Hi Steve,

There should be a way to link the top of 1 door with the bottom of the other, & vv, to make sure they stay parallel AND move in opposite directions (uses cables?). Look at an old draughtsman's table (old refers to the table!). That way, you only need 1 motor! For the First Law part (not closing on a human), 2 photo-electric switches should do the trick - just point them from the top corner to the bottom corner of each door, about 10cm out from the edge (offset 1 of them, of course!). This should protect your appendage!

Good luck!

Richard