BME280 Pressure, Temperature & Humidity Sensor

1. Introduction

The BME280 is a precision environmental sensor manufactured by Bosch Sensortec. Unlike single-function sensors, the BME280 measures three environmental parameters simultaneously: temperature, humidity, and barometric pressure—making it an ideal choice for weather stations, indoor climate monitoring, and altitude estimation projects.

This sensor is particularly popular in IoT applications due to its small size, low power consumption, and high accuracy. It communicates via I2C or SPI, making it compatible with virtually any microcontroller.

2. Technical Specifications

How It Works

The BME280 contains three separate sensing elements:

• Temperature: A precision bandgap temperature sensor
• Humidity: A capacitive humidity sensor with fast response
• Pressure: A piezoresistive pressure sensor for barometric measurements

The internal ADC converts all readings to digital values, and an integrated compensation engine applies factory-calibrated corrections for maximum accuracy.

3. BME280 vs BMP280 vs BME680

4. Wiring Guide

The BME280 module uses I2C for communication, requiring only 4 wires.

Figure 1: BME280 I2C wiring with ESP32

5. Real-Life Project: Weather Station Monitor

Let's build a Weather Station Monitor that reads temperature, humidity, and pressure from the BME280, calculates altitude, and displays weather conditions.

Required Components

• ESP32 or Arduino Uno
• BME280 Sensor Module
• Jumper wires (4x)
• Breadboard (optional)

Required Libraries

Install via Arduino Library Manager:

1. Adafruit BME280 Library
2. Adafruit Unified Sensor (dependency)

Complete Code

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

// ========== CONFIGURATION ==========
#define SEALEVELPRESSURE_HPA (1013.25)  // Standard sea level pressure

Adafruit_BME280 bme;  // Create BME280 object (I2C)

// ========== SETUP ==========
void setup() {
    Serial.begin(115200);
    Serial.println();
    Serial.println("========================================");
    Serial.println("   Weather Station Monitor v1.0");
    Serial.println("   BME280 Environmental Sensor");
    Serial.println("========================================");
    Serial.println();

    // Initialize BME280 at I2C address 0x76
    if (!bme.begin(0x76)) {
        Serial.println("❌ ERROR: BME280 not found!");
        Serial.println("   Check wiring or try address 0x77");
        while (1) delay(10);
    }

    Serial.println("✅ BME280 initialized successfully!");
    Serial.println();
    delay(1000);
}

// ========== MAIN LOOP ==========
void loop() {
    // Read all sensor values
    float temperature = bme.readTemperature();
    float humidity = bme.readHumidity();
    float pressure = bme.readPressure() / 100.0F;  // Convert Pa to hPa
    float altitude = bme.readAltitude(SEALEVELPRESSURE_HPA);

    // Display formatted output
    Serial.println("────────────────────────────────────────");
    Serial.print("🌡️  Temperature:  ");
    Serial.print(temperature, 1);
    Serial.print("°C  (");
    Serial.print(temperature * 9.0 / 5.0 + 32, 1);
    Serial.println("°F)");

    Serial.print("💧 Humidity:     ");
    Serial.print(humidity, 1);
    Serial.println("% RH");

    Serial.print("📊 Pressure:     ");
    Serial.print(pressure, 1);
    Serial.println(" hPa");

    Serial.print("⛰️  Altitude:     ");
    Serial.print(altitude, 1);
    Serial.println(" m");

    // Weather prediction based on pressure
    Serial.print("🌤️  Forecast:     ");
    if (pressure > 1022) {
        Serial.println("☀️ Clear skies");
    } else if (pressure > 1009) {
        Serial.println("⛅ Fair weather");
    } else if (pressure > 1000) {
        Serial.println("☁️ Cloudy");
    } else {
        Serial.println("🌧️ Rain likely");
    }

    delay(3000);  // Update every 3 seconds
}

Expected Serial Output

========================================
   Weather Station Monitor v1.0
   BME280 Environmental Sensor
========================================

✅ BME280 initialized successfully!

────────────────────────────────────────
🌡️  Temperature:  24.3°C  (75.7°F)
💧 Humidity:     48.2% RH
📊 Pressure:     1015.4 hPa
⛰️  Altitude:     18.2 m
🌤️  Forecast:     ⛅ Fair weather

6. Sensor Modes & Power Optimization

The BME280 supports different operating modes for power optimization:

7. Ideas for Extension

• OLED Display: Show real-time weather data on a 0.96" OLED
• Data Logging: Store readings on SD card with timestamps
• IoT Dashboard: Send data to Blynk, ThingSpeak, or Home Assistant
• Weather Alerts: Trigger notifications on pressure drops
• Multi-floor Detection: Use pressure changes to detect floor level

8. Troubleshooting

Problem: "BME280 not found"

• Check wiring connections (especially SDA/SCL)
• Try I2C address 0x77 instead of 0x76
• Run an I2C scanner sketch to detect the sensor

Problem: Altitude readings are incorrect

• Update SEALEVELPRESSURE_HPA to your local sea level pressure
• Check local weather services for current barometric pressure

Problem: Humidity reads 0% or 100%

• Ensure you have a BME280, not BMP280 (which lacks humidity)
• Check that the sensor is not in direct sunlight or near heat sources

9. Summary

The BME280 is an excellent all-in-one environmental sensor for weather monitoring, altitude estimation, and indoor climate control. Its combination of temperature, humidity, and pressure sensing in a single low-power package makes it ideal for IoT and battery-powered applications.

• Measures temperature (±0.5°C), humidity (±3%), and pressure (±1 hPa)
• Ultra-low power consumption (3.6 µA @ 1Hz)
• Easy I2C interface with Adafruit library support
• Can estimate altitude from barometric pressure