As long as we're reviving a one year+ old thread, allow me to ask a naïve question. What, exactly, is being parked in this rotary parking system? Is it actual full-size cars that actual people ride in? If that's the case, then you're talking about putting some pretty heavy-duty equipment under the control of a hobbyist-quality microcontroller board. Probably worse, it's under the control of firmware written by somebody who obviously doesn't know what they're doing.
What kind of safety provisions are in place to prevent somebody from getting hurt?
I'm surprised this wasn't brought up in the original thread.
Like I said, maybe I'm just naïve and everybody else knows this is a system for parking RC cars or something.