I tried experimenting with transistors for the first time and using my Raspberry Pi to try to control a higher voltage circuit. Using a breadboard, this is the circuit I tried to build (apologies for the poor hand-drawing):
My thought was that the 9V battery would operate the motor, and by having a common ground between it and the Pi, I would be able to use the Pi input to turn the transistor on or off.
About midway through, I realized that the pin voltage from the Pi wouldn't be high enough to flip the PNP transistor, but I went ahead anyway thinking that, in the worst case, the transistor would just be left continueously open. What I did not expect was that the circuit would fry my Pi entirely! (at least I was itching to upgrade it anyway :).
I'm pretty certain that I didn't inadvertantly short any pins or connect the 9V hot to the Pi's GND, so what went wrong in this circuit?