// http://playground.arduino.cc/Main/DHT11Lib // // FILE: dht11_test1.pde // PURPOSE: DHT11 library test sketch for Arduino // //Celsius to Fahrenheit conversion double Fahrenheit(double celsius) { return 1.8 * celsius + 32; } // fast integer version with rounding //int Celcius2Fahrenheit(int celcius) //{ // return (celsius * 18 + 5)/10 + 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 DHT11; #define DHT11PIN 2 void setup() { Serial.begin(9600); Serial.println("DHT11 TEST PROGRAM "); Serial.print("LIBRARY VERSION: "); Serial.println(DHT11LIB_VERSION); Serial.println(); } 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)); delay(2000); } // // END OF FILE //