Switch component

i would like to design a automatic pet feeder, but what can i use to open/close the feeder door to feed the pet??

i just wan use battery only, so motor cannot last longer, instead of motor, go any suggestion, is it have any switch, when supply power, the switch will move or push or turn....?

Or other suggestion method on the mechanical part??

I have a pet feeder that uses no electronics, rather it is all mechanical. When the food level gets low in the bowl, the feed door opens up and allows more food to enter the bowl. The filled bowl then closes the door. Quite clever design actually.

i need feed it every 8 hour, the timer i done already, now left the door portion.