actually the set up does not need a timer.
my thermostat has a day night setting and during the night my fans run all the time to keep humidity in check. so all you need is:
1. thermostat
2. fans (obviously)
3. extension cord going out of tent or grow room
4. light bulb
5. plug that turns on when light goes off (i don't know what its called) there 20$ people use it so there light outside turns on at night.
6. co2 system
7. light bulb

NO TIMER IS NEEDED