I just built a 12v door opener. I haven't actually built the whole thing yet, just the controller.
Timer switches on (for 1 minute), motor spins one way and opens the door.
Door hits limit switch, shuts motor off. Timer switches off after 1 minute.
Timer switches on in the evening and the door closes.
Total in parts so far:
$25 for the controller with switches.
$37 for linear actuator (
ebay) but I might use a 12Vmotor I have.
$0 had drawer slides for the door.
$0 wood for the door. I have some, but will probably include it in the coop cost.
$ to be spent so it doesn't have to be plugged in:
12v timer
12v battery
12v solar charger.
Cheers,
B