int calibrationTime = 10;        
long unsigned int lowIn;         
long unsigned int pause = 50;  
boolean lockLow = true;
boolean takeLowTime;  
int pirPin = 7;    
int ledPin = 8;

void setup() {
  Serial.begin(9600);
  pinMode(pirPin, INPUT);
  pinMode(ledPin, OUTPUT);
  digitalWrite(pirPin, LOW);
  Serial.print("calibrating sensor ");
    for(int i = 0; i < calibrationTime; i++){
      Serial.print(".");
      delay(1000);
      }
    Serial.println(" done");
    Serial.println("SENSOR ACTIVE");
    delay(50);
  }

void loop() {
  if(digitalRead(pirPin) == HIGH){
       digitalWrite(ledPin, HIGH);  
       if(lockLow){  
         lockLow = false;            
         Serial.println("---");
         Serial.print("motion detected at ");
         Serial.print(millis()/1000);
         Serial.println(" sec"); 
         delay(50);
         }         
         takeLowTime = true;
       }
  if(digitalRead(pirPin) == LOW){       
       digitalWrite(ledPin, LOW);  
  /*if(takeLowTime){
        lowIn = millis();          
        takeLowTime = false;       
        }
  if(!lockLow && millis() - lowIn > pause){  
            lockLow = true;                        
           Serial.print("motion ended at ");     
           Serial.print((millis() - pause)/1000);
           Serial.println(" sec");
           delay(50);
           }*/
      } 
}