Sensors and thermostats
helped instead of just timers (although timers would probably work just
fine
for a few weeks). I had an extra computer left over from upgrading my
wife's
which I could then program to control most of the sensors.

Where did you find these sensors, and exactly what were you measuring?
Finding suitable sensors has been, and continues to be, the most problematic
part of my efforts to make a growth chamber.

I can not take a vacation since the only person who could conveniently take
care of my plants is my sister, and she has such a black thumb she can even
kill plastic plants. ;-) I DID manage to teach her daughter how to keep
an african violet happy (though I help her out a bit when she's at school or
in bed), but she is still too young to take on such a responsibility for
plants that cost just a wee bit more than her C$2 violet.

Cheers,

Ted