Which sensor do you match your case fans to?

Relentless81

Relentless81

Relentless81

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Joined
18 May 2010
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Hi,

This is driving me nuts and I'm sure its simple and I'm over thinking it but was wondering what everyone else does?

On my previous system I matched all my case fans to CPU, CPU ramps up and so do case fans which was perfect.

On this system my CPU tends to spike the temp whilst doing basic tasks such as browsing the internet, this is driving me nuts because the case fans are ramping up and down all the time, not much I can do about the CPU as its a part of XFR so I tried to set a manual fan curve for the case fans but this has no effect what so ever, case fans just sit at minimum RPM and dont ramp up with the CPU temp, probably a BIOS issue that will be fixed eventually, switch it back to preset manual or silent and they match the CPU again

So I'm wondering, if I match the case fans to the System Temp (Motherboard temp sensor) the case fans dont ramp up under basic tasks which is great, but this sensor always seems to sit around 30C so how are the fans supposed to ramp up if the temp doesnt increase by much if at all?

And what is weird is the plot for all the sensors is the same, eg -

I set Case fan to CPU and the chart makes sense.

I set Case fan to System Temp and the chart remains the same as the CPU and makes no sense.

Its funny how something so simple is so time consuming and frustrating!

Cheers
 
With new motherboards having many more fan headers I would think their source heat to rpm curves could be setup as need, but your not getting them to work.

What you describe sounds like your minimum airflow is set too low causing CPU to build up heat enough to raise fan speed. Have you tried raising the minimum fan speed in the curve to keep enough airflow through system?

You might find this basic guide to case airflow of interest.
https://forums.overclockers.co.uk/t...-i-put-my-temp-sensor.18564223/#post-26159770



I usually use PWM fans for everything, then use PWM 'Y' splitter or hub controlled by CPU fan header for intakes & exhuasts supplying CPU airflow on CPU curve and intake & exhaust fans for GPU airflow controlled by GPU fan header. I've been doing it this way for donkey's years.


Here's a basic guide how fan's percentage PWM to RPM are all different. Also the adapters, splitters and hubs I use.

PWM Fan Independent Speed Curve
PWM fan rpm is not a fixed ratio or percentage of PWM signal. The PWM signal to rpm is part of the programming in PWM circuitry built into each PWM fan.
Here are some examples. Black graph line (top line in chart) is fan rpm; PWM % is shown across bottom of chart. Notice how all of these fans are flat-lining at idle at different minimum fan RPM. PWM% signals below this minimum fan RPM have no effect on fan. Also notice how the PWM% to rpm is not a the same progression for each fan .. it is not a linear progression, but is instead a custom progression that is programmed into each fan's internal PWM circuit. ;)
PWM%20-%20RpM%20curve%20differences_zpswrkbkcd4.png


All graphs are from Thermalbench.com fan tests and reviews.

Normal PWM Splitter with PSU Power & Auxiliary RPM Plugs
PWMSplitterwithPSUPower_zpsb169bbca.jpg


How to Monitor RPM of Fans on Splitters & Hubs
LL


Controlling case fans with PWM signal from motherboard CPU fan header and GPU fan header.

There are some limitations:
  • Obviously motherboard and GPU must have PWM
  • Obviously fans must be PWM
  • Motherboard can only support 8-9 fans (PWM signal strength gets too weak)
  • No idea how many fans GPU can support.

Setting up motherboard PWM control of PWM case fans:
  • Use a PWM splitter with molex/sata connector. Gelid and Swiftech are my preferred. I do not use Akasa PWM splitters because their wire temination into connectors is very poorly designed. Look at one and you will notice all wire distribution is at the connector .. all flex and load is at connector .. while ones like Gelid have cable distribution away form the connectors.
    https://images.********.co.uk/********-4897025780460.jpg
    LL


  • Plug PWM splitter to motherboard CPU fan header and PSU
  • Use CPU cooler fan as "master" fan. This is the fan that sends rpm signal to motherboard PWM header.
  • Additional CPU cooler fans and case fans will ramp u and down with CPU fan.
  • Can use a second PWM splitter on 3-way & 4-way PWM splitter.
  • Setup fan speed curve with motherboard bios or software. Gigabyte has EasyTune 6 and Asus has SmartFan. I set minimum at 30% fan @ 30c and maximum at 100% @ 65c. Than watch temps and see if you want more or less rpm to keep temperature and noise where you want them. My sig rig idles 24-29c @ 700rpm; 100% all cores is 42-48c :950-1050rpm.

Setting up GPU PWM control of case fans:
  • Obviously GPU fans need to be PWM. Because the GPU PWM header/plug is smaller than normal PWM we need a Mini 4-Pin GPU (Female) to Mini 4-Pin GPU (Male) / 4-Pin Fan (Male) Cable Splitter Adapter is needed-. The blue wire going to normal PWM socket needs to be cut off of mini PWM plug. (You can use this wire to monitor rpm on case fan by connecting it to a normal 3pin fan plug in the rpm position.) Plug a PWM splitter into the normal PWM socket and PSU for case fans.
    PWMsplitterGPU_zps3b602058.jpg

  • Case fans hooked onto this splitter will ramp up and down with GPU fans.
  • Use GPU software or Bios to setup fan speed curve


modDIY has several adapters and splitters for this, including mini 4-pin PWM adapters and Mini 5-pin PWM adapters

GPU PWM to Normal PWM Splitter with PSU Power & Auxiliary RPM Plug


modDIY has several adapters and splitters for this.
mini 4-pin PWM adapters
Mini 4-Pin GPU (Female) to Mini 4-Pin GPU (Male) / 4-Pin Fan (Male) Cable Splitter
700
[/URL]
LL

Mini 5-pin PWM adapters
5-Pin VGA PWM Mini PH Connector to Dual PH Mini 4-Pin Fan Cable Splitter
700
[/URL]

5-Pin VGA PWM Mini PH Connector to Dual PWM 4-Pin Fan Cable Splitter
LL

and this
LL
Click to expand...
 
Last edited:
Thanks for the detailed info, I get what you're saying but let me try and explain a little better -

All fan headers are PWM and tied to CPU temp, 2 x Noctua AF14 intakes and 1 x Noctua S12 exhaust

I've changed minimum air flow from 550rpm to 750rpm this has no effect on CPU temps, the CPU will hit temp spike or hit the same temp in stress testing regardless of the minimum. The spike is called by XFR on a Ryzen 1600X which boosts the CPU and Voltage causing all of the fans to ramp and instantly cool the CPU back down to idle until I click a web page or something and it boosts again, this is unavoidable unless I OC it which I dont want to do.

The motherboard does everything listed above as standard, you simply tell each fan to use the CPU temp and set either, Normal, Silent or Manual. On Normal or Silent default curves I get the annoying ramping up and down in turn with CPU boosting.

What I want to understand is with System Temp sensor, it never really gets hot enough to ramp up the fans when the system is under load so setting the fans to that is pointless. Setting them to CPU is annoying due to ramping. So I'm kind of at a loss in terms of what to do.
 
I suspect at least one of your motherboard fan headers can be used to set PWM curves based on temp.

My guess is the pre-set temp to rpm curves do not keep enough airflow moving through the case. CPU spikes happen so fast a fan speed change generally does not happen. I have a 6700k that is always spiking 30-40c above normal temp when surfing web. In the last minute my CPU normal temp is low 20s, but has spiked to 40c four times and spiked to 35c eleven times with fans not changing speed at all. In the last 4 hours it has spiked to 45-47c 3 times .. again no case fan speed changes. Case fans are all running about 550rpm and CPU is about 700rpm .. I can't hear any of them 1 meter away.
 
You're right in a way, there is plenty of air but the default curve allows for the fans to ramp up and down too much between idle and boost temp at idle so to get around it I set a manual curve where between 30C and 50C the case fans stay at 30% and would only start to ramp up from 50C and up which would solve it apart from the fact manual curves dont seem to work, the fans just stay at minimum RPM even when the CPU temp increases which means there must be a BIOS issue

Maybe I just need to wait for that to be fixed and try the manual fan curve again
 
That's what I do too .. manual setting so spikes do not effect fan speed.

Does the motherboard fan utilities have a fan tuning function? If so run it before setting manual fan curves. Don't ask, I have no idea why the fan tuning needs to be run first .. or why it is not pointed out in the utilities manual, but all I've seen or heard indicates it solves a lot of problems if ran before setting manual curves.
 
No not this one, I thought the same but there is no option to test the fans before setting a manual curve.

I'm going to have another go tonight, queue 3 hours of messing about, I'm pretty sure as soon as I change it to manual the fans will just sit at minimum rpm and not ramp up due to a bios issue

only preset curves seem to work
 
I'm confused.
You can't set manual curves like you said above
"so to get around it I set a manual curve where between 30C and 50C the case fans stay at 30% and would only start to ramp up from 50C and up which would solve it ".​
That should solve your problems.

What motherboard do you have?
 
The only case fan I've setup to be controlled by temperatures (CPU) is the rear exhaust fan and even then I have it set so that if it ramps up at all its reactive and aggressively so it doesn't ramp to small spikes, etc.
 
doyll said:
I'm confused.
You can't set manual curves like you said above
"so to get around it I set a manual curve where between 30C and 50C the case fans stay at 30% and would only start to ramp up from 50C and up which would solve it ".​
That should solve your problems.

What motherboard do you have?
Click to expand...

Yeah that's my point, manual curves don't work, soon as you set a manual curve the fans just sit at min rpm for that curve. Will confirm later

Rroff said:
The only case fan I've setup to be controlled by temperatures (CPU) is the rear exhaust fan and even then I have it set so that if it ramps up at all its reactive and aggressively so it doesn't ramp to small spikes, etc.
Click to expand...

what about your intakes?
 
Relentless81 said:
what about your intakes?
Click to expand...

All my intakes (3x 140mm) are connected to a frontpanel (5.25 bay) fan controller and usually run at 600rpm though I slightly bump it up in warmer weather. I do have the 540 Air case though it probably doesn't work as well with a different size/layout case.
 
Rroff said:
All my intakes (3x 140mm) are connected to a frontpanel (5.25 bay) fan controller and usually run at 600rpm though I slightly bump it up in warmer weather. I do have the 540 Air case though it probably doesn't work as well with a different size/layout case.
Click to expand...

I see, used to have that case they are good. I couldn't do that though I like automation and utilising the fans full range

I know I'm weird
 
I'm the opposite hah not quite control freak but I like to be in manual control - I keep everything balanced on the quiet side unless the weather dictates otherwise.
 
I think your over thinking this, so system temp stays constant, that says to me case fans are working ok, and enough air is flowing through the case (or wrong sensor reading).
Run some stress tests, see if you can get system temp to increase, if it rises a lot the this would indicate not enough airflow from the case fans.
 
lude1962 said:
I think your over thinking this, so system temp stays constant, that says to me case fans are working ok, and enough air is flowing through the case (or wrong sensor reading).
Run some stress tests, see if you can get system temp to increase, if it rises a lot the this would indicate not enough airflow from the case fans.
Click to expand...

Probably, I do with most things! System Temp doesn't budge in Aida64 (No GPU heat) or even Heaven (GPU Heat) It just sits around 30C so the fans dont ramp up. Not tried it with gaming, maybe I should game for an hour with case fans set to System Temp and see if they ramp up but if they dont then my CPU might get toasty
 
Relentless81 said:
yeah I wish you could. Would be so much easier to sync case fans with gpu fans. You can set it to pciex temp sensor but again pointless as it never moves
Click to expand...

i suggested it because the NZXT Grid will control the hub based on gpu temps, it avoids sudden cpu spikes.
 
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