const byte pin_LED=13;
const byte pin_Btn=3;
const int interval =3000;
void ISRbtn2();
volatile unsigned long previousMillis = 0;  // will store last time LED was updated
volatile byte ledstate=LOW;
void setup() {
  // put your setup code here, to run once:
  pinMode(pin_Btn, INPUT_PULLUP);
  pinMode(pin_LED, OUTPUT);
  attachInterrupt(digitalPinToInterrupt(pin_Btn), ISRbtn2, RISING);
}
void loop() {
  digitalWrite(pin_LED, ledstate);
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
      ledstate = LOW;
  }
} 

void ISRbtn2() {
  previousMillis=millis();
  ledstate=HIGH;
}