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# cooling and power supplies...

### #1 visily Posted 23 July 2005 - 02:54 PM

visily

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Power supply.

I do not have access to a voltage meter, and am going hypothetical here.

Assuming that 12v comes out of a power supply lead, then hooking up two connectors, from one lead would still give 12v. and two connectors from different leads would give 24v?

The question leads from two differnt thoughts. One is that the video card I have, Gforce7800 is power hungry, and second is that I was looking at adding Peltier cooling.
The GeForce askes for two power cables, yet I cannot find any specs on what the actual input they want is.
The peltier needs 24v @ 32 Amps.
Could I power both of these off of two power leads??

Thank you for the help.
D
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### #2 Samm Posted 25 July 2005 - 03:44 PM

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firstly, in answer to your question re. 2 lots of 12v making 24v:
this all depends on how it's wired up, ie in parallel or in series. In series the voltages add up, in parallel the voltage remains the same.
The same applies with the components on a series/parallel circuit : eg 2 12V components on a 12V circuit must be wired in parallel in order for both to receive 12V each

I don't know how you are proposing to hook up 2 psu's together but I don't like the sound of it.
As far as I know, most Peltier coolers for PCs run off of 12V. I would imagine that if the one you have in mind does indeed require 24V, then it will take this from 2 seperate 12V connectors on the same PSU.

As for the Geforce, this again will require a 12V rail, and possibly a 5V rail.

If you are concerned about the amount of power your system is drawing & whether the PSU can handle it, I suggest you buy a bigger PSU (eg 500 - 600W). The value you really need to look out for are the max currents provided by the 12V & 5V rails, and the 3.3V + 5V combined rating
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### #3 visily Posted 25 July 2005 - 05:23 PM

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Thank you Samm,

To clarify.
I was only planning on using one PSU.
The PSU has disconnectable leads(modular). I was thinking that the modular lead would each provide 12v, but I think that depends on the internal circuitry.
I have not been able to get the schematics for the PSU. Due to that fact I do not have any idea if I could in fact wire them in parallel or series.
The GeForce has its own y connector to attach two molex to the board. The reason I was wondering about the parallel or series in this case was to see if it was getting the power requiered. Since there is no distinction in the instructions that I found, between hooking them up in either fashion, I assume that I cannot hook them up in series. At least there is no warning for attaching them in series and overloading the board.
Through this, albiet faulty, logic I think there is not a practical way to attach to 24v inside. Perhaps the peltier will function fine @12V, but I will contact thier manufactuerer for that info.
Thank you for your time and help.
D
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### #4 Samm Posted 25 July 2005 - 07:56 PM

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You're welcome.
If the geforce card has a Y splitter for the power, this is effectively parallel wiring so it should be fine!

Samm
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