Arduino Buzzer for Knock Knock project is not working - c++

Question

Im trying to generate a knock knock detector using Arduino and a Piezo Buzzer. The one used in this proyect is the same as in this picture
Using this code
const int outputPin = 8; // led indicator connected to digital pin
const int knockSensor = A0; // the piezo is connected to an analog pin
const int thresholdHIGH =150; // threshold value to decide when the detected knock is hard (HIGH)
const int thresholdLOW = 120; // threshold value to decide when the detected knock is gentle (LOW)
const int secretKnockLength = 4; //How many knocks are in your secret knock
/* This is the secret knock sequence
* 0 represents a LOW or quiet knock
* 1 represents a HIGH or loud knock
* The sequence can be as long as you like, but longer codes increase the difficulty of matching */
const int secretKnock[secretKnockLength] = {0, 0, 1, 0};
int secretCounter = 0; //this tracks the correct knocks and allows you to move through the sequence
int sensorReading = 0; // variable to store the value read from the sensor pin
void setup() {
//Set the output pin as an OUTPUT
pinMode(outputPin, OUTPUT);
//analogWrite(knockSensor, LOW);
//Begin Serial Communication.
Serial.begin(9600);
}
void loop() {
// read the piezo sensor and store the value in the variable sensorReading:
sensorReading = analogRead(knockSensor);
Serial.print ("Valor del Sensor: ");
Serial.println(sensorReading);
// First determine is knock if Hard (HIGH) or Gentle (LOW)
//Hard knock (HIGH) is detected
if (sensorReading >= thresholdHIGH) {
//Check to see if a Hard Knock matches the Secret Knock in the correct sequence.
if (secretKnock[secretCounter] == 1) {
//The Knock was correct, iterate the counter.
secretCounter++;
Serial.println("Correct");
} else {
//The Knock was incorrect, reset the counter
secretCounter = 0;
Serial.println("Fail");
digitalWrite(outputPin, LOW);
}//close if
//Allow some time to pass before sampling again to ensure a clear signal.
delay(100);
//Gentle knock (LOW) is detected
} else if (sensorReading >= thresholdLOW) {
//Check to see if a Gentle Knock matches the Secret Knock in the correct sequence.
if (secretKnock[secretCounter] == 0) {
//The Knock was correct, iterate the counter.
secretCounter++;
Serial.println("Correct");
} else {
//The Knock was incorrect, reset the counter.
secretCounter = 0;
Serial.println("Fail");
}//close if
//Allow some time to pass before sampling again to ensure a clear signal.
delay(100);
}//close if else
//Check for successful entry of the code, by seeing if the entire array has been walked through.
if (secretCounter == (secretKnockLength) ) {
Serial.println("Welcome");
//if the sececret knock is correct, illuminate the LED for a couple seconds
digitalWrite(outputPin, HIGH);
//Reset the secret counter to 0.
secretCounter = 0;
}//close success check
}//close loop".
My problem is the buzzer is detecting nothing. I dont know if this is because the buzzer is not the correct one or something else.
Any idea?

Answer 1

If the problem is that the buzzer isn't making any noise, then you should be using the tone() function in your code. (https://www.arduino.cc/reference/en/language/functions/advanced-io/tone/)
Your code compiles successfully, so if that's not your issue, then there's probably something wrong with your project's wiring.

Answer 2

To detect knocking, you need to use piezo without driver circuit.
according to Arduino tutorial said that avoid piezo with plastic housing.
You should use piezo that look like metal disc like this
(image from sparkfun)
Note : piezo with plastic housing might contain drive circuit or not piezo at all (it might be magnetic buzzer)