Annoyingly, doesn't mention how it counts the chickens. :)
My design was Raspberry PI -> sensor/power board -> battery powered drill. And an extra long usb cable to get the wifi dongle to the other side of the roost, because when the chickens were in the coop, they absorbed enough wifi signal to make it drop off the network.
Edit -- changed which twilight. Also, code here: https://github.com/wiredfool/coop-door
Unfortunately, schematics and physical door design are lost to several moves.