Newbie questions concerning supply and grounding

Excuse me my ignorance… I have gotten Arduino for a specific project (although I am generally interested in the platform), so my electrical knowledge may not be up to the task. I feel it is better to ask than to be sorry.

I want to replace pots connected to pedals of a PC gaming wheel with a digital potentiometer controlled by Arduino (see attached diagram). However, I am not sure how to deal with voltage and grounding…

As far as I can see it, I can do it as follows: the digital potentiometer wipers are connected to the controller plug (DB9 in the diagram), while the voltage and grounding of the pot are connected to Arudino (powered with USB). Will it work at all? Or does the pot for the wheel have to be connected to its “own” voltage and grounding (supplied by USB via the wheel)?

Another option: Arduino is powered by USB, while the digital pots are connected to the DB9 plug…

Or the third option (preferable for me): Arduino itself is powered from the DB plug (white wires in the diagram) and the digital pots are connected to voltage and grounding from Arduino. I am not sure this will work either…

Sorry if the question is silly, but I’d hate to fry the board at the first try!

CycleAxis.fz (284 KB)

You may want to power the gaming wheel off a separate power supply; the arduino can only handle ~800mA.

The digital pot supply needs to be such that the signals it handles are in range - read the datasheet to figure this out - with luck you just need to share ground (but watch out for AC-coupled signals going to negative potentials.)

I did not want to power the wheel from Arduino - I wanted to power Arduino from the wheel...

However, the recommended external voltage for Arduino starts at 7V - otherwise the board might supposedly get unstable. Maybe it would not, but I have little incentive to try. The original design was a bit more elegant, but what I have now is not bad either, the only difference is that I have to plug in two USB cords instead of one.

As the whole contraption is just working (wonderfully, I might add - bicycle powered Test Drive Unlimited for the win! :D ), I am content with what I have. If I make changes it will concern software rather than hardware, maybe with the exception of some LED indicators.