monitron

/*
 * Noise Announcer for Arduino
 * Justin Streufert - monitron@gmail.com
 * http://monitron.vox.com/
 *
 * Uses an amplified microphone to detect loud noises. Sets off a light and
 * sound alarm, as well as sending a message over serial that can be used as
 * a remote trigger.
 * Goes into a "cool-down" state after an alarm sounds, so as to mitigate annoyance.
 *
 * TODO possible improvements:
 * - Configurable remotely through XBee
 * - Better noise discrimination?
 * - Serial Heartbeat
 *
 * BOM:
 * Radio Shack 273-059 Piezo Buzzer on pin 5
 * Radio Shack 276-028 "Full Color" LED on pins 9, 10 & 11, connected to +5V through a resistor
 * Radio Shack 270-092 Electret microphone on pin 2
 *   connected through a LM386 X200 amplifier circuit as seen here:
 *   http://www.josepino.com/circuits/?mini_amplifier_lm386.jpc
 * Optional XBee and XBee Shield
 */

// Pins
const int micPin    = 2;  // Analog Input pin for amplified microphone signal
const int buzzerPin = 5;  // Digital Output pin for piezo buzzer
const int redPin    = 9;  // Digital Output pin for red LED   (sink; LOW = on)
const int greenPin  = 10; // Digital Output pin for green LED (sink; LOW = on)
const int bluePin   = 11; // Digital Output pin for blue LED  (sink; LOW = on)

// Configuration Constants
const int micCenter = 490;          // The bias of the LM386 amplifier. Approximate, empirically defined.
const int numToAverage = 300;       // The number of samples to take before taking an average.
const int loudNoiseThreshold = 240; // How loud do things need to get before we complain?
const int buzzDuration = 6000;      // The number of cycles of buzzing
const int buzzPeriod = 185;         // Determines the frequency of the buzzing (us)
const int coolDuration = 60000;     // Minimum time between alarms (ms)

// Working Variables
int numCollected = 0;    // Number of samples collected so far
long sampleTotal = 0;    // The total value of the samples collected so far

void setup() {
  // Declare LED and buzzer pins as outputs
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  // Set initial state of LED (green)
  digitalWrite(greenPin, LOW);
  digitalWrite(bluePin, HIGH);
  digitalWrite(redPin, HIGH);
  // Start serial connection to XBee or PC
  Serial.begin(9600);
}

void loop() {
  int averaged;
  int i;
  int val;
  numCollected++;
  val = abs(analogRead(micPin) - micCenter); // read & normalize value from mic
  sampleTotal += val;
  if (numCollected == numToAverage) { // Ready to check for loudness?
    averaged = sampleTotal / numToAverage;
    // Enable for debugging:
    // Serial.print("Avg: ");
    // Serial.println(averaged);
    if(averaged > loudNoiseThreshold) {
      Serial.println("LOUD!!!"); // Tell the world :)
      digitalWrite(greenPin, HIGH); // Switch to the red light
      digitalWrite(redPin, LOW);
      for(i=1;i!=buzzDuration;i++) { // Make a noise through the piezo buzzer by toggling it on and off
        delayMicroseconds(buzzPeriod);
        digitalWrite(buzzerPin, HIGH);
        delayMicroseconds(buzzPeriod);
        digitalWrite(buzzerPin, LOW);
      }
      digitalWrite(redPin, HIGH); // Go to blue
      digitalWrite(bluePin, LOW);
      delay(coolDuration);
      digitalWrite(greenPin, LOW); // Back to green
      digitalWrite(bluePin, HIGH);
    }
    numCollected = 0; // Reset to collect new samples
    sampleTotal = 0;
  }
}