My board is USB powered. How do I use this for other circuits

[KansaiRobot]

Hello, everybody and thanks for the help

I have been working with 5V and 3.3V PICs that I power from the power outlet on the wall (with a device of course to change AC into DC). Once I also power my small circuit from the USB.

My question is, now I want to use micros other than PICs. For example the Stellaris Lauchpad or the STM32 Nucleo. Now these boards are USB powered, meaning I connect a cable to the PC through a USB cable and I can say turn on and off a LED.

Well that is well and fine but what if I want to implement non-trivial circuits with these boards? Say (DC, stepper) motors, PWM, LCDs, etc. or maybe if I have to use (in the case of motors for example) 12V or 24 V to power that part of the circuit. What do I do? I mean I am guessing that the ground part of the USB power and the ground part of say the motor control circuit should be the same right?

I would very much appreciate if someone can explain this to me in simple terms, perhaps an example...

Thank you very much.

 

[ronsimpson]

I use a ("USB charger" thing like my cell phone uses), to power the micro-computer.
THEN
I use a large "wall wort" (same as above but 4x bitter in size) that outputs 24 volts and up to 4 amps, to power motors.
YES
The grounds need to connect together.

 

[zahwi]

I'm only repeating what ronsimpson already have said, you can connect anything together as long as you common the grounds first (and don't start a fire).
The only thing you can't connect is an old British car wired with positive earth.