Thanks, I was wrestling with that. Especially thanks for the info on cloudy days. We get some dark ones in KS, and sometimes just before a storm, it does get dark.
What brand is the other one? The Fleming one comes highly recommended and has a timer that is inside the coop. I have electricity to the coop, so that isn't a problem.
I looked at the Foy's ones, but I can't figure out what you have to order to make it work. Do you buy the doorkeeper and the door and the idler and the timer separately? Does the door come with a track? The website is awful. http://www.foyspigeonsupplies.com/catalog/2100-2107.html
The "other brand" is whatever MyPetChicken is selling. . I just needed one fast....
With the Foy's Electronic Doorkeeper, I bought the Inside mounted unit, it has the light sensor included, and then the door the size I wanted. It comes with the tracks. That's all I needed. The idler pulley thing is for odd installations or replacement parts. If you have the inside mounted unit, you do not need a timer because the included light sensor controls the door operation.
The light sensor works very, very well. Bright moonlight does not activate it, and yet it still opens on cloudy days.