Use an electric solenoid and a cheap plug-in timer to activate it. Opens the
door via a suitable lever when the solenoid is activated; closes the door by
gravity, or by a spring, when the timer shuts off power to the solenoid.

Keep it simple.

--
Walter
www.rationality.net
-
wrote in message
oups.com...
What do I need (relays? gears?) to have a small electric motor turn on
via a timer, run for the few seconds needed to raise a small (10 x 14
inch) piece of wood via string and pulley (door to a chicken coop),
turn itself off, then turn on again via timer hours later and run in
the opposite direction to lower (close) the door and turn itself off
until it's time to tbe turned on again? This seems to be on the
principle of a garage door opener, only smaller and opening/closing on
a timer switch instead of a push-button or transmitted signal, right?
Are there systems like this already in existence?

Thanks.

Lynn Willis
Indianapolis