piezo knock sensor code

arduino_knock_sensor.ino

/* A simple sketch to detect a secret knock using a piezo transducer

copied from 
https://programmingelectronics.com/how-to-make-a-secret-knock-detector-to-trigger-anything-with-only-an-arduino-and-a-few-cheap-components/
 
 to be combined with solenoid control circuit
 https://core-electronics.com.au/tutorials/solenoid-control-with-arduino.html

Created JUL 2015 by
Michael James
https://programmingelectronics.com/

This code is in the public domain

*/

const int outputPin = 6;    // 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 = {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);

  //Begin Serial Communication.
  Serial.begin(9600);

}

void loop() {

  // read the piezo sensor and store the value in the variable sensorReading:
  sensorReading = analogRead(knockSensor);

  // 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 == 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 - You are a spy!");

    }//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 == 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 - You are a spy!");

    }//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 in fellow Illuminante!");

    //if the sececret knock is correct, illuminate the LED for a couple seconds
    digitalWrite(outputPin, HIGH);
    delay(2000);
    digitalWrite(outputPin, LOW);

    //Reset the secret counter to 0.
    secretCounter = 0;

  }//close success check

}//close loop

piezo_sensor_solenoid_actuator

const int piezoPin = A5; // the piezo is connected to an analog pin
const int solenoidPin = 12; // out
const int threshold = 3;

const int solenoidDur = 5000;   // milliseconds solenoid is active after buzz detection

int piezoVal = 0; // variable to store the value read from the sensor pin

void setup() {
  Serial.begin(9600);
  pinMode(solenoidPin, OUTPUT);
  digitalWrite( solenoidPin, LOW );
}

void loop() {
  
  piezoVal = analogRead( piezoPin );
  
  if (piezoVal >= threshold) {
    Serial.print("Buzz! piezo sensor read: "); Serial.print(piezoVal);
    Serial.print(", threshold: "); Serial.print(threshold);
    Serial.print("\n\tactivating plunger for ms: "); Serial.print(solenoidDur);
    Serial.print(" ...");

    digitalWrite( solenoidPin, HIGH );

    int start_t = millis();
    bool active = true;
    while (active){
      int elapsed = millis() - start_t;
      if ( elapsed % (solenoidDur / 5) == 0){
        Serial.print(" ...");
      }
      else if (elapsed > solenoidDur){
        active = false;
        Serial.print(" done.\n");
          digitalWrite( solenoidPin, LOW );
      }
      delay(1);
    }
  }
  delay(100);

  
}