using cpu pwm control for case fans

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

Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee

Post Reply
lesticx
Posts: 47
Joined: Thu Jan 28, 2010 3:31 am
Location: Finland

using cpu pwm control for case fans

Post by lesticx » Tue Sep 14, 2010 9:33 am

Hi,

I have a mobo that supports pwm control on cpu, but there's no pwm control for case fans.
I thought about splitting the cpu fan control to add 2 pwm case fans to this same control.

would this work?

datapappan
Posts: 199
Joined: Wed Nov 10, 2004 1:44 pm
Location: Sweden

Post by datapappan » Tue Sep 14, 2010 10:26 am

It works, if the fan header can give enough current. Usual figure is 3 W (= 0,25 A @ 12 V), you'll see the rating on the fan hub. Some mobos even declare the rating of the fan header. As you might know, the splitter only has one RPM-cable - you don't need the RPM to control the fan, but it's nice to know.

Hth, d
[size=75][CPU: 2.4 GHz P4 Northwood w. AC Freezer 4 (fanless-Bluefront PSU mod inspired) / MB: ABIT VT7 (Via PT880) / GPU: ATI Radeon X800XL w Zalman ZM80D-HP / HDD: Seagate Barracuda IV SATA 80GB / CD: Samsung CD-DVD combo / Seahawk ALU Case / PSU: FSP 350-THN (fan mod-Everflow connected to CPU fan header)[/size]

JamieG
Posts: 822
Joined: Fri Dec 26, 2008 10:31 pm
Location: Melbourne, Australia

Post by JamieG » Tue Sep 14, 2010 3:21 pm

Akasa makes a PWM fan splitter cable - Google it and you should be able to find some shops stocking it.

Otherwise, Arctic Cooling's PWM fans have an integrated PWM splitting cable that allows multiple PWM fans to be chained together and run off a PWM-capable fan header, like the CPU_FAN header.
My PCs:
Main PC (E5200, G31, Lian Li Q07) | Gaming PC (E6850, X38, 5870 Vapor-X, P182) | HTPC (4850e, 780G, 3450, NSK2480B)

lesticx
Posts: 47
Joined: Thu Jan 28, 2010 3:31 am
Location: Finland

Post by lesticx » Fri Sep 17, 2010 3:03 am

Heyhey, I found that akasa splitter from a local seller for 3 euros :)

In general, is this a good idea?

Who has done this? using pwn fans as case fans? What's your experience?
Is this better than say just 5-volting regular case fans, or using a manual fan controller on case fans?

Is it silent? Do the temperatures keep low?

Klusu
Posts: 196
Joined: Thu Jul 24, 2008 10:57 am
Location: Riga

Post by Klusu » Fri Sep 17, 2010 6:41 am

2 or 3 fans changing speed simultaneously can be annoying.

BlackWhizz
Posts: 266
Joined: Wed Mar 31, 2010 8:19 am
Location: OV, The Netherlands

Post by BlackWhizz » Fri Sep 17, 2010 7:57 am

lesticx wrote:Heyhey, I found that akasa splitter from a local seller for 3 euros :)

[..]
Is it silent? Do the temperatures keep low?
Silent it is. Temperatures are low enough for the Bios.

But its annoying. If multiple fans are ramping up the noise increase is annoying.

In my experience running all fans on one speed (using a fan controller) is the most unannoying way.
My quiet P180 Mini PC
Q6600 Xigmatek HDT-S1283 + TR Bolt Thru | MSI R5770 (soon a)Arctic Accelero S1 rev 2 | 4Gb ram | Asus P5Q-VM | 2.6TB storage | OCZ ModXStream Pro 500w

lodestar
Posts: 1683
Joined: Fri Aug 05, 2005 3:29 am
Location: UK

Post by lodestar » Fri Sep 17, 2010 8:00 am

This is quite a common practice, particularly amongst gamers, where splitter cables are used to create chains of two or three PWM fans,

A chain of PWM fans is driven by the CPU temperature. So it is a thermal control system and will be affected by other factors which affect CPU temperature including ambient temperature. At idle all the fans will run at a low speed, typically around 500 rpm. Under load all the fans will increase in speed. On gaming systems with high end graphics cards I have seen top speeds of around 1100 rpm on a fairly demanding game like Crysis Warhead.

To some extent PWM fan chains are a more convenient alternative (and lower cost) alternative to a manual fan controller. Bear in mind that many gamers use large screen TVs rather than the traditional monitor, and also use wireless keyboards, mice and controllers. So they are not necessarily near to the PC, and need the automatic control that PWM chains bring.

Both PWM chains and manual controllers involve fan speeds increasing as system loads increase. Particulary for gaming systems the increase in speed will not be apparent, since most gaming is fairly noisy. Also bear in mind that a PWM chain will increase fans speed if ambient temperatures rise.

The problem with fixing fan speeds by resistor cables is where do you fix them. If you set it too low then components may run hotter than you want, and certainly there is a risk of over-heating if ambient temperatures increase as well. Fix fan speeds at around 800 rpm say, and it will result in more noise than a PWM chain at idle. Equally it may not be fast enough if you have a high performance graphics card.

There is nothing to stop you from starting with a PWM fan chain using say the Akasa splitter cable, which takes power for all the fans from a molex and not the motherboard. If having tried it you decide you want manual fan control, you could keep the PWM chain and use software such as CPU ID HWMonitor Pro. Or you could still use resistors to set fan speeds to a specific level.

Having tried all the options, I now use PWM chains on my own systems and those that I have built for my gaming relatives. Frankly it is the easiest and most economic method, and using resistors I could not even at 5v get fan speeds down to the levels that PWM will produce.

I accept that some people simply don't like the idea of fans increasing in speed automatically. For them I still think the best option is to use a PWM chain and HWMonitor Pro (or SpeedFan) to fix speeds exactly where they like. This gives a lot more control than resistors, and is certainly cheaper and more convenient.

JamieG
Posts: 822
Joined: Fri Dec 26, 2008 10:31 pm
Location: Melbourne, Australia

Post by JamieG » Fri Sep 17, 2010 6:01 pm

PWM fan speed control with a splitter cable is a basic solution for load or temperature based fan speed changes. Unless you use SpeedFan or similar software to tweak fan speeds at certain temperatures, you are limited by your motherboard's BIOS settings related to PWM fan speeds and CPU temperatures.

For my gaming system, I use a Scythe Kaze Server fan controller in semi auto mode to control most of my fan speeds based on temperature probes stuck onto my graphics card, with a rear exhaust PWM fan on my CPU header. I have set it so that once my GPU temperatures rise enough (triggered by gaming or articifical GPU load), the fan speeds rev up from about 500-600rpm to about 1,000rpm.

Anyway, I don't see a problem with using a PWM splitter chain for all of your fans, but you will need to match it with software to get the fine control that you would otherwise get from a fan controller. Otherwise, you will be stuck with a random increase in fan speed based on CPU temperatures.
My PCs:
Main PC (E5200, G31, Lian Li Q07) | Gaming PC (E6850, X38, 5870 Vapor-X, P182) | HTPC (4850e, 780G, 3450, NSK2480B)

Japesgalore
Posts: 71
Joined: Sat May 21, 2005 12:34 pm

Yes, it works!

Post by Japesgalore » Sat Sep 18, 2010 12:17 pm

Using the Akasa splitter I've managed to hook up 5 case fans to the CPU header. I use a simple 2-way splitter as well as an Arctic Cooling PWM fan to get everything hooked up. I think the power you get from one molex is plenty to power a whole bunch of fans...just daisy chain away!:) Unless anyone can correct me on this?

The result is, in fact, a dream PC in terms of silence (ok more like extreme quietness). Think I'll post about it soon in the gallery. PWM can go a whole lot slower than voltage controlled, I don't have to mess with fan controllers and the reaction time is pretty much instantaneous, going to just the right level without me having to worry and overcompensate.

System is i5 760 @ 3.5ghz (with EIST enabled) on Gigabyte P55A UD3R and ASUS EAH5850 DirectCU (although the fan was bust so I put a AC Twin Turbo PRO on it, using MSI Afterburner to get fan down to 15% at idle - at 25% it was ever so slightly audible) in a modded Silverstone TJ06 case, with Corsair TX650 PSU.

The GFX card mod was the most recent mod that took the silence to the next level (the old fan was scratchy sounding, but I couldn't be effed to RMA it - it's better suited to overclocking now anyway). It's a blessing compared to the fan-controlled setup I had on the dieing AMD 939 system that was in the same case, and I have PWM to thank!

lesticx
Posts: 47
Joined: Thu Jan 28, 2010 3:31 am
Location: Finland

Post by lesticx » Mon Sep 20, 2010 4:05 am

Sounds great! Looks like this will be the best way for me to go.

What's the current draw of arctic coolings pwm fans? How much current does my mobo need to provide, if I wanna daisy chain 2 or 3 of these fans?
I couldn't find this figure at their website.

Redzo
Posts: 464
Joined: Thu Jan 26, 2006 1:51 am
Location: Sweden, Stockholm

Re: Yes, it works!

Post by Redzo » Mon Sep 20, 2010 7:00 am

Japesgalore wrote:Using the Akasa splitter I've managed to hook up 5 case fans to the CPU header. I use a simple 2-way splitter as well as an Arctic Cooling PWM fan to get everything hooked up. I think the power you get from one molex is plenty to power a whole bunch of fans...just daisy chain away!:) Unless anyone can correct me on this?
Nothing to correct there, you are right. A molex can power more fans then anybody in there right mind would need (including serious overclockers).

lodestar
Posts: 1683
Joined: Fri Aug 05, 2005 3:29 am
Location: UK

Post by lodestar » Mon Sep 20, 2010 7:40 am

lesticx wrote:What's the current draw of arctic coolings pwm fans?
Arctic don't say, but they do say that you can daisy-chain a maximum of 5 fans. So I would say that 2 or 3 should be absolutely fine in terms of motherboard power draw.

Arctic PWM fans use their own form of signal amplification, so they do not work with PWM splitter cables such as the one from Akasa. They are the cheapest way of creating a PWM fan chain if you can find them in stock locally. The F12 (non-Pro model) for example can be around €5 each. You do end up with all the fan sockets plugged into the single motherboard CPU PWM header which can be cumbersome. Each fan comes with a separate yellow rpm sensing wire. You normally only use the one for the CPU cooler fan, and it is plugged into the end unit of the group of fan sockets.

A PWM splitter cable gives you a wider choice of PWM fans. Assuming that you are willing to pay a bit more than the cost of the Arctic fans, I would recommend that you consider buying the Akasa cable and the Scythe adjustable PWM fan from sources such as this one http://www.aquatuning.fi/product_info.p ... 25mm-.html. This fan is shipped with the Scythe Yasya and Ninja 3 CPU coolers, see the SPCR reviews of these coolers for details. With the adjustable PWM feature you can set the idle speed of the fan where you want it, and still have automatic PWM control.

lesticx
Posts: 47
Joined: Thu Jan 28, 2010 3:31 am
Location: Finland

Post by lesticx » Wed Sep 22, 2010 1:44 am

Hmm, lets see about making a pwm splitter, since this akasa thing seems to be out of stock everywhere.

Is it like this:
the splitter takes pwm control and sense from motherboard header, which would be pins #3 & 4 according to this
http://pinouts.ru/Motherboard/mb_pwm_fan_pinout.shtml

Take the 12v and ground from a molex, and split these to all the fans - make a parallel connection.

Doesn't seem too hard :) I'm always been one for good cable management.

themaster1
Posts: 95
Joined: Fri Apr 23, 2010 9:01 pm
Location: Southern France

Post by themaster1 » Wed Sep 22, 2010 5:25 am

Are we talking about premium / deluxe version motherboards here ?
Someone's confirmed he's fried his when he played with the fan header, i wouldn't try on mine for example (standard mb).

lodestar
Posts: 1683
Joined: Fri Aug 05, 2005 3:29 am
Location: UK

Post by lodestar » Wed Sep 22, 2010 11:42 am

lesticx wrote:Hmm, lets see about making a pwm splitter
The PWM splitter supplies one fan with PWM control and fan speed sensing, the others have PWM control only without fan speed sensing. Yes you could supply the power separately like Akasa, but you end up with a mess of thin fan wires. You are also dealing with black and dark blue wires so there is the potential for mistakes.

I would recommend the Arctic Cooling F12 fans as the next best alternative if you can't get a PWM splitter.

lesticx
Posts: 47
Joined: Thu Jan 28, 2010 3:31 am
Location: Finland

Post by lesticx » Fri Sep 24, 2010 1:49 am

lodestar wrote:
lesticx wrote:Hmm, lets see about making a pwm splitter
The PWM splitter supplies one fan with PWM control and fan speed sensing, the others have PWM control only without fan speed sensing. Yes you could supply the power separately like Akasa, but you end up with a mess of thin fan wires. You are also dealing with black and dark blue wires so there is the potential for mistakes.
Come on, it's not that difficult :) I'm also an electronics engineer, so maybe I' m more qualified to do this..

Das_Saunamies
*Lifetime Patron*
Posts: 2000
Joined: Tue May 15, 2007 1:39 am
Location: Finland

Post by Das_Saunamies » Fri Sep 24, 2010 4:49 am

+1 for the Akasa PWM splitter cable. It works. (and has very poor quality plastic and connector design, typical Akasaâ„¢)
Case: Define Mini
Parts: P8Z77-M Pro µATX, i5-3570K, STRIX-GTX960-DC2OC-4GD5, 8 GB G.Skill DDR3U, Xonar DX, WD B-G 1 TB, mx100 256 GB, RX-5300 PSU
Cooling: Noctua NH-U12P SE2 + Scythe SS PWM, 2x Noctua NF-P12
Extras: Eaton UPS, Dell 24" EIPS, MS Sculpt, Logitech G303, Synology DS213j 3+3 TB NAS

lesticx
Posts: 47
Joined: Thu Jan 28, 2010 3:31 am
Location: Finland

Post by lesticx » Wed Sep 29, 2010 12:32 am

Well, that was easy :)

I just plugged the two case fans into motherboards 3-pin case fan headers, and then i split the pwm-signal from cpu fan header into these two fans.
Now I have 3 fans, all are pwm-controlled, and I can read the exact speed of each fan as well :)

themaster1
Posts: 95
Joined: Fri Apr 23, 2010 9:01 pm
Location: Southern France

Post by themaster1 » Wed Sep 29, 2010 4:11 am

lesticx wrote:Well, that was easy :)

I just plugged the two case fans into motherboards 3-pin case fan headers, and then i split the pwm-signal from cpu fan header into these two fans.
I don't get it
Once the two fans are connected to the 3pin fan headers how can you connect the "control" wire from the cpu header, practically speaking...

lodestar
Posts: 1683
Joined: Fri Aug 05, 2005 3:29 am
Location: UK

Post by lodestar » Wed Sep 29, 2010 4:53 am

That's quite a neat solution. The 3 pin fan header provides 12v power (black and red wires), and fan speed sensing (yellow wire). The 4 pin PWM fan connector has an additional PWM control wire. So you just remove the PWM fan control wires from the additional two fans using a small screwdriver or the correct tool, and connect them to the CPU fan PWM control wire. Gives you a PWM fan chain without a splitter cable, each fan draws its own power and there is a fan RPM reading for each fan too.

themaster1
Posts: 95
Joined: Fri Apr 23, 2010 9:01 pm
Location: Southern France

Post by themaster1 » Wed Sep 29, 2010 5:40 am

I see, that's some kind of MacGyver type of work with wires cut, other parts half-open, hanging in the air lol.This don't sound appealing to me but i suppose when it's cheap one has no rights to question such design , eh ?

lodestar
Posts: 1683
Joined: Fri Aug 05, 2005 3:29 am
Location: UK

Post by lodestar » Wed Sep 29, 2010 8:01 am

Not really. I don't know if you have ever removed a fan wire from a connector, but it does not involve cutting. What is being suggested here can of course be done without removing any fan wires at all. You could just run additional PWM fan control wires from the CPU fan connector to each of the case fan connectors. So just a couple of wires with a connection at each end, and a minimum of work and disturbance. So a really neat solution from lesticx, in every sense of the word.

themaster1
Posts: 95
Joined: Fri Apr 23, 2010 9:01 pm
Location: Southern France

Post by themaster1 » Wed Sep 29, 2010 8:43 am

Yeah, i'd need HQ pictures to have the confirmation of such assertion.

By the way, i have already pointed out the major problem of such "MacGyverism": the temps sensor. Assuming you only got 1 pwm-able header (more often than not the cpu header) it read the temps of the cpu only. So based on that only why would one control the gpu or hdd's fans? Makes no sense from an efficiency standpoint.

Arbutus
Posts: 234
Joined: Wed Jun 02, 2010 9:15 pm
Location: Calgary, Alberta, Canada

Post by Arbutus » Wed Sep 29, 2010 9:27 am

I've never had any trouble running 3 low current fans on the CPU fan header. The stated current requirement on the fan's label is the worst case startup current draw. Fans use approximately 1/2 the startup current when running. Mainboard manufacturers aren't making a commitment about the capability of the cpu fan header, but current conjecture is that there is at least a 500ma capability. Some evidence of this capability is evidenced in that the factory supplied fan on the Pentium 840EE is rated at 420ma (which would be the startup current). Currently I am using 3 Gelid Silent 12 fans on PWM y-adapters to the Cpu fan Header. The current on the label says 0.18A. I have not had any startup problems. There are quieter fans than the Gelid Silent 12 PWM, such as the fan that accompanies the current Ninja and Mugen models, but my ASUS mainboard complains if the fan speed drops below 600 rpm.

lodestar
Posts: 1683
Joined: Fri Aug 05, 2005 3:29 am
Location: UK

Post by lodestar » Wed Sep 29, 2010 10:01 am

themaster1 wrote:Assuming you only got 1 pwm-able header (more often than not the cpu header) it read the temps of the cpu only.
It's a fair point that PWM fan chains are usually tied to the CPU temperature. But how hot the CPU gets is normally a good guide to what load the system is under, and the whole point of PWM fan chains is that you get automatic variable case air flow based on system load. This ties in with for example modern motherboards which underclock and undervolt CPUs at idle, but will switch on additional cores and/or Turbo modes when more load is put on the processor.

The most common PWM chain is I suspect the CPU fan plus the exhaust fan, but it can be useful to add an intake fan (or a side fan if the case supports it) if you have a performance graphics card. While there are some issues over the degree of BIOS control, the main benefit of PWM chains remains the automation.

I agree that the lesticx solution for PWM fan chains may not be for everyone, but to me it seems a bit unfair to describe it as "MacGyverism". If it's not for you there are the off-the-shelf alternatives.

lesticx
Posts: 47
Joined: Thu Jan 28, 2010 3:31 am
Location: Finland

Post by lesticx » Wed Sep 29, 2010 11:48 am

Haha, thanks! I'm quite happy about my solution, and it does work.
I actually ended up cutting the blue wires (that's the pwm signal wire) of the case fans and soldering them together with the cpu fan signal wire. Not much work, and you can measure the wires so you end up with neat wires - instead of a mess of wires from an off-the-shelf splitter.. The solder isn't probably that necessary, there's not much current in these wires, you could just use heatshrink to join them together.

I'm using this for intake (120mm nexus) and exhaust (92mm nexus) fans.

Lol, you really don't need to be Macgyver to do this, but man, I'd love to be Macgyver! :)

Post Reply