ARDUINO Burglar Alarm Using Infrared Emitter-Detector Pair

1. Arduino uno R3
2. Breadboard
3. Connecting wires / Jumper cables
4. Infrared Emitter and Detector pair LED(not the sensor module)
5. PCB mount BUZZER
6. 1kohm Resistor
7. 10kohm PotentiometeR

** the white LED is the Infrared emitter ,While the black is the Infrared Detector .

int dtect=8;

int sense=A0;
int buzzpin=9;
void setup()
{
  pinMode(dtect,OUTPUT);
  pinMode(sense,INPUT);
  pinMode(buzzpin,OUTPUT);
  digitalWrite(dtect,HIGH);
  Serial.begin(9600);
}

void loop()
{
  int val=analogRead(sense);
  Serial.println(val);
  if(val>=1005)
  {
    buzz(50);
  }
  
  
}

void buzz(unsigned char time)
  {
    analogWrite(buzzpin,170);
    delay(time);
    analogWrite(buzzpin,0);
    delay(time);
  }

First build the circuit according to the circuit diagram provided .

Now i will explain to you how the circuit works .

• The white Led you see in the pictures is an Infrared Emitter . You power it on like a normal LED .
• Now if this is your first time with an IR Led , its very common that you'll mistake your LED to be spoiled as you wont find it glowing ,but that isn't the case really .
• Infrared light is out of the visible spectrum range so even if it is glowing , you wont be able to see it with naked eyes.
• To see if your emitter LED(White) is working properly : switch on your cell phone camera and see the LED through it , you will see that there is a purple Glow .
• This ensures that your IR emitter (White ) is working perfectly and it is emitting light of a particular range of frequency . Now lets come to the Black LED .
• The back LED is the IR detector. The reason that it is made black is that Black color has the highest absorption ; so it Absorbs most of the infrared light Emitted by the Emitter .
• Now what happens if an object stands in between the Emitter and the detector ?? . OBVIOUSLY the amount of infrared radiations intercepted by the detector will now be lesser due to the obstruction .This is the catch !! .
• When such a situation occurs , I trigger the alarm to denote Intrusion .

Now that you've got your concept right , LETS FOCUS ON THE CODE .

• In line 10 we begin the serial communication to see the values being intercepted on the serial monitor for both the cases i.e
• case 1.) no obstruction in the path of the emitter and the detector .
• case 2.)obstruction in the path of the emitter and the detector .
• for both these cases , we have to observe the values being reflected on the serial monitor , based on which we will decide for which value being exceeded we will be triggering the alarm .
• Note that for my experiment the threshold value was set to 1005 . This might not be the case for you. Hence try to monitor the values that you are intercepting and choose your threshold accordingly .

**Well , hope I have covered all the concepts in detail regarding this project . If you face problems or if you need further detailing on any sub-topic , then please do leave me a comment .

Thank you all for watching .