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Created March 14, 2023
Last modified March 15, 2023
Tags 555   one-shot   timer  


555 used as a "one shot" timer.


555 used as a one shot timer.

Vsim simulates the push of the NO push button SW1. The output of the timer will be on for (approx.) 6.15 seconds (determined by R7*C7) after pushing down the NO button.

Run the simulation. We push the button (blue line in the simulation) at 12 s. The output (gold line) is on from 12 sec up to 18.15 sec. (Even if we release the NO button before that 18.15 sec). Even if we push again the button before the 18.15 sec (at 16 sec), the timing does NOT restart a new delay of 6.15sec. That behavior, completing the delay before launching another "timing", is what is called a "one shot" timer and can be used to de-bounce a mechanical switch.

The use of a 555 is fading out, given that the chip is not so energy-friendly, compared to the use of MCUs (such at Arduino) which are, in addition, much more flexible than the respectable 555.


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