// This project uses two temperature sensors (indoor & outdoor) and if the temperature indoor is lower than outdoor the relay is triggered to tur on a FAN to increase indoor temperature.

#include "DHT.h"


#define DHT_INDOOR_PIN 2
#define DHT_INDOOR_TYPE DHT22

#define DHT_OUTDOOR_PIN 3
#define DHT_OUTDOOR_TYPE DHT22

#define REL_PIN 10

// Initialize DHT sensor.
// Note that older versions of this library took an optional third parameter to
// tweak the timings for faster processors.  This parameter is no longer needed
// as the current DHT reading algorithm adjusts itself to work on faster procs.
DHT dht_indoor(DHT_INDOOR_PIN, DHT_INDOOR_TYPE);
DHT dht_outdoor(DHT_OUTDOOR_PIN, DHT_OUTDOOR_TYPE);

void setup() {
  Serial.begin(9600);
  Serial.println(F("FAN test!"));

  pinMode(REL_PIN, OUTPUT);
  // Utilise inbuild LED pin 13
  pinMode(LED_BUILTIN, OUTPUT);
  dht_indoor.begin();
  dht_outdoor.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_in = dht_indoor.readHumidity();

  // Read temperature as Celsius (the default)
  float t_in = dht_indoor.readTemperature();
  float t_out = dht_outdoor.readTemperature();

  Serial.print(F("Humidity IN: "));
  Serial.print(h_in);
  Serial.print(F("%  Temperature IN: "));
  Serial.print(t_in);
  Serial.print(F("°C "));
  Serial.print(F("Temperature OUT: "));
  Serial.print(t_out);
  Serial.println(F("°C "));

  if(t_in <= t_out) {
    digitalWrite(REL_PIN, HIGH);
    digitalWrite(LED_BUILTIN, HIGH);
  } else {
    digitalWrite(REL_PIN, LOW);
    digitalWrite(LED_BUILTIN, LOW);
  }
}