کد بالا جواب نمیده
برای جواب گرفتن کافیه به صورت نرم افزاری pullup کنیم

کد:
int led = 13 ;//define led pin
int sensor  = 10; //sensor pin
int val; //define numeric variable selection
void setup ()
{
  pinmode (led, output); // define led as output 
  pinmode (sensor, input_pullup); // define sensor as input
}
void loop ()
{
  val = digitalread (sensor) ;//  sensor and put it into election
     digitalwrite(led,low);
 
  if (val == low) // when the sensor detects a signal, the led flashes
  {
    digitalwrite (led, high);
          delay(100);

  }

 }