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Hackaday Links: May 16, 2021

With the successful arrival of China’s first Mars lander and rover this week, and the relatively recent addition of NASA’s Perseverance rover and its little helicopter sidekick Ingenuity, Mars has collected a lot of new hardware lately. But while the new kids on the block are getting all the attention, spare a thought for the reliable old warhorse which has been plying Gale Crater for the better part of a decade now — Curiosity. NASA has been driving the compact-car-sized rover around Mars for a long time now, long enough to rack up some pretty severe damage to its six highly engineered wheels, thanks to the brutal Martian rocks. But if you think Curiosity will get sidelined as its wheels degrade, think again — the rover’s operators have a plan to continue surface operations that includes ripping off its own wheels if necessary. It’s a complex operation that would require positioning the wheel over a suitable rock and twisting with the steering motor to peel off the outer section of the wheel, leaving a rim to drive around on. JPL has already practiced it, but they predict it won’t be necessary until 2034 or so. Now that’s thinking ahead.

With all the upheaval caused by the ongoing and worsening semiconductor shortage, it might seem natural to expect that manufacturers are responding to market forces by building new fabs to ramp up production. And while there seems to be at least some movement in that direction, we stumbled across an article that seems to give the lie to the thought that we can build our way out of the crisis. It’s a sobering assessment, to say the least; the essence of the argument is that 20 years ago or so, foundries thought that everyone would switch to the new 300-mm wafers, leaving manufacturing based on 200-mm silicon wafers behind. But the opposite happened, and demand for chips coming from the older 200-mm wafers, including a lot of the chips used in cars and trucks, skyrocketed. So more fabs were built for the 200-mm wafers, leaving relatively fewer fabs capable of building the chips that the current generation of phones, IoT appliances, and 5G gear demand. Add to all that the fact that it takes a long time and a lot of money to build new fabs, and you’ve got the makings of a crisis that won’t be solved anytime soon.

From not enough components to too many: the Adafruit blog has a short item about XScomponent, an online marketplace for listing your excess inventory of electronic components for sale. If you perhaps ordered a reel of caps when you only needed a dozen, or if the project you thought was a done deal got canceled after all the parts were ordered, this might be just the thing for you. Most items offered appear to have a large minimum quantity requirement, so it’s probably not going to be a place to pick up a few odd parts to finish a build, but it’s still an interesting look at where the market is heading.

Speaking of learning from the marketplace, if you’re curious about what brands and models of hard drives hold up best in the long run, you could do worse than to look over real-world results from a known torturer of hard drives. Cloud storage concern Backblaze has published their analysis of the reliability of the over 175,000 drives they have installed in their data centers, and there’s a ton of data to pick through. The overall reliability of these drives, which are thrashing about almost endlessly, is pretty impressive: the annualized failure rate of the whole fleet is only 0.85%. They’ve also got an interesting comparison of HDDs and SSDs; Backblaze only uses solid-state disks for boot drives and for logging and such, so they don’t get quite the same level of thrash as drives containing customer data. But the annualized failure rate of boot SDDs is much lower than that of HDDs used in the same role. They slice and dice their data in a lot of fun and revealing ways, including by specific brand and model of drive, so check it out if you’re looking to buy soon.

And finally, you know that throbbing feeling you get in your head when you’re having one of those days? Well, it turns out that whether you can feel it or not, you’re having one of those days every day. Using a new technique called “3D Amplified Magnetic Resonance Imaging”, or 3D aMRI, researchers have made cool new videos that show the brain pulsating in time to the blood flowing through it. The motion is exaggerated by the imaging process, which is good because it sure looks like the brain swells enough with each pulse to crack your skull open, a feeling which every migraine sufferer can relate to. This reminds us a bit of those techniques that use special algorithms to detects a person’s heartbeat from a video by looking for the slight but periodic skin changes that occurs as blood rushes into the capillaries. It’s also interesting that when we spied this item, we were sitting with crossed legs, watching our upper leg bounce slightly in time with our pulse.

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Repurpose A Monitor Arm As Microscope Mount

Being a bit shocked at the prices of articulating arm microscope mounts, not to mention the shipping fees to the UK, [CapTec] realized they looked substantially similar to your typical computer monitor arm mount. Thinking he could adapt a monitor arm for much less money, he fired up FreeCAD and started designing.

[CapTec] is using this to support his Amscope / Eakins camera-equipped trinocular microscope, but notes that the same mechanical bracket / focus rack interface is found on binocular ‘scopes as well. He observes that the mount is no more stable than your desk or lab bench, so keep that in mind.

Ultimately the monitor arm set him back less than $40, and all told he reckons the whole thing was under $55. Based on prices he’s been researching online, this represents a savings of well over $200. In his calculations, the shipping fee comprised quite a hefty percentage of the total cost. We wonder if they are artificially high due to coronavirus — if so, the make / buy price comparison might yield different results in the future.

This type of project is a perfect use-case for a home 3D printer — making your own parts when the normal supply channels are unavailable or overpriced. Are articulating arms that are purpose-built for microscopes significantly different than those designed for big computer monitors? If you know, please comment down below.

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Thought Control Via Handwriting

Computers haven’t done much for the quality of our already poor handwriting. However, a man paralyzed by an accident can now feed input into a computer by simply thinking about handwriting, thanks to work by Stanford University researchers. Compared to more cumbersome systems based on eye motion or breath, the handwriting technique enables entry at up to 90 characters a minute.

Currently, the feat requires a lab’s worth of equipment, but it could be made practical for everyday use with some additional work and — hopefully — less invasive sensors. In particular, the sensor used two microelectrode arrays in the precentral gyrus portion of the brain. When the subject thinks about writing, recognizable patterns appear in the collected data. The rest is just math and classification using a neural network.

If you want to try your hand at processing this kind of data and don’t have a set of electrodes to implant, you can download nearly eleven hours of data already recorded. The code is out there, too. What we’d really like to see is some easier way to grab the data to start with. That could be a real game-changer.

More traditional input methods using your mouth have been around for a long time. We’ve also looked at work that involves moving your head.

Scratch Built Tricycle Maximizes Fuel Efficiency

While the bicycling community is welcoming an influx of electric bikes, there’s a group of tuners on the fringes that are still intent on strapping gas motors of all sizes to bicycles and buzzing down the roads in a loud and raucous fashion. Kits are readily available and are much cheaper than comparable e-bike kits, and with a little bit of work it’s possible to squeeze a lot of excitement from these small motors. With a lot of work, though, you might end up with something like this incredibly fuel efficient and fully customized reverse trike from [Paul Elkins].

The entire goal with this build was fuel efficiency, so the plan is to eventually enclose the vehicle in aerodynamic fairings, most likely using his favorite material, Coroplast. The frame itself is completely hand-made from square tube and welded by [Paul] himself to his own custom specifications. He bolts on a suspension and custom steering rack with levers to control the two front wheels, and the small engine and gas tank are attached to the back above the single drive wheel. The engine hadn’t been started in ten years, but once he got it all put together, it started right up and he was able to take his latest prototype out on the road for a test drive.

While the build isn’t completely finished, the video below (eleventh so far in the build log) is far enough along to show the fruits of years of [Paul]’s labor. It’s taken a while to get a design that worked like he wanted, but with this iteration, he finally has what he was looking for.

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3D Printed Tank Takes On The Elements

Commercially available radio control tanks are fun and all, but sometimes you’ve just got to build your own. [Let’s Print] did just that, whipping up a tank on his 3D printer before taking it out in the snow.

The tank is a fairly straightforward build, relying on a pair of brushed motors for propulsion, controlled by twin speed controllers hooked up to standard radio control hardware. Everything else is bespoke, however, from the 3D printed gearboxes, to the chassis and the rather aggressive-looking tracks. The pointed teeth of the latter leave deep indentations when the tank cruises around on mud, though weren’t quite enough to stop the little tank from getting high-centered in deep snow.

The build isn’t for the impatient, however. [Let’s Print] notes that the tracks alone took over 80 hours to run off in PETG, let alone the rest of the frame and gearboxes. However, we’re sure it was a great learning experience, and great fun to drive outside. Now the next step is surely to go bigger. Video after the break.

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Tape Cutter Makes Short Work Of Through-Hole Resistor Reels

As the world of electronics makes its inexorable movement from through-hole parts to surface-mount, it’s easy to forget about the humble wire-ended resistor. But a stack of them is still a very useful resource for any experimenter, and most of us probably have a bunch of them with their accompanying twin strips of tape. We’re entranced by [Sandeep]’s automated resistor tape cutting machine, which uses a fearsome looking pair of motorized knives to slice the tape into predetermined lengths.

At its heart is an Arduino and a set of stepper drivers, and it uses a PCB that he’s designed as a multipurpose board for motor-based projects. One motor advances the reel of resistors, while the other two operate those knives that simultaneously slice the two tapes. The whole is held in a wooden frame with 3D-printed parts, and control is through a touch screen. This feels more like an industrial machine than a maker project, and as can be seen in the video below, it makes short work of those tapes. Full details can be found on his website, including code.

We’ve not had so many through hole tape cutters, but we’ve seen at least one SMD cutter.

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Vintage HP-25 Calculator Gets Wireless Charging

[Jan Rychter] really likes his multiple HP-25C calculators, but the original battery pack design is crude and outdated. No problem — he whips up a replacement using Fusion 360 to design an enclosure, prints a few on his SLS 3D printer, and packs them with LiPo batteries and Qi/WPC wireless charging circuits.

In his blog post, he explains the goals and various design decisions and compromises that he made along the way. We like [Jan]’s frank honesty as he remarks on something we have all been guilty of at one time or another:

In the end, I went with design decisions which might not be optimal, but in this case (with low power requirements) provide acceptable performance. In other words, I winged it.

One problem which proved difficult to solve was how to provide a low battery indicator. Since low voltage on a LiPo is different from the original HP-25’s NiCad cells, it wasn’t straightforward, especially since [Jan] challenged himself to build this without using a microcontroller. He discovered that the HP-25’s internal low battery circuit was triggered by a voltage of 2.1 volts or lower.

In a really clever hack, [Jan] came up with the idea of using an MCU reset supervisor chip with a low voltage threshold of 3.0 volts, which corresponds with the low voltage threshold of the LiPo battery he is using. The reset signal from the supervisor chip then drives one of the pins of the TPS62740 programmable buck converter, changing its output from 2.5 volts to 2.1 volts.

This project is interesting on several levels — extending the life of a useful but end-of-life calculator, improving the original battery design and introducing new charging techniques not available in the early 1970s, and it is something that a hobbyist can afford to do in a home electronics lab. We do wonder, could such a modification could turn an HP-25 into an HP-25C?

We’ve written about battery pack replacement project before, including one for the Sony Discman and another for an electric drill. Let us know if you have any battery pack replacement success (or failure) stories in the comments below.