Ive managed to destroy two pro mini boards, and i think its been caused by negative voltage spikes...
Investigating this i created the following circuit (attached) and found negative voltage spikes on the ground pin when the push-switch gets released.
It only occurs when using 10MOhm pullup resistor but does not occur with a 680KOhm pullup resistor.
It also only occurs with this a PP80P03P4L-04, P-channel mosfet, (attached) not with other P-channel mosfets.
Has anyone seen this before? The only cause i can think of is the mosfet, has some inductance?
p.s. i am a hobbyist with not much experience.