Speed Controlling a non-RPM fan?

Strawberry · 4 Mar 2010 at 20:27

Hey,

Currently I have my Noctua NF-S12B FLX (which is not RPM controllable, as it only has 3 pins) connected directly to my PSU through a downvolting adapter which drops it to 900 rpm (the adapter is from Noctua as well, was shipped with the fan).

I also have a single RPM-controllable 4-pin CPU fan socket on my mobo. Is there any way I can easily connect the Noctua fan to the CPU socket, so I can RPM control / downvolt it? What kind of adapter do I need to achieve that?

Ie. a 4pin to 3pin adapter but one that controls the voltage based on the RPM data it's getting. I'd like my fan to spin up to 1200rpm when gaming but drop to 600rpm when sleeping / 900rpm when idling.

Frozennova · 4 Mar 2010 at 20:43

if its plugged into a fan header on the motherboard you should be able to controll it via software such as speedfan as the 4th pin is used for PWM which I believe is controlled by the bios

Strawberry · 5 Mar 2010 at 11:58

Can speedfan modify the voltages? I tried using speedfan before but I've been unable to make it go any slower.

Diggsy · 5 Mar 2010 at 12:40

I think you are getting mixed up between RPM control and PWM control.

A 3pin fan is RPM controlled. The yellow wire is the RPM sensing wire. Some older ones didn't have the yellow wire, and generally these can only be controlled with a fan controller that allows voltage adjustment, or a motherboard that does likewise.

A 4pin fan is PWM controlled. This still has a RPM sensing wire, only this also has a 4th wire that allows the board to step the voltage up/down as needed.

Speedfan or similar should be able to control the RPM of your 3pin fans.

eddyc · 5 Mar 2010 at 12:46

Diggsy said:
Speedfan or similar should be able to control the RPM of your 3pin fans.

But only if the mobo allows. My mobo has one 3 pin that can be controlled by speedfan and another that cant.

Diggsy · 5 Mar 2010 at 13:03

eddyc said:
But only if the mobo allows. My mobo has one 3 pin that can be controlled by speedfan and another that cant.

Yes, thats right. Some motherboards/chipsets do not fully support Speedfan.

Strawberry · 5 Mar 2010 at 13:22

Oh yes, I was getting confused between RPM and PWM. Thanks, that cleared it up a bit.

I'll have to see if I can get SpeedFan to work though.

theron · 5 Mar 2010 at 13:36

best thing to do, honestly, is get a fan controller. cheap/expensive they are all good value for money in my oppinion. ive got 2, a scythe kaze master ace and a scythe kama panel2 (also a card reader).

.walls · 5 Mar 2010 at 15:45

Diggsy said:
A 4pin fan is PWM controlled. This still has a RPM sensing wire, only this also has a 4th wire that allows the board to step the voltage up/down as needed.

That's not how PWM works. PWM stands for Pulse Width Modulation and the voltage is not variable, instead the speed of the fan is controlled by pulses of voltage (all 12V) with the pulses being different lengths of time (width), which allows for very fine control of the speed.

Strawberry · 5 Mar 2010 at 15:50

Alright, going to buy a fan controller either way.

Something I can use in all future builds.

Diggsy · 6 Mar 2010 at 12:51

.walls said:
That's not how PWM works. PWM stands for Pulse Width Modulation and the voltage is not variable, instead the speed of the fan is controlled by pulses of voltage (all 12V) with the pulses being different lengths of time (width), which allows for very fine control of the speed.

Yes, just read that, thanks. My bad, I assumed (bad thing to do in this game

) it stepped the voltage.