/*
Wiring Guide - Based on DuinoKit

NANO D13 -> Piezo Buzzer (+)
Piezo Buzzer (-) -> NANO GND
NANO A0 -> CDS Cell (Center Pin)
CDS Cell (Resistor side) -> GND
CDS CEll (CDS Cell Side) -> NANO 5V

These constants describe the pins. They won't change:
*/
int i; // Declare Variables
int analog0;
int CurrentValue;
int Senstivity = 10; // Change in light level adjustment
// Lower numbers make device more sensitive
void setup()
{
Serial.begin(9600); // initialize the serial communications:
pinMode(13, OUTPUT); // Buzzer alarm on Pin 13
for(i=0; i < 5; i++) // Take i readings of A0 pin
{
delay (100); // Place a small delay between reading
analog0=analog0+analogRead(A0);
}

analog0=analog0/i; // Divide by i to get average integer A0 value
CurrentValue=analog0; // set initial reading and analog value the same

}

void loop()
{
analog0=0;
for(i=0; i < 5; i++) // Take i readings of A0 pin
{
delay (10); // Small delay between readings
analog0=analog0+analogRead(A0); // Add up total of i readings
}

analog0=analog0/i; // Divide by i to get average integer A0 value

Serial.println(analog0); // Display current light levels in serial monitor
delay(10);

if(abs(analog0-CurrentValue)>Senstivity) { // If change in light level >5, sound alarm
Serial.print(analog0); // Display readings in Serial monitor
Serial.print("t");
Serial.print(CurrentValue);
Serial.print("t");
Serial.println("ALARM");
CurrentValue=analog0;
digitalWrite(13, HIGH); // Turn on alarm buzzer on pin 13
delay(100);
}
else{
CurrentValue=analog0; // if change is <5, then take the new reading as current light level.
digitalWrite(13, LOW); // Turn off buzzer on pin 13

}
}