Recommendations on auto door

I just assembled this coop and want to install a automatic sliding door for when I am at work later than I want. But I have read a lot of the reviews saying the safety features didn't work on the ones I looked at. Does anyone have any recommendations on a side sliding door that I can use that is less likely to kill my chickens?

I do plan on hooking it up to a car battery and solar panel (not sure why the picture won't upload)