hardware debouncing

did you try to google: capasitor value for switch debounce

http://www.eng.utah.edu/~cs5780/debouncing.pdf
page 13-16

on page 16 top part he state that good values are: C:1 μF and R2: 18K

saloni yadav1 said:

how do i kno which R and C to select to get a proper hardware debounce?

You need to know several things...

1. What is the bounce characteristic of the switch? (You can find out how long it bounces by making measurements with an O'scope)

2. What is the Vih-min and Vil-max of the device the signal is going into?

3. What is the max rise/fall time spec of the device the signal is going into?

Once you have this information you can design a suitable lowpass filter.

saloni yadav1 said:

how do i kno which R and C to select to get a proper hardware debounce?

i kno its like a basic question. but plz help!

You shall start with C = 100nF and R = 47K, as for instance used in LaunchPad. When you see that this does not work well for your application, then try to increase or decrease R accordingly.

Ilmars said:

When you see that this does not work well for your application, then try to increase or decrease R accordingly.

I generally try to dissuade people from employing "Goldilocks Engineering"...

Brian Boorman said:

I generally try to dissuade people from employing "Goldilocks Engineering"..

You did not explain everything one needs to know about properly working hardware debounce anyway :) - It's quite lot of things to tell, even about such seemingly trivial task. I better give first push using minimum effort (from my side) and see how trainee finds the truth himself or how good he is to ask further/proper questions.

[edit] Are you sure that one who asks about RC nominals for debounce - can understand what's Vih-min and Vil-max of the device or max rise/fall time spec?