Quote Originally Posted by Freman View Post
I am prepared to fall back on pullies, string, and a piece of pvc with a magnet/reed switches if I have to - this will allow me to put the sensors out of sight... hopefully
Haven't read the whole thread..but...
Couldn't you put a small piece of something reflective on the back of the screen, have an IR led/detector module or similar mounted in the wall behind the screen, if even a few feet behind the screen, and use the detector output as the start/stop sensor? One gets set up so when the beam is there (i.e. reflective piece is bouncing back the light), the screen is all the way down, the other is set up at the top so when the beam is there, the screen isn't quite all the way up. You really wouldn't even need the beam on continuously, just a quick blip every second or so might tell you what you want to know.