I love this forum 
Im stuck, trying to get the DHT11 sensor to print the temp to the LCD screen.
#include <LiquidCrystal_I2C.h>
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);
}
#include "DHT.h"
#define DHTPIN 11 // what pin we're connected to
// Uncomment whatever type you're using!
#define DHTTYPE DHT11 // DHT 11
//#define DHTTYPE DHT22 // DHT 22 (AM2302)
//#define DHTTYPE DHT21 // DHT 21 (AM2301)
// Initialize DHT sensor for normal 16mhz Arduino
DHT dht(DHTPIN, DHTTYPE);
//DHT dht(DHTPIN, DHTTYPE, 30);
int intakefan = 2; // Intake fan for Humid box and dry box
int humidv = 3; // Valve for humud intake
int dryv = 4; // dry box valve
int exfan = 5; // exhaust fan
int exv = 6; // exhaust valve
int returnfan = 7; // fan to bring air from inside box
int returnv = 8; // return valve, air from inside box
int DHTpower = 12; // constant 5v to DHT11
LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16x2 display
void setup() {
pinMode(intakefan, OUTPUT);
pinMode(humidv, OUTPUT);
pinMode(dryv, OUTPUT);
pinMode(exfan, OUTPUT);
pinMode(exv, OUTPUT);
pinMode(returnfan, OUTPUT);
pinMode(returnv, OUTPUT);
pinMode(DHTpower, OUTPUT);
digitalWrite(intakefan, LOW);
digitalWrite(humidv, LOW);
digitalWrite(dryv, LOW);
digitalWrite(exfan, LOW);
digitalWrite(exv, LOW);
digitalWrite(returnfan, LOW);
digitalWrite(returnv, LOW);
digitalWrite(DHTpower, HIGH);
Serial.begin(9600);
lcd.init(); // Initialize the LCD
lcd.backlight(); // Turn on the backlight
lcd.clear(); // Clear the LCD screen
lcd.setCursor(3, 0);
lcd.print("The Green");
lcd.setCursor(4, 1);
lcd.print("Ninja");
delay(1000); // Display the startup message for 2 seconds
dht.begin();
}
void loop() {
// Wait a few seconds between measurements.
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity();
// Read temperature as Celsius
float t = dht.readTemperature();
// Read temperature as Fahrenheit
float f = dht.readTemperature(true);
float currentDew = dewPoint(t, h); // Dew Point for setting pins high
// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t) || isnan(f)) {
Serial.println("Failed to read from DHT sensor!");
return;
}
// Compute heat index
// Must send in temp in Fahrenheit!
float hi = dht.computeHeatIndex(f, h);
float hiDegC = dht.convertFtoC(hi);
delay(50);
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Checking");
lcd.setCursor(0, 1);
lcd.print("Dew Point");
delay(800);
lcd.clear();
//Serial.print(f);
//Serial.print(" *F\t");
//Serial.print("Heat index: ");
// Serial.print(hiDegC);
// Serial.print(" *C ");
// Serial.print(hi);
// Serial.print(" *F ");
lcd.print("Dew Point (*C): ");
lcd.print(dewPoint(t, h));
if (currentDew > 11 && (currentDew < 13)) // Level to aim for dew point 12
{
digitalWrite(intakefan, LOW);
digitalWrite(humidv, LOW);
digitalWrite(dryv, LOW);
digitalWrite(exfan, LOW);
digitalWrite(exv, LOW);
digitalWrite(returnfan, LOW);
digitalWrite(returnv, LOW);
lcd.print("Dew point OK");
lcd.print(dewPoint(t, h));
}
if (currentDew > 13) { // High dew point, send to dry box
digitalWrite(humidv, LOW);
digitalWrite(dryv, HIGH);
digitalWrite(exv, HIGH);
digitalWrite(returnv, HIGH);
lcd.clear();
lcd.print("Dew Point");
lcd.print(dewPoint(t, h));
lcd.setCursor(0,1);
//lcd.print(dht.readTemperature); /// ????
delay(3000);
digitalWrite(intakefan, HIGH);
digitalWrite(exfan, HIGH);
digitalWrite(returnfan, HIGH);
}
if (currentDew < 13) { // Dew point low, send to humid box
digitalWrite(humidv, HIGH);
digitalWrite(dryv, LOW);
digitalWrite(exfan, LOW);
digitalWrite(exv, HIGH);
digitalWrite(returnfan, LOW);
digitalWrite(returnv, LOW);
lcd.print("Dew point OK");
lcd.print(dewPoint(t, h));
delay(3000);
digitalWrite(intakefan, HIGH);
digitalWrite(exfan, HIGH);
}
}
