So got it all spinning in each direction. Rigged up a coffee cup lid and connected it to the motor.
Didn't use my brain and the motor wasn't able to lift the chicken door (<500g) but ignored it, and we'll the wires started smoking, from memory impedance?
Anyway I've now ordered a higher torque motor which I can just swap in (it can lift up to 2.5kg apparently) https://www.amazon.co.uk/WINOMO-3V-6V-Short-Shaft-Torque/dp/B010SP427I/ref=redir_mobile_desktop?_encoding=UTF8&psc=1&ref_=ya_aw_od_pi
So will give that a go on Friday. The next step is to get some sort of small solar panel and charge unit, seem them for around £6 (I may need to bug you again Gordon!). Just to keep things topped up.
Short term I think it'll just be an LDR and sitting outside with my laptop takin g measurements for door opening Vs closing times. Eventually I'd like to link to WiFi, have a minimum opening time of 7am, and then something ~45 minutes after sunset. LDR is cheaper and doesn't involve me doing the WiFi/cat5 to our garden (longer term plan regardless). Oh and to report that the door is open and closed (WiFi could also periodically sync the time).
Once the motor is working on the door it'll just be two reed switches to ensure door opens and closes at the right point rather than relying on timing which could go wrong, or something could slip (I think commercial systems just rely on time and calibration - maybe good enough, bit reed switches aren't expensive!).
I'll write up the chicken door at some point. Theres a couple of Arduino examples. But it would be good to get an espruino example shared because it's such a great project and I've done it with very little experience and knowledge (except my JS).