1const int TrigPin = 2;
2const int EchoPin = 3;
3const int Data = 8;
4float   cm;
5void setup()
6{
7  Serial.begin(9600);
8  pinMode(TrigPin, OUTPUT);
9   pinMode(EchoPin, INPUT);
10  pinMode(Data,OUTPUT);
11}
12void loop()
13{
14   digitalWrite(TrigPin, LOW);       
15  delayMicroseconds(2);
16  digitalWrite(TrigPin,   HIGH);
17  delayMicroseconds(10);
18  digitalWrite(TrigPin, LOW);
19  cm = pulseIn(EchoPin,   HIGH) / 58.0; //The echo time is converted into cm
20  cm = (int(cm * 100.0)) /   100.0;     //Keep two decimal places
21  Serial.println();
22  if(cm<15){ //if   you are puting the sensor behind the door use ">" sysmbole insted of ">" p.s.   make sure tat the door nob is less than 15 cm away
23      digitalWrite(Data,HIGH);
24       delay(200);
25      Serial.print("Door closed");
26    }
27    else
28     {
29      digitalWrite(Data,LOW);
30      delay(200);  
31      Serial.print("Door   open");
32    }
33  delay(200);
34}
35

1const int TrigPin = 2;
2const int EchoPin = 3;
3const int Data = 8;
4float
5  cm;
6void setup()
7{
8  Serial.begin(9600);
9  pinMode(TrigPin, OUTPUT);
10
11  pinMode(EchoPin, INPUT);
12  pinMode(Data,OUTPUT);
13}
14void loop()
15{
16
17  digitalWrite(TrigPin, LOW);       
18  delayMicroseconds(2);
19  digitalWrite(TrigPin,
20  HIGH);
21  delayMicroseconds(10);
22  digitalWrite(TrigPin, LOW);
23  cm = pulseIn(EchoPin,
24  HIGH) / 58.0; //The echo time is converted into cm
25  cm = (int(cm * 100.0)) /
26  100.0;     //Keep two decimal places
27  Serial.println();
28  if(cm<15){ //if
29  you are puting the sensor behind the door use ">" sysmbole insted of ">" p.s.
30  make sure tat the door nob is less than 15 cm away
31      digitalWrite(Data,HIGH);
32
33      delay(200);
34      Serial.print("Door closed");
35    }
36    else
37
38    {
39      digitalWrite(Data,LOW);
40      delay(200);  
41      Serial.print("Door
42  open");
43    }
44  delay(200);
45}
46