Barometer | Technology Tutorials

In this video lesson we take you through the project of building an Arduino Barometric Pressure Weather Station. It builds on the last two lessons in this series. We measure and display instantaneous Barometric Pressure, normalized to Sea Level. Then in the lower portion on the OLED SSD1306 display, we show a graph of the barometric pressure over the last 24 hours.

Schematic for the Portable Arduino Barometric Pressure Sensor

Below we include the code we develop in the above video. Make sure to set the ‘alt’ variable to your elevation at your location, in meters.

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_BMP085.h>

int lastUpdate = 0;
int updateInterval = 600000;

float rawXdata[128];
int normXdata[128];

float rawYdata[128];
int normYdata[128];

float xMin = 0;
float xMax = 127;

float yMin = 28;
float yMax = 31;

float Pt = 14;
float Pb = 63;

float Pl = 0;
float Pr = 127;

int numPoints = 128;

Adafruit_BMP085 BP;
bool BMPconnected = false;

float BarPress = 30;
float BarPressNow = 30;
float alt = 1127;

int screenWidth = 128;
int screenHeight = 64;
int oledReset = -1;
#define SCREEN_ADDRESS 0x3C
Adafruit_SSD1306 oled(screenWidth, screenHeight, &Wire, oledReset);

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  BMPconnected = BP.begin();
  if (BMPconnected == true) {
    Serial.println("BMP180 found and Connected");
  }
  if (BMPconnected == false) {
    Serial.println("BMP180 not found, Check Connections");
  }
  oled.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS);
  oled.clearDisplay();
  oled.display();
  for (int i = 0; i < numPoints; i= i + 1) {
    rawXdata[i] = i;
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  BarPressNow = normPress(alt);
  BarPress = .95 * BarPress + .05 * BarPressNow;
  if (millis() - lastUpdate >= updateInterval) {
    for (int i = 0; i < numPoints - 1; i = i + 1) {
      rawYdata[i] = rawYdata[i + 1];

    }
    lastUpdate=millis();
    rawYdata[numPoints-1]=BarPress;
    normData();
    oled.clearDisplay();
    plotGraph();
  }
  oled.clearDisplay();
  oled.setCursor(0, 0);
  oled.setTextColor(WHITE);
  oled.setTextSize(2);
  oled.print(BarPress);
  oled.setTextSize(1);
  oled.println(" In HG");
  normData();
  plotGraph();
  oled.display();
  delay(.1);
}

float normPress(float elev) {
  float BPRaw;
  float BPNorm;
  float T0 = 288.15;
  float L = .0065;
  float R = 8.3144598;
  float M = .0289644;
  float g = 9.8;
  float c = M * g / (R * L);
  BPRaw = BP.readPressure() * .0002953;
  BPNorm = BPRaw / pow(1 - L * elev / T0, c);
  return BPNorm;
}
void normData() {
  for (int i = 0; i < numPoints; i = i + 1) {
    normYdata[i] = (Pb - Pt) / (yMin - yMax) * (rawYdata[i] - yMax) + Pt;
    normXdata[i] = (Pr - Pl) / (xMax - xMin) * (rawXdata[i] - xMin) + Pl;
  }
}
void plotGraph() {
  oled.drawLine(Pl, Pt, Pl, Pb, WHITE);
  oled.drawLine(Pl, Pb, Pr, Pb, WHITE);
  int MID = (Pb - Pt) / (yMin - yMax) * (29.92 - yMax) + Pt;
  oled.drawLine(Pl, MID, Pr, MID, WHITE);
  for (int i = 0; i < numPoints - 1; i = i + 1) {
    oled.drawLine(normXdata[i], normYdata[i], normXdata[i + 1], normYdata[i + 1], WHITE);
  }
}

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#include <SPI.h>

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

#include <Adafruit_BMP085.h>

int lastUpdate = 0;

int updateInterval = 600000;

float rawXdata[128];

int normXdata[128];

float rawYdata[128];

int normYdata[128];

float xMin = 0;

float xMax = 127;

float yMin = 28;

float yMax = 31;

float Pt = 14;

float Pb = 63;

float Pl = 0;

float Pr = 127;

int numPoints = 128;

Adafruit_BMP085 BP;

bool BMPconnected = false;

float BarPress = 30;

float BarPressNow = 30;

float alt = 1127;

int screenWidth = 128;

int screenHeight = 64;

int oledReset = -1;

#define SCREEN_ADDRESS 0x3C

Adafruit_SSD1306 oled(screenWidth, screenHeight, &Wire, oledReset);

void setup() {

// put your setup code here, to run once:

Serial.begin(9600);

BMPconnected = BP.begin();

if (BMPconnected == true) {

Serial.println("BMP180 found and Connected");

}

if (BMPconnected == false) {

Serial.println("BMP180 not found, Check Connections");

}

oled.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS);

oled.clearDisplay();

oled.display();

for (int i = 0; i < numPoints; i= i + 1) {

rawXdata[i] = i;

}

void loop() {

// put your main code here, to run repeatedly:

BarPressNow = normPress(alt);

BarPress = .95 * BarPress + .05 * BarPressNow;

if (millis() - lastUpdate >= updateInterval) {

for (int i = 0; i < numPoints - 1; i = i + 1) {

rawYdata[i] = rawYdata[i + 1];

}

lastUpdate=millis();

rawYdata[numPoints-1]=BarPress;

normData();

oled.clearDisplay();

plotGraph();

}

oled.clearDisplay();

oled.setCursor(0, 0);

oled.setTextColor(WHITE);

oled.setTextSize(2);

oled.print(BarPress);

oled.setTextSize(1);

oled.println(" In HG");

normData();

plotGraph();

oled.display();

delay(.1);

}

float normPress(float elev) {

float BPRaw;

float BPNorm;

float T0 = 288.15;

float L = .0065;

float R = 8.3144598;

float M = .0289644;

float g = 9.8;

float c = M * g / (R * L);

BPRaw = BP.readPressure() * .0002953;

BPNorm = BPRaw / pow(1 - L * elev / T0, c);

return BPNorm;

}

void normData() {

for (int i = 0; i < numPoints; i = i + 1) {

normYdata[i] = (Pb - Pt) / (yMin - yMax) * (rawYdata[i] - yMax) + Pt;

normXdata[i] = (Pr - Pl) / (xMax - xMin) * (rawXdata[i] - xMin) + Pl;

}

void plotGraph() {

oled.drawLine(Pl, Pt, Pl, Pb, WHITE);

oled.drawLine(Pl, Pb, Pr, Pb, WHITE);

int MID = (Pb - Pt) / (yMin - yMax) * (29.92 - yMax) + Pt;

oled.drawLine(Pl, MID, Pr, MID, WHITE);

for (int i = 0; i < numPoints - 1; i = i + 1) {

oled.drawLine(normXdata[i], normYdata[i], normXdata[i + 1], normYdata[i + 1], WHITE);

}

In this video lesson we show how to build an Arduino based Weather Barometer. We will use the BMP180 pressure sensor on the GY-87 module. This lesson will likely also work fine if you are just using the BMP180 directly. We show how to measure barometric pressure, convert it to Inches of Mercury, stabilize it with a low pass filter, and then normalize it to standard sea level pressure. With this, our values should very closely match what is being seen on weather maps. This is the schematic of the circuit we will be working on.

Schematic for the Portable Arduino Barometer

For your convenience, here is the code we developed in the video.

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_BMP085.h>

Adafruit_BMP085 BP;
bool BMPconnected = false;

float BarPress = 30;
float BarPressNow = 30;
float alt =  1127;

int screenWidth = 128;
int screenHeight = 64;
int oledReset = -1;
#define SCREEN_ADDRESS 0x3C
Adafruit_SSD1306 oled(screenWidth, screenHeight, &Wire, oledReset);

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  BMPconnected = BP.begin();
  if (BMPconnected == true) {
    Serial.println("BMP180 found and Connected");
  }
  if (BMPconnected == false) {
    Serial.println("BMP180 not found, Check Connections");
  }
  oled.begin(SSD1306_SWITCHCAPVCC,SCREEN_ADDRESS);
  oled.clearDisplay();
  oled.display();
}

void loop() {
  // put your main code here, to run repeatedly:
  BarPressNow = normPress(alt);
  BarPress = .95*BarPress + .05*BarPressNow;
  oled.clearDisplay();
  oled.setCursor(0,12);
  oled.setTextColor(WHITE);
  oled.setTextSize(3);
  oled.println(BarPress);
  oled.println("In HG");
  oled.display();
}

float normPress(float elev){
  float BPRaw;
  float BPNorm;
  float T0 = 288.15;
  float L = .0065 ;
  float R = 8.3144598;
  float M = .0289644;
  float g = 9.8;
  float c = M*g/(R*L);
  BPRaw =BP.readPressure()*.0002953;
  BPNorm = BPRaw/pow(1-L*elev/T0,c);
  return BPNorm;
}

#include <SPI.h>

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

#include <Adafruit_BMP085.h>

Adafruit_BMP085 BP;

bool BMPconnected = false;

float BarPress = 30;

float BarPressNow = 30;

float alt = 1127;

int screenWidth = 128;

int screenHeight = 64;

int oledReset = -1;

#define SCREEN_ADDRESS 0x3C

Adafruit_SSD1306 oled(screenWidth, screenHeight, &Wire, oledReset);

void setup() {

// put your setup code here, to run once:

Serial.begin(9600);

BMPconnected = BP.begin();

if (BMPconnected == true) {

Serial.println("BMP180 found and Connected");

}

if (BMPconnected == false) {

Serial.println("BMP180 not found, Check Connections");

}

oled.begin(SSD1306_SWITCHCAPVCC,SCREEN_ADDRESS);

oled.clearDisplay();

oled.display();

}

void loop() {

// put your main code here, to run repeatedly:

BarPressNow = normPress(alt);

BarPress = .95*BarPress + .05*BarPressNow;

oled.clearDisplay();

oled.setCursor(0,12);

oled.setTextColor(WHITE);

oled.setTextSize(3);

oled.println(BarPress);

oled.println("In HG");

oled.display();

}

float normPress(float elev){

float BPRaw;

float BPNorm;

float T0 = 288.15;

float L = .0065 ;

float R = 8.3144598;

float M = .0289644;

float g = 9.8;

float c = M*g/(R*L);

BPRaw =BP.readPressure()*.0002953;

BPNorm = BPRaw/pow(1-L*elev/T0,c);

return BPNorm;

}

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Technology Tutorials

Tag Archives: Barometer

Portable Arduino Barometric Weather Station

Arduino Weather Barometer

Making The World a Better Place One High Tech Project at a Time. Enjoy!