Light Gate using Arduino

1int timer = 0; //For the counting of the breaked time of light.
2bool
3  checking = false; //Checks if the the object is being monitored.
4float speed
5  = 0; //The final speed of the object.
6float lengthOfBreaker = 0.04; //The length
7  of the breaker used in the object.
8
9void setup() {
10  pinMode(8, OUTPUT);
11  //An LED for showing the 'checking' variable.
12  Serial.begin(9600); //Begin the
13  serial communication.
14}
15
16void loop() {
17  if (analogRead(A0) < 900) {
18  //Checks if the light intensity is below 900. That means the light is breaked.
19
20    checking = true;
21    digitalWrite(8, checking);
22    timer = 0;
23    while
24  (analogRead(A0) <= 900) { //Increment the timer until the object is gone.
25      timer++;
26
27      delay(1); //A fixed time of 1 millisecond is given for counting.
28    }
29
30    if (timer > 0) { //Check if the timer value is greater that 0 milliseconds.
31
32      checking = false; //Set the completed variable to true since the checking
33  is completed.
34      digitalWrite(8, checking);
35      float timeInSec = (float(timer)
36  / float(1000)); //Convert the time in milliseconds to seconds. Output is a float
37  value.
38      speed = lengthOfBreaker / timeInSec; //Calculates the speed of the
39  object by using this formula: Speed = Distance / Time
40      Serial.print("Object
41  Instantaneous Speed: "); //
42      Serial.print(speed);                          //
43  Print the object speed
44      Serial.print(" m/s");                         //
45  in the Serial monitor.
46      Serial.print("\
47");                           //
48
49      timeInSec = 0; // Reset the seconds value.
50    }
51    speed = 0;           //
52
53    checking = false;    //  Reset other values too.
54    timer = 0;           //
55
56  }
57}

1int timer = 0; //For the counting of the breaked time of light.
2bool  checking = false; //Checks if the the object is being monitored.
3float speed  = 0; //The final speed of the object.
4float lengthOfBreaker = 0.04; //The length  of the breaker used in the object.
5
6void setup() {
7  pinMode(8, OUTPUT);  //An LED for showing the 'checking' variable.
8  Serial.begin(9600); //Begin the  serial communication.
9}
10
11void loop() {
12  if (analogRead(A0) < 900) {  //Checks if the light intensity is below 900. That means the light is breaked.
13    checking = true;
14    digitalWrite(8, checking);
15    timer = 0;
16    while  (analogRead(A0) <= 900) { //Increment the timer until the object is gone.
17      timer++;
18      delay(1); //A fixed time of 1 millisecond is given for counting.
19    }
20    if (timer > 0) { //Check if the timer value is greater that 0 milliseconds.
21      checking = false; //Set the completed variable to true since the checking  is completed.
22      digitalWrite(8, checking);
23      float timeInSec = (float(timer)  / float(1000)); //Convert the time in milliseconds to seconds. Output is a float  value.
24      speed = lengthOfBreaker / timeInSec; //Calculates the speed of the  object by using this formula: Speed = Distance / Time
25      Serial.print("Object  Instantaneous Speed: "); //
26      Serial.print(speed);                          //  Print the object speed
27      Serial.print(" m/s");                         //  in the Serial monitor.
28      Serial.print("\
29");                           //
30      timeInSec = 0; // Reset the seconds value.
31    }
32    speed = 0;           //
33    checking = false;    //  Reset other values too.
34    timer = 0;           //
35  }
36}