A couple of years ago we built a henhouse.
Not so different you might say but this one comes with a timer controlled automatic door powered by the sun.
The prototype used a recycled battery drill, the charger and batteries were shot, there must be tens of thousands defunct drills out there. The power is supplied by 6V SLA battery with shunt regulation, the door position is signalled by ONE security reed switch with two magnets attached to vertically sliding door, a picaxe micro supplies the smarts. The door uses counterweights to lessen load.
The original used a AA cell general purpose timer module, I can't find these now, the alternative being to pull apart mains timers to access the low power electronics. A better idea, since I'm already using a micro is to use RTC module.
I will use simple timing set-up, no need to program timers, simply press a "button" on the unit at the times of day when you want open and shut.
If you want to change open or shut points, operate the button within plus or minus one hour of the existing set time and the time is reset. This way we don't have to worry about winter/summer time dawn dusk changes, re-setting takes seconds.
Do the chooks (hens) know when to go to bed?
The shed ran for over a year, three generations of chooks and we never had an "unhoused hen". Our chooks would take themselves to bed about 15 minutes before sunset.
Set shut time to 10-15 minutes into sunset leaves 30-45 minute margin of error.
If you are in Australia, I might be interested in developing/distributing plans and supplying the control electronics.