Hackaday Links: May 17, 2020

Consider it the “Scarlet Letter” of our time. An MIT lab is developing a face mask that lights up to alert others when the wearer has COVID-19. The detection technology is based on sensors that were developed for the Ebola virus scare and uses fluorescently tagged DNA fragments freeze-dried onto absorbent strips built into the mask. The chemistry is activated by the moisture in the sputum expelled when the wearer coughs or sneezes while wearing the mask; any SARS-CoV-2 virus particles in the sputum bind to the strips, when then light up under UV. The list of problems a scheme like this entails is long and varied, not least of which is what would possess someone to willingly don one of these things. Still, it’s an interesting technology.

Speaking of intrusive expansions of the surveillance state, Singapore is apparently now using a Boston Dynamics Spot robot to enforce social-distancing rules in its public parks and gardens. The familiar four-legged, bright yellow dog-bot is carrying cameras that are relaying images of park attendees to some sort of image analysis program and are totally not capturing facial or personal data, pinky swear. If people are found to be violating the two-meter rule, Spot will bark out a prerecorded reminder to spread out a bit. How the system differentiates between people who live together who are out getting some fresh air and strangers who should be staying apart, and whether the operators of this have ever seen how this story turns out are open questions.

Those who lived through 9/11 in the United States no doubt remember the deafening silence that descended over the country for three days while every plane in the civil aviation fleet was grounded. One had no idea how much planes contributed to the noise floor of life until they were silenced. So too with the lockdown implemented worldwide to deal with the COVID-19 pandemic, except with the sometimes dramatic reduction in pollution levels. We’ve all seen pictures where people suddenly realize that Los Angeles isn’t necessarily covered by an orange cloud of smog, and that certain mountain ranges are actually visible if you care to look. But getting some hard data is always useful, and these charts show just how much the pollution situation improved in a number of countries throughout the world after their respective lockdowns. For some cities, the official lockdown was a clear demarcation between the old pollution regime and the new, but for some, there was an obvious period before the lockdown was announced where people were obviously curtailing their activity. It’s always interesting pore over data like this and speculated what it all means.

While the in-person aspects of almost every conference under the sun have been canceled, many of them have switched to a virtual meeting that can at least partially make up for the full experience. And coming up next weekend is Virtually Maker Faire, in the slot where Bay Area Maker Faire would normally be offered. The call for makers ends today, so get your proposals in and sign up to attend.

And finally, there aren’t too many times in life you’ll get a chance to get to visualize a number so large that an Evil Empire was named for it. The googol, or 10100, was a term coined by the nine-year-old nephew of mathematician Edward Kasner when he asked the child for a good name for a really big number. To put the immensity of that number into perspective, The Brick Experiment Channel on YouTube put together an improbably long gear train using Lego pieces we’ve never seen before with a reduction ratio of 10103.4:1. The gear train has a ton of different power transmission elements in it, from plain spur gears to worm drives and even planetary gears. We found the 2608.5:1 harmonic gear particularly fascinating. There’s enough going on to keep even a serious gearhead entertained, but perhaps not for the 5.2×1091 years it’ll take to revolve the final gear once. Something, something, heat-death of the universe. [Ed note: prior art, which we were oddly enough thinking of fondly just a few days ago. Synchronicity!]

3D-Printed COVID Stuff That’s Not Face Shields Or Ventilators

The coolest stories from the hacker community this year are the rapid manufacturing efforts that have gone on in response to COVID-19. But [Mark Rehorst], frequently featured on these pages for his clever takes on 3D printing, shared a couple of really useful prints that are out of the ordinary for what we’ve been seeing: bias tape folders and ear savers.

Initial bias tape folding jig design by ongaroo

Tailors around the world have threaded the needle on grass-roots face mask production. One of the more labor intensive parts of sewing a face mask is the fastening mechanism. With elastic straps, the size of the loops needs to be just right, but when you run out of elastic you need to sew straps. Bias tape is a popular material for that, but it’s finicky to fold and hold it for sewing. [Mark] heard of the need and grabbed a bias tape folder design from Thingiverse. These work kind of like a zipper, pulling in the unfolded tape on one side and feeding it out the other, folded nicely for the needle and thread to take over. But of course he did one better, refining the original design to use less plastic to get more parts, faster, with less material use — win, win, win.

Speaking of those mask straps, it turns out the backs of your ears don’t like being rubbed raw for back-to-back-to-back 12-hour shifts at the hospital. We’ve seen health workers, themselves skilled hackers, recommend sewing buttons onto a headband to hold the mask straps.

But the 3D-printing world has an “earsaver” that provides a series of hooks on a plastic band that loops behind your head. Once again, [Mark] iterated on the standard design, finding ways to reduce material use while also fitting more units onto a single printer bed.

These functional prints are glamorous in their own ways. We love seeing hard-working 3D-printed items, but we love it even more when we see them getting better and better with each new version. The back story and the design files for the improved versions are available on his project writeup. Go [Mark]!

Hackaday Links: March 22, 2020

Within the span of just two months, our world of unimaginable plenty and ready access to goods manufactured across the globe has been transformed into one where the bare essentials of life are hard to find at any price. The people on the frontline of the battle against COVID-19 are suffering supply chain pinches too, often at great risk to their health. Lack of proper personal protective equipment (PPE), especially face masks, is an acute problem, and the shortage will only exacerbate the problem as healthcare workers go down for the count. Factories are gearing up to make more masks, but in the meantime, the maker and hacker community can pitch in. FreeSewing, an open-source repository of sewing patterns, has a pattern for a simple face mask called the Fu that can be made quickly by an experienced threadworker. Efficacy of the masks made with that pattern will vary based on the materials used, obviously; a slightly less ad hoc effort is the 100 Million Mask Challenge, where volunteers are given a pattern and enough lab-tested materials to make 100 face masks. If you know how to sew, getting involved might make a difference.

As people around the world wrap their heads around the new normal of social distancing and the loss of human contact, there’s been an understandable spike in interest in amateur radio. QRZ.com reports that the FCC has recorded an uptick in the number of amateur radio licenses issued since the COVID-19 outbreak, and license test prep site HamRadioPrep.com has been swamped by new users seeking to prepare for taking the test. As we’ve discussed, the barrier for entry to ham radio is normally very low, both in terms of getting your license and getting the minimal equipment needed to get on the air. One hurdle aspiring hams might face is the cancellation of so-called VE testing, where Volunteer Examiners administer the written tests needed for each license class. Finding a face-to-face VE testing session now might be hard, but the VEs are likely to find a way to adapt. After all, hams were social distancing before social distancing was cool.

The list of public events that have been postponed or outright canceled by this pandemic is long indeed, with pretty much everything expected to draw more than a handful of people put into limbo. The hacking world is not immune, of course, with many high-profile events scuttled. But we hackers are a resourceful bunch, and the 10th annual Open Source Hardware Summit managed to go off on schedule as a virtual meeting last week. You can watch the nearly eight-hour livestream while you’re self-isolating. We’re confident that other conferences will go virtual in the near-term too rather than cancel outright.

And finally, if you’re sick of pandemic news and just want some escapist engineering eye candy, you could do worse than checking out what it takes to make a DSLR camera waterproof. We’ve honestly always numbered cameras as among the very least waterproof devices, but it turns out that photojournalists and filmmakers are pretty rough on their gear and expect it to keep working even so. The story here focuses (sorry) on Olympus cameras and lenses, which you’ll note that Takasu-san only ever refers to as “splash-proof”, and the complex system of O-rings and seals needed to keep water away from their innards. For our money, the best part was learning that lenses that have to change their internal volume, like zoom lenses, need to be vented so that air can move in and out. The engineering needed to keep water out of a vented system like that is pretty impressive.

Homemade Masks In A Time Of Shortage

Due to the worldwide pandemic of COVID-19, there has been a huge shortage of N95 masks. [] from Smart Air has been working on designs for a DIY mask that may be able to protect those who haven’t been able to secure their own masks. While there may be an abundance of memes around the various material people have been able to use to substitute for the filters, there is some very real science behind the sorts of materials that can effectively protect us from the virus.

According to a studied performed at Cambridge University during the 2009 H1N1 flu pandemic, while surgical masks perform the best at capturing Bacillus atrophaeus bacteria (0.93-1.25 microns) and Bacteriophage MS virus (0.023 microns), vacuum cleaner bags, and tea towels, and cotton T-shirts were not too far behind. The coronavirus is 0.1-0.2 microns, well within the range for the results of the tests.

As it turns out, cotton homemade masks may be quite effective as alternatives – not to mention reusable. They also found out that double layering the masks didn’t help with improving the protection against viruses. On the other hand, one significant design choice was the breathability of the material. While vacuum cleaner bags may be quite effective at keeping out small particles, they aren’t as comfortable or easy to breathe in as cotton masks.

Have you tried making your own cotton masks? In a time when hospitals are running low on surgical masks, it’s possibly the best option for helping to keep much-needed medical supplies in the hands of those helping at the front line.

[Thanks to pie for the tip!]

Hacked Protective Gear Keeps Doctor Safe In The Hot Zone

It’s rarely a wise idea to put a plastic bag over one’s head, but when the choice is between that and possibly being exposed to a dangerous virus, you do what you have to. So you might as well do it right and build a field-expedient positive pressure hood.

We’ve all been keeping tabs on the continuing coronavirus outbreak in China, but nobody is following as closely as our many friends in China. Hackaday contributor [Naomi Wu] is in from Shenzhen, posting regularly from the quarantined zone, and she found this little gem of ingenuity from a [Doctor Cui] in one of the hospitals in Wuhan. Quarantines and travel restrictions have put personal protective equipment like masks and gowns in limited supply, with the more advanced gear needed by those deal most closely with coronavirus patients difficult to come by.

There’s no build information, but from the pictures we can guess at what [Dr. Cui] came up with. The boxy bit is an AirPro Car, a HEPA filter meant to clean the cabin air in a motor vehicle. He glued on a USB battery pack to power it, used a scrap of plastic and some silicone adhesive to adapt a heat-moisture exchange filter from a mechanical ventilator to the AirPro’s outlet, and stuck the tube into a plastic bag sealed around his neck. The filter provides dry, positive pressure air to keep the bag from fogging up, and to keep [Dr. Cui] from asphyxiating. Plus he’s protected from droplet contact, which is a big plus over simple paper masks.

With the news always so dark, it’s heartening to see stories of ingenuity like this. We wish [Dr. Cui] and all our friends in China the best during this outbreak.

These Bit Twiddling Tricks Will Make Your Coworkers Hate You

In the embedded world, twiddling a few bits is expected behavior. Firmware is far enough down the stack that the author may care about the number of bits and bytes used, or needs to work with registers directly to make the machine dance. Usually these operations are confined to the typical shifting and masking but sometimes a problem calls for more exotic solutions. If you need to descend down these dark depths you invariably come across the classic Bit Twiddling Hacks collected by [Sean Eron Anderson]. Here be dragons.

Discussions of bit math are great opportunities to revisit Wikipedia’s superb illustrations

Bit Twiddling Hacks is exactly as described; a page full of snippets and suggestions for how to perform all manner of bit math in convenient or efficient ways. To our surprise upon reading the disclaimer at the top of the page, [Sean] observes that so many people have used the contents of the page that it’s effectively all been thoroughly tested. Considering how esoteric some of the snippets are we’d love to know how the darkest corners found use.

The page contains a variety of nifty tricks. Interview content like counting set bits makes an early appearance.  There’s more esoteric content like this trick for interleaving the bits in two u16’s into a single u32, or rounding up to the next power of two by casting floats. This author has only been forced to turn to Bit Twiddling Hacks on one occasion: to sign extend the output from an unfortunately designed sensor with unusual length registers.

Next time you need to perform an operation with bitmatch, check out Bit Twiddling Hacks. Have you ever needed it in production? How did you use it? We’d love to hear about it in the comments.

Be Anyone Or Anything With Facial Projection Mask

In the market for a low-poly change to your look? Hate the idea of showing up for a costume party only to find out someone is wearing the same mask as you? Then this face changing front-projection mask may be just the thing for you.

To be honest, we’re not sure just how much [Sean Hodgins]’ latest project has to do with cosplay. He seems to be making a subtle commentary about dealing with life in the surveillance state, even though this is probably not a strategy for thwarting facial-recognition cameras. [Ed Note: Or maybe it’s just Halloween?]

The build consists of a Raspberry Pi and a pico projector of the kind we’ve seen before. These are mated together via a custom PCB and live inside a small enclosure that’s attached to the end of a longish boom. The boom attaches to the chin of 3D-printed mask, which in turn is connected to the suspension system of a welding helmet. Powered by a battery pack and controlled by a smartphone app, the projector throws whatever you want onto the mask – videos, effects, even images of other people. Even with some Photoshop tweaks to account for keystone distortion from the low angle of projection, there’s enough distortion that the effect is more artistic than masquerade. But honestly, having your face suddenly burst into flames is pretty cool. We just wonder what visibility is like for the wearer with a bright LED blasting into your eyes.

As a bonus, [Sean] has worked this build into a virtual treasure hunt. Check out 13thkey.com and see what you can make from the minimal clues there.

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