/* Knock Sensor This sketch reads a piezo element to detect a knocking sound. It reads an analog pin and compares the result to a set threshold. If the result is greater than the threshold, it writes "knock" to the serial port, and toggles the LED on pin 13. The circuit: * + connection of the piezo attached to analog in 0 * - connection of the piezo attached to ground * 1-megohm resistor attached from analog in 0 to ground http://www.arduino.cc/en/Tutorial/Knock created 25 Mar 2007 by David Cuartielles modified 30 Aug 2011 by Tom Igoe This example code is in the public domain. */ // these constants won't change: const int ledPin = 13; // led connected to digital pin 13 const int knockSensor = A0; // the piezo is connected to analog pin 0 const int threshold = 100; // threshold value to decide when the detected sound is a knock or not // these variables will change: int sensorReading = 0; // variable to store the value read from the sensor pin int ledState = LOW; // variable used to store the last LED status, to toggle the light void setup() { pinMode(ledPin, OUTPUT); // declare the ledPin as as OUTPUT Serial.begin(9600); // use the serial port } void loop() { // read the sensor and store it in the variable sensorReading: sensorReading = analogRead(knockSensor); // if the sensor reading is greater than the threshold: if (sensorReading >= threshold) { // toggle the status of the ledPin: ledState = !ledState; // update the LED pin itself: digitalWrite(ledPin, ledState); // send the string "Knock!" back to the computer, followed by newline Serial.println("Knock!"); } delay(100); // delay to avoid overloading the serial port buffer }