The Strain Of Flu Shot Logistics

Did you get a flu shot this year? How about last year? In a world of next-day delivery and instant downloads, making the yearly pilgrimage to the doctor or the minute clinic feels like an outdated concept. Even if you get your shots free at the office, it’s still a pain to have to get vaccinated every year.

Unfortunately, there’s really no other way to deal with the annual threat of influenza. There’s no single vaccine for the flu because there are multiple strains that are always mutating. Unlike other viruses with one-and-done vaccinations, influenza is a moving target. Developing, producing, and distributing millions of vaccines every year is a massive operation that never stops, or even slows down a little bit. It’s basically Santa Claus territory — if Santa Claus delivered us all from mass epidemics.

The numbers are staggering. For the 2018-19 season, as in last year, there were 169.1 million doses distributed in the United States, up from 155.3 million doses the year before. How do they do it? We’re gonna roll up our sleeves and take a stab at it.

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Mike Harrison Knows Everything About LEDs

Driving an LED and making it flash is probably the first project that most people will have attempted when learning about microprocessor control of hardware. The Arduino and similar boards have an LED fitted, and turning it on and off is a simple introduction to code. So it’s fair to say that many of us will think we have a pretty good handle on driving an LED; connect it to a I/O pin via a resistor and that’s it. If this describes you, then Mike Harrison’s talk at the recent Hackaday Superconference (embedded below) will be an education.

Mike has appeared on these pages multiple times as he pushes LEDs and PCB techniques to their limits, even designing our 2017 Superconference badge, and his many years of work in the upper echelons of professional LED installations have given him an unrivaled expertise. He has built gigantic art projects for airports, museums, and cities. A talk billed as covering everything he’s learned about LEDs them promises to be a special one.

If there’s a surprise in the talk, it’s that he’s talking very little about LEDs themselves. Instead we’re treated to a fundamental primer in how to drive a lot of LEDs, how to do so efficiently, with good brightness and colour resolution, and without falling into design traps. It’s obvious that some of his advice such at that of relying on DIP switches rather than software for configuration of multi-part installations has been learned the hard way.

Multiple LEDs at once from your driver chip, using a higher voltage.
Multiple LEDs at once from your driver chip, using a higher voltage.

We are taken through a bit of the background to perceived intensity and gamma correction for the human eyesight. This segues neatly into the question of resolution, for brightness transitions to appear smooth it is necessary to have at least 12 bits, and to deliver that he reaches into his store of microcontroller and driver tips for how to generate PWM at the right bitrate. His favoured driver chip is the Texas TLC5971, so we’re treated to a primer on its operation. A useful tip is to use multiple smaller LEDs rather than a single big one in the quest for brightness, and he shows us how he drives series chains of LEDs from a higher voltage using just the TI chip.

Given the content of the talk this shouldn’t come as a shock, but at the end he reminds us that he doesn’t use all-in-one addressable LEDs such as the WS2932 or APA102. These are  the staple of so many projects, but as he points out they are designed for toy type applications and lack the required reliability for a multi-thousand LED install.

Conference talks come in many forms and are always fascinating to hear, but it’s rare to see one that covers such a wide topic from a position of experience. He should write it into a book, we’d buy it!

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Tales From The Sysadmin: Dumped Into The Grub Command Line

Today I have a tale of mystery, of horror, and of hope. The allure of a newer kernel and packages was too much to resist, so I found myself upgrading to Fedora 30. All the packages had downloaded, all that was left was to let DNF reboot the machine and install all the new packages. I started the process and meandered off to find a cup of coffee: black, and darker than the stain this line of work leaves on the soul. After enough time had elapsed, I returned, expecting the warming light of a newly upgraded desktop. Instead, all that greeted me was the harsh darkness of a grub command line. Something was amiss, and it was bad.

(An aside to the reader, I had this experience on two different machines, stemming from two different root problems. One was a wayward setting, and the other an unusual permissions problem.)

How does the fledgling Linux sysadmin recover from such a problem? The grub command line is an inscrutable mystery to the uninitiated, but once you understand the basics, it’s not terribly difficult to boot your system and try to restore the normal boot process. This depends on what has broken, of course. If the disk containing your root partition has crashed, then sorry, this article won’t help.

In order to get a system booting, what exactly needs to happen? How does booting Linux work, even? Two components need to be loaded into memory: the kernel, and the initramfs. Once these two elements are loaded into memory, grub performs a jump into the kernel code, which takes over and finishes the machine’s boot. There is one more important detail that we care about — the kernel needs to know where to find the root partition. This is typically part of the kernel parameters, specified on the kernel boot line.

When working with an unfamiliar shell, the help command is a good starting point. grub runs in a very limited environment, and running the help command scrolls most of the text off the screen. There is an environment variable that helps out here, enabling output paging:set pager=1.
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Hackaday Links: November 24, 2019

It barely seems like it, but it’s been a week since the 2019 Hackaday Superconference wrapped up in sunny Pasadena. It was an amazing weekend, filled with fun, food, camaraderie, and hacks galore. For all who were there, it’ll likely take quite some time before spinning down to Earth again from the post-con high. For those who couldn’t make it, or for those who did but couldn’t squeeze in time for all those talks with everything else going on, luckily we’ve got a ton of content for you to review. Start on the Hackaday YouTube channel, where we’ve got videos already posted from most of the main stage talks. Can’t-miss talks include Chris Gammell’s RF deep-dive, Kelly Heaton’s natural electronic art, and Mohit Bhoite’s circuit sculpture overview. You’ll also want to watch The State of the Hackaday address by Editor-in-Chief Mike Szczys. More talks will be added as they’re edited, so watch that space for developments.

One of the talks we missed – and video of which appears not to be posted yet – was Adam Zeloof’s talk on thermodynamic design for your circuits. While we wait for that, here’s an interesting part that might prove useful for your next high-power design. It’s a Thermal Jumper Chip, which is essentially a ceramic SMD component that can conduct heat but not electricity. It’s intended to be used where a TO-220 case needs to be electrically isolated but thermally connected to a heatsink. Manufacturer TT Electronics has a whole line of the chips in various sizes and specs, plus a lot of other cool components like percussive igniters.

We got an interesting tip this week about a new development in the world of 3D-printing. A group from Harvard demonstrated a multinozzle extruder that can print multimaterial objects in a single pass. The work is written up in a Nature article entitled “Voxelated soft matter via multimaterial multinozzle 3D printing”, which is unfortunately paywalled, but the abstract and supplementary videos are really interesting. This appears not to be a standard hot plastic extrusion process; rather, the extruder uses elastomeric inks that cure after they’re extruded. They manage some clever tricks, including a millipede-like, vacuum-powered soft robot extruded in one pass from both soft and rigid silicone elastomers. It’s genuinely interesting stuff, and watching the multimaterial extruder head switch materials at up to 50 times per second is mesmerizing.

People really seemed to get worked up over the transit of Mercury across the face of the Sun last week, and for good reason – astronomical alignments such as these which can be seen from Earth are rare indeed, and worth taking time to see. Not everyone was in the right place at the right time with the right gear to view the transit directly, though, which is why we were glad that Justin over at The Thought Emporium did a video on leveraging online assets for space-based observations. We’ve featured a ton of hacks using SDRs and the like to intercept data from weather satellites, and while those hacks are fun and you should totally try them, Justin points out that most of these streams are readily available for free over the Internet. Clouds, lightning, forest fires and Earth changes, and yes, even the state of the Sun can all be monitored from the web.

Speaking of changes, do you know what has changed in Unix over the last 50 years? For that matter, did you know that Unix turned 50 recently? Sean Haas did after reading this article in Advent of Computing, which he shared on the tipline. The article compares a modern Debian distro to documentation from 1971 that pre-dates Unix version 1; we assume the “Dennis_v1” folder in the doc’s URL refers to none other than Dennis Ritchie himself. It turns out that Unix is remarkably well-conserved over 50 years, at least in the userspace. File system navigation and shell commands are much the same, while programming was much different. C didn’t yet exist – Dennis was busy – but there were assemblers and linkers, plus a FORTRAN compiler and an interpreter for BASIC. It’s comforting to know that if you drop into a wormhole and end up sitting in front of a PDP-11 with Three Dog Night singing “Joy to the World” on the radio in the background, you’ll at least be able to look like you belong there.

And finally, it’s nearly Sparklecon time again. Sparklecon VII will be held on January 25 and 26, 2020, at the 23b Shop hackspace in Fullerton, California. We’ve covered previous Sparkelcons and we’ve even sponsored the meetup in the past, and it looks like a blast. The organizers have put out a Call for Proposals for talks and workshops, so if you’re in the mood for some mischief, get your application going. And be quick about it – the CFP closes on December 8.

Retrotechtacular: 934 MHz CB Radio

The radio spectrum is carefully regulated and divided up by Governments worldwide. Some of it is shared across jurisdictions under the terms of international treaties, while other allocations exist only in individual countries. Often these can contain some surprising oddities, and one of these is our subject today. Did you know that the UK’s first legal CB radio channels included a set in the UHF range, at 934 MHz? Don’t worry, neither did most Brits. Behind it lies a tale of bureaucracy, and of a bungled attempt to create an industry around a barely usable product.

Hey, 2019, Got Your Ears On?

Did this car make you want a CB radio? Stuurm [CC BY-SA 3.0]
Did this car make you want a CB radio? Stuurm [CC BY-SA 3.0]
Mention CB radio in 2019 it’s likely that the image conjured in the mind of the listener will be one from a previous decade. Burt Reynolds and Jerry Reed in Smokey and the Bandit perhaps, or C. W. McCall’s Convoy. It may not be very cool in the age of WhatsApp, but in the 1970s a CB rig was the last word in fashionable auto accessories and a serious object of desire into which otherwise sane adults yearned to speak the slang of the long-haul trucker.

If you weren’t American though, CB could be a risky business. Much of the rest of the world didn’t have a legal CB allocation, and correspondingly didn’t have access to legal CB rigs. The bombardment of CB references in exported American culture created a huge demand for CB though, and for British would-be CBers that was satisfied by illegally imported American equipment. A vibrant community erupted around UK illegal 27 MHz AM CB in the late 1970s, and Government anger was met with campaigning for a legal allocation. Brits eventually got a legal 27 MHz allocation in November 1981, but the years leading up to that produced a few surprises.

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Texas Tesla Tower Titillates

One of the nice things about a road trip is you often get to see something that really surprises you. A recent trip through Texas may have resulted in my second most surprising sighting. There’s a strange tower that looks oddly like a Tesla tower in the middle of rural Texas, right off the main interstate. What is it? Although Google did answer the question — sort of — I’m still not sure how legitimate its stated purpose is.

First Sighting

I was driving between Wimberly and Frisco — two towns that aren’t exactly household names outside of Texas. Near Milford, there’s a very tall structure that looks like a giant mechanical mushroom on top of a grain silo. If the mushroom were inverted or pointing towards the horizon, it would be easy to imagine it was some very odd antenna. This dish, however, is pointed right down its own odd-shaped mast. The top of the thing sure looks like the top of a Van de Graf generator.

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KiCad Action Plugins

The last two years has been a particularly exciting time for KiCad, for users, casual contributors, and for the core developers too. Even so, there are many cool new features that are still in process. One bottleneck with open-source development of complex tools like KiCad is the limited amount of time that developers can devote for the project. Action plugins stand to both reduce developer load and increase the pace of development by making it easier to add your own functionality to the already extensible tool.

Sometime around version 4.0.7 (correct us if we’re wrong), it was decided to introduce “action plugins” for KiCad, with the intention that the larger community of contributors can add features that were not on the immediate road map or the core developers were not working on. The plugin system is a framework for extending the capabilities of KiCad using shared libraries. If you’re interested in creating action plugins, check out documentation at KiCad Plugin System and Python Plugin Development for Pcbnew. Then head over to this forum post for a roundup of Tutorials on python scripting in pcbnew, and figure out how to Register a python plugin inside pcbnew Tools menu. Continue reading “KiCad Action Plugins”