int led_pin = 5;


void setup() {
  // put your setup code here, to run once:
  pinMode(led_pin, OUTPUT); //set the led_pin as output

}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(led_pin, HIGH); //set the Voltage HIGH (3V) and Led turns on
  delay(1000); //wait 1000 millisecond (1.0sec)
  digitalWrite(led_pin, LOW); //set the Voltage LOW (ground) and Led turns off
  delay(1000); //wait 1000 millisecond (1.0sec)

}