This 555 will trigger an output if it has been on for a specific amount of time or longer.
The Potentiometer controls the time before latching.
The switch would be a sensor, magnetic contact or a simple button.
when the potentiometer is at:
1%, wait time is ~30 seconds
50%, wait time is ~60 seconds
100%, wait time is ~90 seconds
(if you use a larger scale pot, you could get a higher margin of time)
(this specific circuit is meant to trigger a door opened for too long alarm)
