The chicken door started because we let our backyard chickens out at about 6pm, then close the door again when they have re-entered the enclosure to sleep.

They have a limited time outside because they tend to  wreck the garden and plants if they are left out all day.

Unfortunately we forget sometimes:

So a light based chicken door was called for

Start with a sliding door run on a ball chain drive - motor driven by arduino with motor shield
- run on solar power.

At present using a LDR for the light sensing but will move to solar cell voltage

Later  additions would include a chicken feed holder door as well.
To lock up the chicken feed from the attack of the rats. But that is a later project.