Arduino Dark Activated Motion Alarm

/*
 * Arduino Dark Activated Motion Alarm
 *
 * learnelectronics
 * 12 SEPT 2017
 *
 * www.youtube.com/c/learnelectronics
 * [email protected]
 */





#define ldr   A0                        //ldr is on pin A0 (voltage divider with 1.5k)
#define pir    7                        //pir is on pin 7
#define alm    8                        //active buzzer is on pin 8
#define led    6                        //armed indicator led is on pin 6



int dark = 200;                         //darkness threshold - adjust to suit
bool armed = 0;                         //0 if light, 1 if dark


void setup() {
pinMode(ldr,INPUT);                    //ldr set as input
pinMode(pir,INPUT);                    //pir set as input
pinMode(alm,OUTPUT);                   //buzzer set as output
pinMode(led,OUTPUT);                   //led set as output
//Serial.begin(9600);


}

void loop() {

if (analogRead(ldr)<dark){            //if it's darker than the threshold
  armed = 1;                          //arm the system
  digitalWrite(led,HIGH);             //turn on led
}
else{                                 //if it's not dark enough
  armed = 0;                          //disarm the sytem
  digitalWrite(led,LOW);              //turn of the led
}
//Serial.println(analogRead(ldr));    //for debugging

while (armed){                        //if the system is armed
  if (digitalRead(pir) == 1){         //has the pir been triggered
    digitalWrite(alm,HIGH);           //sound the alarm
  }
  else {                              //if the pir has not been triggered
    digitalWrite(alm,LOW);            //silence the alarm
  }
}
}