Originally Posted by Sceadwian

Current limiting resistors look like dead shorts to an EMF spike.
I'm having trouble finding models (not sure of the capacitance one should use) to calculate the size of the actual pulse in order to determine junction temperature, but the voltage of a small static spark is 1000 volts and some produced like I get from my car all the time (I hate those) is in the neighboorhood of 10kv's Even a 100k resistor is going to let 10ma's through on the low side, and with 10kv the current pulse would be as high as 100ma's though the duration is going to be virtually instantanious the junction size of the diode suddenly becomes VERY important because even if it's just for a few nano seconds, violating the junction temperature will instantly destroy the device. I'll see if I can find any other information on the actual size of the junction involved in a micro controllers diode compared to say a 1/8th watt discrete but I'm going to guess that 10 to 100 times the physical size isn't going to be over estimating which makes the EMF pulse handling ability of a micro controller diode virtually nill compared to a discrete.

Originally Posted by Sceadwian

My car would make short work of any PIC =) I have a pavlovian reaction of stark terror every time I get out of my car they're so bad. I shouldn't complain though all I need to do is tack a grounding strap to the bottom of the car so it drags but I'm too lazy to put it on =\. I try to remember to touch the car with my key instead of my hand when I get out but I usually remember AFTER I get the shock. I'm not sure how to calculate the voltage from the length of the spark in damp air but I've pulled sparks over an inch off my car, it's enough to make me actually drop my keys.