Strut

I like the RFID idea.

What happens if one of your birds does get eaten, RFID tag and all... Then door would open right up for the next course

My auto door isn't timed, it uses a photosensor to detect dawn and dusk to match the clock of the birds and their natural behavior. Detecting the birds themselves is problematic, as their isn't much difference in a plump hen and small red fox knocking on the door (of which I have a lot of here)

My "coop" runs on solar power for everything. I have a 100w panel and 60ah battery to run my charge controller, volt meter, thermostat controlled exhaust fan, motion detecting led spot light, several indoor led lights, and a small 200w inverter for minor 120v needs. In reality this building is a small "garden workshop"/greenhouse with a small area segregated off for a few birds to sleep in. To call this a "coop" is a bit of a stretch on my part, but that's where the initial idea spawned (all because my parents took me inquiring about guinea hens to control the ticks around the house, into meaning they should buy me a bunch of various fowl hatchlings at the local market...Thanks again, mom)

Let me know if you'd like more info.

I have been doing research on this exact same thing for some time. My parents run a small self-sustaining farm with about 30 chickens. First, anytime its cold enough to freeze water you'll need to supply supplemental heat to your birds also. This usually involves a couple hundred watt heat lamp. My parents position the lamp so it heats the water and the birds (lamp -> water -> birds). 12v simply won't work without massive expense. (P.S. Chickens don't lay much in cold weather, whether they have supplemental light or not)

I've seen some interesting solar heater setups that you may think about. The most basic is a large black water container inside a coop that is setup as part "greenhouse". The premise is that solar energy heats the water reservoir during the day, and it's heat is slowly released into the coop at night. If you have fairly mild winters the water should never freeze, and keep the coop warm(er). Insulating the coop will help greatly here. Of course their are many variations on this premise. This is the route I chose, but I went big, combining a coop and proper greenhouse into one building. I have pictures if your interested.

I discovered complicated feeders and waterers just aren't needed, off the shelf equipment will do the job for days without intervention, unless your just up for the challenge.

Auto coop doors work great, especially for keeping out the varmints at night while your gone, but I haven't figured out how to handle the occasional straggler(s) that doesn't make back in time. Many birds are content sleeping on or around the coop if they don't get a bit of coercing . Timed treats with an audio announcement (and training) could work well here.