void setup() {
  // put your setup code here, to run once:
  pinMode(5, INPUT);
  pinMode(13, OUTPUT); //will use the built in led to show the result

}

void loop() {
  // put your main code here, to run repeatedly:
  power = digitalRead(5);
  if (power) {
    digitalWrite(13, HIGH);
    // do other things if you want
  }

}