int sensor = 0;
  int ldr = A0;
  int led = 5;

void setup() {
  Serial.begin(9600);
  pinMode(led, OUTPUT);
  pinMode(ldr, INPUT);
}

void loop() {
  sensor = analogRead(ldr);
  Serial.print("A leitura deu: ");
  Serial.println(sensor);
  delay(500);
 
  if (sensor >= 400) {
    digitalWrite(led, HIGH);
    } else {
    digitalWrite(led, LOW);
}

}