This Air Particulate Sensor Can Also Check Your Pulse Rate

March 26, 2024 by Lewin Day 7 Comments

The MAX30105 is an optical sensor capable of a great many things. It can sense particulate matter in the air, or pick up the blinking of an eye. Or, you can use it as a rudimentary way to measure your heart rate and blood oxygen levels. It’s by no means a medical grade tool, but this build from [Taste The Code] is still quite impressive.

The MAX30105 contains red, green, and infrared LEDs, and a very sensitive light detector. The way it works is by turning on its different LEDs, and then carefully measuring what gets reflected back. In this way it can measure particles in the air, such as smoke, which is actually what it was designed for originally. Or, if you press your finger up against it, it can measure the light coming back from your blood and determine its oxygenation level. By detecting the variation in the light over time, it’s possible to pick up your pulse, too.

Getting this data out of the sensor is remarkably easy. One need only hook it up to a suitable microcontroller like the ESP8266 and use the MAX3010X library to talk to it. [Taste The Code] did exactly that, and also hooked up a screen for displaying the captured data. Alternatively, if you want the raw data from the sensor, you can get that too.

It should be noted that this build was done for educational purposes only. You shouldn’t rely on a simple DIY device for gathering useful medical data; there are reasons the real gear is so expensive, after all. We’ve looked at this sensor before, too, not long after it first hit the market. Continue reading “This Air Particulate Sensor Can Also Check Your Pulse Rate” →

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?

Voidstar’s Vitals, Visualized For Video

May 26, 2021 by Kristina Panos 4 Comments

Great news for fans of [Voidstar Labs] — [Zack] is going to be streaming future builds live on YouTube instead of trying to keep up with a grueling and limiting schedule of releasing a build video every week. The only problem is that the wall behind him is totally blank and boring, which matters quite a bit for pretty much any streamer that doesn’t broadcast from a hot tub. Well, not anymore! Now the wall has twenty square feet of rainbow hexagons, because blinkenlights.

But these aren’t just any blinkenlights. They’re informative. They dance to the beat of [Zack]’s bio-metrics, or in other words, they are visualizing how sweaty and anxious [Zack] may be at a given moment, and turning that information into art.

At the heart of this build is a brand-new bio-metric board called the EmotiBit which boasts sixteen sensors in a small package, including a pulse oximeter. The EmotiBit sends vitals to [Zack]’s PC, which is running an oscilloscope app to interpret the signals. Then they are sent over Open Sound Control to an ESP32, which runs the light show.

Like [Zack] says in the video after the break, this isn’t a terribly difficult project, but the construction takes time. [Zack] used aluminum extrusion meant for under-cabinet lighting and ran forty strips of fourteen DotStar LEDs each. The nodes are printed in carbon-fiber PLA and hold the lights away from the wall so it looks cooler. Worried about the current draw? It’s okay, because the brightness and number of lit LEDs at any one time is limited. Add in the fact that none of the LEDs are ever turned off — they fade by one percent each loop — and you have some really cool animations. Check them out after the break.

Want some localized blinkenlights to wear about town? Wear your heart on your sleeve and show them how hard you’re crushing the elliptical at the gym.

Continue reading “Voidstar’s Vitals, Visualized For Video” →

An LED Heartbeat Display You Can Wear On Your Sleeve

April 30, 2021 by Lewin Day 3 Comments

There are a few different ways to take a person’s pulse, with varying utility depending on the categories said patient fits in to. [Nitin Nair]’s method doesn’t really have a medical application, but it’s certainly a neat example of what you can do with modern sensors.

The build combines an EmotiBit sensor platform with an Adafruit Feather and accompanying Charlieplexed LED module. The EmotiBit packs a PPG, or photoplethysmogram sensor, otherwise known as a pulse oximeter, which uses optical methods to detect changes in blood volume beneath the skin. From this data, a pulse rate can be derived, and the LEDs flashed with a heart graphic in concert with the rhythm of the wearer’s heart. The benefit of the PPG in the EmotiBit is that it can be worn on the wearer’s arm, or other location with suitable vascularization. This allows the wearer to place the sensor on the arm, and thus wear their heart on their sleeve.

It’s a cool concept, and we’d love to see it neatly packaged with a smoothly animated fade as a sports accessory. It’d be an easy way to signal how fast your heart rate recovers on a run with friends – the device could brag about your fitness for you. Alternatively, if pulse oximetry isn’t enough for you, go ahead and build an ECG instead!

A Pulse Oximeter From Very Little

May 16, 2020 by Jenny List 31 Comments

Against the backdrop of a global respiratory virus pandemic, it’s likely that more than a few readers have been thinking about pulse oximeters. You may even have looked at one closely and seen that it’s little more than a device which shines light through your finger, and wondered how they work. It’s something [Giulio Pons] has done, and to show us how it’s done he’s created a working pulse oximeter of his own.

He started with an infra-red heartbeat sensor module, which is revealed as nothing more than an IR LED and a photodiode. Sampling the output from the photodiode allows measurement of heartbeat, but gives not clue as to oxygen saturation. The interesting part comes via the property of red light in that it’s transmission through flesh varies with oxygen saturation, so adding a red LED and alternately measuring from the IR and red illuminations allows a saturation figure to be derived.

Commercial pulse oximeters are pretty cheap, so many of us will no doubt simply order one from the usual sources and call it good. But it’s always interesting to know how any device works, and this project reveals something simpler than we might have expected. If pulse oximeters interest you, compare it with this one we featured a few years ago.

Hackaday Prize Entry: Open Source Patient Monitor

July 22, 2017 by John Baichtal 24 Comments

Vital sign monitors are usually found in developed countries; they just cost too much for less affluent communities to afford. The HealthyPi project aims to change that by developing an inexpensive but accurate monitor using a Raspberry Pi, a custom hat studded with sensors, and a touch screen. The resulting monitor could be used by medical professionals as well as students and private researchers.

[Ashwin K Whitchurch] and his team created HealthyPi, a Raspberry Pi hat that includes an AFE4490 chip serving as the pulse oximeter front end, an analog to digital converter that interprets the ECG and respiration data, and a MAX30205 body temperature sensor. The hat has its own microcontroller, a ATSAMD21 Cortex M0+ that can also be loaded with the Arduino Zero bootloader.

This project is capable of monitoring a patient’s pulse, respiration, body temperature, and all the other vital signs made measure d by other ‘medical-grade’ vital sign monitors at a fraction of the cost. It’s a democratizing technology, and [Ashwin] already has some working hardware available on Crowd Supply.

Learn more about HealthyPi at the project page or download the code from GitHub.

Continue reading “Hackaday Prize Entry: Open Source Patient Monitor” →

Pulse Oximeter Is A Lot Of Work

March 11, 2017 by Al Williams 24 Comments

These days we are a little spoiled. There are many sensors you can grab, hook up to your favorite microcontroller, load up some simple library code, and you are in business. When [Raivis] got a MAX30100 pulse oximeter breakout board, he thought it would go like that. It didn’t. He found it takes a lot of processing to get useful results out of the device. Lucky for us he wrote it all down with Arduino code to match.

A pulse oximeter measures both your pulse and the oxygen saturation in your blood. You’ve probably had one of these on your finger or earlobe at the doctor’s office or a hospital. Traditionally, they consist of a red LED and an IR LED. A detector measures how much of each light makes it through and the ratio of those two quantities relates to the amount of oxygen in your blood. We can’t imagine how [Karl Matthes] came up with using red and green light back in 1935, and how [Takuo Aoyagi] (who, along with [Michio Kishi]) figured out the IR and red light part.

The MAX30100 manages to alternate the two LEDs, regulate their brightness, filter line noise out of the readings, and some other tasks. It stores the data in a buffer. The trick is: how do you interpret that buffer? Continue reading “Pulse Oximeter Is A Lot Of Work” →