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computer fan ventilation for germ box

megamoo

megamoo

This is sort of a computer tech thing and I need some advice.... I have a 12v DC fan which I just mounted into my newly built germination/grow box. In my old house I had it wired up to a 12v AC adaptor that was plugged into a timer and wall socket and it worked perfectly.

But I've moved and now my computer is sitting right next to my new germination/grow box. I leave the side panel off my computer all the time and I was thinking that it would be a simple thing to connect the fan to one of the motherboard fan jumpers (plugs, headers whatever they are called). My motherboard has at least one free and according to the manual it is 12V DC.

I'm not sure but the third wire from the fan is for monitoring the temp? If I then got the right program the computer would be the thermostat, timer and power source.

So what do you think? Anyone know a reason why it wouldn't work? Anyone more computer savvy than me and know if this is possible?

edit: I should add that all the heat in my grow box is from fluorescent lights and aside from ventilation I need the fan to cool it down a bit.
 
Monitoring the temp is only the cpu. You can wire it and it will work but it will never shut off because the temp of the cpu will always stay hot enough where the fan will never cut off. It would work great for venting your seedlings though.

Charles
 
Since your computer is a mini room heater wouldn't having it as far away from your box as possible be a good thing?
Seems hot air exhaust from a computer thats close by would make heated air get sucked up into your box.
As opposed to cooler room temp. air getting sucked in.

I have 4 - 5 computers running in my room at times and it gets hotter in that room pretty quick when all are running,lots hotter the closer you get to the computers.

Depending on why you use fans in your box-for air circulation(humidity control) or heat removal - it might make a difference as to how close your computer is to your air intake for your box.

I also think running a long wire to run a fan from your CPU might not be a good idea as far as voltage draw etc. goes.
You'd have to ask a geek,I don't know what the difference in voltage or amp. drop would be over 3ft.,6ft. or whatever.
I do know using too long of an extension cord to run some stuff stresses the power source(flips the breaker),cooks the extension cord or fries whatever you are tryingto run on the long power cord.
 
Thanks for the replies. I will have to explain a bit more. I need the heat because it is a grow box AND germination box. There is a shelf with light globes below it to grow seedlings, and heat the germinating seeds above. When the seeds are eventually all sprouted the shelf will be removed and the light globes raised to give more headroom for the growing plants.

The problem is... the lower section is ok without lots of fan action at the moment because I only have tiny seedlings and a few globes on but the upper section gets a bit too hot for the seeds. The computer is to the side and doesn't add any heat to the system as the box is thick wood and well insulated. I have absolutely nowhere else to put the seeds to germinate them. It's winter here so if the globes are off for long the seed section temp drops too low.

I don't want to run the fan nonstop because it is a large size one and is noisy. On the ceiling of the box I have mounted the fan in a hole and there is another hole at the bottom ready for a second fan for air intake. I was only going to connect the fans up when the seeds are done and the growing plants need ventilation but I'm trying to do it now for cooling. I hope that is all understandable. In hindsight I really should have designed it better but this is what I have now.

So ideally I need a thermostat controlled fan to keep the right temp now, and when the box is only a growbox it will ventilate as well. My computer has the regular cpu fan which keeps the chip cool but the motherboard has the option for case fans to be installed. In the motherboard manual it specifies what each pin of the fan headers does.

1 = ground
2 = +12V / Speed control
3 = sense
4 = reserve

The fan I have has three wires, the red and black are for the first two pins and these are the ones I connected to the AC adaptor before which worked. The orange wire I have ignored in the past must be for `sense`. I'm only guessing this means you can connect a fan with an inbuilt thermostat? or at least some sort of data is being received. There would be no need for this wire if the computer only got its temp readings from the cpu. I will have to post this question in an overclockers forum and they will no doubt assume I'm growing weed. :rolleyes: I'm sure they will know of software that can independently control case fans etc.

If anyone has read this far then I'm impressed! Any ideas would be appreciated.
 
The fourth pin is simply a speed control based on what the computer thinks it needs it to run at (ie when under load some motherboards will run the fans at a higher speed to cool it) My computer has 3 settings on the fans at high/low/optimal and the optimal is based on the software telling it what to do based on cpu temps and chip temps.

A four pin fan will simply be variable speed. A 3 pin fan will run at one speed only.

A 3 pin fan will plug into a 4 pin header though.

It however by itself does not sense the temperature.

Best idea is to rig the Fan onto a 3 pin plug go to DSE and grab the appropriate bits and pieces or simply hack off the cord of another 12v DC applicance and use a thermostat to control when it goes on/off. Like this one.


Thermostat
 
Sounds like you should hit up a swap meet for a brushless $2.00 fan(4-5 inch) and a plug in the wall power supply($2.00-1 amp.12 volts).
Why possibly stress out your computers power supply.
Unless your computer is only on for a certain amount of hours the fan would only run when the computer is on.
Fans don't have a thermostat,the CPU does/might have.
The computer would have no idea how hot your box gets.

Get a heat mat thermostat and plug the fans power supply into it if you want the box temp to be constant.
A heat mat thermostat can run something like 1700 amps of stuff through it.
It would control your fans on and off according to the temp in the box.

I never figured out why a person would make a box rather than using a heat pad and a shelf with fluoros or whatever.

seems like a lot of work-wasted time and effort using a box...can't see any advantages...

Trippa must have posted the same time.
A heat mat thermostat is a little less.

At my local nursery they are $30. after taxes.
 
The sense plug 'sences' the RPMs of the fan with proper programs will alert the user of shutdown the computer if a fan fails to spin and therefore fails to cool. But again there is absolutete no temperature sensing ports directly on the motherboard, they are built in to the CPU and harddrive.

You can however buy an aftermarket fan controller with a temp sensor for around 30$ usually it is bay mounted in a 5.25 bay. But then again computers will take temps up to around 160f so you will really need to watch which on you get and even then you may cook the seeds.
 
The sense plug 'sences' the RPMs of the fan with proper programs will alert the user of shutdown the computer if a fan fails to spin and therefore fails to cool. But again there is absolutete no temperature sensing ports directly on the motherboard, they are built in to the CPU and harddrive.

You can however buy an aftermarket fan controller with a temp sensor for around 30$ usually it is bay mounted in a 5.25 bay. But then again computers will take temps up to around 160f so you will really need to watch which on you get and even then you may cook the seeds.
 
That tells me stuff I didn't know, good answers. I didn't make the box, I picked it up of the side of the road on bulk rubbish day. It was clean and newish and has a rollerdoor on the front and just happened to be the perfect size to sit my TV on. All I did was put the light fittings in. I have to keep the tv elevated and the door on the box closed because of small children with sticky mayhem causing fingers.

From what everyone has said it will be easier to forget the computer and use it the way I did before. Wire the fan to an ac adaptor and then plug it into a timer which will turn it on now and then. I will have to find a different place for my seeds.

Thanks everyone for the info.
 
smokemaster said:
I never figured out why a person would make a box rather than using a heat pad and a shelf with fluoros or whatever.

seems like a lot of work-wasted time and effort using a box...can't see any advantages...
Click to expand...

Maybe not in California, but I start my seedlings in my frigid basement in January or February. Its about 55 degrees down there in the winter. The box with lights and heat mats is usually in the high 70's. It is also extremely dry here in winter.
 
Wall warts work just fine, I wouldn't want to risk my computer to a garden fan, especially if it is plugged into a motherboard header rather than the PSU. To control the speed you can just use voltages as low as 5v. If you want to switch the speed antec makes fans with a hi med low switch, and there are manufacturers of fans that have built in temp sensors. Try searching newegg.com for item N82E16835426004 or N82E16835426014 , they have an integrated external temp sensor you can put wherever you like. I don't know the temp range that affects fan speed though you might be able to place sensor in a warmer or cooler location to get desired results.
Note that it is a 4 pin PWM connector, I don't know what happens if you just hook up the positive and negative but it may just run at full speed. I'm buying one now to test and will get back with the results.
And RE: box vs shelf, my house temps get into the 40's in the winter and the box provides great reflection/insulation with reflectix insulation affixed with velcro for easy removal during the heat of the summer. You can easily convert a shelf with this stuff, home depot sells it by the 2ft or 4ft roll for about $1-2 per foot.
 
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