Steve,

I'll bow to Richard's input of 12/04, 12:45 advocating use of a light beam to detect an obstruction. His idea makes mores sense than trying to fabricate and hang movable "bumper doors".

I guess the only issue is the doors must close in less distance than lies between the beam and the edge of the door.

I don't have a site available to post a block diagram of the control scheme, so I'l send you a direct email of the diagram.

Bruce