Pressure Sensor BMP280: Weather Station and Altitude Meter

The BMP280 barometric pressure sensor by Bosch measures atmospheric pressure with ±1 hPa accuracy and temperature with ±1°C precision. These two readings let you build weather prediction systems and altitude meters with about 1-metre resolution. At ₹120-200 for a module, the BMP280 is one of the most cost-effective environmental sensors for Arduino projects. This guide covers wiring, code, weather forecasting logic, and a complete altitude meter build.

BMP280 Sensor Overview

BMP280 vs BME280: What’s the Difference?

The names differ by one letter but the capabilities are different:

• BMP280 — Measures pressure and temperature only. Costs ₹120-200.
• BME280 — Measures pressure, temperature, AND humidity. Costs ₹180-350.

If you need humidity data (weather stations, HVAC, comfort monitoring), get the BME280. If you only need pressure and temperature (altitude meters, weather prediction), the BMP280 saves money. The boards look identical — check the chip marking to confirm which you received.

Wiring to Arduino (I2C)

Default I2C address is 0x76 (SDO pin low) or 0x77 (SDO pin high). Most modules default to 0x76.

Basic Pressure and Temperature Reading

#include <Wire.h>
#include <Adafruit_BMP280.h>

Adafruit_BMP280 bmp;

void setup() {
  Serial.begin(9600);
  if (!bmp.begin(0x76)) {
    Serial.println("BMP280 not found! Check wiring.");
    while (1);
  }

  // Recommended settings for weather monitoring
  bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,
                   Adafruit_BMP280::SAMPLING_X2,   // temperature
                   Adafruit_BMP280::SAMPLING_X16,  // pressure
                   Adafruit_BMP280::FILTER_X16,
                   Adafruit_BMP280::STANDBY_MS_500);
}

void loop() {
  float temperature = bmp.readTemperature();
  float pressure = bmp.readPressure() / 100.0; // Pa to hPa
  float altitude = bmp.readAltitude(1013.25);  // Sea-level pressure

  Serial.print("Temperature: ");
  Serial.print(temperature, 1);
  Serial.print(" C | Pressure: ");
  Serial.print(pressure, 1);
  Serial.print(" hPa | Altitude: ");
  Serial.print(altitude, 1);
  Serial.println(" m");

  delay(2000);
}

Building a Weather Station

Barometric pressure changes predict weather 12-24 hours in advance:

This works particularly well during Indian monsoon season when pressure systems move through regularly. Track pressure readings every 30 minutes, store a 3-hour history, and calculate the trend.

// Simple 3-hour pressure trend tracker
float pressureHistory[6]; // 6 readings at 30-min intervals = 3 hours
int historyIndex = 0;
bool historyFull = false;

void updateHistory(float currentPressure) {
  pressureHistory[historyIndex] = currentPressure;
  historyIndex = (historyIndex + 1) % 6;
  if (historyIndex == 0) historyFull = true;
}

String getForecast() {
  if (!historyFull) return "Collecting data...";

  int oldestIndex = historyIndex; // Oldest reading
  float oldest = pressureHistory[oldestIndex];
  float newest = pressureHistory[(historyIndex + 5) % 6];
  float change = newest - oldest;

  if (change > 1.0) return "Fair weather ahead";
  if (change > 0.5) return "Mostly stable";
  if (change > -1.0) return "Slight change possible";
  if (change > -3.0) return "Rain likely";
  return "Storm approaching!";
}

Altitude Measurement

Atmospheric pressure decreases with altitude at approximately 12 Pa per metre near sea level. The BMP280’s relative pressure accuracy of ±0.12 hPa translates to about ±1 metre altitude resolution.

The altitude formula requires knowing the current sea-level pressure (QNH in aviation terms). This varies daily and must be set from a reference source (weather report, airport METAR, or a known-elevation reference point).

Altitude Applications

• Drone altitude hold: BMP280 provides smoother altitude data than GPS for short-term height maintenance
• Trekking altimeter: Track elevation profile during hikes in the Himalayas or Western Ghats
• Floor detection in buildings: Detect floor changes in multi-storey buildings for indoor navigation
• Variometer for paragliding: Measure rate of climb/descent (differentiate altitude over time)

Frequently Asked Questions

Why does the BMP280 altitude reading keep changing even when I’m stationary?

Atmospheric pressure changes constantly due to weather systems, which the sensor correctly measures. A 1 hPa natural pressure change appears as an 8-metre altitude change. For absolute altitude, update the sea-level reference pressure frequently. For relative altitude (height change from a starting point), take a reference reading at startup and compute the difference — this cancels out weather-related drift.

Can I use BMP280 as a weather forecaster?

Yes, and it works surprisingly well. Falling pressure indicates approaching low-pressure systems (rain, storms), while rising pressure indicates clearing weather. The key is tracking the trend over 3+ hours, not instantaneous readings. This method has been used by barometers for centuries.

Is the BMP280 accurate enough for indoor floor detection?

Yes. A standard floor height is 3-4 metres, producing about 36-48 Pa of pressure difference. The BMP280’s noise level is about 1 Pa, so floor changes are clearly detectable. Many smartphone navigation apps use this principle for indoor floor detection.

Does the BMP280 need calibration?

The sensor comes factory-calibrated and stores calibration coefficients in its internal registers. The Adafruit and other libraries read these coefficients automatically. You don’t need to calibrate the sensor itself — just set the correct sea-level pressure reference for accurate altitude readings.

Can I combine BMP280 with other I2C sensors?

Yes. I2C is a bus protocol — multiple devices share the same SDA and SCL wires. The BMP280 (address 0x76 or 0x77) works alongside an OLED display (0x3C), MPU6050 (0x68), and other I2C devices on the same two wires. Just ensure no address conflicts.

Conclusion

The BMP280 is a remarkably capable sensor for its price. For ₹120-200, you get barometric pressure and temperature measurements that enable weather forecasting and altitude estimation. Whether you’re building a desktop weather station, a drone flight controller, or a trekking altimeter for your next Himalayan adventure, the BMP280 delivers the data reliably and efficiently.

Find BMP280 and BME280 modules at Zbotic’s sensor modules store.