaned from the brilliant “Hello world!” segment at the start of the video below. [Fletcher] uses OpenCV and MediaPipe’s Pose library for pose estimation to decode the classic flag semaphore alphabet, which encodes characters in the angle of the signaler’s extended arms relative to their body. To extend the character set, [Fletcher] added a squat gesture for numbers, and a shift function controlled by opening and closing the hands. The jazz-hands thing is just a bonus.

Honestly, the hack here is mostly a brain hack — learning a complex series of gestures and stringing them together fluidly isn’t easy. [Fletcher] used a few earworms to help him master the character set and tune his code; the inevitable Rickroll was quite artistic, and watching him nail the [Johnny Cash] song was strangely satisfying. We also thoroughly enjoyed the group number at the end. Ooga chaka FTW.

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Hackaday Does Berlin

If you’re wondering why there was no newsletter last weekend, it was because we had our hands full with Hackaday Berlin. But boy, was it worth it! Besides being the launch party for the tenth annual Hackaday Prize, it was the first Hackaday gathering in Europe for four years, and it was awesome to see a bunch of familiar faces and meet many more new ones.

In a world that’s so interconnected, you might think that social media can take care of it all for you. And to some extent that’s true! If I could count the number of times I heard “I follow you on Twitter/Mastodon” over the course of the event!

But then there were tons of other meetings. People who are all interested in building and designing analog synthesizers, even some who live in the same urban megalopolis, meeting each other and talking about modules and designs. People who love flip dots. On the spot collaborations of people writing video drivers and people making huge LED walls. And somehow there’s still room for this to happen, even though the algorithms should have probably hooked these folks up by now.

From the perspective of hosting the conference, I get the most satisfaction from seeing these chance meetings and the general atmosphere of people learning not only new things, but new people. This cross-fertilization of friendships and project collaborations is what keeps our community vital, and especially coming out of the Pandemic Years, it’s absolutely necessary. I came away with a long list of new plans, and I’m sure everyone else did too. And for some reason, social media just isn’t a substitute. Take that, TwitFace!

Photo of the Echo Dot PCB, highlighting the capacitor that needs to be shorted out for the exploit to work

Squeezing Secrets Out Of An Amazon Echo Dot

As we have seen time and time again, not every device stores our sensitive data in a respectful manner. Some of them send our personal data out to third parties, even! Today’s case is not a mythical one, however — it’s a jellybean Amazon Echo Dot, and [Daniel B] shows how to make it spill your WiFi secrets with a bit of a hardware nudge.

There’s been exploits for Amazon devices with the same CPU, so to save time, [Daniel] started by porting an old Amazon Fire exploit to the Echo Dot. This exploit requires tactically applying a piece of tin foil to a capacitor on the flash chip power rail, and it forces the Echo to surrender the contents of its entire filesystem, ripe for analysis. Immediately, [Daniel] found out that the Echo keeps your WiFi passwords in plain text, as well as API keys to some of the Amazon-tied services.

Found an old Echo Dot at a garage sale or on eBay? There might just be a WiFi password and a few API keys ripe for the taking, and who knows what other kinds of data it might hold. From Amazon service authentication keys to voice recognition models and maybe even voice recordings, it sounds like getting an Echo to spill your secrets isn’t all that hard.

We’ve seen an Echo hijacked into an always-on microphone before, also through physical access in the same vein, so perhaps we all should take care to keep our Echoes in a secure spot. Luckily, adding a hardware mute switch to Amazon’s popular surveillance device isn’t all that hard. Though that won’t keep your burned out smart bulbs from leaking your WiFi credentials.