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
demoreal Reviewed by demoreal on . DIY co2 controller if you own thermostat. i had this idea to build a co2 venting controller. items needed: -light detecting outlet - about 20$ -thermostat you plug in your fans to the thermostat and have them go on and off. you also have a light plugged into the thermostat one that goes on outside the grow room. a small light the smallest cfl you can find. plug your co2 into the light detecting outlet. now you can kind of see how it would work. when the light goes off and fans too, the light detecting outlet would turn Rating: 5