Automatic Temperature Control

[RobsGreen]

Hi, I'm in the process of building a stealth grow box and its coming along great, now I'm just trying to fix some small details. The box is a cabinet about 6' tall 2 1/2' wide and 1 1/2' deep. I have a 200watt cfl lamp in there with a 4" inline fan with a carbon filter on the end of it.

Right now my temperature is all over the place as I'm experimenting. My question is this. What would be the best/cheapest method to have the exhaust fan turn on when the temperature gets to high?

I put a dimmer switch inline so I can slow the fan down so I don't cool it too much but would prefer not to run the fan 24 hours a day at a slower speed. when the fan is on full it gets below 70 degrees, and with no fan up to 90 degrees.

I was thinking of a digital thermostat that controlled an air conditioner as well so it would switch on the fan when it got to warm but I'm not sure how I would wire it, anyone think this is possible?

Anyone ideas would be appreciated! I'll be sure to post some pictures and info on this box when I'm done, I think its gonna work great.

Thanks!

[RobsGreen]

Well I'm answering my own question, in case anyone else wants to know here's how you do it.

Buy a 24volt digital thermostat that controls both heat and cool. (you want cool) Next you need to get a transformer that brings 120volts down to 24volts so you can wire up the thermostat. Its quite small in size. You also need to get a 24volt 10amp relay which will turn the fan on/off. 10amp is overkill but thats ok.

So with that you can control the temperature in your grow box automatically. Here's a drawing on how it's wired.




There it is, its a pretty simple circuit. The 120volts going into the relay doesn't go throw the relay until the thermostat switches it. When that happens 120volts flows throw the relay and comes out the other end where the fan is connected.

Well I hope this helps someone out there, if anyone needs more info let me know.

One other thing to note, I mentioned I put a dimmer switch inline, thats a no no on AC fans I found out unless the fan is a variable speed fan, not likely the case. Using a dimmer switch will shorten the life of your AC fan quite a bit.

[Rumpleforeskin]

I try and maintain an even temperature in my grow, so I plug my exhust fan into a thermostat. I would not recommend pluging your cooling system into a timer. I would rather have normal air then un-even temps or an over-heated grow. I found the best thermostats to be the ones made by Ranco. They are $45 unwired (ebay) and $70 wired to an extension cord. Very simple to wire your self.

[screwdababylon!]

great!

any idea how to plug in he speed control in there?
i have a fan with 2 speeds 250 and 110 m/h

and i want it to swich between them depanding on the temprature

peace

[brian5555]

how do you set when you want the fan to come on

[RobsGreen]

I have updated the setup slightly since then, I added a speed control and timer. This is how it works.

The timer is the very first thing inline, I can turn it to auto or on. For the first part of my grow (in my smaller cab) I didn't need the fan to run all the time so I put a thermostat inline. Power was alway on but it was up to the thermostat to kick a relay and feed power to the fan. I wired it on the cool side of the thermostat not the heat part. This way when temps got to lets say 76f the thermo would kick the relay and allow the fan to turn on until it got down to 75f. Just like your furnace but backwards. But then later in flowering I needed the fan to cut in every 15 minutes or the humidity got to high so thats when the timer came into play. I would set the thermostat down to say 65f, a temp that would never happen, that would always keep the relay kicked, they when the timer came on power would get to the fan. Hope all that makes sense. Here's an updated diagram, not much but might help.

[fishjedi]

Hi

This is my 1st post, been lurking for a few weeks planning my 1st grow!

I came accross a "Aquarium Temperature & Lighting Controller With Remote" 150245256013 on ebay today and thought it would be perfect as it controls light and temp!

But its a bulk buy of 10 so I didnt want to waste my money if it was no good! (cant really aford it anyway would have to resell some to cover it!)

The other thing that cuaght my eye was the remote control, so I could shut off the grow box if the rozzers/inlaws came knocking!

Do you think it would be suitable?

[RobsGreen]

Hey fishjedi, that looks pretty cool, I'm sure you could sell some of them easily. Looks like it would work ok.