const  int LDR = A0; 
const int  LED = 13; 
int ldr_val  = 0;

void setup()  
{
pinMode(LDR, INPUT);
pinMode(LED, OUTPUT);
Serial.begin(9600);
}

void loop () {
ldr_val = analogRead(LDR);
Serial.print("LDR Value is : ");
Serial.println(ldr_val);

delay(1000);

if (ldr_val>800)
{
digitalWrite(LED,HIGH);
delay(5000);
}

else{
digitalWrite(LED,LOW);
delay(5000);
}
}