int led_pin = 7; int pin_B_sensor = 3; int value_B_sensor = 0; void setup() { pinMode(led_pin, OUTPUT); pinMode(pin_B_sensor, INPUT_PULLUP); } void loop() { value_B_sensor = digitalRead(pin_B_sensor); if (value_B_sensor == HIGH) { digitalWrite(led_pin, LOW); } else { digitalWrite(led_pin, HIGH); } }