ใช้ Arduinoต่อกับDHT11 วัดอุณหภูมิและความชื้น

ใช้ R ขนาด 10k 

ตัวอย่างโค้ด

/* YourDuino.com Example Software Sketch

   DHT11 Humidity and Temperature Sensor test

   Credits: Rob Tillaart

   http://arduino-direct.com/sunshop/index.php?l=product_detail&p=162

   terry@yourduino.com */

  

/*-----( Import needed libraries )-----*/

#include <dht11.h>



/*-----( Declare objects )-----*/

dht11 DHT11;



/*-----( Declare Constants, Pin Numbers )-----*/

#define DHT11PIN 2



void setup()   /*----( SETUP: RUNS ONCE )----*/

{

  Serial.begin(9600);

  Serial.println("DHT11 TEST PROGRAM ");

  Serial.print("LIBRARY VERSION: ");

  Serial.println(DHT11LIB_VERSION);

  Serial.println();

}/*--(end setup )---*/



void loop()   /*----( LOOP: RUNS CONSTANTLY )----*/

{

  Serial.println("\n");



  int chk = DHT11.read(DHT11PIN);



  Serial.print("Read sensor: ");

  switch (chk)

  {

    case 0: Serial.println("OK"); break;

    case -1: Serial.println("Checksum error"); break;

    case -2: Serial.println("Time out error"); break;

    default: Serial.println("Unknown error"); break;

  }



  Serial.print("Humidity (%): ");

  Serial.println((float)DHT11.humidity, 2);



  Serial.print("Temperature (oC): ");

  Serial.println((float)DHT11.temperature, 2);



  Serial.print("Temperature (oF): ");

  Serial.println(Fahrenheit(DHT11.temperature), 2);



  Serial.print("Temperature (K): ");

  Serial.println(Kelvin(DHT11.temperature), 2);



  Serial.print("Dew Point (oC): ");

  Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));



  Serial.print("Dew PointFast (oC): ");

  Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));



  delay(2000);

}/* --(end main loop )-- */



/*-----( Declare User-written Functions )-----*/

//

//Celsius to Fahrenheit conversion

double Fahrenheit(double celsius)

{

        return 1.8 * celsius + 32;

}



//Celsius to Kelvin conversion

double Kelvin(double celsius)

{

        return celsius + 273.15;

}



// dewPoint function NOAA

// reference: http://wahiduddin.net/calc/density_algorithms.htm

double dewPoint(double celsius, double humidity)

{

        double A0= 373.15/(273.15 + celsius);

        double SUM = -7.90298 * (A0-1);

        SUM += 5.02808 * log10(A0);

        SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;

        SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;

        SUM += log10(1013.246);

        double VP = pow(10, SUM-3) * humidity;

        double T = log(VP/0.61078);   // temp var

        return (241.88 * T) / (17.558-T);

}



// delta max = 0.6544 wrt dewPoint()

// 5x faster than dewPoint()

// reference: http://en.wikipedia.org/wiki/Dew_point

double dewPointFast(double celsius, double humidity)

{

        double a = 17.271;

        double b = 237.7;

        double temp = (a * celsius) / (b + celsius) + log(humidity/100);

        double Td = (b * temp) / (a - temp);

        return Td;

}



/* ( THE END ) */