Seeing that I'm an impromptu vacation for a few days, I have time to go over some of the construction and background without the wife, kids, job, nothing but the ocean, and a couple of joints to pass the time... so on we go.

Some background operations of how this works.

First the 12v that I call for in the transformer are to operate the two relays, thermostat (any 24vac/milivolt thermostat will work for this design so if you have one around... BONUS on 15 buck savings). I didn't want to run multiple voltages for relays/thermostat, and didn't want to push 120v through the telaire 8001 (but could have... since it's a low current draw on the relay). So we have this need for 12VDC here.

We don't want CO2 to be discharged at lights-out... without designing a ground up circuit that would cost more in parts than an off the shelf one with some work... I chose to use the one from Lowes... this will turn the red wire hot when lights out... which is what the 120v relay is for... we want the current to shut off at lights out, but the light sensor does the opposite... so with the relay we use the sensor to pull it down, and force the circuit to be broken!

The fans... those important fans to turn on when we gets HOT in the room... As I noted any 24vac/millivolt thermostat that has a heating/cooling switch will work. We want to set it to cool, and use it to close our circuit on a 12v relay to turn on the 120v to the fans (now dont draw more than about 250w on the fans... remember that's about 2 amps at 120v... more than enough for 2 400+cfm squirel cage fans.)

The flip side of the relay for the fans is that when the thermostat closes the 12v coil, that will turn on the fan side (120v circuit closed) it also will open the other side of the DPDT relay used to force an open circuit on the other 12v relay to prevent the 120v circuit.

your thinking we have alot going on here... well we do. We don't want CO2 at lights out, and don't want it to be dumping when we're running the fans (this is pointless in both situations)... and to keep this an off the shelf parts controller we need to do some additional circuit designing.

For those of you who want to also dump the room air when the humidity gets too high... no problem...if you have a humidistat that has a relay in it when the humidity gets to a certain point you can put that in parallel with the thermostat... when either one hits it's high point... fans on/co2 off, and we dump the air in the room... better choice is to run an airconditioner on low. This will keep the humidity down, and temps down too so you won't be cycling the co2 and using it up. But for the price of 2-3 tanks of co2 over a decent sized tomato havest... well worth it compared to the amount of fruit you'll get .

Now that I've covered what we are doing I will continue on with construction and schematics... but first... a toke, and some rest. I came here to get the fuck away from life for a bit...

Tomorrow we cut plastic! get our switches in, fuse holder and talk about maybe adding a few lights to know what's going on if your controller will be outside your flowering room.... um, your tomato growing room I mean!

Night all...