Over-voltage protection

[Demon]

the red led will never fly with base of tr shorted to gnd

try
Attachment 9386

red should light at 5.5v

But why reduce Zener to 4.7V? Out of all the PICs I'm looking at, the one with the lowest max VDD was 6.0V; hence why I chose 5.6V Zener as "fuse".

Is this because of influence of 1K resistor below it?

And how did you arrive at 4.7V? Math? or a spec in some doc?

In this particular case, I was doing this for the 18F14K22 which has absolute max VDD rated at 6.0V.


EDIT: I ask how, because I will have the same over-voltage circuit at other voltage levels(for other purposes).


EDIT SOME MORE: These are the specs for the 1N5232BTR that I was planning on using.