//program to interface Arduin with LDR and LED
int ledPin=5;
int ldrPin=A0;
void setup() {
Serial.begin(9600);
pinMode(ledPin,OUTPUT);
pinMode(ldrPin, INPUT);

}

void loop() {
int ldrstatus=analogRead(ldrPin);
if(ldrstatus<=400){
digitalWrite(ledPin, HIGH);  
delay(100);
Serial.println(ldrstatus);
}
else
{
digitalWrite(ledPin, LOW);
delay(100);
Serial.println(ldrstatus);

}
}