On a motor after a continuous input of a certain amount of time

Question

I would like to produce an output after a constant input is detected for a certain amount of time. Below is a simple code of what I am trying to do minus the time factor. Can someone help me on how to code out the duration of an input occurrence? i.e.

if (sensorValue > threshold);
    //if this occurs for more than 4 hours, then
    digitalWrite (3, HIGH);

Answer 1

You must store the state of the last readings and do something like this:

    //Off-loop:
    bool state_changed = false;
    unsigned long time_in_state = 0;
    unsigned long last_reading = 0;

    //On-loop:
    if (sensorValue > treshold && !state_changed) {
        time_in_state += millis() - last_reading;
        last_reading = millis();
    }
    else {
        state_changed = true;
        time_in_state = 0;
    }

    if (time_in_state > TIME_REQUIRED) {
      digitalWrite (3, HIGH);
    }