int pino_ldr = A1;
float luz;
int led = 2;

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(pino_ldr, INPUT);
pinMode(led, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
luz = analogRead(A1);
Serial.println(luz);
delay(100);
if(luz>100) {
 digitalWrite(led, HIGH);
};
if(luz<=100); {
  digitalWrite(led, LOW);
}
}