Showing pulse oximeter and color sensor combining to measure oxygen in blood and skin tone

Perfecting The Pulse Oximeter

August 7, 2023 by Orlando Hoilett 28 Comments

We’re always looking for interesting biohacks here on Hackaday, and this new research article describing a calibrated pulse oximeter for different skin tones really caught our attention.

Pulse oximeters are handy little instruments that measure your blood oxygen saturation using photoplethysmography (PPG) and are a topic we’re no strangers to here at Hackaday. Given PPG is an optical technique, it stands to reason that its accuracy could be significantly affected by skin tone and that has been a major topic of discussion recently in the medical field. Given the noted issues with pulse oximeter accuracy, these researchers endeavored to create a better pulse oximeter by quantifying skin pigmentation and using that data to offset errors in the pulse oximeter measurements. A slick idea, but we think their results leave a lot to be desired.

Their idea sounds pretty straightforward enough. They created their own hardware to measure blood oxygen saturation, a smartwatch that includes red and infrared (IR) light-emitting diodes (LED) to illuminate the tissue just below the surface of the skin, and a photosensor for measuring the amount of light that reflects off the skin. But in addition to the standard pulse oximeter hardware, they also include a TCS34725 color sensor to quantify the user’s skin tone.

So what’s the issue? Well, the researchers mentioned calibrating their color sensor to a standard commercially-available dermatology instrument just to make sure their skin pigmentation values match a gold standard, but we can’t find that data, making it a bit hard to evaluate how accurate their color sensor actually is. That’s pretty crucial to their entire premise. And ultimately, their corrected blood oxygen values don’t really seem terribly promising either. For one individual, they reduced their error from 5.44% to 0.82% which seems great! But for another user, their error actually increases from 0.99% to 6.41%. Not so great. Is the problem in their color sensor calibration? Could be.

We know from personal experience that pulse oximeters are hard, so we applaud their efforts in tackling a major problem. Maybe the Hackaday community could help them out?

All About USB-C: Example Circuits

August 7, 2023 by Arya Voronova 8 Comments

In the six months that have passed after the last USB-C article has been released, I have thought up a bunch of ways that these articles could have been improved. It’s, of course, normal to have such a feeling — expected, even. I now believe that there’s a few gaps that I could bridge. For instance, I have not provided enough example circuits, and sometimes one schematic can convey things better than a thousand words.

Let’s fix that! I’ll give you schematics for the kinds of USB-C devices you’re actually likely to want to build. I’ll also share a bunch of IC part numbers in this article, but I don’t have an exhaustive collection, of course – if you find more cool ICs that work for USB-C purposes and aren’t mentioned here, please do let us all know in the comments!

Continue reading “All About USB-C: Example Circuits” →

What Can We Do With These Patient Monitor Videos?

August 7, 2023 by Tom Nardi 22 Comments

So we’ll admit from the start that we’re not entirely sure how the average Hackaday reader can put this content to use. Still, these simulated patient monitor videos on YouTube gotta be useful for something. Right?

Uploaded by [themonitorsolution], each fourteen-minute 1080p video depicts what a patient monitor would look like in various situations, ranging from an adult in stable condition to individuals suffering from ailments such as COPD and sepsis. There’s even one for a dead patient, which makes for rather morbid watching.

Now we assume these are intended for educational purposes — throw them up on a display and have trainees attempt to diagnose what’s wrong with the virtual patient. But we’re sure clever folks like yourselves could figure out alternate uses for these realistic graphics. They could make for an impressive Halloween prop, or maybe they are just what you need to get that low-budget medical drama off the ground, finally.

Honestly, it seemed too cool of a resource not to point out. Besides, it’s exceedingly rare that we get to post a YouTube video that we can be confident none of our readers have seen before…at the time of this writing, the channel only has a single subscriber. Though with our luck, that person will end up being one of you lot.

Continue reading “What Can We Do With These Patient Monitor Videos?” →

Review: Beepy, A Palm-sized Linux Hacking Playground

August 7, 2023 by Tom Nardi 45 Comments

In the long ago times, when phones still flipped and modems sang proudly the songs of their people, I sent away for a set of Slackware CDs and embarked on a most remarkable journey. Back then, running Linux (especially on the desktop) was not a task to be taken lightly. The kernel itself was still in considerable flux — instead of changing some obscure subsystem or adding support for a niche gadget you don’t even own, new releases were unlocking critical capabilities and whole categories of peripherals. I still remember deciding if I wanted to play it safe and stick with my current kernel, or take a chance on compiling the latest version to check out this new “USB Mass Storage” thing everyone on the forums was talking about…

But modern desktop Linux has reached an incredible level of majority, and is now a viable choice for a great number of computer users. In fact, if you add Android and Chrome OS into the mix, there are millions and millions of people who are using Linux on daily basis and don’t even realize it. These days, the only way to experience that sense of adventure and wonderment that once came pre-loaded with a Linux box is to go out and seek it.

Which is precisely how it feels using using the Beepy from SQFMI. The handheld device, which was formerly known as the Beepberry before its creators received an all-too-predicable formal complaint, is unabashedly designed for Linux nerds. Over the last couple of weeks playing with this first-run hardware, I’ve been compiling kernel drivers, writing custom scripts, and trying (though not always successfully) to get new software installed on it. If you’re into hacking around on Linux, it’s an absolute blast.

There’s a good chance that you already know if the Beepy is for you or not, but if you’re still on the fence, hopefully this in-depth look at the hardware and current state of the overall project can help you decide before SQFMI officially starts taking new orders for the $79 gadget.

Continue reading “Review: Beepy, A Palm-sized Linux Hacking Playground” →

A Magnetohydrodynamic Drive In The Kitchen Sink

August 7, 2023 by Tom Nardi 58 Comments

The magnetohydrodynamic (MHD) drive certainly sounds like something out of science fiction — using an array of magnets and electrodes, this high-tech propulsion technology promises to silently propel a craft through the water without any moving parts. As long as you can provide it with a constant supply of electricity, anyway.

Of course, as is often the case, the devil is in the details. Even with the obvious scientific and military applications of such a propulsion unit, scaling MHD technology up has proven difficult. But as [Jay Bowles] of Plasma Channel shows in his latest video, that doesn’t mean you can’t experiment with the concept at home. Even better, getting verifiable results is much easier than you’d think.

Continue reading “A Magnetohydrodynamic Drive In The Kitchen Sink” →

This Kinetic Art Display Uses A Gin Bottle

August 7, 2023 by Dave Rowntree 8 Comments

[David McDaid] likes gin. So in homage to their favourite tipple, a certain brand of Scottish origin, a kinetic art project was brewed. Tabled as a Rube Goldberg machine — it’s not — but it is a very smart marble run type installation, dripping with 3D printed parts and a sprinkling of blinkenlights.

The write-up shows the degree of pain we go through with building such contraptions, apparently [David] burned through 2.5 kg of PLA filament despite the bill of materials requiring a mere 660 g. Much experimentation, trial and error, and plenty of print-and-reprint-until-good-enough, resulted in a clean looking run with some neat features. We particularly like the use of a stainless steel jigger to add a touch of metallic ting, to the soundscape produced. The whole show was put together in Fusion 360, since all those tight tolerances do not make for a simple construction without a lot of fiddling around with the layout. Once it was a sound, layout was prototyped on a wood board, which was subsequently used a drill template for the final acrylic version.

On the electronics side of things, an Arduino Nano clone is on control duty, reading an IR trip sensor to fire of a simple light effect, illuminating the gin bottle in a slick fashion. These machines need a mechanism to raise the balls against that pesky force of gravity, in this instance a 3D printed custom chain was constructed, driven with a stepper motor in turn driven from a TMC2208. You see, this thing lives in the kitchen, so the aim was to keep all the noise from the mechanics to a minimum so only the noise of LDPE balls rattling around can be heard. They are the star of the show after all! The build looks nice and would certainly be something we’d like to see on the wall. Obviously we’ve seen a few marble runs over the years. Here’s an interesting one that uses an elevator mechanism, and another project that shows how to generate runs procedurally.

Continue reading “This Kinetic Art Display Uses A Gin Bottle” →

An Open Firmware For LILYGO’s E-ink Smart Watch

August 6, 2023 by Bryan Cockfield 21 Comments

The world’s first quartz wristwatches were miles ahead of electric and mechanical wristwatches by most standards of the time, their accuracy was unprecedented and the batteries typically lasted somewhere on the order of a year. Modern smart watches, at least in terms of battery life, have taken a step backwards — depending on use, some can require daily charging.

If you’re looking to bridge the gap between a day and a year, you might look into a smart watch with an e-ink display. One option is the ESP32-based LILYGO T-Wrist. Of course, it’s not a smart watch without some software to run on it, which is where qpaperOS comes in.

Developed by [qewer33], this open source firmware for the T-Wrist is designed to get the most out of the battery by updating only once per minute. With a 250 mAh battery, it should last about five days on a charge. Of course, with the power of the ESP32 comes a whole host of other features including GPS, a step counter, and a weather display, although since the firmware is still under development, some of these features have yet to be implemented.

With all of the code available, qpaperOS could make an excellent platform from which to build your own smart watch around. Or perhaps you could chip in and add some of the features on the whislity. The ESP32 is a capable and versatile chip, even capable of playing popular 8-bit video games, although we’re not sure this functionality would fit in a smart watch and preserve battery life at the same time.