Arduino sketch to read piezoelectric sensor for Florence's science project.

piezo_shock_sensor.ino

// Use a Radio Shack 273-059 piezo buzzer as a shock sensor
// Based on recipe from http://www.eng.utah.edu/~cs5789/handouts/piezo.pdf
// and the Knock example (http://arduino.cc/en/Tutorial/Knock)

const int ledPin = 13; // Built in LED is pin 13
const int piezoPin = 0; // Piezoelectric element is attached to analog pin 0
const int threshold = 7; // Ignore readings below this value;
const int delayTime = 500; // HTime to pause during each loop

int val, t;

void setup() {
  pinMode(ledPin, OUTPUT);
  
  // Open serial communications and wait for port to open:
  Serial.begin(57600);
  Serial.println("Starting");
}

void loop() {
  digitalWrite(ledPin, LOW);
  
  val = analogRead(piezoPin); // Read the piezo
  
  if (val >= threshold) {
    // Read a value over the threshold

    // Trigger a visual notification that a shock was detected
    digitalWrite(ledPin, HIGH);    
       
    // Start our record of time at the initial over-threshold value   
    t = 0;
    
    // Read values until they are well below the threshold
    while(val > 0) {
      // Output the time and value in the format "TIME,VALUE"
      Serial.print(t);
      Serial.print(",");
      Serial.print(val);
      Serial.print("\n");
      
      // Read another value
      val = analogRead(piezoPin);
      // Increment the time
      t++;
    }
    
    // Wait before taking another reading
    delay(delayTime);
  }
}