Arduino lath delay

Projects Programming
1

Hi, I am trying to make a burglar alarm panel with an Arduino, the problem i am having is for the time delay. Pin 2 is a switch, which will be the door contacts for the alarm, when opened, there is a 10 second delay before pin 13 becomes HIGH, which will be the siren. The problem i am having is, he delay can be stopped by closing the door, so it is rendered useless. I need it to continue counting down, even if the door is closed and activate pin 13, is it simple to make it latch the delay?

Thanks in advance

2

You can set a flag variable:

if(digitalRead(doorSwitchPin)==HIGH){
  doorWasOpened = true;
}

Then make your alarm code dependent on doorWasOpened, not the door switch state.

3

You could do it like this:

#define DOOR_TRIGGER_MILLIS 10000
#define DOOR_PIN 2
#define SIREN_PIN 13

unsigned long doorOpened = 0, loopMillis;

void loop()
{
  loopMillis = millis();
  if ( (digitalRead(DOOR_PIN) == HIGH) && (doorOpened == 0) ) doorOpened = loopMillis;
  if ( (doorOpened != 0) && (loopMillis - doorOpened >= DOOR_TRIGGER_MILLIS) ) digitalWrite(SIREN_PIN, HIGH);
}