 
 #define GREEN_PIN 3
 #define RED_PIN 4
+#define POWER_SWITCH_PIN 0
 #define SECONDS_TO_SLEEP 16 // Multiple of 8
 #define SECONDS_ON 3
 

      }
    } else {
      // Not much voltage left, flash green pin 1s.
      digitalWrite(RED_PIN, LOW);
      for (int i=0; i<5; i++) {
        digitalWrite(GREEN_PIN, HIGH);

        delay(100);
        digitalWrite(RED_PIN, LOW);
        delay(100);      
    }
    
    digitalWrite(POWER_SWITCH_PIN, LOW);
  }

  enterSleep();
