PIR - Relay problem

This sketch will turn the LED on and off with motion detected, but when the relay is included, the sketch is repetitive; flashing the LED and tripping the relay regardless of PIR input. Any idea what I am doing wrong?

int calibrationTime = 30;        

[code]int calibrationTime = 30;        

//the time when the sensor outputs a low impulse
long unsigned int lowIn;         

//the amount of milliseconds the sensor has to be low 
//before we assume all motion has stopped
long unsigned int pause = 1500; //5000 

boolean lockLow = true;
boolean takeLowTime;  

int pirPin = 8;    //the digital pin connected to the PIR sensor's output
int ledPin = 13;
int relayPin = 2;


/////////////////////////////
//SETUP
void setup(){
  Serial.begin(9600);
  pinMode(pirPin, INPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(relayPin,OUTPUT);
  digitalWrite(pirPin, LOW);
  digitalWrite(relayPin,LOW);

}

////////////////////////////
//LOOP
void loop(){

  if(digitalRead(pirPin) == HIGH){
    digitalWrite(ledPin,LOW);
    digitalWrite(relayPin,LOW);
    //the led visualizes the sensors output pin state
    if(lockLow){  
      //makes sure we wait for a transition to LOW before any further output is made:
      lockLow = false;            
      Serial.println("---");
      Serial.print("motion detected at ");
      Serial.print(millis()/50);//1000
      Serial.println(" sec"); 
      delay(50);
    }         
    takeLowTime = true;
  }

  if(digitalRead(pirPin) == LOW){       
    digitalWrite(ledPin, HIGH);
    digitalWrite(relayPin,HIGH);
    delay(5000);
    digitalWrite(ledPin, LOW);
    digitalWrite(relayPin,LOW);
    if(takeLowTime){
      lowIn = millis();          //save the time of the transition from high to LOW
      takeLowTime = false;       //make sure this is only done at the start of a LOW phase
    }
    //if the sensor is low for more than the given pause, 
    //we assume that no more motion is going to happen
    if(!lockLow && millis() - lowIn > pause){  
      //makes sure this block of code is only executed again after 
      //a new motion sequence has been detected
      lockLow = true;                        

      delay(50);
    }
  }
}

[/code]

Schematic?