TEMPKG1155.ino

const int knockPin = 8; //https://kitsguru.com/products/the-knock-sensor-module
const int ledPin = 7;
int knockVal = HIGH;
boolean knockAlarm = false;
unsigned long prevKnockTime;
int knockAlarmTime = 100;

void setup ()
{
  Serial.begin(9600);  
  pinMode (ledPin, OUTPUT) ;
  pinMode (knockPin, INPUT) ;
}

void loop ()
{
  knockVal = digitalRead (knockPin) ;
  if (knockVal == LOW)
  {
    prevKnockTime = millis();
    if (!knockAlarm)
    {
      Serial.println("KNOCK, KNOCK");
      digitalWrite(ledPin,HIGH);
      knockAlarm = true;
      delay(1000);
    }
  }
  else
  {
    if( (millis()-prevKnockTime) > knockAlarmTime &&  knockAlarm)
    {
      digitalWrite(ledPin,LOW);
      Serial.println("No Knocks");
      knockAlarm = false;
    }
  }
} //CREDITS : https://www.electronicshub.org/knock-sensor-with-arduino/