int lm35_pin = A1; /* LM35 O/P pin */
int fan =3;
void setup() 
{
 Serial.begin(9600);
 pinMode(fan,OUTPUT);
 pinMode(lm35_pin ,INPUT);
}
void loop() 
{
 int temp_adc_val;
 float temp_val;
 temp_adc_val = analogRead(lm35_pin); /* Read Temperature */
 temp_val = (temp_adc_val * 4.88); /* Convert adc value to equivalent voltage */
 temp_val = (temp_val/10); /* LM35 gives output of 10mv/°C */
 Serial.print("Temperature = ");
 Serial.print(temp_val);
 Serial.print(" Degree Celsius\n");
 delay(1000);
 if(temp_val > 50)
{
 digitalWrite(fan, HIGH);
}
else 
{ 
 digitalWrite(fan, LOW);
}
}