How to Test a B-52 Against EMP: Project ATLAS-I

Audacious times generate audacious efforts, especially when national pride and security are perceived to be at stake. Such was the case in the 1950s and 1960s, with the Space Race that started with a Russian sphere whizzing around the planet and ended with Neil Armstrong’s footprint on the Moon. But at the same time, other efforts were underway to answer big questions of national import, such as determining how durable the United States’ strategic assets were, and whether they could withstand the known effects of electromagnetic pulse (EMP), a high-intensity burst of electromagnetic energy that could potentially disable a plane in flight. Finding out just what an EMP could do to a plane would take big engineering and a large forest’s worth of trees.

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Hackaday Links: February 11, 2018

Are you a student? Are you part of a hackerspace? We have a contest going on right now where you can win a fancy new Prusa i3 MK3. The Repairs You Can Print contest is a challenge to do something useful with that machine that spits out tugboats. We’re looking for functional repairs of items around your house, office, or garage. Did you repair something with a 3D printer? Then you too can get in on the action! Enter now! Check out the entries!

You may know Flite Test as the group who do everything surrounding remote control flight (mostly fixed wings, a nice counter to the quadification of the hobby over the last few years). Flite Test designs and sells airplanes made out of Dollar Tree foam board, they have yearly, bi-coastal meetups, and they’re all-around awesome dudes. Now, they want to build the Disneyland of RC flight. [Josh Bixler], the face of Flite Test and a guy who has a plane named after him, wants to buy a golf course and turn it into the world’s best RC flying park, with a ~2000 foot grass strip for general aviation. We’re looking at their crowdfunding campaign, and it looks promising it might be funded by the time this goes live.

A while ago, [Peter Jansen], the guy who built a tricorder and a laser-cut CT scanner, made a magnetic camera. This Hall Effect camera is a camera for magnetism instead of light. Now, this camera has been fully built and vastly improved. He’s capturing ‘frames’ of magnetism in a spinning fan at 2000 Hz (or FPS, terminology kind of breaks down here), and it’s beautiful.

Oh thank God we can finally buy GPUs again. Try buying them with Bitcoin.

In the last few years, CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, has expanded. Originally, this was one of the treaties that banned the import or export of rhino horn, but recently this expanded to the export of rosewood thanks to increased demand in China for rosewood furniture. The laws of unintended consequences kicked into effect, and importing anything made out of rosewood is now a mess of permits and inspections at the border, including musical instruments. Travelling orchestras, for example, are at risk of having their string section confiscated because of rosewood tuning pegs. Cooler minds may now be prevailing, and there’s some hope the regulations may be changed during the next meeting of the CITES convention next year.

As noted a few months ago, there was a possibility of Broadcom buying Qualcomm for one… hundred… Billion dollarsThis offer was rejected, with Qualcomm saying the offer wasn’t high enough. Broadcom fired back with an offer of $82 per share, or $121B. This offer was rejected this week.

Need some EMC testing? [Zach]’s got your back. He’s reserved some time in a 10m EMC chamber for testing NeuroBytes this week. If you have an Open Source project that needs a pre-test scan for unintentional radiator, you can get in on the action. This is just a pre-test, you’re not getting certification, and you’re not going to test anything with radios, and you need to ship [Zach] your stuff. But still, free test time. Woo.

Careful Testing Reveals USB Cable Duds

What’s worse than powering up your latest build for the first time only to have absolutely nothing happen? OK, maybe it’s not as bad as releasing the Magic Smoke, but it’s still pretty bewildering to have none of your blinky lights blink like they’re supposed to.

What you do at that point is largely a matter of your troubleshooting style, and when [Scott M. Baker]’s Raspberry Pi jukebox build failed to chooch, he returned to first principles and checked the power cable. That turned out to be the culprit, but instead of giving up there, he did a thorough series of load tests on multiple USB cables to see which ones were suspect, with interesting results.

[Scott] originally used a cable with a USB-A on one end and a 3.5-mm barrel plug on the other with a switch in between, under the assumption that the plug on the Pi end would be more robust, as well as to have a power switch for the jukebox. Testing that cable using an adjustable DC load would prove that the cable was unfit for Pi duty, dropping the voltage to under 2 volts at a measly 500-mA load. Other cables proved much better under load, even those with USB mini jacks and even one with a 5.5-mm barrel. But the larger barrel-plug cable also proved to be a stinker when it was paired with an inline switch. In the video below, [Scott] walks through not only the testing process, but also gives a quick tour of his homebrew DC load.

The lesson is clear: not all USB cables are created equal, so caveat hacker. And if you’ve got a yen to check the cables in your junk bin like [Scott] did, this full-featured smart DC load might be just the thing.

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Statistics and Hacking: An Introduction to Hypothesis Testing

In the early 20th century, Guinness breweries in Dublin had a policy of hiring the best graduates from Oxford and Cambridge to improve their industrial processes. At the time, it was considered a trade secret that they were using statistical methods to improve their process and product.

One problem they were having was that the z-test (a commonly used test at the time) required large sample sizes, and sufficient data was often unavailable. By studying the properties of small sample sizes, William Sealy Gosset developed a statistical test that required fewer samples to produce a reasonable result. As the story goes though, chemists at Guinness were forbidden from publishing their findings.

So he did what many of us would do: realizing the finding was important to disseminate, he adopted a pseudonym (‘Student’) and published it. Even though we now know who developed the test, it’s still called “Student’s t-test” and it remains widely used across scientific disciplines.

It’s a cute little story of math, anonymity, and beer… but what can we do with it? As it turns out, it’s something we could probably all be using more often, given the number of Internet-connected sensors we’ve been playing with. Today our goal is to cover hypothesis testing and the basic z-test, as these are fundamental to understanding how the t-test works. We’ll return to the t-test soon — with real data. Continue reading “Statistics and Hacking: An Introduction to Hypothesis Testing”

Precision Pantograph Probes PCBs

Electronic components are getting smaller and for most of us, our eyesight is getting worse. When [Kurt] started using a microscope to get a better view of his work, he realized he needed another tool to give his hands the same kind of precision. That tool didn’t exist so he built it.

The PantoProbe is a pantograph mechanism meant to guide a probe for reaching the tiny pads of his SMT components. He reports that he has no longer has any trouble differentiating pins 0.5 mm apart which is the diameter of the graphite sticks in our favorite mechanical pencils.

[Kurt] has already expanded his machine’s capability to include a holder for a high-frequency probe and even pulleys for a pick-and-place variation. There’s no mention of dual-wielding PantoProbes as micro-helping-hands but the versatility we’ve seen suggests that it is only a matter of time.

Four bar linkages are capable of some incredible feats and they’re found all around us. Enjoy one of [Kurt]’s other custom PCBs in his Plexitube Owl Clock, or let him show you to make 3D objects with a laser engraver.

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Innovating A Better Printing Platform

Just because you have a fancy new 3D printer doesn’t mean that innovation should stop there. Almost everyone has had a print go foul if the first layer doesn’t properly adhere to the printing platform — to say nothing of difficulty in dislodging the piece once it’s finished. Facing mixed results with some established tricks meant to combat these issues, [D. Scott Williamson] — a regular at Chicago’s Workshop 88 makerspace — has documented his trials to find a better printer platform.3D Printer Steel Print Plate 1

For what he had (a printer without a heated plate), painter’s tape and hairspray wasn’t cutting it, especially when it came time to remove the print as the tape wouldn’t completely come off the part. How then, to kill two birds with one stone? Eureka! A flexible metal covering for the printing plate.

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An Overview Of The Dreaded EMC Tests

There is one man whose hour-long sessions in my company give me days of stress and worry. He can be found in a soundless and windowless room deep in the bowels of an anonymous building in a town on the outskirts of London. You’ve probably driven past it or others like it worldwide, without being aware of the sinister instruments  that lie within.

The man in question is sometimes there to please the demands of the State, but there’s nothing too scary about him. Instead he’s an engineer and expert in electromagnetic compatibility, and the windowless room is a metal-walled and RF-proof EMC lab lined with ferrite tiles and conductive foam spikes. I’m there with the friend on whose work I lend a hand from time to time, and we’re about to discover whether all our efforts have been in vain as the piece of equipment over which we’ve toiled faces a battery of RF-related tests. As before when I’ve described working on products of this nature the specifics are subject to NDAs and in this case there is a strict no-cameras policy at the EMC lab, so yet again my apologies as any pictures and specifics will be generic.

There are two broadly different sets of tests which our equipment will face: RF radiation, and RF injection. In simple terms: what RF does it emit, and what happens when you push RF into it through its connectors and cables? We’ll look at each in turn as a broad overview pitched at those who’ve never seen inside an EMC lab, sadly there simply isn’t enough space in a Hackaday article to cover every nuance.

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