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ACTIVE LOW TRIGGER Circuit

2018-02-26 10:51  
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ACTIVE LOW TRIGGER Circuit


This circuit sits LOW and the output goes HIGH when the push-button is pressed. When the normally-closed push button is pressed, it opens and the uncharged 1u will be pulled to nearly 0v rail via the 10k and this will take pin 2 LOW to make output pin 3 HIGH for the duration determined by the 22u and 100k. If the push-switch stays open, the 1u will charge via the 100k and eventually the output of the 555 will go low.
But normally the switch must be pressed for a short period of time so that the timing components (100k and 22u) make the output go HIGH for a short period of time. This circuit is called an ACTIVE LOW TRIGGER










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