Arduino security alarm

• Ultrasonic sensor

• 6 Ohm 5W speaker

• Arduino Uno

• Jumper wire

• Trig pin to digital pin 5

• Echo pin to digital pin 6

• positive p of speaker to digital pin 8

//security alarm.

const int pingPin = 5; //trig pin of arduino

int inPin = 6; //echo pin of arduino.

//range in cm which is considered safe to enter, anything

//coming within less than 5 cm triggers red LED

int safeZone = 10;

int tonepin=8;

//LED pin numbers

int greenLed = 3;

int redLed = 2;

void setup() {

// initialize serial communication

Serial.begin(9600);

}

void loop()

{

//raw duration in milliseconds, cm is the

//converted amount into a distance

long duration, cm;

//initializing the pin states

pinMode(pingPin, OUTPUT);

pinMode(greenLed, OUTPUT);

pinMode(redLed, OUTPUT);

pinMode(tonepin, OUTPUT);

//sending the signal, starting with LOW for a clean signal

digitalWrite(pingPin, LOW);

delayMicroseconds(2);

digitalWrite(pingPin, HIGH);

delayMicroseconds(5);

digitalWrite(pingPin, LOW);

//setting up the input pin, and receiving the duration in

//microseconds for the sound to bounce off the object infront

pinMode(inPin, INPUT);

duration = pulseIn(inPin, HIGH);

// convert the time into a distance

cm = microsecondsToCentimeters(duration);

//printing the current readings to ther serial display

//Serial.print(cm);

//Serial.print("cm");

//Serial.println();

//checking if anything is within the safezone, if not, keep

//green LED on if safezone violated, activate red LED instead

if (cm > safeZone)

{

digitalWrite(greenLed, HIGH);

digitalWrite(redLed, LOW);

}

else

{

digitalWrite(redLed, HIGH);

digitalWrite(greenLed, LOW);

for(int i=0;i<20;i++)

{tone(tonepin, 500); //you can change the sound by changing numbers.

delay(50);

tone(tonepin, 400); //you can change the sound by changing numbers.

delay(50);

}

noTone(tonepin);

}

delay(100);

}

long microsecondsToCentimeters(long microseconds)

{

// The speed of sound is 340 m/s or 29 microseconds per centimeter.

// The ping travels out and back, so to find the distance of the

// object we take half of the distance travelled.

return microseconds / 29 / 2;

}