Temporized sensor

Using Arduino Programming Questions
1

Hi!
I'm working on a project where I have to do the following:

An object is passing throught a photo interrupter sensor and 5 seconds later is passing another photo interrupter, both connected to Arduino.

A LED must be turned on if the object spends more than 5 seconds on passing the second sensor after passing the first sensor. What could I do?

2

did you even attempt to write a sketch?

3

Use millis() to record the time of the first passing into a variable (unsigned long) startTime . When the second sensor records the passing, subtract startTime from millis(). That give the elapsed time between passing. Is it more than 5000? Yes, turn on LED.

4

Hello again, thank you for your feedback. I've written this code, but I think it could be done better:

int sensorValueA0 = 0;
int sensorValueA1 = 0; 
unsigned long time1 = 0;
unsigned long time2 = 0;
unsigned long time3 = 0;
int control = 0;

void setup() {
  Serial.begin(9600); 
}

void loop() {
  
time3 = time2 - time1;  
if  (sensorValueA0 < 70 && control == 0)
{
  time1=millis();
  control=1;
}
else if (sensorValueA1 < 70 && control == 1)
{
  time2=millis();
  control=0;
}
else
{
}
if (time3 > 5000)
{
  Serial.println("LEDon");
}
else
{
  Serial.println("LEDon");
}
}
5 
if  (sensorValueA0 < 70 && control == 0)

0 is less than 70, always. No real point in testing that.

6

Not. It is a photo interrupter sensor which is always giving positive signal (about 300 bits). When an object interrupts it, it gives 0.

7

Not. It is a photo interrupter sensor which is always giving positive signal (about 300 bits). When an object interrupts it, it gives 0.

Really?

int sensorValueA0 = 0;

Where do you assign a different value?

8

Hint, read up on state machines - you need a state to represent when an object
is between sensors, and a time-out for when it is over-due at the 2nd sensor.