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De-bouncing the Mechanical Switch

The pushbutton or toggle switch is a simple form of data entry into a digital system. However, a problem occurs since the normal human reaction time is about  s and digital electronics responds to times of the order of  s. Thus any unnoticed mechanical contact bounce of a few milliseconds will be seen as several distinct switch closures by a digital system. We may de-bounce the mechanical switch by using an RC circuit and Schmitt trigger logic or a flip-flop latch. The latter design requires a break-before-make action, which means that during the throw there is a time when the common is connected to neither terminal.

Doug Gingrich
Tue Jul 13 16:55:15 EDT 1999