# Tube Design Tips To Save A Writer’s Project

Most of the stories we cover here are fresh from the firehose, the newest and coolest stuff to interest you during your idle moments. Sometimes though, we come across a page that’s not new, but is interesting in its own right enough to bring to your attention. So it is with our subject here, because when faced with a tube circuit design problem, we found salvation in a page from [The Valve Wizard].

Do you need to apply negative feedback to a triode amplifier? The circuit is simplicity itself, but sadly when we were at university they had long ago stopped teaching the mathematics behind the component values. Step forward everything you need to know about triode amplifier negative feedback.

Negative feedback is a pretty simple idea: subtract a little of the amplifier’s output from the input. It reduces the amplifier’s gain with a flat response, so it’s useful for removing humps in the frequency response and reducing the tendency for distortion. In a single-ended triode amp it’s done with a resistor and capacitor from anode to grid, but the question is, just what resistor or capacitor?. Here the page has all the answers, taking the reader through calculating the desired gain, and picking the value of the capacitor to avoid affecting the frequency response. We wish that someone had taught us this three decades ago!

The website is full of really useful info about valve or tube amps, and it’s worth mentioning that he’s made it available in book format too. There’s no reason not to have a go at vacuum electronics. Meanwhile in case you are wondering what project prompted this, it was a quest to improve upon this cheap Chinese kit amplifier.

# Localizing Fireworks Launches With A Raspberry Pi

If you have multiple microphones in known locations, and can determine the time a sound arrives at each one, you can actually determine the location that sound is coming from. This technique is referred to as sound localization via time difference of arrival. [Kim Hendrikse] decided to put the technique to good use to track down the location of illicit fireworks launches.

The build is based on the Raspberry Pi, with [Kim] developing an “autonomous recording unit” complete with GPS module for determining their location and keeping everything time synchronized. By deploying a number of these units, spread out over some distance, it’s possible to localize loud sounds based on the time stamps they show up in the recording on each unit.

Early testing took place with an air horn and four recording units. [Kim] found that the technique works best for sounds made within the polygon.  Determining the location was achieved with a sound investigation tool called Raven Lite, developed by Cornell University. The process is very manual, involving hunting for peaks in sound files, but we’d love to see a version that automated comparing sound peaks across many disparate recording units. In any case, it worked incredibly well for [Kim] in practice. Later testing with friends and a network of six recorders spread over Limburg, Netherlands, [Kim] was later able to localize fireworks launches with an accuracy down to a few meters.

Similar techniques are used to locate gunshots, and can work well with pretty much any loud noise that’s heard over a great distance. If you’ve been using your hacker skills to do similar investigative work, don’t hesitate to let us know on the tipsline!

# 37C3: When Apple Ditches Lightning, Hack USB-C

[Thomas Roth], aka [Ghidraninja], and author of the [Stacksmashing] YouTube channel, investigated Apple’s Lightning port and created a cool debugging tool that allowed one to get JTAG on the device. Then, Apple went to USB-C for their new phones, and all his work went to waste. Oh well, start again — and take a look at USB-C.

Turns out, though, that the iPhone 15 uses the vendor-defined messages (VDM) capability of USB-PD to get all sorts of fun features out. Others had explored the VDM capabilities on Mac notebooks, and it turns out that the VDM messages on the phone are the same. Some more fiddling, and he got a serial port and JTAG up and running. But JTAG is locked down in the production devices, so that will have to wait for an iPhone 15 jailbreak. So he went poking around elsewhere.

He found some other funny signals that turned out to be System Power Management Interface (SPMI), one of the horribly closed and NDA-documented dialects owned by the MIPI Alliance. Digging around on the Interwebs, he found enough documentation to build an open-source SPMI plugin that he said should be out on his GitHub soon.

The end result? He reworked his old Lightning hardware tool for USB-C and poked around enough in the various available protocols to get a foothold on serial, JTAG, and SPMI. This is just the beginning, but if you’re interested in playing with the new iPhone, this talk is a great place to start. Want to know all about USB-C? We’ve got plenty of reading for you.

# 37C3: You Think It’s Bad With Pluto? A History Of The Planets

Not every talk at the Chaos Communication Congress is about hacking computers. In this outstanding and educational talk, [Michael Büker] walks us through the history of our understanding of the planets.

The question “What is a planet?” is probably more about the astronomers doing the looking than the celestial bodies that they’re looking for. In the earliest days, the Sun and the Moon were counted in. They got kicked out soon, but then when we started being able to see asteroids, Ceres, Vesta, and Juno made the list. But by counting all the asteroids, the number got up above 1,200, and it got all too crazy.

Viewed in this longer context, the previously modern idea of having nine planets, which came about in the 1960s and lasted only until 2006, was a blip on the screen. And if you are still a Pluto-is-a-planet holdout, like we were, [Michael]’s argument that counting all the Trans-Neptunian Objects would lead to madness is pretty convincing. It sure would make it harder to build an orrery.

His conclusion is simple and straightforward and has the ring of truth: the solar system is full of bodies, and some are large, and some are small. Some are in regular orbits, and some are not. Which we call “planets” and which we don’t is really about our perception of them and trying to fit this multiplicity into simple classification schemas. What’s in a name, anyway?

# Quivering Facehugger Is All Geared Up

[Jason Winfield] shared with us a video describing a project with a lot of personality: a mounted, lit, and quivering Alien facehugger triggered by motion. The end result is a delightful jump scare, and the Raspberry Pi that controls everything also captures people’s reactions.

It starts with a little twitch when motion is sensed, then launches into a perfectly unsettling quiver combined with light and sound. We particularly like the wave-like effect from the LED lighting, which calls to mind illumination from rotating hazard beacons.

One challenge was how to efficiently move the legs. Rather than use a motor for each limb, [Jason] settled on a single motor driving a rotating cam arrangement. You can see the results for yourself in the video below, but getting there was not simple.

The surplus motor [Jason] chose is thin and high-torque, but runs extremely fast. Since he wanted the legs to quiver creepily rather than vibrate, something needed to be done to mitigate this.

The solution is a planetary gear assembly that drives a rotating ring and cam arrangement coupled to the facehugger’s legs. There’s only one motor, but the effect is that each leg’s motion is independent of the others. The whole assembly is quite slim, and everything is contained within the frame.

Facehuggers and gear assemblies are not exactly an everyday combination, but believe it or not this isn’t the first time the two have joined forces. Check out the Aliens-themed cuckoo clock, complete with crew member torso and emerging chestburster!

# Don’t Give Up

I’m at Chaos Communication Congress this weekend, and it’s like being surrounded by the brightest, most creative, and being honest, nerdiest crowd imaginable. And that’s super invigorating.

But because of the pandemic, this is the first in-person conference in four years, and it’s been a rather unsettling time in-between. There are tons of unknowns and issues confronting us all, geeks or otherwise, at the moment. I know some people who have fallen prey to this general malaise, and become more or less cynical.

Especially in this context, watching a talk about an absolutely bravado hack, or falling into a conversation that sparks new ideas, can be inspiring in just the right way to pull one out of the slump. Every talk is naturally a success story — of course they are, otherwise they wouldn’t be up there presenting.

But all of the smaller interactions, the hey-why-didn’t-I-think-of-that moments or the people helping each other out with just the right trick, that give me the most hope. That’s because they are all around, and I’m sure that what I’m seeing is just the tip of the iceberg. So stick together, nerds, share your work, and don’t give up!

# How To Build A Small Solar Power System

We live in an exciting time with respect to electrical power, one in which it has never been easier to break free from mains electricity, and low-frequency AC power in general. A confluence of lower-power appliances and devices using low-voltage external switch-mode supplies, readily available solar panels and electronic modules, and inexpensive high-capacity batteries, means that being your own power provider can be as simple as making an online order.

But which parts should you choose? Low Tech Magazine has the answer, in the form of a guide to building a small solar power system. The result is an extremely comprehensive guide, and though it’s written for a general audience there’s still plenty of information for the Hackaday reader.

Perhaps the most important part is that it’s demystifying the subject, there in front of us are a set of pretty straightforward recipes for personal power. The computer this is being written on spends a significant proportion of its time on the road with the ever-present company of a very hefty USB-C power pack for example, and the realization that a not-too-expensive solar panel and USB PD source could lessen the range anxiety and constant search for a train seat with a socket for a writer on the move is quite a powerful one.

Take a look and see whether your life could use bit of inexpensive off-grid power, meanwhile we’re quite pleased that the USB-C PD standard has eased some of the DC problems we expressed frustration at back in 2016.