PWM controlled case fans from GPU signal

Hybridtheory · 11 Oct 2012 at 00:17

I was wondering is it possible to split/splice off the pwm signal from a gpu fan and use that to control all my case fans, of which would be separately powered by a molex connector ?

I wouldn't want to alter the original GPU fan wire, but I've seen a 4 pin extension cable for GPU fans so i could mod this, then this would plug inline with the PWM signal spliced off

Is this feasible ?

Basically what i want is my case fans/or a selection of case (I have 7 in total) fans to ramp up/slowdown along with my GPU fans

What do you think ?

doyll · 11 Oct 2012 at 00:46

I think it's a good idea. Tealc is the man to talk to about doing it.

Hybridtheory · 11 Oct 2012 at 01:10

Yeah I figured he'd be the man to ask about this =D

I'll wait till he chimes in on this thread to get his thoughts on it.

It's starting to be a right pain in the backside to get out of my chair to turn my case fans down when i wanna just browse the net in between gaming lol

doyll · 11 Oct 2012 at 01:15

Hybridtheory said:
It's starting to be a right pain in the backside to get out of my chair to turn my case fans down when i wanna just browse the net in between gaming lol

I use remote desktop much of the time so not GPU but CPU I need case fan to run with. My system has been automatic for over a year now with no problems.

bremen1874 · 11 Oct 2012 at 02:51

Why can't you just use the PWM control provided by all but one of the motherboard headers?

How did you end up with a system in a Fractal R3 that requires 7 fans, and is obviously noisy enough to be annoying?

Have you just tried running the fans slower all of the time? With the number of fans you mention you should be able to keep the temperatures down to a reasonable level without having excessive noise.

Uncle Petey · 11 Oct 2012 at 02:58

It's feasible, but one problem would be the fact that gpu fans usually have very high rpm capabilities compared to most 120/140mm fans which would make it a bit difficult to get both them and the case fans doing the right thing based on one pwm signal.

Or does it work in a simple percentage manner?

Tealc may have some trickery

Tealc · 11 Oct 2012 at 07:21

I had my GPU PWM shared between my Thermalright fan and an Akasa Apache for around a year with no issues. Of course I made a special cable to do it that got the power from separate motherboard headers and gave rpm feedback for both fans.

Here's the cable I made..

As far as I can tell the GPU PWM is similar enough to CPU PWM as makes no difference. I even ran my PWM converter circuit off the GPU PWM an it gave the same result as my CPU PWM.

Connecting 3 pin fans natively to the GPU PWM will have them run at full speed, to rectify this you'd need some magical way to convert that PWM signal into a varying straight DC voltage to regulate the speed of the fans.... read on...

I have also made a PWM converter for 3 pin fans for GPUs that allows non PWM fans to be controlled via the GPU PWM signal. It's useful for the Gelid Icy VIsion as it comes with non PWM fans.

And an update the design for fully varied control

http://forums.overclockers.co.uk/showthread.php?t=18421145

doyll · 11 Oct 2012 at 10:25

the Wizard has spoken of the wonderous magic box.

Too bad my GPU is cursed and cannot use magic box.. The curse goes by the name of "Passive Cooling"

Hybridtheory · 11 Oct 2012 at 11:45

bremen1874 said:
Why can't you just use the PWM control provided by all but one of the motherboard headers?

How did you end up with a system in a Fractal R3 that requires 7 fans, and is obviously noisy enough to be annoying?

Have you just tried running the fans slower all of the time? With the number of fans you mention you should be able to keep the temperatures down to a reasonable level without having excessive noise.

TBH I've not even tried it at the moment, it is something I'm trying this week as im off work, maybe i'm looking too deep when there's a simpler solution

Well i started off with the 2x120mm fronts and 2x140mm rears and this i could have set pretty much silent with just 1x7950 oc'd hovering around 60-65c
Now i have 2x 7950's oc'd in crossfire temps are more of an issue, both cards are getting up to late 80's early 90's until i added the other case fans.

The noise of the extra case fans is much much lower then 2x Twin Frozr coolers near full whack, these are loud when over 60%

The case as it is now with 7 fans isnt terribly loud i'd just like it to be able to auto turn down to the lowest fans speeds when not gaming with out any intervention from me and up full when i do

doyll · 11 Oct 2012 at 13:23

Hybridtheory said:
TBH I've not even tried it at the moment, it is something I'm trying this week as im off work, maybe i'm looking too deep when there's a simpler solution

Well i started off with the 2x120mm fronts and 2x140mm rears and this i could have set pretty much silent with just 1x7950 oc'd hovering around 60-65c
Now i have 2x 7950's oc'd in crossfire temps are more of an issue, both cards are getting up to late 80's early 90's until i added the other case fans.

The noise of the extra case fans is much much lower then 2x Twin Frozr coolers near full whack, these are loud when over 60%

The case as it is now with 7 fans isnt terribly loud i'd just like it to be able to auto turn down to the lowest fans speeds when not gaming with out any intervention from me and up full when i do

2x 140mm rear fans? :confused:

You don't need 7 fans

Two good 120mm front fans, bottom 140mm and side 140mm should be more than enough.

Front fans are restricted by doors, vent slots, etc. (door help keep things quiet), plus the hdd cage.

Bottom and side have much less restriction but still the hole pattern is probably restricting 50% of airflow... and making noise if fans are moving much air.

With good intake fans you don't need back and top exhaust fans. All they will be doing is increasing the fan/air noise.

If you are not afraid of modding case there are several things you can do to increase airflow:
* Raise case so bottom fan can get unrestricted airflow. 50mm clearance is good.
* Remove stock bottom fan mount and use a Silverstone 140mm magnetic filter on bottom.

If you want to get real serious:
* Move HDD cage back 15mm.. assuming you have room in front of your GPUs.. or completely if you don't need it.
* Remove front fan/filter mount and install 140mm fans with Silverstone or DEMCiflex filters
* Remove vent grill from bottom and back. (my next project)

Tealc · 11 Oct 2012 at 15:22

Removing vent grills has a fairly large effect on airflow but does also allow extra noise to escape.

With two GPUs you Could have 2 boxes of magic each controlling 3 or 4 fans. That would work very well. You can even dial in a desired idle fan speed and the converter does its magic from there.

I have some spare GPU connectors of both types.

I've had multiple different types and speeds of fan running of my circuit without issues, although it does get a touch warm when loads of fans are fitted.

doyll · 11 Oct 2012 at 16:00

Tealc said:
Removing vent grills has a fairly large effect on airflow but does also allow extra noise to escape.

I think the disruption of airflow by most grilles creates more air noise than the noise they are stopping.

That's normal stamped round or octagonal hole grilles.

Now if you mean the baffled grilles on a few cases, yes. they do baffle/dampen the internal noise.

Example:

Opening up the front door and grille/filter cover of a Define case.

If CPU / GPU coolers are big enough to cool with low rpm fans there is very little noise inside the case. HDD noise is usually the vibration resonance as they read/write, not their motor. Without good vibration mounting they become the drum sticks and the case is their drum.

Hybridtheory · 11 Oct 2012 at 19:33

I been messing this afternoon and it appears that my new corsair tx850 psu is probably the loudest fan i have in my case :mad:

looking around on the net seems like others have it too.

After that my side intake is the next loudest, all the other are pretty quiet, maybe i should cut the honeycomb section out ?

I heard Fractal were doing replacement side panels that were windowed, I've not seen any available to buy tho of know if they have fan holes cut

Tealc · 11 Oct 2012 at 19:38

One small issue with cutting out the honeycomb on side panels is that they will lose some of their rigidity. It might not be much of an issue for an R4 but it certainly might be for some other cases.

If you do go cutting up your case side panel do make sure you get some U channel moulding for the jagged edge and a Dremel would be handy for the cutting. I used a pair of tin snips for my front fan slots and rear but as they are mostly hidden by the door and dust filter, and for the rear, obscured from view I was't too bothered about how they looked afterwards.

See how it looks. Bit squared off.

doyll · 11 Oct 2012 at 19:41

Corsair and their quote:

Ultra-quiet 120mm (140mm on TX750W and TX850W) double ball-bearing fan delivers excellent airflow

Yeah, right!
Total carp!

doyll · 11 Oct 2012 at 19:53

Tealc said:
One small issue with cutting out the honeycomb on side panels is that they will lose some of their rigidity. It might not be much of an issue for an R4 but it certainly might be for some other cases..

Can be an issue with side panels for sure... and tops. But a round hole usually doesn't do too much structural damage... and a wire grille replacement with fan mounted on other side help strengthen it.

Best tool for removing vent grilles is a hand nibbler
Klein Nibbler are best but hard to find here.

Not a Klein but serviceable

But you can see how they work.
Nice clean cuts

This kind are no where near as good to use.. And need more space to work with.