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Le capteur de pression barométrique et de température BMP085:

(Barometric Pressure + Temp sensor):

Capteur BMP085

Caractéristiques :
• Interface numérique à 2 fils (I2C)
• Large échelle de pression barométrique (échelle de mesure de 300 à 1 100 hPa)
• Gamme de tension d'alimentation flexible (entre 1,8 et 3,6 Vcc)
• Consommation d'énergie ultra-faible
• Mesure de bruits faibles
• Totalement calibré
• Mesure de la température comprise
• Ultra-plat, faible encombrement

Vendeurs chinois sur Ebay  5 à 20€ : tx-hang

testé avec l'alimentation  en 3.3v et 5v, ça fonctionne bien.


BMP085

Exemple d'utilisation avec la librairie Adafruit

#include <Wire.h>
#include <Adafruit_BMP085.h>

/***************************************************
  This is an example for the BMP085 Barometric Pressure & Temp Sensor

  Designed specifically to work with the Adafruit BMP085 Breakout
  ----> https://www.adafruit.com/products/391

  These displays use I2C to communicate, 2 pins are required to  
  interface
  Adafruit invests time and resources providing this open source code,
  please support Adafruit and open-source hardware by purchasing
  products from Adafruit!

  Written by Limor Fried/Ladyada for Adafruit Industries.  
  BSD license, all text above must be included in any redistribution
 ****************************************************/

// Connect VCC of the BMP085 sensor to 3.3V (NOT 5.0V!)
// Connect GND to Ground
// Connect SCL to i2c clock - on '168/'328 Arduino Uno/Duemilanove/etc thats Analog 5
// Connect SDA to i2c data - on '168/'328 Arduino Uno/Duemilanove/etc thats Analog 4
// EOC is not used, it signifies an end of conversion
// XCLR is a reset pin, also not used here

Adafruit_BMP085 bmp;
 
void setup() {
  Serial.begin(9600);
  if (!bmp.begin()) {
    Serial.println("Could not find a valid BMP085 sensor, check wiring!");
    while (1) {}
  }
}
 
void loop() {
    Serial.print("Temperature = ");
    Serial.print(bmp.readTemperature());
    Serial.println(" *C");
    
    Serial.print("Pressure = ");
    Serial.print(bmp.readPressure());
    Serial.println(" Pa");
    
    // Calculate altitude assuming 'standard' barometric
    // pressure of 1013.25 millibar = 101325 Pascal
    Serial.print("Altitude = ");
    Serial.print(bmp.readAltitude());
    Serial.println(" meters");

  // you can get a more precise measurement of altitude
  // if you know the current sea level pressure which will
  // vary with weather and such. If it is 1015 millibars
  // that is equal to 101500 Pascals.
    Serial.print("Real altitude = ");
    Serial.print(bmp.readAltitude(101500));
    Serial.println(" meters");
    
    Serial.println();
    delay(500);
}

résultat obtenu :

Temperature = 30.76 *C
Pressure = 98245 Pa
Altitude = 259.56 meters
Real altitude = 274.03 meters