Connecting fans to motherboard and/or power supply

Control: management of fans, temp/rpm monitoring via soft/hardware

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anleva
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Joined: Tue Jan 27, 2009 10:26 am
Location: Colorado

Connecting fans to motherboard and/or power supply

Post by anleva » Tue Jan 27, 2009 10:55 am

Pardon me for a newb question. This will be my first PC build and I've been researching the project on this and other forums.

I'm looking at a PC configuration that would have 3 fans (CPU cooler, intake, exhaust) in a Antec Solo case. The motherboard I'm considering has 2 4-pin fan headers on the motherboard (cpu fan, system fan). My questions:

1) Given I have 1 more fan than fan header on the motherboard would the 3rd fan (probably the intake fan) then be connected directly to the power supply? I'm assuming that's how it would need to be connected.

2) Is connecting 2 fans to the motherboard and 1 fan to the power supply the best way to go about things?

3) I'm assuming that the fan connected directly to the power supply would then be always on (while the motherboard fans could be controlled via the Bios)? Is that a problem or do I need to add some sort of on/off or control to that fan?

Thanks for your help!

relitz
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Location: sweden

Post by relitz » Tue Jan 27, 2009 11:11 am

1) Not necessarily, you could also use a 3pin Y cable on the motherboard that allows you to connect 2 fans to one connector, I'm not really sure how this works with 4pin connectors though.

2) Probably, yes.

3) You can control fans connected to the PSU by hardwiring them for 5V, 7V or 12V, or you can solder resistors to the fan cable and get pretty much any speed you want. But the fans will allways be "on" as long as you PC is turned on.

Another way of handling things is to use a dedicated fan controler, such as the Zalman MFC1 (just an example, there are tons of them).

anleva
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Joined: Tue Jan 27, 2009 10:26 am
Location: Colorado

Post by anleva » Tue Jan 27, 2009 12:19 pm

relitz wrote:1) Not necessarily, you could also use a 3pin Y cable on the motherboard that allows you to connect 2 fans to one connector, I'm not really sure how this works with 4pin connectors though.

2) Probably, yes.

3) You can control fans connected to the PSU by hardwiring them for 5V, 7V or 12V, or you can solder resistors to the fan cable and get pretty much any speed you want. But the fans will allways be "on" as long as you PC is turned on.

Another way of handling things is to use a dedicated fan controler, such as the Zalman MFC1 (just an example, there are tons of them).
Thank you. I didn't realize a Y cable existed.

Does anyone know what would happen if I connected a 3 pin fan cable directly to a 4 pin motherboard header? Would that fan still be controllable from the Bios?

I also found a 4 pin PWM Y cable via Google so another option I suppose would be to use this as well to connect 2 PWM fans to a single 4 pin motherboard header and both would have PWM control.

jmpsmash
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Joined: Sun Jul 18, 2004 9:52 pm

Post by jmpsmash » Tue Jan 27, 2009 6:46 pm

Hi,

a 3pin fan is not speed controllable via the motherboard (assuming all mb uses PWM to control fan speed). the 3 pins are ground, +12/5V and tachometer signal.

a 4pin fan is controllable via PWM.

if you plug a 3pin fan into a 4pin header, the fan will always run at full speed.

baconandeggs
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Location: New Zealand

Post by baconandeggs » Tue Jan 27, 2009 7:57 pm

i can control the speed of my 3 pin fans (connected to the mb) in the bios and also within windows using speedfan.

iirc the rear fan that comes with the solo is a 4pin molex connector antec tricool (speed adjustable, high medium low). which will leave you with the two motherboard fan headers free. one for cpu fan and other for intake.

anleva
Posts: 5
Joined: Tue Jan 27, 2009 10:26 am
Location: Colorado

Post by anleva » Tue Jan 27, 2009 8:35 pm

jmpsmash wrote:Hi,

a 3pin fan is not speed controllable via the motherboard (assuming all mb uses PWM to control fan speed). the 3 pins are ground, +12/5V and tachometer signal.

a 4pin fan is controllable via PWM.

if you plug a 3pin fan into a 4pin header, the fan will always run at full speed.
I thought I had read that 3 pin fan's could be controlled via the motherboard through voltage control. That you can control 4 pin fans via PWM RPM and 3 pin fans via varying voltage. Is this incorrect?

anleva
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Joined: Tue Jan 27, 2009 10:26 am
Location: Colorado

Post by anleva » Tue Jan 27, 2009 8:39 pm

baconandeggs wrote:i can control the speed of my 3 pin fans (connected to the mb) in the bios and also within windows using speedfan.

iirc the rear fan that comes with the solo is a 4pin molex connector antec tricool (speed adjustable, high medium low). which will leave you with the two motherboard fan headers free. one for cpu fan and other for intake.
Thank you. I was planning on replacing the tricool with a different fan. Either something like a Nexus or Scythe Slipstream or possibly a PWM Scythe fan (and the same on the cooler). So I would connect that to the system fan header and the other to the cpu header and then would need to connect the intake fan to the power supply or to the motherboard via a Y cable.

baconandeggs
Posts: 71
Joined: Mon Jan 19, 2009 1:15 pm
Location: New Zealand

Post by baconandeggs » Tue Jan 27, 2009 8:57 pm

yeah looks like your options are:
- the Y cable for the 3pin fan header for cpu fan and the exhaust
- or just use a 3pin to molex convertor for the other fan (assuming its a 3 pin plug) http://tinyurl.com/ct44pq but i think the fan will run at full speed unless you volt mod the molex adaptor
- or multi fan controller if necessary

just out of interest what make and model is the motherboard

anleva
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Joined: Tue Jan 27, 2009 10:26 am
Location: Colorado

Post by anleva » Tue Jan 27, 2009 9:15 pm

This is the motherboard that I'm thinking of going with.

GIGABYTE GA-E7AUM-DS2H

http://www.newegg.com/Product/Product.a ... 6813128363

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