Rheostats and Pelts....
 

Has anyone ever tried using a rheostat on a pelt setup before to control a pelt? I know this sound strange.

I am in the process of planing out my upgrades to my machine and it possibly incudes adding a pelt and WB to my GF3 to keep the overal case temp down. I want to put a pelt that will cool both the core and the memory using a GF3 copper plate that Sysfailur designed. However I dont want to freeze the plate, I only want to cool it down (AKA I dont want to deal with condensation forming on the plate) So I want to see if I can stick an 80W pelt on the setup, power the pelt through my PSU (it's strong enough), and control the amount of heat that the pelt will move. I was hoping that there might be a way of adjusting the pelt to just above the dew point and keep it there.

I know that an external linear power supply would be ideal, however I dont want to invest in such a setup.

One other though was that I could use only a 56W pelt in that setup but that might be too weak/strong. What are your thoughts........

Well, it's possible, but you have to keep in mind a few things:

1-You'll still have to isolate for condensation. Why? because condensation is a phenomenon that occurs under a specific temperature differential, but is affected also by the level of humidity. i.e. the more humid it is, the more likely you are to encounter condensation. If you live I Canada (where I was) then it's probably not much of a worry, but if you live in a coastal city (like Houston, TX, where I am now) then it's an issue. Either way, you should always isolate for condensation, or at the very, very least, use some conformal coating (at your own risk).

2-The obvious solution is to run a simple power supply composed of a transformer, a bridge rectifier, and a few good caps. This will get you the basic current, and if you select your components just right, you'll limit the voltage ripple to under 10%, as is required by a Pelt. What you do then, is replace the transformer with a variac (a variable transformer) and voila: you have a really cool looking big-ass knob (like in "Back to The Future"), and make all your friends envious.

3-Given #1, you will have to find the exact voltage at which the Pelt will give the exact amount of cooling you need.

4-Given #2, you'll have to keep in mind that the GPU's temp will vary, and will require a varying supply to be provided by the Pelt. Given #3, you should then understand why you would want the power supply to do this automatically, because if you set your big-ass knob a little too high, then exit a graphic intensive game, you're facing condensation, and it will happen faster than you can say it.

The Rheostat is not likely to be available, nor practical, given the high power demand of a Pelt (someone prove me wrong here, please!)

You should find out the power output of the GPU (I'm sure someone here knows it!). Then you pick a Pelt than you can use at 80-85% of Max (for energy efficiency's sake), to compensate for that power, but keep in mind that the heat transfer between the GPU and Pelt is not 100% efficient, so you should pick something a step more powerfull.

In essence, your stating what I already was thinking...... you were just confirming it.

I knew that the best solution was to get an external PSU for the pelt and that I should probably worry about condensation. Hmmmm........

Well, then I guess my best solution is to try a 56W pelt at 12V and get what I get. A 56W pelt should be enough to pull the heat produced from a 250+Mhz clocked core and say 550+Mhz clocked RAM chips without too much trouble. Also I think with that much heat being produced, it will be just enough to not cause a large temperature difference to produce condensation. Suppose I should just put some protection on the outside of the plate just to make sure that nothing "drips".

Hmmmmm..... wonder if sysfailur would be willing to try that experiment for me...................

Thanks for your input Bigben.

You're welcome.

I'm not sure what would happen if the pelt was underpowered. You should really find out the power rating of the GPU, just for safety's sake...

Well according to one post in another thread that I started, the "suspected" output of a GF3 core is about 20-30W. So an OC core would put out say 25-35W and OC memory will put out say 10-15W. SO, an 80W would easily do the job and a 56W should be able to keep up with it.

Can some one verify this? Please?!

I'm planning on running one of my 80W pelts on the NB and I will build a simple PI-regulator to control a high current transistor (or likeworthy component) which will apply the right amount of voltage for the pelt.
To avoid condensation i vill use two tempdevices, either thermistors or Pt-100, in a wheatstonebridge. One on the coldplate and the other outside the case to measure roomtemp.
This setup will keep the coldplate at room temp all the time and will not require a separate PSU.

It sounds like you and I should get together... I'd still isolate for condensation though, just in case. Are you planning on cooling the Pelt with air or water? I would still use a seperate PSU, just to make sure that there's no extra load that will make the PSU's voltage drop to where the mobo/cpu crashes, but hey, that's just me.

Well the NB consumes a few watts only and running it on the 12V wouldn't be that hard on the PSU.

And yes I'm going to cool the pelt with my watercooling setup.
Right now I'm trying to get my new MSI K7D master to run with the new cooling setup. Since real life is taking so much time this has allready taken 10 days. So my NB experiment won't be happening in the near future unfortunatley.

Dix Dogfight:

Your building a device that will run off the 12V line from your cases PSU that will control your pelt and auto adjust to a specific temp to avoid condensation..... am I reading that correct? If so and if you get it to work correctly, I would be very interested in either borrowing your diagrams or purchasing a unit from you.

BTW if you case PSU is big enough (over 500W) and your 12V line is strong enough (over 20A) then you shouldnt have to worry too much about causing problems with the rest of the system. Even my system with 4 SCSI HDDs, 3 CDROMS, and lots of other goodies is barely using say 10A on my 12V line where my PSUs 12V line is rated at 24A. An 80W pelt running at say say 7-8A SHOULD not cause that much of a problem (it will just be running closer to its optimal effeicency mark).

Hence the reason why I wanted to use only a 56W pelt. Then I would only be drawing about 6A all the time BUT if I can control an 80W pelt with a setup that Dogfight is talking about, that would be even better (no guess work) :)

Keep me informed Dogfight.

jtroutma:
You understood it correctly. I can send you som drawings when I get it up and running but I probably won't start working on it untill september-october. So don't wait up OK.
Cheers

Awwwwww you got my hopes up :(

Well then I guess I will just have to stick with my original idea and find a 56W pelt.

Where the HECK can you find one of those these days?!?! DangerDen, BECooling, Cooltechnica, Dtek....... almost everyone I have tried has an 80W or higher but no 56W pelts.

Can someone assist?

Well if you get the 56W or 80W you can allways add the controller at a later date so it wont be a waste of money.
Sorry to dissapoint you on my timeschedule but I'm working 60h a week right now:cry: . And i don't want to start a new proj untill the others are finished at home. The G/f isn't to happy about all my computerstuff lying about in the apartment. I think it looks really nice though :p .

About the G/F, join the club! :) I think mine is about ready to kick me out of the house pretty soon. Seriously.

But thanks for trying. Just keep me posted. Thanks

You folks appear to be intrested in a way to regulate a pelt on the fly........

Try this link : Cool stuff

Look under NEW PROJECTS and then VOLTAGE UP/VOLTAGE DOWN.......