Ethics In Engineering: Volkswagen’s Diesel Fiasco

September 23, 2015 by Brian Benchoff 360 Comments

Every so often – and usually not under the best of circumstance – the field of engineering as a whole is presented with a teaching moment. Volkswagen is currently embroiled in a huge scandal involving emissions testing of 11 Million diesel cars sold in recent years. It’s a problem that could cost VW dearly, to the tune of eighteen Billion dollars in the US alone, and will, without a doubt, end the careers of more than a few Volkswagen employees. In terms of automotive scandals, this is bigger than Unsafe at Any Speed. This is a bigger scandal than the Ford Pinto’s proclivity to explode. This is engineering history in the making, and an enormously teachable moment for ethics in engineering.

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Drawbacks Of Laser Cut Delrin–and How To Slip Around Them

September 22, 2015 by Sonya Vasquez 34 Comments

Welcome back to part II in this ensemble of techniques with laser-cut Delrin. Thanks for many of the great insights along the way in the comments. In this guide, I’d like to go over some of the more immediate kinks that come to mind when getting started with this material.

Sourcing Delrin Sheets

When it comes to shopping, there are a variety of suppliers to choose from, but there are a few key words and thoughts to keep in mind.

Names

First, Delrin, is the “brand name” that refers to the Acetal homopolymer. Variants may also be labeled, acetal or acetal homopolymer. Delrin’s natural color is a soft white, but dyes can take it into a range of other colors. Black and white are, by far, the most common, though.

Tolerances

In the previous guide, all of the examples were cut from a small range of sheet thicknesses (0.0625[in], 0.09375[in], and .125[in]) sourced from OnlineMetals. As the thickness of the sheet increases, the tolerances on the thickness rating will also become more loose. You might buy a .125[in] plate and find it to be .124[in] in some places and .126[in] in others. If you purchase a .250[in] sheet, however, you’ll find that it may vary as much as .126[in] oversize though!

Buy it Flat

Despite McMaster-Carr being my go-to solution for one-off prototypes where rapid build iterations trump BOM cost, I don’t recommend purchasing Delrin from them as their sheets don’t have a flatness rating and often gets shipped bent in (oddly sized) boxes. (Seriously, has anyone else gotten a few oddly-sized parts in a gigantic McMaster-box before?)

Internal Stresses

Extruded Delrin has internal stresses built up inside of the sheet. There are a variety of reasons why this could be the case, but my biggest hunch is that the extrusion process at the factory results in different parts of the sheets solidifying at different times as the sheet cools, possibly causing some parts of the sheet to tighten from the cooling before other gooier sections have yet to finish cooling. What this means for you is that as your part gets lased out of the sheet, you’re, in a sense, relieving that stress. As a result, the part that you cut–especially for thin sheets–may come out of the laser cutter slightly warped.

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Why Are You Still Making PCBs?

September 21, 2015 by Al Williams 223 Comments

Few things have had the impact on electronics that printed circuit boards (PCBs) have had. Cheap consumer electronics would not be as cheap if someone still had to wire everything (although by now we’d be seeing wiring robots, I’m sure). Between removing the human from the wiring process and providing many excellent electrical properties (at least, on a well-designed board), it isn’t surprising that even the cheapest examples of electronics now use PCBs.

For many years, the hallmark of being a big-time electronic hacker was the ability to make your own PCBs. There have been many ways that people have tried to bring PCB manufacturing into the hacker’s garage: stick on decals, light-sensitive blank PCBs, and even using laser printer toner (that last one spurred me to write a book on PCB layout many years back). You also see a lot of people using 3D printers or CNC mills to create PCBs. Hardly a week goes by that someone doesn’t ask me how to make a PCB in a home or small business lab.

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This Is What A Real Bomb Looks Like

September 21, 2015 by Adam Fabio 403 Comments

In 1980, Lake Tahoe, Nevada was a popular tourist spot. The area offered skiing, sailing, hiking in the mountains, and of course, gambling on the Nevada side of the lake. It was in this somewhat unlikely place where the authorities found the largest improvised bomb seen to that date in the USA.

Harvey’s casino was opened by former butcher Harvey Gross in 1944. In less than 20 years it grew to a 192 room, 11 story hotel casino. Thousands of people played Harvey’s slot machines and table games. Some were winners, but most were losers. John Birges was one of the latter. Formerly a successful landscaping company owner worth millions, he lost all of it to his gambling addiction.

Born in Hungary in 1922 as János Birges, John grew up in Budapest. When WWII hit, he flew an Me-109 for the Luftwaffe. He was arrested by the Gestapo for disobeying orders during the war, but was released. After the war, he again found himself in hot water – this time with the Russians. He was arrested in 1948 and charged with espionage. His sentence was 25 years of hard labor in the Gulag. The stories vary, but most agree that Birges was able to escape his work camp by detonating a bomb as a diversion.

In 1957 Birges and his wife Elizabeth immigrated to California. He changed his name from János to John to fit in. The couple had two sons, Johnny and Jimmy. John built up a successful landscaping business and bought a restaurant, working his way into the millionaires’ club. From the outside, they were the perfect example of the American dream.

Appearances can be deceiving. Behind closed doors, Birges was a right bastard to his family. He beat his wife and his children, even forcing them to kneel on gravel when they disobeyed him. Eventually, Johnny left home to escape his father’s fists. Elizabeth filed for divorce, and was later found dead under mysterious circumstances. Birges began gambling heavily, especially at Harvey’s Wagon Wheel casino in Lake Tahoe. He eventually burned through his personal savings, as well as the income from his businesses. The once millionaire was now penniless, but he had a plan. Just as a bomb had helped him escape the Gulag, he’d use a bomb to extort his money back from Harvey’s.

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Embed With Elliot: Interrupts, The Good…

September 18, 2015 by Elliot Williams 32 Comments

What’s the biggest difference between writing code for your big computer and a microcontroller? OK, the memory and limited resources, sure. But we were thinking more about the need to directly interface with hardware. And for that purpose, one of the most useful, and naturally also dangerous, tools in your embedded toolchest is the interrupt.

Interrupts do exactly what it sounds like they do — they interrupt the normal flow of your program’s operation when something happens — and run another chunk of code (an interrupt service routine, or ISR) instead. When the ISR is done, the microcontroller picks up exactly where it left off in your main flow.

Say you’ve tied your microcontroller to an accelerometer, and that accelerometer has a “data ready” pin that is set high when it has a new sample ready to read. You can wire that pin to an input on the microcontroller that’s interrupt-capable, write an ISR to handle the accelerometer data, and configure the microcontroller’s interrupt system to run that code when the accelerometer has new data ready. And from then on everything accelerometer-related happens automagically! (In theory.)

This is the first part of a three-part series: Interrupts, the Good, the Bad, and the Ugly. In this column, we’ll focus on how interrupts work and how to get the most out of them: The Good. The second column will deal with the hazards of heavyweight interrupt routines, priority mismatches, and main loop starvation: the Bad side of interrupts. Finally, we’ll cover some of the downright tricky bugs that can crop up when using interrupts, mainly due to a failure of atomicity, that can result in logical failures and corrupted data; that’s certainly Ugly.

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Tiny Headless Servers Everywhere

September 17, 2015 by Elliot Williams 30 Comments

Quick, what do “cloud compute engines” and goofy Raspberry Pi Internet of Things hacks have in common? Aside from all being parody-worthy buzzword-fests, they all involve administering remote headless (Linux) installations. It’s for exactly that reason that a new Ubuntu distribution flavor, Ubuntu (Snappy) Core, targets both the multi-bazillion-dollar Amazon Elastic Compute Cloud and the $55 BeagleBone Black.

If that combination seems unlikely to you, you’re not alone. But read on as we hope to make a little more sense of it all.
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The Ubiquitous Atari Punk Console

September 17, 2015 by Nava Whiteford 11 Comments

The Atari Punk Console (APC) is a dual 555 (or single 556) based synth. Designed by the famous (and somewhat infamous) Forrest Mims in 1980 and originally simply named “Sound Synthesizer”, the circuit gained it’s more recent popularity when re-dubbed the “Atari Punk Console” by Kaustic Machines. The circuit however doesn’t bear much relation to the Atari 2600 which didn’t contain a 555 timer chip. However we assume the 2600 produced a similarly glitchy square wave audio output.

The circuits operation is easy to grasp and uses only 9 components. This ease of design and construction has allowed builders to focus more on the aesthetics of its construction, hacking it into interesting, and often unlikely enclosures and systems. One such hack is the “Atari Punk Bucket” (shown here) where the APC along with a simple amp was hacked into an old rusted bucket. The APC was built up on strip-board along with a simple amp and reclaimed speakers. [Farmer glitch] has used this as a prop in live sets and it both looks and sounds awesome. Continue reading “The Ubiquitous Atari Punk Console” →