DHT11_test.txt

//
//   FILE:  dht11_test1.pde
// PURPOSE: DHT11 library test sketch for Arduino
//

//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;
}


#include <dht11.h>

dht11 DHT11;

#define DHT11PIN 2
#define DHT12PIN 4
const int ledPin1 = 13;       // pin that the LED is attached to
const int ledPin2 = 8;
const int feuchtemax = 58;   // an arbitrary threshold level that's in the range of the analog input

void setup()
{
  // initialize the LED pin as an output:
  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);
  Serial.begin(115200);
  Serial.println("DHT11 TEST PROGRAM ");
  Serial.print("LIBRARY VERSION: ");
  Serial.println(DHT11LIB_VERSION);
  Serial.println();
}

void loop()
{
  Serial.println("\n");

  int chk1 = DHT11.read(DHT11PIN);

  Serial.print("Read sensor: ");
  switch (chk1)
  {
    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);

  int chk2 = DHT11.read(DHT12PIN);

  Serial.print("Read sensor: ");
  switch (chk2)
  {
    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);

  if (DHT11.humidity > feuchtemax) {
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin2, LOW);    
  }
  else {
    digitalWrite(ledPin1,LOW);
    digitalWrite(ledPin2, HIGH);    
  }
  Serial.print("Grenzwert (oC): ");
  Serial.println((float)feuchtemax, 2);

  delay(2000);
}
//
// END OF FILE
//