Max load on Arduions Gnd

I am running a 12v motor with a microcontroller. Is it ok to put the 12v to Gnd on the Arduino board, or should I put it to a "proper" ground since it exeeds the 5v that the board uses.

thanks

Not sure what the question is. That is what do you mean by a "proper ground".

Have a read of this:-

http://www.thebox.myzen.co.uk/Workshop/Motors_1.html

That is grounds should be connected together, +12V and +5V should not be.

http://www.tigoe.net/pcomp/img/unipolar_stepper.png

Where it says (logic supply), I guess that is 5v power from the Arduino board. But where it says (Motor supply) is a different circuit which in my case supplys the motor with 12v. This one also goes to GND through the microprocessor. I was wondering if the "GND" referrs to the "GND" on the Arduino board? I thought putting 12v in the "GND" on the Arduino might blow the board.

Sorry, I have a hard time beeing exact in english.

I thought putting 12v in the “GND” on the Arduino might blow the board.

No putting the 12V ground to the Arduino ground is what you should do. It will not work if you don’t do this.

Read this:-

http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

Thank you!

That .png you posted is confusing me. I'm trying to put together a similar project using a 12v 6-lead unipolar stepper motor, which looks like it fits in that example. But in my case I was expecting to have 4 control wires into the ULN2003, not just the 2 that are shown.

Maybe I'm missing something, but it looks like you give up half of the phases of the stepper motor when you try to control it that way.

Can someone confirm what the circuit in the picture does?

The example I posted works, but it is a hazzle setting up.
This one also works with the ULN2003:
http://www.tigoe.net/pcomp/img/stepper-wiring.jpg

Ah, that looks more like what I expected. Does the first example you posted have any advantages? I'm not quite sure what it does.

No advatages as I know of. Both examples work just fine for me. But you can clearly see which one is a hassle to set up.

Good luck