increase protection of port

[gelecg]

Hi,
Which one is better?
is The diode in second circuit effect to reduce noise?
and the switch is connected with 20 meter wire.

 

[ronsimpson]

I do not understand the diodes at all.

 

[JimB]

I agree, that diode configuration is not sensible.

JimB

 

[alec_t]

This would be the way to use diodes:

 

[gelecg]

thanks.
someone protecting port with optocoupler.
why we must isolation with optocoupler?

 

[alec_t]

If you are measuring signals from equipment which may be at mains potential or higher you would isolate the micro (and yourself!) from that.