While searching for a cheaper alternative to
power an automatic door I found this linear actuator that sells
for 30 bucks plus 14 for shipping.
It's rated to pull 450 pounds! Which is more than you need for the
average chicken coop door, but with a little imagination this device
could be used as a light duty gate opener and closer.
You'll need 120 volts of electricity to power it, unless you rig up
some sort of solar cell and battery combination.
This could also be used to open and close a window for green house
ventilation.
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!