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The code follows below:<\/p>\n\n\n\n
\n\n\/\/ John Main added dewpoint code from : http:\/\/playground.arduino.cc\/main\/DHT11Lib\n\/\/ Also added DegC output for Heat Index.\n\/\/ dewPoint function NOAA\n\/\/ reference (1) : http:\/\/wahiduddin.net\/calc\/density_algorithms.htm\n\/\/ reference (2) : http:\/\/www.colorado.edu\/geography\/weather_station\/Geog_site\/about.htm\n\/\/\n\/\/ januari 2021 Geert Stams, PA3CSG added LCD display and switching of a solid state relay to heat, preventing condensation.\n\/\/ Pin 11 switches the led on\n\/\/ Pin 12 drives the solid state realy\n\/\/\n\/\/******************************************************************************************************************************\n\/\/******************************************************************************************************************************\n\n\ndouble dewPoint(double celsius, double humidity)\n{\n \/\/ (1) Saturation Vapor Pressure = ESGG(T)\n double RATIO = 373.15 \/ (273.15 + celsius);\n double RHS = -7.90298 * (RATIO - 1);\n RHS += 5.02808 * log10(RATIO);\n RHS += -1.3816e-7 * (pow(10, (11.344 * (1 - 1 \/ RATIO ))) - 1) ;\n RHS += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;\n RHS += log10(1013.246);\n\n \/\/ factor -3 is to adjust units - Vapor Pressure SVP * humidity\n double VP = pow(10, RHS - 3) * humidity;\n\n \/\/ (2) DEWPOINT = F(Vapor Pressure)\n double T = log(VP \/ 0.61078); \/\/ temp var\n return (241.88 * T) \/ (17.558 - T);\n}\n\n\/\/ Example testing sketch for various DHT humidity\/temperature sensors\n\/\/ Written by ladyada, public domain\n\n#include \"DHT.h\"\n#include <Wire.h> \/\/ Library for I2C communication\n#include <Wire.h> \/\/ Comes with Arduino IDE\n#include <LiquidCrystal_I2C.h>\nLiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); \/\/ Set the LCD I2C address\n\n\n#define DHTPIN 2 \/\/ what pin we're connected to\n\n\/\/ Uncomment whatever type you're using!\n\/\/#define DHTTYPE DHT11 \/\/ DHT 11\n#define DHTTYPE DHT22 \/\/ DHT 22 (AM2302)\n\/\/#define DHTTYPE DHT21 \/\/ DHT 21 (AM2301)\n\n\/\/ Connect pin 1 (on the left) of the sensor to +5V\n\/\/ NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1\n\/\/ to 3.3V instead of 5V!\n\/\/ Connect pin 2 of the sensor to whatever your DHTPIN is\n\/\/ Connect pin 4 (on the right) of the sensor to GROUND\n\/\/ Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor\n\n\/\/ Initialize DHT sensor for normal 16mhz Arduino\nDHT dht(DHTPIN, DHTTYPE);\n\/\/ NOTE: For working with a faster chip, like an Arduino Due or Teensy, you\n\/\/ might need to increase the threshold for cycle counts considered a 1 or 0.\n\/\/ You can do this by passing a 3rd parameter for this threshold. It's a bit\n\/\/ of fiddling to find the right value, but in general the faster the CPU the\n\/\/ higher the value. The default for a 16mhz AVR is a value of 6. For an\n\/\/ Arduino Due that runs at 84mhz a value of 30 works.\n\/\/ Example to initialize DHT sensor for Arduino Due:\n\/\/DHT dht(DHTPIN, DHTTYPE, 30);\n\nfloat DP = 0;\nint Heatpin = 12;\nint Ledpin = 11;\n\nvoid setup() {\n Serial.begin(9600);\n Serial.println(\"DHTxx test!\");\n\n dht.begin();\n lcd.begin(16,2); \/\/ initialize the lcd for 16 chars 2 lines, turn on backlight\n \n}\n\nvoid loop() {\n \/\/ Wait a few seconds between measurements.\n delay(5000);\n \n \/\/ Reading temperature or humidity takes about 250 milliseconds!\n \/\/ Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)\n float h = dht.readHumidity();\n \/\/ Read temperature as Celsius\n float t = dht.readTemperature();\n \/\/ Read temperature as Fahrenheit\n float f = dht.readTemperature(true);\n\n \n \/\/ Check if any reads failed and exit early (to try again).\n if (isnan(h) || isnan(t) || isnan(f)) {\n Serial.println(\"Failed to read from DHT sensor!\");\n return;\n }\n\n \/\/ Compute heat index\n \/\/ Must send in temp in Fahrenheit!\n float hi = dht.computeHeatIndex(f, h);\n float hiDegC = dht.convertFtoC(hi);\n\n Serial.print(\"Humidity: \");\n Serial.print(h);\n Serial.print(\" %\\t\");\n Serial.print(\"Temperature: \");\n Serial.print(t);\n Serial.print(\" *C \");\n Serial.print(f);\n Serial.print(\" *F\\t\");\n Serial.print(\"Heat index: \");\n Serial.print(hiDegC);\n Serial.print(\" *C \");\n Serial.print(hi);\n Serial.print(\" *F \");\n Serial.print(\"Dew Point (*C): \");\n Serial.println(dewPoint(t, h));\n\n DP=(dewPoint(t, h));\n lcd.setCursor(0,0); \n lcd.print(\" \");\n lcd.setCursor(0,0); \n lcd.print(\"T=\");\n lcd.setCursor(2,0);\n lcd.print(t,0);\n lcd.setCursor(5,0);\n lcd.print(\"H=\");\n lcd.setCursor(7,0);\n lcd.print(h,0);\n lcd.setCursor(10,0);\n lcd.print(\"DP=\");\n lcd.setCursor(13,0);\n lcd.print(DP, 0);\n\n if (t - DP <= 5)\/\/ Your temp has to be >3 degrees above the dewpoint\n {\n digitalWrite (Heatpin, HIGH);\n digitalWrite (Ledpin, HIGH);\n lcd.setCursor(0,1);\n lcd.print(\"HEATER ON \");\n }\n else\n {\n digitalWrite (Heatpin, LOW);\n digitalWrite (Ledpin, LOW);\n lcd.setCursor(0,1);\n lcd.print(\"HEATER OFF\");\n }\n \n}<\/code><\/pre>\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"