Arduino Practical Workshop: MAX30102 Wrist Heart Rate Monitor

I have organized a series of experiments to explore various sensor and actuator modules, based on the principle that genuine understanding comes from hands-on experience. The aim of these experiments is to facilitate learning and idea exchange. Regardless of whether they succeed (with the program running smoothly) or face challenges, I will document the progress and obstacles encountered, with the hope of contributing insights and inspiring others.

【Arduino】168 Sensor Module Series Experiments (Data Code + Simulation Programming + Graphical Programming)

Experiment: MAX30102 Pulse Oximeter Wrist Heart Rate Pulse Detection Sensor Module.

The MAX30102 is a comprehensive module designed for pulse oximetry and heart rate monitoring. It integrates internal LEDs, photodetectors, optical components, and low-noise electronics with the capability to suppress ambient light. This provides a complete system solution that simplifies the design process for mobile and wearable devices. The MAX30102 operates on a single 1.8V power supply and includes a separate 5.0V power supply specifically for its internal LEDs. Communication with the module is conducted via a standard I2C-compatible interface. Additionally, the module can be configured through software to minimize standby current, allowing the power rails to stay energized continuously.

Applications:

Wearable devices

Fitness assistance devices

Advantages and Features of MAX30102:

Heart rate monitor and pulse oximeter sensor input LED reflection solution
Miniature 5.6mm x 3.3mm x 1.55mm 14-pin optical module
Integrated cover glass for optimal and robust performance
Ultra-low power operation for mobile devices
Programmable sampling rate and LED current saving
Low-power heart rate monitor (<1mW)
Ultra-low standby current (0.7μA, typical)
Fast data output capabilities
High sampling rate
Powerful motion artifact recovery capability
High signal-to-noise ratio
Operating temperature range of -40°C to +85°C

MAX30102 Wrist Heart Rate Module

It consists of two light-emitting diodes, one photodetector, optimized optics, and low-noise analog signal processing to detect pulse oxygen saturation and heart rate signals.

1.By simply placing a finger on the sensor, it is possible to estimate the pulse oxygen saturation (SpO2) and pulse rate (equivalent to heartbeat).

2.Red blood cells carrying oxygen absorb more infrared light (850-1000nm), while red blood cells without oxygen absorb more red light (600-750nm).

3.Therefore, a pulse oximeter is like a mini spectrometer that analyzes oxygen saturation based on the absorption spectra of different types of red blood cells.

4.This real-time and fast measurement method is widely used in many clinical applications.

Schematic Diagram of MAX30102 Wrist Heart Rate Module

The MAX30102 is an integrated module designed for pulse oximetry and heart rate monitoring biosensing. It incorporates a red LED, an infrared LED, photodetectors, optical components, and low-noise electronic circuits with ambient light suppression capabilities. Operating on a 1.8V power supply along with a separate 5.0V supply for the internal LEDs, the MAX30102 is used in wearable devices to measure heart rate and blood oxygen levels. It can be worn on the finger, earlobe, or wrist. A standard I2C-compatible communication interface transmits the collected data to microcontrollers like Arduino or KL25Z for heart rate and blood oxygen calculations. The module can be configured via software to minimize standby current, ensuring continuous power supply availability.

Due to its excellent performance, the MAX30102 has been widely used in Samsung Galaxy S series smartphones. Compared to its predecessor, the MAX30100, this chip includes a glass cover that effectively eliminates external and internal light interference, providing optimal and reliable performance.

MH-ET LIVE

MAX30102 Heart Rate and Blood Oxygen Sensor Module

Main Parameters:

LED Peak Wavelength: 660nm/880nm
LED Supply Voltage: 3.3~5V
Detection Signal Type: Photoplethysmographic (PPG) signal
Output Signal Interface: I2C interface
Communication Interface Voltage: 1.8~3.3V to 5V (selectable)
Reserved Mounting Hole Size on Board: 0.5x8.5mm

Principle Explanation:

Photoplethysmography (PPG): This method measures pulse and blood oxygen saturation by exploiting the variations in light transmission through body tissue caused by vascular pulsations.
Light Source: Utilizes light-emitting diodes (LEDs) with specific wavelengths that selectively target oxyhemoglobin (HbO2) and hemoglobin (Hb) within arterial blood.
Conversion of Light Transmission to Electrical Signal: As arterial pulsation causes changes in blood volume, the light transmission alters accordingly. A photodetector captures the light reflected through the body tissue, converting it into an electrical signal, which is then amplified for output.
Pulse average
• The average pulse is 60-100 beats per minute
You can check your pulse at your neck or your wrist
Pin Description:
VIN: Main power supply input, 1.8V-5V.
3-Pad Selector: Used to select the pull-up level for the bus, depending on the voltage of the main control pin. You can choose either the 1.8V pad or the 3.3V pad (which includes 3.3V and above).
SCL: Clock line for the I2C bus.
SDA: Data line for the I2C bus.
INT: Interrupt pin for the MAX30102 chip.
RD: Ground for the RED LED on the MAX30102 chip; typically left unconnected.
IRD: Ground for the IR LED on the MAX30102 chip; typically left unconnected.
GND: Ground line.

After extensive research and exploration, I have discovered a validated practical blood oxygen calibration formula from a program dedicated to studying the MAX30102 algorithm:

The value of R can be calculated by taking the logarithm of the intensity of red light and infrared light. This calibration expression is actually a quadratic curve fitting for blood oxygen saturation, obtained through measurements. Finally, the data on blood oxygen saturation can be outputted.

The MAX30102 wrist heart rate module is primarily used in the following applications:

Fitness devices

Smartphones

Tablets

Wearable devices

The MAX30102 module's light-emitting section consists of two LEDs: a red LED with a wavelength of 660nm and an infrared LED at 880nm. This configuration is commonly used for measuring blood oxygen saturation (SpO2). The receiving component features a photodiode sensitive to both visible and infrared light, which converts the light intensity into a current signal. This signal is processed through an ambient light elimination circuit before being sampled and converted by the built-in 18-bit ADC. After conversion, the digital data is stored in a data register, accessible to an external MCU via the I2C bus.

In terms of hardware design, the LED power supply is separate from the rest of the components. This separation is necessary because the LEDs require a high instantaneous current, up to 50mA, to ensure adequate light emission, demanding a forward voltage of at least 3.1V. Conversely, the AD conversion and I2C bus components need to run at a lower voltage of 1.8V to meet low-power consumption requirements. Therefore, the sensor is designed with independent power supplies for these functions. Additionally, due to the high instantaneous current draw from the LED power supply, it's recommended to place a large capacitor near the power supply pin to stabilize the power voltage.

There are three main traditional methods for pulse measurement: extracting from the electrocardiogram signal, calculating pulse rate from the fluctuations measured by a pressure sensor during blood pressure measurement, and using the photoplethysmography method. The first two methods of signal extraction impose limitations on the patient's activities, and prolonged use may cause physical and psychological discomfort. In contrast, the photoplethysmography method is one of the most common methods for monitoring pulse measurement due to its simplicity, convenience, and high reliability.

The fundamental principle of photoplethysmography involves measuring pulse and blood oxygen saturation by detecting changes in light transmittance caused by blood vessel pulsations in the body. This method uses a sensor comprised of a light source and a photodetector, usually attached to a patient's finger, wrist, or earlobe with a strap or clip. The light source typically includes LEDs that emit light at specific wavelengths around 660nm (red light) and 900nm (infrared light), which are selectively absorbed by oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) in arterial blood. As the light beam passes through peripheral blood vessels, its transmittance varies due to volume changes caused by arterial pulsations. The photodetector captures the light reflected from the tissue, converts it into an electrical signal, amplifies it, and outputs it. Because the pulse is a periodic signal that fluctuates with the heartbeat and arterial blood volume also changes periodically, the variation period of the electrical signal from the photodetector corresponds to the pulse rate.

Schematic diagram of the MAX30102 wrist heart rate module experimental wiring.

Open source code for experimentation.

Initializing…

Place your index finger on the sensor with steady pressure.

Module Electrical Schematic Number 2