Force required to pull open door?

Qdeathstar:
I got it to work at a minimum acceptable level.

Glad your system works, but I don't see a dog-system interface. IOW, how does the dog get the door to open?
Also, how does the system know when it's safe to close the door, without squashing the dog?
You say that the door doesn't open all the way. Does it open far enough to let a human through?