// tested on tinkercad project https://www.tinkercad.com/things/lhSup2d9LTP-team-practice-added-rain-switch-for-interrupt/editel?sharecode ...
// comparator interrupt https://forum.arduino.cc/index.php?topic=149840.0, https://www.youtube.com/watch?v=QdJrJXQaiy8, http://www.gammon.com.au/forum/?id=11916 ...