Capacitor Decoupling Chaos, And Why You Should Abandon 100 NF

January 25, 2025 by Maya Posch 35 Comments

Everyone knows that the perfect capacitor to decouple the power rails around ICs is a 100 nF ceramic capacitor or equivalent, yet where does this ‘fact’ come from and is it even correct? These are the questions that [Graham] set out to answer once and for all. He starts with an in-depth exploration of the decoupling capacitor (and related) theory. [Graham] then dives into the way that power delivery is affected by the inherent resistance, capacitance, and inductance of traces. This is the problem that decoupling capacitors are supposed to solve.

Effectively, the decoupling capacitor provides a low-impedance path at high frequencies and a high-impedance path at low frequencies. Ideally, a larger value capacitor would be better, but since this is the real world and capacitors have ESL and ESR parameters, we get to look at impedance graphs. This is the part where we can see exactly what decoupling effect everyone’s favorite 100 nano-farad capacitors have, which as it turns out is pretty miserable.

Meanwhile, a 1 µF (ceramic) capacitor will have much better performance, as shown with impedance graphs for MLCC capacitors. As a rule of thumb, a single large decoupling capacitor is better, while two MLCC side-by-side can worsen noise. Naturally, one has to keep in mind that although ‘more capacity is better for decoupling’, there is still such a thing as ‘inrush current’ so don’t go too crazy with putting 1,000 µF decoupling capacitors everywhere.

Sony Ends Blu-Ray, MD And MiniDV Media Production

January 24, 2025 by Maya Posch 28 Comments

With the slow demise of physical media the past years, companies are gradually closing shop on producing everything from the physical media itself to their players and recorders. For Sony this seems to have now escalated to where it’ll be shuttering its recordable optical media storage operations, after more than 18 years of producing recordable Blu-ray discs. As noted by [Toms Hardware] this also includes minidisc (MD) media and MiniDV cassettes.

We previously reported on Sony ending the production of recordable Blu-ray media for consumers, which now seems to have expanded to Sony’s remaining storage media. It also raises the likelihood that Sony’s next game console (likely PlayStation 6) will not feature any optical drive at all as Blu-ray loses importance. While MiniDV likely was only interesting to those of us still lugging one of those MiniDV camcorders around, the loss of MD production may be felt quite strongly in the indie music scene, where MD is experiencing somewhat of a revival alongside cassette tapes and vinyl records.

Although it would appear that physical media is now effectively dead in favor of streaming services, it might be too soon to mark its demise.

Trap Naughty Web Crawlers In Digestive Juices With Nepenthes

January 23, 2025 by Maya Posch 44 Comments

In the olden days of the WWW you could just put a robots.txt file in the root of your website and crawling bots from search engines and kin would (generally) respect the rules in it. These days, however, we have especially web crawlers from large language model (LLM) companies happily ignoring such signs on the lawn before proceeding to hover up every scrap of content on websites. Naturally this makes a lot of people very angry, but what can you do about it? The answer by [Aaron B] is Nepenthes, described on the project page as a ‘tar pit for catching web crawlers’.

More commonly known as ‘pitcher plants’, nepenthes is a genus of carnivorous plants that use a fluid-filled cup to trap insects and small critters unfortunate enough to slip & slide down into it. In the case of this Lua-based project the idea is roughly the same. Configured as a trap behind a web server (e.g. /nepenthes), any web crawler that accesses it will be presented with an endless number of (randomly generated) pages with many URLs to follow. Page generating is deliberately quite slow to not soak up significant CPU time, while still giving the LLM scrapers plenty of random nonsense to chew on.

Considering that these web crawlers deemed adhering to the friendly sign on the lawn beneath them, the least we can do in response, is to hasten model collapse by feeding these LLM scrapers whatever rolls out of a simple (optionally Markov-based) text generator.

Making Wire Explode With 4,000 Joules Of Energy

January 21, 2025 by Maya Posch 80 Comments

The piece of copper wire moments before getting vaporized by 4,000 joules. (Credit: Hyperspace Pirate, Youtube)

In lieu of high-explosives, an exploding wire circuit can make for an interesting substitute. As [Hyperspace Pirate] demonstrates in a recent video, the act of pumping a lot of current very fast through a thin piece of metal can make for a rather violent detonation. The basic idea is that by having the metal wire (or equivalent) being subjected to a sufficiently large amount of power, it will not just burn through, but effectively vaporize, creating a very localized stream of plasma for the current to keep travelling through and create a major shockwave in the process.

This makes the exploding wire method (EWM) an ideal circuit for any application where you need to have a very fast, very precise generating of plasma and an easy to synchronize detonation. EWM was first demonstrated in the 18th century in the Netherlands by [Martin van Marum]. These days it finds use for creating metal nanoparticles, brief momentary light sources and detonators in explosives, including for nuclear (implosion type) weapons.

While it sounds easy enough to just strap a honkin’ big battery of capacitors to a switch and a piece of wire, [Hyperspace Pirate]’s video demonstrates that it’s a bit more involved than that. Switching so much current at high voltages ended up destroying a solid-state (SCR) switch, and factors like resistance and capacitance can turn an exploding wire into merely a heated one that breaks before any plasma or arcing can take place, or waste a lot of potential energy.

As for whether it’s ‘try at home’ safe, note that he had to move to an abandoned industrial site due to the noise levels, and the resulting machine he cobbled together involves a lot of high-voltage wiring. Hearing protection and extreme caution are more than warranted.

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Bambu Lab Tries To Clarify Its New “Beta” Authentication Scheme

January 20, 2025 by Maya Posch 61 Comments

Perhaps one of the most fascinating aspects of any developing tech scandal is the way that the target company handles criticism and feedback from the community. After announcing a new authentication scheme for cloud & LAN-based operations a few days ago, Bambu Lab today posted an update that’s supposed to address said criticism and feedback. This follows the original announcement which had the 3D printer community up in arms, and quickly saw the new tool that’s supposed to provide safe and secure communications with Bambu Lab printers ripped apart to extract the security certificate and private key.

In the new blog post, the Bambu Lab spokesperson takes a few paragraphs to get to the points which the community are most concerned about, which is interoperability between tools like OrcaSlicer and Bambu Lab printers. The above graphic is what they envision it will look like, with purportedly OrcaSlicer getting a network plugin that should provide direct access, but so far the Bambu Connect app remains required. It’s also noted that this new firmware is ‘just Beta firmware’.

As the flaming wreck that’s Bambu Lab’s PR efforts keeps hurtling down the highway of public opinion, we’d be remiss to not point out that with the security certificate and private key being easily obtainable from the Bambu Connect Electron app, there is absolutely no point to any of what Bambu Lab is doing.

Bambu Connect’s Authentication X.509 Certificate And Private Key Extracted

January 19, 2025 by Maya Posch 122 Comments

Hot on the heels of Bambu Lab’s announcement that it would be locking down all network access to its X1-series 3D printers with new firmware, the X.509 certificate and private key from the Bambu Connect application have now been extracted by [hWuxH]. This application was intended to be the sole way for third-party software to send print jobs to Bambu Lab hardware as we previously reported.

The Bambu Connect app is a fairly low-effort Electron-based affair, with some attempt at obfuscation and encryption, but not enough to keep prying eyes out. The de-obfuscated main.js file can be found here (archived), with the certificate and private key clearly visible. These are used to encrypt HTTP traffic with the printer, and is the sole thing standing in the way of tools like OrcaSlicer talking with authentication-enabled Bambu Lab printers.

As for what will be the next steps by Bambu Lab, it’s now clear that security through obfuscation is not going to be very effective here. While playing whack-a-mole with (paying) users who are only interested in using their hardware in the way that they want is certainly an option, this might be a wake-up call for the company that being more forthcoming with their userbase would be in anyone’s best interest.

We await Bambu Lab’s response with bated breath.

Investigating USB-to-Ethernet Dongles With “Malware” Claims

January 18, 2025 by Maya Posch 52 Comments

Recently a video surfaced from someone claiming that certain USB-to-Ethernet dongles contained ‘malware’ among other big claims. Basically these dongles were said to be designed by China (and Russia) to spy on users and so on, but how much of this is actually grounded in reality? When [lcamtuf] dove into the topic, what he found was not so much a smoking gun, but rather a curious relic from the era when drivers-on-CD were being phased out.

The item that the video went bananas about was namely an additional SPI Flash chip on the PCB alongside the USB 2.0 – Ethernet IC, with many conspiracy theories being floated as to what it would be used for. After some digging, [lcamtuf] found that the IC used in these dongles (SR9900) is by a company called CoreChips Shenzhen, with a strong suggestions that it is a clone of the (2013-era) Realtek RTL8152B.

Both chips have an external SPI Flash option, which is used with the USB side to present a ‘virtual CD drive’ to the user when the dongle is plugged in. This was borne out with the SR9900 Windows system mass production tool that [lcamtuf] obtained a copy of. Included with the flashing tool is a 168 kB ISO image (containing the SR9900 driver package) which happily fits on the 512 kB Flash chip.

Although it’s always possible for chips and firmware to contain backdoors and malware, in this particular case it would appear to be that it’s merely a cruel reminder that 2013 is now already vanishing into the realm of ‘retro computing’ as us old fogies cling to our driver installation floppies and CDs.