Arduino LCD + Humidity Sensor

// original humidity sensor code taken from: http://playground.arduino.cc/main/DHT11Lib

//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 (1) : http://wahiduddin.net/calc/density_algorithms.htm
// reference (2) : http://www.colorado.edu/geography/weather_station/Geog_site/about.htm
//
double dewPoint(double celsius, double humidity)
{
    // (1) Saturation Vapor Pressure = ESGG(T)
    double RATIO = 373.15 / (273.15 + celsius);
    double RHS = -7.90298 * (RATIO - 1);
    RHS += 5.02808 * log10(RATIO);
    RHS += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/RATIO ))) - 1) ;
    RHS += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;
    RHS += log10(1013.246);

        // factor -3 is to adjust units - Vapor Pressure SVP * humidity
    double VP = pow(10, RHS - 3) * humidity;

        // (2) DEWPOINT = F(Vapor Pressure)
    double T = log(VP/0.61078);   // temp var
    return (241.88 * T) / (17.558 - T);
}

// delta max = 0.6544 wrt dewPoint()
// 6.9 x 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*0.01);
    double Td = (b * temp) / (a - temp);
    return Td;
}


#include <dht11.h>

// library required for the LCD:
#include <LiquidCrystal.h>

dht11 DHT11;

// pin 7 for the humidity sensor
#define DHT11PIN 7

// these pins are used by the LCD
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup()
{
  Serial.begin(9600);
  Serial.println("DHT11 TEST PROGRAM ");
  Serial.print("LIBRARY VERSION: ");
  Serial.println(DHT11LIB_VERSION);
  Serial.println();

  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
}

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

  int chk = DHT11.read(DHT11PIN);

  Serial.print("Read sensor: ");
  switch (chk)
  {
    case DHTLIB_OK:
        Serial.println("OK");
        break;
    case DHTLIB_ERROR_CHECKSUM:
        Serial.println("Checksum error");
        break;
    case DHTLIB_ERROR_TIMEOUT:
        Serial.println("Time out error");
        break;
    default:
        Serial.println("Unknown error");
        break;
  }

  Serial.print("Humidity (%): ");
  Serial.println((float)DHT11.humidity, 2);

  Serial.print("Temperature (°C): ");
  Serial.println((float)DHT11.temperature, 2);

  Serial.print("Temperature (°F): ");
  Serial.println(Fahrenheit(DHT11.temperature), 2);

  Serial.print("Temperature (°K): ");
  Serial.println(Kelvin(DHT11.temperature), 2);

  Serial.print("Dew Point (°C): ");
  Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));

  Serial.print("Dew PointFast (°C): ");
  Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));

  // set the cursor to column 0, line 0
  lcd.setCursor(0, 0);
  lcd.print("Humidity (%): ");
  lcd.print(DHT11.humidity);

  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  lcd.print("Temp. ('C): ");
  lcd.print(DHT11.temperature);

  delay(500);
}
//
// END OF FILE
//