Christian
Wolpert's automatic chicken coop door opener and closer is the second one I've seen so
far that is completely off the grid and designed to work on a battery
that gets charged with a solar panel.
It uses an MSP430
microcontroller as the brain along with a customized Linux source code
that Christian is kindly offering as a free download.
I know building and
programming your own microcontroller can sound advanced, but Christian
describes a clever short cut where he makes use of a tutorial as his
starting point. This trick reduces most of the number crunching work to
a process of adjusting specific interrupt routines to fit your
automatic coop opening needs.
Edited to add:
After years of research, Mark eventually settled on this automatic chicken door.
You can see
a summary of the best
chicken door alternatives and why he chose this version here.
If you're planning on
automating your coop, don't forget to pick up one of our chicken waterers. They never spill or
fill with poop, and if done right, can only need filling every few days
or weeks!