how to prevent the noise to digital input microprofessor

[minhducpham2009@gmail.com]

Hi every one

This is the first time I post in this forum.
I am an electrical engineer and i am new to electronic. When I work in my comapany related to design controller ( actually its not my advance ) .
After finished design and solder it. When i am testing the controller, every thing is good (output relay, analog read , etc) but I face this problem the digital input.
My colleague recommend me to use capacitor between button and Its WORK. the circuit now no more noise (auto turn on button remote)

This is the way he do:




So could you please help me know why he do that and the capacitor mean ?

 

[Audioguru]

Microprofessor, ha, ha, that is a good joke.:lol:
A switch contacts bounce when the pushbutton is activated which results in many pulses fed to the digital input that counts all of them. The capacitor is normally charged and is discharged very quickly on the first contacts closure and during the bounces its slow charging by the 10k resistor results in a noiseless logic high signal.