Debouncing; What is it and what is used for? Well, if you ever looked at the current through (or the voltage across) a mechanical switch or a relay as it was changing states you would notice that the transition is not always a nice, clean step function. Often there are several changes before the switch makes its transition. In this case, the switch is said to be "bouncing". However, the same behavior can be observed in dirty switches or switches that are switching a heavy load. Some times the bouncing can be removed with mild (a good vague term) analog filtering and a comparator with hysteresis. Unfortunately this won't work for all cases. And even if it did, the extra cost in hardware may not be justifiable; especially since you can do most of the work in software. - http://tinyurl.com/m24xvn