I'm using a mosfet for the first time. My breadboard is powered by the 9V battery, and I'm driving a motor that is hooked up to a separate set of 2 AA batteries. I have the mosfet source connected to breadboard ground, the gate to the microcontroller, and the drain to the negative terminal of the motor. I then have the positive terminal of the motor connected to the positive terminal of the AA battery box. My question is, what should I be connecting the negative terminal of the AA box to? Right now I have it going to breadboard ground, and everything seems to be working properly, but I wanted to make sure that was correct and wouldn't cause any issues.

Thanks for your help! Neil

You did it right. :P

Thank you!