Day: October 18, 2019

The True Cost Of Multimeters

October 18, 2019 by 70 Comments

If you are building a home shop, it is common to try to get the cheapest gear you can possibly get. However, professionals often look at TCO or total cost of ownership. Buying a cheap car, for example, can cost more in the long run compared to buying an expensive car that requires less maintenance. Most consumers will nod sagely and think of ink jet printers. That $20 printer with the $80 cartridges might not be such a deal after all. [JohnAudioTech] bought a few cheap multimeters and now has problems with each of them. Maybe that $120 meter isn’t such a bad deal, after all.

The problems he’s seen are the same ones we’ve all seen: noisy selector switches, suspect display readings, and worn off lettering. You can see the whole story in the video below.

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This Week In Security: A Digital Café Américain, The Linux Bugs That Weren’t, The Great Nation, And More

October 18, 2019 by 16 Comments

A government is going after a human rights activists in Morocco. It sounds familiar, but I don’t think Humphrey Bogart is running the gin joint this time around.

Questionable Casablanca references aside, Amnesty International has reported another attack against human rights workers. In this case, a pair of Moroccan activists were targeted with what appears to be NSO’s Pegasus malware suite. Researchers identified text message phishing that led to malicious web pages, as well as HTTP man in the middle attacks against their mobile devices. Once the target was successfully directed to the malicious site, A collection of zero-day vulnerabilities were used to compromise the phone with the NSO malware.

NSO is an Israeli company that specializes in building malware and other cybersecurity tools for governments. As you can imagine, this specialization has earned NSO the scorn of quite a few organizations. NSO claims to have a policy framework in place that allows them to evaluate and terminate the use of their software when it is deemed illegal or abusive, but due to the nature of their contracts, that process is anything but transparent. Continue reading “This Week In Security: A Digital Café Américain, The Linux Bugs That Weren’t, The Great Nation, And More” →

Lessons Learned Building A DIY Rebreather

October 18, 2019 by 41 Comments

While the homebrew rebreather the [AyLo] describes on his blog looks exceptionally well engineered and is documented to a level we don’t often see, he still makes it very clear that he’s not suggesting you actually build one yourself. He’s very upfront about the fact that he has no formal training, and notes that he’s already identified several critical mistakes. That being said, he’s taken his rebreather out for a few dives and has (quite literally) lived to tell the tale, so he figured others might be interested in reading about his experiments.

For the landlubbers in the audience, a rebreather removes the CO2 from exhaled air and recirculates the remaining O2 for another pass through the lungs. Compared to open circuit systems, a rebreather can substantially increase the amount of time a diver can remain submerged for a given volume of gas. Rebreathers aren’t just for diving either, the same basic concept was used in the Apollo PLSS to increase the amount of time the astronauts could spend on the surface of the Moon.

The science behind it seemed simple enough, so [AyLo] did his research and starting designing a bare-minimum rebreather system in CAD. Rather than completely hack something together with zip ties, he wanted to take the time to make sure that he could at least mate his hardware with legitimate commercial scuba components wherever possible to minimize his points of failure. It meant more time designing and machining his parts, but the higher safety factor seems well worth the effort.

[AyLo] has limited the durations of his dives to ten minutes or less out of caution, but so far reports no problems with the setup. As with our coverage of the 3D printed pressure regulator or the Arduino nitrox analyser, we acknowledge there’s a higher than usual danger factor in these projects. But with a scientific approach and more conventional gear reserved for backups, these projects prove that hardware hacking is possible in even the most inhospitable conditions.

Next Level Spirit Level Is On The Level

October 18, 2019 by 10 Comments

Miss your shot and scratch on the eight ball? It’s natural to blame the table for not being level so you can save face, but in all likelihood, you’re probably right. [Huygens Optics]’s father never misses a billiards shot on his home table, until one day he did. [Huygens Optics] rushed to his aid and built an extremely precise spirit level for the table so it will never happen again.

First and foremost, he had to decide how sensitive the spirit level should be. Obviously, the table should be as level as possible, though other factors like the condition of the felt will come into play as well. In doing some calculations, he found that every degree of leveling error in the table translates to several millimeters of ball unevenness and deviation, so he wanted the level to have .01 degrees of accuracy. How he manages this feat of grinding and polishing in a hobbyist workshop is all captured in the fascinating video after the break.

The level is made from two disks cut from leftover 15mm borosilicate glass. Between the disks is a 4mm cavity for the liquid (ethyl alcohol) and the air bubble to move around. To avoid introducing error with uneven adhesive application, [Huygens Optics] tried to join the disks using optical contact bonding, wherein two surfaces stick together through the magic of intermolecular forces, like the one that keeps geckos attached to vertical things. That worked quite well until he added the liquid, which broke the bond. Instead, he used a thin, UV-curable epoxy.

Getting into optics doesn’t have to cost a lot. Instead of buying or grinding lenses for experimentation, you can laser-cut lens profiles out of acrylic.

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