This is the first draw bridge coop door opener I’ve seen.
It has the added benefit of working as part of the entrance ramp.
The motor is a common electric car window mechanism that can be found on Ebay and the Youtube video has a nice component animation that explains each piece and where it goes.
One of the nice things about converting a PetSafe electronic pet feeder into a chicken coop door opener and closer is the fact that it has a built in timer to control your opening and closing time.
You’ll need a small structure with a pulley mounted like in the picture and some heavy duty string or fishing line.
The door should be light and travel freely in an up and down motion.