Pulse oximetry

9 Articles

How Pulse Oximetry Figures Out Your Blood Oxygen Levels

May 19, 2026 by 14 Comments

If you’ve ever had a medical team investigating cardiac issues, you’ve probably had a bunch of electrodes stuck all over your chest and been hooked up to an electrocardiogram. This is the gold standard when it comes to understanding electrical activity in the heart and can diagnose a great many conditions. However, sometimes doctors just need the basic information—your pulse rate, and whether or not there’s actually any oxygen in your blood.

Thankfully, there’s a cheap and simple device that can offer that exact information. It’s the pulse oximeter, and it’s a key piece of equipment that’s just about vital for monitoring vitals. Let’s learn how it works!

Continue reading “How Pulse Oximetry Figures Out Your Blood Oxygen Levels” →

Biofeedback Butterfly Beats With A Pulse

May 19, 2026 by 1 Comment

Biofeedback is the idea of making one conscious of a biological process or feature, and then using this to try and exert control over the very same. [Mariia Hruntes] demonstrates this ably with a fluttering build of her own design.

In this case, the biological process being made clear is that of the user’s heartbeat. This is tracked with a MAX30102 pulse oximetry sensor, which can be used to measure both heart rate and blood oxygen levels if so desired. It’s hooked up to an Arduino Uno, which polls for pulse rate data, and then actuates an SG90 micro servo in turn. This operates the wings of a 3D printed butterfly, such that they flap in pace with the wearer’s pulse. The goal is to observe this, and then try and calm one’s self to relax and slow the flapping through the power of the mind.

It’s a simple build, but one that clearly demonstrates the concepts of biofeedback in action. We’ve seen similar principles applied to everything from aiding sleep to improving the practice of mediation. If you’re working on your own neat biofeedback project, be sure to let us know on the tipsline.

2025 One Hertz Challenge: An Arduino-Based Heart Rate Sensor

August 15, 2025 by 2 Comments

How fast does your heart beat? It’s a tough question to answer, because our heart rate changes all the time depending on what we’re doing and how our body is behaving. However, [Ludwin] noted that resting heart rates often settle somewhere near 60 bpm on average. Thus, they entered a heart rate sensor to our 2025 One Hertz Challenge!

The build is based around a Wemos D1 mini, a ESP8266 development board. It’s hooked up to a MAX30102 heart beat sensor, which uses pulse oximetry to determine heart rate with a photosensor and LEDs. Basically, it’s possible to determine the oxygenation of blood by measuring its absorbance of red and infrared wavelengths, usually done by passing light through a finger. Meanwhile, by measuring the change in absorption of light in the finger as blood flows with the beat of the heat, it’s also possible to measure a person’s pulse rate.

The Wemos D1 takes the reading from the MAX30102, and displays it on a small OLED display. It reports heart rate in both beats per minute and in Hertz. if you can happen to get your heartrate to exactly 60 beats per minute, it will be beating at precisely 1 Hertz. Perhaps, then, it’s the person using Ludwin’s build that is actually eligible for the One Hertz Challenge, since they’re the one doing something once per second?

In any case, it shows just how easy it is to pick up biometric data these days. You only need a capable microcontroller and some off-the-shelf sensors, and you’re up and running.

Continue reading “2025 One Hertz Challenge: An Arduino-Based Heart Rate Sensor” →

A light grey box about the size of a brick with exposed screws held in a person's hand. There are two illuminated push buttons on the bottom left of the top panel. One is illuminated blue while the other is green. A small square screen sits next to a bank of nine different sections with an LED indicator and text of "HW, BAT, HBEAT, ECG, LOD +, LOD -, PPG, Pump, Valve."

Open Cardiography Signal Measuring Device

November 13, 2024 by 10 Comments

Much of the world’s medical equipment is made by a handful of monopolistic megacorps, but [Milos Rasic] built an open cardiography signal measuring device for his master’s thesis.

Using a Pi Pico W for the brains, [Rasic]’s device can record, store and analyze the data from an arm cuff, stethoscope, electrocardiograph (ECG), and pulse oximeter. This data can be used for monitoring blood pressure in patients and he has results from some of his experiments to determine the optimal algorithm for the task on the GitHub if you really want to get into the nitty gritty details.

Inside the brick-sized enclosure is the custom PCB, an 18650 Li-ion cell, and a pneumatic assembly for the arm cuff. Medical sensors attach via GX12 connectors on the back, a USB type B connector is used for data, and a USB C connector provides power for the device. The brightly colored labels will no doubt come in handy in a clinical setting where you really want to be sure you’ve got everything plugged in correctly.

Want more open medical equipment? How about an open ECG or this less accurate, but more portable, credit card ECG? We’d be remiss not to mention the huge amount of work on ventilators during the worst days of the COVID-19 pandemic as well.

Hackaday Prize Entry: A Complete Suite Of Biomedical Sensors

April 22, 2017 by 13 Comments

The human body has a lot to tell us if we only have the instruments to listen. Unfortunately, most of the diagnostic gear used by practitioners is pricey stuff that’s out of range if you just want to take a casual look under the hood. For that task, this full-featured biomedical sensor suite might come in handy.

More of an enabling platform than a complete project, [Orlando Hoilett]’s shield design incorporates a lot of the sensors we’ve seen before. The two main modalities are photoplethysmography, which uses the MAX30101 to sense changes in blood volume and oxygen saturation by differential absorption and reflection of light, and biopotential measurements using an instrumentation amplifier built around an AD8227 to provide all the “electro-whatever-grams” you could need: electrocardiogram, electromyogram, and even an electrooculogram to record eye movements. [Orlando] has even thrown on temperature and light sensors for environmental monitoring.

[Orlando] is quick to point out that this is an educational project and not a medical instrument, and that it should only ever be used completely untethered from mains — battery power and Bluetooth only, please. Want to know why? Check out the shocking truth about transformerless power supplies.

The HackadayPrize2017 is Sponsored by:

Thanks to [fustini] for the tip.

Wireless Wearable Watches Your Vital Signs

March 13, 2017 by 10 Comments

Is it [Dr. McCoy]’s long-awaited sickbay biobed, with wireless sensing and display of vital signs? Not quite, but this wearable patient monitor comes pretty close. And from the look of it, [Arthur]’s system might even monitor a few more parameters than [Bones]’ bleeping bed from the original series.

Starting with an automatic blood pressure cuff that [Arthur] had previously reversed engineered, he started adding sensors. Pulse, ECG, respiration rate, galvanic skin response, and body temperature are all measured from one compact, wrist-wearable device. It’s not entirely wireless – the fingertip pulse oximetry dongle and chest electrodes still need to be wired back to the central unit – but the sensors all talk to a Teensy 3.2 which then communicates to an Android app over Bluetooth, so there’s no need to be tethered to the display. And speaking of electrodes, we’re intrigued by the ADS1292 chip [Arthur] uses, which not only senses the heart’s electrical signals but also detects respirations by the change in impedance as the chest wall expands and contracts. Of course there’s also pneumography via radar that could be rolled into this sensor suite.

It’s all pretty cool, and we can easily see a modified version of this app displayed on a large tablet or monitor being both an accurate prop reconstruction and a useful medical device.

Continue reading “Wireless Wearable Watches Your Vital Signs” →

Pulse Oximeter Is A Lot Of Work

March 11, 2017 by 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” →