Thanks MarkT!
I'm sorry I didn't mention it is Chinese. The manual is almost useless..
I have just tested it! With the pot completely disconnected the motor doesn't even turn on.
But, while running, when removing the ground connection of the pot the motor goes to full speed. So.. it has no fail-safe...
Can it be done if it has no fail-safe? If so, how could I connect arduino to it?
Also... is it a better option than using a digital pot? My pot has 100 steps on the wiper.. and the pwm output has more...
Thanks a lot one more time!