Motor control Micro controller

[jase1979]

Hi,

I'm a Technology teacher in a school and have a problem with a students circuit. We have a microcontroller output pin feeding into the base of a transistor, the motor is on the collector side of the transitor. I can't seem to get the motor to work. We have seperate power sources for the motor and microcontroller. The ground of each power source is not common. Do they need to be common to work? I'm still learning a lot about electronics my self, so please be easy with me.

Thank you for your time.
Jase

[Simon (Webmaster)]

Hi

From your description the grounds do need to be commoned, yes. The only circumstances where they should be isolated is if the controller and motor drive circuit were totally isolated via an optoisolator.