//set pin numbers //const won't change const int ledPin = 13; //the number of the LED pin const int ldrPin = A0; //the number of the LDR pin void setup() { Serial.begin(9600); pinMode(ledPin, OUTPUT); //initialize the LED pin as an output pinMode(ldrPin, INPUT); //initialize the LDR pin as an input } void loop() { int ldrStatus = analogRead(ldrPin); //read the status of the LDR value //check if the LDR status is <= 300 //if it is, the LED is HIGH if (ldrStatus <=300) { digitalWrite(ledPin, HIGH); //turn LED on Serial.println("LDR is DARK, LED is ON"); } else { digitalWrite(ledPin, LOW); //turn LED off Serial.println("---------------"); } }