💬 Atmospheric Pressure Sensor

hek

This thread contains comments for the article "Atmospheric Pressure Sensor" posted on MySensors.org.

Noobduino

Just a small heads-up... Using the BMP180 ordered from the linked AliExpress shop I was getting no data until I realized the SDA SDL pins on my board were incorrectly marked. Swapping them fixed the issue.

hek

Oh, my... Thanks for the heads up.

kramer

Just so people are aware, the variable "ALTITUDE" should be in units of meters (according to Adafruit's BMP library).

ksga

Anybody feeling like adopting this to the BME280 and including temperature and humidity readings?? Low cost single chip and power usage looks fairly low...

flopp

@ksga
I think I will do that. It seems to be able to run it from 1.8V to 5V.
Now BME280 is cheaper than it was 1 year ago, i think.
http://www.ebay.com/itm/I2C-SPI-Breakout-Temperature-Humidity-Barometric-Pressure-BME280-Digital-Sensor-/272267632353?hash=item3f646a5ee1:g:07oAAOSwnFZXV9L2

ksga

@flopp
That would be awesome. I have one in the mail and are trying to get things ready 😀

It will replace my SI7021 on my solar powered node...

emc2

BME280 is quite nice. I got one last year that I added to my gateway and it worked flawlessly since then.

If you remove the gateway/esp8266 top part you should be able to directly use code from https://github.com/emc2cube/MyWeatherGatewayESP8266 (which was updated from this one anyway)

Heinz

I just ordered one at ebay...
Nice to see that other weatherstations make use of this code.

Luc3as

I tried to modify the weather forecast script to run each 5 minutes instead of every minute but now I am getting strange forecasts and sometimes unknown conditions.
Doesn't anybody tried to accomplish this ?

boblasure

So I added the My Sensors board file, added the my sensors libary through library manager, coped the adafruit library and tried to compile. Arduino: 1.8.1 (Windows 8.1), Board: "Arduino Mini, ATmega328"

C:\Users\eddy\Documents\Arduino\bmpTest\bmpTest.ino: In function 'void setup()':

bmpTest:95: error: 'getConfig' was not declared in this scope

 metric = getConfig().isMetric;

                    ^

exit status 1
'getConfig' was not declared in this scope

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.
Did I miss something?

boblasure

Okay, I changed the library to version 2.0.0 and it now compiles.

mfalkvidd

@boblasure I am not sure why, but the name of getConfig was changed. See https://forum.mysensors.org/topic/5841/getconfig-was-not-declared-in-this-scope-v2-1-1-fixed/ if you want to upgrade to 2.1.1 again.

DavidZH

@Luc3as

The forecast script is meant to be running every minute to collect the averaging data. If you run it every 5 minutes, you need to change the dividers in the script to come to a hPa/h value that actually makes sense.

ghislain

i've got a problem, pressure always stay to 1013 mbar and i'm at 350m of altitude. Something is wrong but what ? I test the BMP180 alone and it said the good value.

ghislain

I found some problems in code. I did make some change to be able to get value. I replace "float pressure = bmp.readSealevelPressure(ALTITUDE) / 100.0;" by "float pressure = bmp.readPressure() / 100 ;"

I'll make a PR on GitHub when everything will be well tested. :)

James Flosse

Hi, i've a problem with the bmp180 with domoticz. I use raspberry pi with domoticz and mysensor v2 and nrf24 on gpio, i receive data but i think is wrong. The temperature is 31°C and pressure is 728. I put my altitude in the sketch.
Can you help me?
Best regards.

mfalkvidd

Welcome to the MySensors community @James-Flosse !

Could you post your sketch and debug output from the node and the gateway?

If you haven't looked at it already, https://www.mysensors.org/build/debug#enabling-debug-logging has information on how to enable debug logging.

James Flosse

Hi @mfalkvidd. This is the debug output and my code

2269 MCO:REG:REQ
2277 TSF:MSG:SEND,3-3-0-0,s=255,c=3,t=26,pt=1,l=1,sg=0,ft=0,st=OK:2
2287 TSF:MSG:READ,0-0-3,s=255,c=3,t=27,pt=1,l=1,sg=0:1
2293 MCO:PIM:NODE REG=1
2295 MCO:BGN:STP
2306 MCO:BGN:INIT OK,TSP=1
Forecast at minute 1 dP/dt = 0.00kPa/h --> unknown
Temperature = 31.00 *C
Pressure = 728.00 hPa
Forecast = unknown
2359 TSF:MSG:SEND,3-3-0-0,s=1,c=1,t=0,pt=7,l=5,sg=0,ft=0,st=OK:31.0
2369 TSF:MSG:SEND,3-3-0-0,s=0,c=1,t=4,pt=7,l=5,sg=0,ft=0,st=OK:728
2381 TSF:MSG:SEND,3-3-0-0,s=0,c=1,t=5,pt=0,l=7,sg=0,ft=0,st=OK:unknown
2387 MCO:SLP:MS=60000,SMS=0,I1=255,M1=255,I2=255,M2=255
2394 MCO:SLP:TPD

// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

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

#define BARO_CHILD 0
#define TEMP_CHILD 1

const float ALTITUDE = 688; // <-- adapt this value to your own location's altitude.

// Sleep time between reads (in seconds). Do not change this value as the forecast algorithm needs a sample every minute.
const unsigned long SLEEP_TIME = 60000; 

const char *weather[] = { "stable", "sunny", "cloudy", "unstable", "thunderstorm", "unknown" };
enum FORECAST
{
    STABLE = 0,            // "Stable Weather Pattern"
    SUNNY = 1,            // "Slowly rising Good Weather", "Clear/Sunny "
    CLOUDY = 2,            // "Slowly falling L-Pressure ", "Cloudy/Rain "
    UNSTABLE = 3,        // "Quickly rising H-Press",     "Not Stable"
    THUNDERSTORM = 4,    // "Quickly falling L-Press",    "Thunderstorm"
    UNKNOWN = 5            // "Unknown (More Time needed)
};

Adafruit_BMP085 bmp = Adafruit_BMP085();      // Digital Pressure Sensor 

float lastPressure = -1;
float lastTemp = -1;
int lastForecast = -1;

const int LAST_SAMPLES_COUNT = 5;
float lastPressureSamples[LAST_SAMPLES_COUNT];

// this CONVERSION_FACTOR is used to convert from Pa to kPa in forecast algorithm
// get kPa/h be dividing hPa by 10 
#define CONVERSION_FACTOR (1.0/10.0)

int minuteCount = 0;
bool firstRound = true;
// average value is used in forecast algorithm.
float pressureAvg;
// average after 2 hours is used as reference value for the next iteration.
float pressureAvg2;

float dP_dt;
bool metric;
MyMessage tempMsg(TEMP_CHILD, V_TEMP);
MyMessage pressureMsg(BARO_CHILD, V_PRESSURE);
MyMessage forecastMsg(BARO_CHILD, V_FORECAST);


void setup() 
{
    if (!bmp.begin()) 
    {
        Serial.println("Could not find a valid BMP085 sensor, check wiring!");
        while (1) {}
    }
    metric = getControllerConfig().isMetric;
}

void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Pressure Sensor", "1.1");

  // Register sensors to gw (they will be created as child devices)
  present(BARO_CHILD, S_BARO);
  present(TEMP_CHILD, S_TEMP);
}

void loop() 
{
    float pressure = bmp.readPressure() / 100 ;
    float temperature = bmp.readTemperature();

    if (!metric) 
    {
        // Convert to fahrenheit
        temperature = temperature * 9.0 / 5.0 + 32.0;
    }

    int forecast = sample(pressure);

    Serial.print("Temperature = ");
    Serial.print(temperature);
    Serial.println(metric ? " *C" : " *F");
    Serial.print("Pressure = ");
    Serial.print(pressure);
    Serial.println(" hPa");
    Serial.print("Forecast = ");
    Serial.println(weather[forecast]);


    if (temperature != lastTemp) 
    {
        send(tempMsg.set(temperature, 1));
        lastTemp = temperature;
    }

    if (pressure != lastPressure) 
    {
        send(pressureMsg.set(pressure, 0));
        lastPressure = pressure;
    }

    if (forecast != lastForecast)
    {
        send(forecastMsg.set(weather[forecast]));
        lastForecast = forecast;
    }

    sleep(SLEEP_TIME);
}

float getLastPressureSamplesAverage()
{
    float lastPressureSamplesAverage = 0;
    for (int i = 0; i < LAST_SAMPLES_COUNT; i++)
    {
        lastPressureSamplesAverage += lastPressureSamples[i];
    }
    lastPressureSamplesAverage /= LAST_SAMPLES_COUNT;

    return lastPressureSamplesAverage;
}



// Algorithm found here
// http://www.freescale.com/files/sensors/doc/app_note/AN3914.pdf
// Pressure in hPa -->  forecast done by calculating kPa/h
int sample(float pressure)
{
    // Calculate the average of the last n minutes.
    int index = minuteCount % LAST_SAMPLES_COUNT;
    lastPressureSamples[index] = pressure;

    minuteCount++;
    if (minuteCount > 185)
    {
        minuteCount = 6;
    }

    if (minuteCount == 5)
    {
        pressureAvg = getLastPressureSamplesAverage();
    }
    else if (minuteCount == 35)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change * 2; // note this is for t = 0.5hour
        }
        else
        {
            dP_dt = change / 1.5; // divide by 1.5 as this is the difference in time from 0 value.
        }
    }
    else if (minuteCount == 65)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) //first time initial 3 hour
        {
            dP_dt = change; //note this is for t = 1 hour
        }
        else
        {
            dP_dt = change / 2; //divide by 2 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 95)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 1.5; // note this is for t = 1.5 hour
        }
        else
        {
            dP_dt = change / 2.5; // divide by 2.5 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 125)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        pressureAvg2 = lastPressureAvg; // store for later use.
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 2; // note this is for t = 2 hour
        }
        else
        {
            dP_dt = change / 3; // divide by 3 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 155)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 2.5; // note this is for t = 2.5 hour
        }
        else
        {
            dP_dt = change / 3.5; // divide by 3.5 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 185)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 3; // note this is for t = 3 hour
        }
        else
        {
            dP_dt = change / 4; // divide by 4 as this is the difference in time from 0 value
        }
        pressureAvg = pressureAvg2; // Equating the pressure at 0 to the pressure at 2 hour after 3 hours have past.
        firstRound = false; // flag to let you know that this is on the past 3 hour mark. Initialized to 0 outside main loop.
    }

    int forecast = UNKNOWN;
    if (minuteCount < 35 && firstRound) //if time is less than 35 min on the first 3 hour interval.
    {
        forecast = UNKNOWN;
    }
    else if (dP_dt < (-0.25))
    {
        forecast = THUNDERSTORM;
    }
    else if (dP_dt > 0.25)
    {
        forecast = UNSTABLE;
    }
    else if ((dP_dt > (-0.25)) && (dP_dt < (-0.05)))
    {
        forecast = CLOUDY;
    }
    else if ((dP_dt > 0.05) && (dP_dt < 0.25))
    {
        forecast = SUNNY;
    }
    else if ((dP_dt >(-0.05)) && (dP_dt < 0.05))
    {
        forecast = STABLE;
    }
    else
    {
        forecast = UNKNOWN;
    }

    // uncomment when debugging
    Serial.print(F("Forecast at minute "));
    Serial.print(minuteCount);
    Serial.print(F(" dP/dt = "));
    Serial.print(dP_dt);
    Serial.print(F("kPa/h --> "));
    Serial.println(weather[forecast]);

    return forecast;
}

2017-03-09 10:52:56.474 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:52:56.475 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:52:56.488 (GATEWAY) Temp (Temp)
2017-03-09 10:52:56.497 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:52:56.503 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:53:40.053 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:53:40.054 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:53:40.067 (GATEWAY) Temp (Temp)
2017-03-09 10:53:40.075 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:53:40.081 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:14.102 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:14.104 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:14.148 (GATEWAY) Temp (Temp)
2017-03-09 10:54:14.162 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:14.172 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:26.662 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:26.664 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:26.676 (GATEWAY) Temp (Temp)
2017-03-09 10:54:26.685 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:26.691 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:44.122 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:44.123 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:44.136 (GATEWAY) Temp (Temp)
2017-03-09 10:54:44.145 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:44.150 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:50.417 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:51.225 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:51.227 (GATEWAY) Temp (Temp)
2017-03-09 10:54:51.236 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:51.242 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:55:55.513 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:58:05.600 (GATEWAY) Temp (Temp)
2017-03-09 10:58:05.608 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:59:10.651 (GATEWAY) Temp (Temp)
2017-03-09 11:01:20.704 (GATEWAY) Temp (Temp)
2017-03-09 11:02:00.701 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:00.702 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:00.715 (GATEWAY) Temp (Temp)
2017-03-09 11:02:00.723 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:00.728 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:31.650 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:31.652 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:31.664 (GATEWAY) Temp (Temp)
2017-03-09 11:02:31.673 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:31.678 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:38.872 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:38.873 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:38.886 (GATEWAY) Temp (Temp)
2017-03-09 11:02:38.894 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:38.900 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:41.863 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:41.864 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:41.887 (GATEWAY) Temp (Temp)
2017-03-09 11:02:41.895 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:41.901 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:49.208 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:49.209 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:49.232 (GATEWAY) Temp (Temp)
2017-03-09 11:02:49.240 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:49.245 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:03:54.286 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:04:59.319 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:06:04.359 (GATEWAY) Temp (Temp)
2017-03-09 11:06:04.368 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:06:36.109 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:06:36.111 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:06:36.123 (GATEWAY) Temp (Temp)
2017-03-09 11:06:36.132 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:06:36.137 (GATEWAY) General/Barometer (Baro)

mfalkvidd

The node sends the data received from the bmp180, so everything seems to be correct. Could you clarify what you expected?

💬 Atmospheric Pressure Sensor

6

11.7k

11.2k

113.0k