IoT Heart Rate Monitoring System — MAX30102 + MPU6050 + OLED (Step-by-step)

Complete step-by-step guide, wiring, firmware, algorithms, troubleshooting, and deployment notes — written in Markdown so you can copy, print, or paste into a repo README.

1. Project summary

This project builds a portable IoT heart-rate monitor using the MAX30102 sensor (PPG: heart rate + SpO₂), the MPU6050 (accelerometer + gyro), and an SSD1306 OLED display connected to an ESP32. The ESP32 will process the raw signals, detect heart beats (BPM), monitor motion/fall events, display results locally on OLED, and publish JSON telemetry over MQTT to a cloud/dashboard.

What you’ll get:

Real-time BPM telemetry on OLED
Basic SpO₂ estimation (note: SpO₂ calculation is non-trivial; use a library for production accuracy)
Motion / fall detection and activity context from MPU6050
MQTT publishing for dashboards/alerts

⚠️ Medical disclaimer: This is a hobbyist project. Do not use it as a medical diagnostic device. Always consult professionals for medical-grade monitoring.

2. Parts & BOM

ESP32 development board (any variant with Wi‑Fi)
MAX30102 (or MAX30105) sensor module
MPU6050 module
SSD1306 OLED display (128x64 I²C)
Breadboard and jumper wires
LiPo battery + charger (TP4056) for portability

Libraries you will need (Arduino/PlatformIO):

SparkFun MAX3010x (or MAX30105) — for MAX30102 sensor
Adafruit_MPU6050 and Adafruit_Sensor — for MPU6050
Adafruit_GFX and Adafruit_SSD1306 — for OLED display
WiFi.h (built-in)
PubSubClient — for MQTT

3. Wiring / Pinout (ESP32)

I²C bus (shared):

MAX30102 VCC → 3.3V
MAX30102 GND → GND
MAX30102 SDA → GPIO 21 (SDA)
MAX30102 SCL → GPIO 22 (SCL)
MPU6050 VCC → 3.3V
MPU6050 GND → GND
MPU6050 SDA → GPIO 21 (SDA)
MPU6050 SCL → GPIO 22 (SCL)
OLED SSD1306: VCC → 3.3V, GND → GND, SDA → 21, SCL → 22

All devices share the same I²C bus.

4. Step-by-step assembly (hardware)

Place ESP32, MAX30102, MPU6050, and OLED on the breadboard.
Connect all devices to the shared I²C bus (GPIO 21 SDA, GPIO 22 SCL).
Ensure a stable 3.3V supply for all modules.
Double-check wiring before powering.

5. Firmware (ESP32 sketch with OLED)

This sketch now includes OLED support to show BPM, fall status, and basic sensor data locally.

#include <Wire.h>
#include "MAX30105.h"
#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
#include <WiFi.h>
#include <PubSubClient.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// ======= CONFIG =======
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

const char* WIFI_SSID = "YOUR_WIFI_SSID";
const char* WIFI_PASS = "YOUR_WIFI_PASS";
const char* MQTT_SERVER = "test.mosquitto.org";
const char* MQTT_TOPIC  = "iot/heartmonitor";

WiFiClient espClient;
PubSubClient mqtt(espClient);

MAX30105 particleSensor;
Adafruit_MPU6050 mpu;

unsigned long lastBeatMs = 0;
int bpm = 0;
bool pulseDetected = false;

void connectWiFi(){
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  while (WiFi.status() != WL_CONNECTED) delay(300);
}

void reconnectMQTT(){
  while (!mqtt.connected()){
    mqtt.connect("ESP32Heart");
    delay(100);
  }
}

void setup() {
  Serial.begin(115200);
  Wire.begin();

  connectWiFi();
  mqtt.setServer(MQTT_SERVER, 1883);

  // MAX30102 init
  if (!particleSensor.begin(Wire)){
    Serial.println("MAX301xx not found");
    while(1) delay(1000);
  }
  particleSensor.setup();

  // MPU6050 init
  if (!mpu.begin()){
    Serial.println("MPU6050 not found");
    while(1) delay(1000);
  }

  // OLED init
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 not found"));
    while(1);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  display.println("Heart Monitor Ready");
  display.display();
}

void loop() {
  if (!mqtt.connected()) reconnectMQTT();
  mqtt.loop();

  // --- Read PPG ---
  long irValue = particleSensor.getIR();
  unsigned long now = millis();

  if (irValue > 50000 && !pulseDetected) {
    if (now - lastBeatMs > 250) {
      bpm = 60000 / (now - lastBeatMs);
      lastBeatMs = now;
      pulseDetected = true;
    }
  }
  if (irValue < 50000) pulseDetected = false;

  // --- Read MPU6050 ---
  sensors_event_t a, g, temp;
  mpu.getEvent(&a, &g, &temp);
  float accelMag = sqrt(a.acceleration.x*a.acceleration.x + a.acceleration.y*a.acceleration.y + a.acceleration.z*a.acceleration.z);
  bool fallDetected = (accelMag > 25.0);

  // --- Update OLED ---
  display.clearDisplay();
  display.setCursor(0,0);
  display.setTextSize(2);
  display.print("BPM: ");
  display.println(bpm);
  display.setTextSize(1);
  display.setCursor(0,30);
  display.print("AccelMag: ");
  display.println(accelMag);
  display.setCursor(0,45);
  display.print("Fall: ");
  display.println(fallDetected ? "YES" : "NO");
  display.display();

  // --- Publish JSON ---
  static unsigned long lastPublish = 0;
  if (now - lastPublish >= 1000) {
    lastPublish = now;
    String payload = "{\"bpm\":" + String(bpm) + ",\"fall\":" + String(fallDetected) + "}";
    mqtt.publish(MQTT_TOPIC, payload.c_str());
    Serial.println(payload);
  }

  delay(50);
}

6. OLED Display output

The SSD1306 will show:

BPM (updated in real time)
Accel magnitude (total acceleration vector)
Fall detected status (YES/NO)

This allows you to monitor locally without needing MQTT.

7. Next steps

Add SpO₂ calculation and display it on OLED.
Add history graph or scrolling BPM trend on OLED.
Optimize text layout for clarity (big BPM number, smaller motion data).

IoT Heart Rate Monitoring System using max30102