Original SPA Project Idea - Opening Fridge Detection

Opening Refrigerator Detection

Situation: The refrigerator door is closed.

Decision: If the refrigerator opens and it's been opened several times within a short amount of time and there is nothing inside or nothing has been taken out, then blink the red LED and play an ominous tune.

Action: Execute script that blinks LED and plays ominous tune.

I began my experiment with a simplified version of the decision: just detecting whether or not the refrigerator door has been opened. I would figure out how to determine if nothing has been taken out later.

Initially, I had a couple of ideas for how to detect whether or not the refrigerator has been opened: sense changes in temperature, changes in light intensity levels, or motion of the door swinging.

I eventually decided to use the photoresistor to detect changes in light intensity from the outside of the refrigerator and a paper towel roll to point the sensor at the refrigerator door and block out ambient light.

Circuit

Code

const int ledPin=9;
const int sensorPin = A0;

#include "pitches.h"

// notes in the melody:
int melody[] = {
  NOTE_C4, NOTE_G3, NOTE_G3, NOTE_A3, NOTE_G3, 0, NOTE_B3, NOTE_C4
};

// note durations: 4 = quarter note, 8 = eighth note, etc.:
int noteDurations[] = {
  4, 8, 8, 4, 4, 4, 4, 4
};

void setup() {
// initialize serial communications (for debugging only):
Serial.begin(9600);
pinMode(ledPin, OUTPUT);
pinMode(sensorPin,INPUT);
}

void loop() {
// read the sensor:
int sensorReading = analogRead(A0);
// print the sensor reading so you know its range
Serial.println(sensorReading);
// map the analog input range (in this case, 70 - 400 from the photoresistor)
// to the output LED range (0-255)

if (sensorReading <= 950) {
digitalWrite(ledPin, HIGH);
    for (int thisNote = 0; thisNote < 8; thisNote++) {

    // to calculate the note duration, take one second divided by the note type.
    //e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
    int noteDuration = 1000 / noteDurations[thisNote];
    tone(8, melody[thisNote], noteDuration);

    // to distinguish the notes, set a minimum time between them.
    // the note's duration + 30% seems to work well:
    int pauseBetweenNotes = noteDuration * 1.30;
    delay(pauseBetweenNotes);
    // stop the tone playing:
    noTone(8);
  }
} else {
// turn LED off:
digitalWrite(ledPin, LOW);
}
}