Hi again.
Our son had a big obsession with cars, Match Box to be exact. He like to lay on the floor and watch the wheels. We actually embraced it. It was a socially accepted one and he eventually outgrew it. We have always thought that our son was going to do something wonderful with that passion-like redesigned the wheel

He would get obsessed with a toy for a week or two. If it got too much we would re-direct him. It seems like they replace one thing with another. I have heard of one child (I think it was on here,) who was obsessed with pulling his hair out. The parents shaved his hair off and he exchanged it with shredding paper. That seems to be the case with a lot of kids....exchanging.
Maybe having a schedule for the day with break periods to play or do the obsessed thing at a specific time and place might help control it a little better?
Hey you never know......a obsession now might ease into a passion and become a career for them later.