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Few PSU Questions


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#1
Sublimistri

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I want to hook up a psu just to run a few pc fans.

Have a few questions.

1. Does the psu have to be connected to a mobo, if so, what's the way around that? (I just read something about it having to be connected but never noticed this before.)

2. If I used say a 300 watt psu, does it always pull 300 watts while plugged in or does it only pull what is needed?
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#2
rubber7

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A PSU supplies power to almost all components in your PC...so yes,it does connect to the MOBO and also the hard drives, fans, cards etc. If you want to find out a bit more about the subject and want a bit more specifics on it then check Hardware Secrets . It will give you more than enough info on what you want to know. :)
Otherwise it almost sounds to me like you are trying to use two power supplies...?
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#3
Sublimistri

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Not trying to use two psus.

Trying to hook up 2-4 computer fans to a PSU.
Nothing to do with a computer, a separate unit for powering fans.

I'm wanting to test building a small thing similar to a food dehydrator with pc fans for miracle fruits.

It's cheaper to buy a few fans and build something rather than spend 50-100 dollars on a food dehydrator.

I have a psu, the fans are really cheap.

Edited by Sublimistri, 07 September 2010 - 06:10 AM.

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#4
rubber7

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If you are only going to connect it to the fans then it shouldn't be a problem. :) The PSU supplies power but the fans normally connect to the mobo, which is fed from the psu. I also just thought of it now,if you can connect it directly to the fans it could work . Hope that answers it...

Edited by rubber7, 07 September 2010 - 06:18 AM.

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#5
Sublimistri

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k, Does the power supply if its 300 watts always pull 300 watts or only enough to power the fans?

I've always been wondering this for my pc since it seems to power a lot of stuff.

Here's what made me think I needed a motherboard
http://www.geekstogo...ide-a-computer/

Edited by Sublimistri, 07 September 2010 - 06:21 AM.

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#6
rubber7

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If I'm right ,only the fans will pull the current...It is labled 300w as that is the maximum amount of wattage it will supply to each component.
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#7
rubber7

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Here's what made me think I needed a motherboard
http://www.geekstogo...ide-a-computer/


The only problem I can think of is the on/off switch for the comp that gets connected to the board...thats the only reason why a mobo should be needed. As he said it can be done by switching wires...sounds like it could turn out to be a fun experiment! :)
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#8
Sublimistri

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"A power supply will not run without being connected to a motherboard unless you jumper a couple of wires in the connector. I think you would jumper the green wire to any black wire."


I don't really get what he is saying to do.
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#9
rubber7

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I'm a bit unsure of that as well. I'll try and see if I can't find something on it for you.
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#10
rshaffer61

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In other words the power supply has to be switched on.
Without the power switch from the system to do this you would have to hook up a switch to do it. What he is suggesting is shorting the wires that are used for the switch. hough it will work it is not advised to do this since it can cause the psu to short out and worse catch fire destroying everything connected to it.
In order to run a psu needs a load to start. Connecting just fans to it will work but you need to have a switch like the ones on a computer case to connect to the PSU so that you can turn it off and on safely.
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#11
Sublimistri

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In other words the power supply has to be switched on.
Without the power switch from the system to do this you would have to hook up a switch to do it. What he is suggesting is shorting the wires that are used for the switch. hough it will work it is not advised to do this since it can cause the psu to short out and worse catch fire destroying everything connected to it.
In order to run a psu needs a load to start. Connecting just fans to it will work but you need to have a switch like the ones on a computer case to connect to the PSU so that you can turn it off and on safely.



I have a spare case. The switch in the case requires a motherboard though don't it?
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#12
Digerati

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The best solution here is to get a PSU tester like this FrozenCPU Ultimate PSU Tester. This does several things. It puts a small "dummy load" on the power supply. Running any power supply without a decent load puts a strain on the supply, and can cause it to be unstable. The tester will also give you a pretty good idea if your PSU is working right or not. And it will allow the PSU to power on to test your fans.

Do NOT go by the colors of the wires! Although there is a recommended color coding, it is NOT a standard requirement and not all PSU makers follow it. You can only go by the pin number of the connectors - which is standardized by the ATX Form Factor Standard.

A power supply only delivers what is demanded of it. So in a computer for example, if the motherboard, CPU, RAM, graphics card and drives require 280 watts to run, the PSU will deliver 280W regardless if the PSU is a 300W supply or a 650W supply. And the PSU will draw from wall only what it needs, which will be 280W, plus overhead due to inefficiency, typically another 15 - 30%. The typical generic PSU has an efficiency rating of 70% so it will draw from the wall 364W (280 + 84) with the 84 (30%) wasted in the form of heat.
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#13
rshaffer61

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I see our resident PSU expert ( Digerati) is here so he can answer most any question you have about the psu.
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#14
Sublimistri

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would one of these work?
http://cgi.ebay.com/...=item43a006a5a6

are there other methods of getting cpu fans to work without using a psu? Or is there a name for such a fan just likea cpu fan that doesn't go in pcs?
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#15
iammykyl

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Hi.
Depending on where you are, using Google, type in 110v AC to 12v DC, or 110v AC to 12v DC.

This link > http://www.quietpcus...ter-P602C1.aspx Has axactly the type of unit you will need. I don/t know if it will power more than one fan at a time,, depends on how much each fan requires (this unit delivers up to 500mA) or if you need 1 for each fan or there may be a type to power multiple fans.

Please let use know if this works.

Edited by iammykyl, 07 September 2010 - 05:00 PM.

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