#include <DHT.h>

const int PIN_DHT = 8;
DHT dht(PIN_DHT,DHT11);

// added newly
float humidity = 0.0;
float temperature = 0.0;
int flg_on_off = 0;
const int PIN_FAN = 7;
const float humidity_min = 65.0;
const float humidity_max = 70.0;
const float temperature_min = 28.0;
const float temperature_max = 30.0;

void setup() {
  Serial.begin(9600);
  Serial.println("DHT11");
  dht.begin();

  // added newly
  pinMode(PIN_FAN, OUTPUT);
}

void loop() {

  delay(3000);

  humidity = dht.readHumidity();
  temperature = dht.readTemperature();
  Serial.print("Humidity:  ");
  Serial.print(humidity);
  Serial.println("%\t");
  Serial.print("Temperature:  ");
  Serial.print(temperature);
  Serial.println("degC\t");
 
  // added newly
  if (humidity > humidity_max || temperature > temperature_max) { 
    flg_on_off = 1;
  }
  if (humidity < humidity_min && temperature < temperature_min) { 
    flg_on_off = 0;
  }
  Serial.print("flg_on_off: ");
  Serial.print(flg_on_off);
  Serial.println("\t");

  if (flg_on_off = 1) { 
    digitalWrite(PIN_FAN, HIGH);
  }
  else { 
    digitalWrite(PIN_FAN, LOW);
  }
}