int Led = 13 ; // define LED Interface int Shock = 3 // define the percussion Sensor Interface int val ; // define numeric variables val void setup () { pinMode (Led, OUTPUT) ; // define LED as output interface pinMode (Shock, INPUT) ; // define knock sensor output interface } void loop () { val = digitalRead (Shock) ; // read digital interface is assigned a value of 3 val if (val == HIGH) // When the percussion when the sensor detects a signal, LED flashes { digitalWrite (Led, LOW); } else { digitalWrite (Led, HIGH); } }