Stresses Revealed With A Polariscope

There are a lot of ways that stresses can show up, at least when discussing materials science. Cracks in concrete are a common enough example, but any catastrophic failure in a material is often attributable to some stress that couldn’t be withstood. If you’re interested in viewing those stresses before they result in damage to the underlying material, take a look at this DIY polariscope which can view internal stresses in glass and other clear objects.

The polariscope takes its name from the fact that it uses polarized light to view the internal structure of a transparent object such as glass. When the polarized light passes through glass in a certain way, the stresses show up as lighter areas thanks to the stressed glass bending the light back into view. This one is constructed with a polarizing filter placed in front of an LCD screen set to display a completely white image. When glass is placed between the screen and the filter no light is seen through the polariscope unless there are stresses in the glass. Even placing a force on an otherwise un-stressed glass tube can show this effect, and [Advanced Tinkering], this project’s creator, has several other creations which show this effect in striking detail.

The effect can also be observed as colored areas in other plastic materials as well. It’s an interesting tool which can help anyone who frequently works with glass, but it’s also interesting on its own to see clues left behind from the manufacturing process of various household items. We’ve seen some other investigative methods for determining how other household items are mass produced as well, like this project which breaks down the injection molding process.

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A Stress Monitor Designed Specifically To Help You Work From Home

There are quite a bit of mixed emotions regarding working from home. Some people love it and are thriving like they haven’t before, but others are having a bit of a hard time with it all. [Brandon] has been working from home for the last 12 years, but even after so many years of managing this type of work culture, he admits that it can still be a little stressful. He says he doesn’t take enough time in between tasks to simply relax and to breathe a little and the day-to-day minutia of his work can drive his stress level up if he doesn’t take some time to calm himself. He figured he could make something to monitor his stress level and remind himself to take a break and the results are pretty impressive.

He develops a system to monitor his heart rate and the ambient noise level in his room and uses these metrics as a measure of stress. If his heart rate or the ambient noise level goes above a certain threshold, then he sends himself a text message reminding himself to relax and take a break. You’ve probably seen people use heart rate as a measure of stress already, but you’re probably less familiar with using sound. [Brandon] basically thought the sound sensor would detect if he starts ranting for prolonged periods of time or if he’s in a Zoom meeting that gets too heated. We thought that was pretty neat.

[Brandon] used an off-the-shelf chest strap heart rate monitor to save himself a bit of time in trying to build his own. The device sends heart rate data to an nRF52840 over Bluetooth and then pushes the data to the cloud using a Blues Wireless Notecard. The Notecard also offers data encryption which gave [Brandon] some added peace of mind knowing his biometric data wasn’t floating around in the cloud without any sort of protection. This certainly isn’t medical-grade encryption, but it gave him a bit of comfort, nonetheless. All that data is processed in his custom-designed web app and when the appropriate thresholds are reached, he sends a text message to himself using Twilio reminding him to relax and unwind for a bit.

For his next iteration, [Brandon] might try making his own heart rate monitor. But until then, stay safe everybody, and remember to take a break whenever you need it.

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Remoticon Video: The Mechanics Of Finite Element Analysis

Hardware hacking can be extremely multidisciplinary. If you only know bits and bytes, but not solder and electrons, you’re limited in what you can build. The same is true for mechanical design, where the forces of stress and strain suddenly apply to your project and the pile of code and PCBs comes crashing to the ground.

In the first half of his workshop, Naman Pushp walks you through some of the important first concepts in mechanical engineering — how to think about the forces in the world that act on physical objects. And he brings along a great range of home-built Jugaad props that include a gravity-defying tensegrity string sculpture and some fancy origami that help hammer the topics home.

In the second half of the workshop, Naman takes these concepts into computer simulation, and gives us good insight into the way that finite-element analysis simulation packages model these same forces on tiny chunks of your project’s geometry to see if it’ll hold up under real world load. The software he uses isn’t free by any definition — it’s not even cheap unless you have a student license — but it’s nonetheless illuminating to watch him work through the flow of roughly designing an object, putting simulated stresses and strains on it, and interpreting the results. If you’ve never used FEA tools before, or are looking for a compressed introduction to first-semester mechanical engineering, this talk might be right up your alley. Continue reading “Remoticon Video: The Mechanics Of Finite Element Analysis”

Squeezing Every Bit From An ATMega

While the ATMega328 is “mega” for a microcontroller, it’s still a fairly limited platform. It has plenty of I/O and working memory for most tasks, but this Battleship game that [thorlancaster328] has put together really stretches the capabilities of this tiny chip. Normally a Battleship game wouldn’t be that complicated, but this one has audio, an LED display, and can also play a fine rendition of Nyan Cat to boot, which really puts the Atmel chip through its paces.

The audio is played through a 512-byte buffer and an interrupt triggers the microcontroller when to fill the buffer while it works on the other processes. The 12×12 LED display is also fed through a shift register triggered by the same interrupt as the audio, and since the build uses so many shift registers the microcontroller can actually output four separate displays (two players, each with a dispaly for shots and one for ships). It will also eventually support a player-vs-computer mode for the battleship game, and also has a mode where it plays Nyan cat just to demonstrate its own capabilities.

We’re pretty impressed with the amount of work this small microcontroller is doing, largely thanks to code optimization from its creator [thorlancaster328]. If there’s enough interest he also says he will provide the source code too. Until then, be sure to check out this other way of pushing a small microcontroller to its limits.

Thanks to [Thinkerer] for the tip!

Hyundai Mini 45 EV Is A Small Car With Grand Ambitions

One of Hyundai’s recent concept cars was an electric vehicle named “45” in honor of its inspiration, another concept car from 45 years ago. When footage of a child-sized “Mini 45” surfaced, it was easy to conclude the car was a motorized toy for children. But Jalopnik got more information from Hyundai about this project, where we learned that was not nearly the whole picture.

The video (embedded below) explained this little vehicle is a concept car in its own right, and most of the video is a scripted performance illustrating their concept: using technology to help calm young patients in a hospital, reducing their anxiety as they faced treatment procedures. Mini 45 packs a lot more equipment than the toy cars available at our local store. The little driver’s heartbeat and breathing rate are monitored, and a camera analyzes facial expressions to gauge emotional stress. The onboard computer has an animated avatar who will try to connect with the patient, armed with tools like colorful animations, happy music, candy scent dispenser, and a bubble-blowing machine.

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DIY Stress Meter

Stress monitoring has always been a tricky business. As it turns out, there is a somewhat reliable way of monitoring stress by measuring how much cortisol, the so-called “stress hormone,” the human body produces. With that in mind, bioengineering researchers at the University of Texas at Dallas decided to make CortiWatch, a wearable device for continuously monitoring cortisol excreted in sweat, as a sort of DIY stress meter.

They made their own potentiostat, a device for measure small amounts of current produced by electrochemical reactions, similar to the glucometer. We’ve talked about these types of measurements before. Simply put, the potentiostat contains a voltage reference generator which biases the sensing electrodes at a preset potential. The voltage bias causes local electrochemical reactions at the sensing electrodes (WE in the image above), stimulating electron flow which is then measured by a transimpedance amplifier or “current-to-voltage” converter. The signal is then analyzed by an onboard analog-to-digital converter. Simply put, the more cortisol in the system, the higher the transimpedance amplifier voltage.

To validate their system a bit more thoroughly than simple benchtop studies, the researchers did some “real-life” testing. A volunteer wore the CortiWatch for 9 hours. The researchers found a consistent decrease in cortisol levels throughout the day and were able to verify these measurements with another independent test. Seems reasonable, however, it’s not quite clear to us what cortisol levels they were expecting to measure during the testing period. We do admit that it takes quite a bit of calibration to get these systems working in real-life settings, so maybe this is a start. We’ll see where they go from here.

Maybe the CortiWatch can finally give us a proper lie detector.¬†We’ll let you be the judge.

Punch The World With A Raspberry Pi

Robots have certainly made the world a better place. Virtually everything from automobile assembly to food production uses a robot at some point in the process, not to mention those robots that can clean your house or make your morning coffee. But not every robot needs such a productive purpose. This one allows you to punch the world, which while not producing as much physical value as a welding robot in an assembly line might, certainly seems to have some therapeutic effects at least.

The IoT Planet Puncher comes to us from [8BitsAndAByte] who build lots of different things of equally dubious function. This one allows us to release our frustration on the world by punching it (or rather, a small model of it). A small painted sphere sits in front of a 3D-printed boxing glove mounted on a linear actuator. The linear actuator is driven by a Raspberry Pi. The Pi’s job doesn’t end there, though, as the project also uses a Pi camera to take video of the globe and serve it on a webpage through which anyone can control the punching glove.

While not immediately useful, we certainly had fun punching it a few times, and once a mysterious hand entered the shot to make adjustments to the system as well. Projects like this are good fun, and sometimes you just need to build something, even if it’s goofy, because the urge strikes you. Continue reading “Punch The World With A Raspberry Pi”