all you need is this

1-Co2 tank 30lb
1-low pressure tank regulator
1-1/4" parker solenoid valve 12v
1-photo switch from lowes
2-rechargable 9v batteries - wired in series-
1-cheap solar battery charger

when the lights are on it charges the 9v when the lights go out it turns the solenoid on and releases Co2
Micsog Reviewed by Micsog 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