#include <DHT.h>

#define DHTPIN 2     
#define DHTTYPE DHT22   

#define RELAY_PIN 3 

DHT dht(DHTPIN, DHTTYPE); 

float targetTemp = 20.0; 
float minTemp = 15.0;    
unsigned long maxRunTime = 3600000; 
unsigned long startTime; 

void setup() {
  pinMode(RELAY_PIN, OUTPUT); 
  dht.begin(); 
  digitalWrite(RELAY_PIN, LOW); 
}

void loop() {
  float temperature = dht.readTemperature();
  
  if (isnan(temperature)) {
    return;
  }
  
  if (temperature < minTemp && millis() - startTime > maxRunTime) {
    digitalWrite(RELAY_PIN, LOW); 
    startTime = 0; 
  } else if (temperature < targetTemp) {
    digitalWrite(RELAY_PIN, HIGH); 
    if (startTime == 0) {
      startTime = millis(); 
    }
  } else {
    digitalWrite(RELAY_PIN, LOW); 
    startTime = 0; 
  }
  
  delay(2000); 
}