Peltiers

[Guest]

I'm thinking about building a peltier/water cooled system and have two questions. 1) how do you connect the peltier to the power supply if it comes with just "bare" wires. also the peltier i am thinking of getting draws a lot of current, 11.3 Amps. are there any power supplies that can handle this or do i need a seperate one for it.

2) i would like the peltier to turn on only after the processor has reached a certain temp so i don't freeze and crack the chip. i have heard that this (temp control) is possible but can anyone help me find the right equipment to do this.

i had a drink the other day... opinions were like kittens i was givin' away

 

[Grizely1]

if the peltier only turns on at a certain temp, what would happen the peltier is off? there would be nothing to cool the cpu, therefore the temperature would rise quickly anyways so there is really not point.

---------
Grass is a beautiful weed

 

[Guest]

huh? maybe i wasn't clear, but the peltier would turn on when the cpu hit the threshold level... so yes there is a point... not damaging the cpu.

i had a drink the other day... opinions were like kittens i was givin' away

 

[Guest]

Use a cold block (solid copper block) on your cpu and the peilter on that. Peltier to cpu is dangerious but not if you have the cold block between them.

 

[Ncogneto]

I would highly advise against any circuitry that would cycle on and off via temperature control. Just one more component to fail. I assume that you wish to use a peltier then cool the hot side of the pelt via water cooling is this correct? First we need some details, what voltage is the pelt? 12v? At 11 amps you probably would need a seperate power supply ( if you have one in the range of 300 watts now) seeing how you are drawing nearly 135 watts just for the pelt itself. If I am reading this correctly your concern is when using the second power supply for the pelt it is concievable that the pelt could be on while this system is not, thus giving excessive cooling and possibly damaging your CPU. As long as the CPU is on this should not be a problem ( otherwise how can they use liquid nitrogen??) What you need to be sure of is that the pelt and the CPU both turn on and off at the same time. This could be accomplished several ways, the easiest being getting your self a mammoth power supply ( 500 watts plus ). It used to be with the older power supplies they came with a funny looking plug that was used for connecting the 115v of the monitor directly to your power supply, which would in term shut the monitor down when you turned your computer off. I don;t recall seeing this plug on any atx power supplies but they very well may exist. If you could find such a power supply you could run this into a second power supply(AT) and use this just for your pelt.

A little bit of knowledge is a dangerous thing!

 

[Guest]

yes i am worried that with an additional power supply the peltier will be on when the cpu is not (even if they turn on at the same time it seems possible that the peltier could freeze the processor before it warms up) and i will be cooling the hot side with a water cooler. i don't see why a temp control device is any more likely to fail than an additional power supply, but agreed the less components the better. Vmax for the peltier is 24.6V, Imax is 11.3 and Qmax is 172W. Antec has a 400W power supply that at +12V can handle 17A and at -12V can handle 1A. it seems that this is sufficient for the amperage but will i have enough power left over?

i had a drink the other day... opinions were like kittens i was givin' away

 

[Ncogneto]

I would stick with what I suggested and I checked and one of my machines has such a plug on the power supply ( 350 watter) form this you could run any dc power supply that ran of of AC 115 volts. Seeing how an athlon can literly fry itself in 2 seconds without a heatsink I would not worry about it getting to cold upon power up. I really don't even think that a pelt can get cold enough to do damage anyways, remember they are rated in heat displacement not minimun temps. With a temperature activated device the question is would it be quick enough...remember if a two second lag then poof!

A little bit of knowledge is a dangerous thing!

 

[Guest]

i'll give it a shot... thanx


i had a drink the other day... opinions were like kittens i was givin' away

 

[peteb]

You'll never freeze and crack and CPU.

Most cpus will heat almost instantly (a top AMD cpu is like 40A or something). There is little to cool a cpu in a peltier setup unless the peltier is running.

The coldplate next to to the cpu will absorb a little heat, but then the peltier has to take over. If the peltier is off, it insulates...

You can wire your seond PSU to power on from the first, preventing energy wasting. The changes are you'll need a stupendously big PSU to run a 170W TEC + decent PC setup + watercooler...

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[Guest]

A peltier's construction is incredibly poor at conducting heat when no voltage is applied... they are two ceramic (awesome insulator) plates, with little bits of metal glued between. When you switching hardware turned the peltier off, the heat from the processor will basically have nowhere to go but the coldplate/heatspreader... some heat will migrate through the ceramic of the peltier, but not that much-your circuitry designed to prevent cracking the processor will actually be responsible for frying it. Now, a few principles are it work in doing something like cracking a processor. Mainly, differences in thermal expansion rates of different materials should be considered. Also, the rate at which the temperature change occurs. If you take a hot glass, and run cold water over it, it will crack, due to the rapid change in temperature. If you run hot water over it, then gradually cooler, you will bring the temperature of the glass down and it won't crack from contraction. The same principle, in reverse, can be applied to using heat pumps or other forms of supercooling. As long as the temperature change is gradual, cracking won't be a problem. Many people even fire their peltiers up before they boot their computer when they're trying to get amazing overclocks, with no ill effects, since the peltier gradually cools the chip to a ridiculous temperature. Now, if you had your hands on some liquid nitrogen, and dumped it on the chip, it _will_ crack, since the temperature change was so rapid. As for powering the peltier... they don't come with molex connectors for a good reason. Most computer PSUs aren't really up to the task. A good place to look for high current 12V power supplies is the ham radio market. Good luck, hope I was of some assistance, even if I'm loquacious.

3C2X1(<b><i>Genius</i></b>).
Even though I'm a newbie, at least my average post is intelligent!

 

[ejsmith2]

Check down at the local grease monkey shop for a 'slighly dented but still in good condition' battery charger. Chargers are the way to go for powering peltiers, because you don't need particularly 'clean' power. The one I'm using now churns out 14.2 volts, and cost me $25 plus a cooling fan. You can always mod it for higher than stock voltage, but you might shorten the lifespan.

 

[Guest]

2) i would like the peltier to turn on only after the processor has reached a certain temp so i don't freeze and crack the chip. .....

You have it backwards. Some Systems like the VapoChill have a delay to not power up the CPU until it is Cooled.

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[Bud]

What CPU are you talking about? An Athlon 1G+ will go from zero to fried in about 5 seconds without heat transfer.
So why would you want a delay?


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