How to keep fan normally off?

[euimin]

In short: I want my fan to spin only when above a temperature threshold, can anyone tell me how to do this?

Background: My bedroom computer has no moving parts at the moment. For safety, I would like to install a fan that only spins when my processor temperature is above 65 degrees. I wanted to make sure that my motherboard was capable of fan control before I buy Nexus D12SL-12 PWM, so I tried a PWM fan that was attached to an AMD stock heatsink. First, I tried ASUS Q-Fan control, but the fan would still spin even when below the start temperature. Next, I tried SpeedFan, but like the Q-Fan, the fan will still spin below the set temperature threshold even though the fan speed is set at 0 %. Any input is greatly appreciated.

[pcy]

Hi,


You could try putting a Zenner Diode in series with the fan to reduce its voltage by a fixed amount.



Peter

[jessekopelman]

First, I tried ASUS Q-Fan control, but the fan would still spin even when below the start temperature. Next, I tried SpeedFan, but like the Q-Fan, the fan will still spin below the set temperature threshold even though the fan speed is set at 0 %.

Did you very that Speedfan was changing the speed based on your settings (ie did setting it to 50% result in a slower fan than setting it to 100%)? If not, you may need to play around with your Speedfan settings to get proper control. If so, the problem is probably that you still have BIOS fan control turned on and it is overriding Speedfan.

[K.Murx]

In short: I want my fan to spin only when above a temperature threshold, can anyone tell me how to do this?

Hm, kind of difficult to do in software.
Use speedfan to control one fan header, hook up a zener diode to that and have this control a fan? Easiest solution I can think of if you don't mind the soldering iron...

[Klusu]

You could try putting a resistor in series with the fan to reduce its voltage by a fixed amount.
Or - another fan header on the MB may be capable of 0 output (with Speedfan). Probably a 3-pin header (would adjust a 4pin fan, too).

[euimin]

Did you very that Speedfan was changing the speed based on your settings (ie did setting it to 50% result in a slower fan than setting it to 100%)? If not, you may need to play around with your Speedfan settings to get proper control. If so, the problem is probably that you still have BIOS fan control turned on and it is overriding Speedfan.

You are right, I should have been more thorough before I threw a towel and posted here. After I read your message, I double checked my BIOS to make sure that Q-Fan was indeed "Disabled." I tried changing the fan speed to varying levels with SpeedFan, and the fan responded accordingly. At 0%, the AMD stock PWM fan spins at 1000 rpm. It is too bad that there does not seem to be a way to completely cut the voltage supplied to the fans using SpeedFan.

Hi,


You could try putting a Zenner Diode in series with the fan to reduce its voltage by a fixed amount.



Peter

Hm, kind of difficult to do in software.
Use speedfan to control one fan header, hook up a zener diode to that and have this control a fan? Easiest solution I can think of if you don't mind the soldering iron...

Indeed, zener diode seems to be the only way at this point. There is a chance that the Nexus D12SL-12 PWM requires a higher start-up voltage than the AMD stock fan (120mm versus 60mm after all) and might actually turn off at the lowest setting. I will buy the fan and test it. If that fails, then I will look into zener diodes.

You could try putting a resistor in series with the fan to reduce its voltage by a fixed amount.
Or - another fan header on the MB may be capable of 0 output (with Speedfan). Probably a 3-pin header (would adjust a 4pin fan, too).

I have couple of those lying around. They are 3 pin fan header extensions with a resistor in the middle, so it would not work for PWM fans. I tested to see if my mainboard fan headers can control 3 pin fans, it didn't seem like they could.

Thanks everyone!

[frenchie]

that's the thing with PWM fans, they never stop...
However, if you use a 3 pin fan on another fan header on your mobo that speedfan can control, you can do just what you want.

[thejamppa]

I think that could be done with mcube T-balancer... Or at least very close to it. When idle you should at least if not being turned of you should be making fan spin so slow that you cannot really percieve it from distance of 20 cm's or so.

Check if this fits the bill. Some user's in here ( very few of them ) swear in the name of T-balancer.
http://www.t-balancer.com/english/produ ... _bigng.htm

[dukla2000]

that's the thing with PWM fans, they never stop...

Mine does - stock Xigmatek PWM fan (as per sig) using sensors, pwmconfig & fancontrol.

/etc/fancontrol is

Code: Select all

# Configuration file generated by pwmconfig, changes will be lost
INTERVAL=10
FCTEMPS=hwmon2/device/pwm2=hwmon2/device/temp2_input
FCFANS= hwmon2/device/pwm2=hwmon2/device/fan2_input
MINTEMP=hwmon2/device/pwm2=40
MAXTEMP=hwmon2/device/pwm2=55
MINSTART=hwmon2/device/pwm2=195
MINSTOP=hwmon2/device/pwm2=195
MINPWM=hwmon2/device/pwm2=0
MAXPWM=hwmon2/device/pwm2=255

When CPU core temp is below 40C the CPU fan is off.

[jessekopelman]

that's the thing with PWM fans, they never stop...

Not true at all. Indeed the general case is that if you set the PWM % too low, the fan will stop. Maybe some motherboards have a fail-safe to prevent this, but most do not. There is definitely nothing in the fan to prevent it from stopping.

[frenchie]

oups, my mistake

I thought PWM fans only worked within a certain rpm range, the minimum never being zero... I've had Nexus and an Arctic Cooling PWM fans and I couldn't get them to stop. Even with the % set to zero in speedfan, they woudn't slow down below their threshold limit.

Nexus fan : http://www.nexustek.nl/NXS-92mm-pwm-fan-ultra-quiet.htm

Arctic Cooling fan : http://www.arctic-cooling.com/catalog/p ... &page=spec

EDIT : motherboard at the time was P5N-E SLI... Maybe it's a motherboard feature.

[jessekopelman]

oups, my mistake

I thought PWM fans only worked within a certain rpm range, the minimum never being zero... I've had Nexus and an Arctic Cooling PWM fans and I couldn't get them to stop. Even with the % set to zero in speedfan, they woudn't slow down below their threshold limit.

They do only work over a certain RPM range. When they are stopped, they are not working! You can think of it this way: PWM fans have two basic states, on and off. The Off State contains only a single speed -- 0 RPM. The On State contains a range of speeds (eg 500-1500RPM). There is no way using PWM control alone to get the fan to operate between 0RPM and its minimum rated speed. Apparently, certain motherboards have feature that prevents connected fans from ever being in the OFF State. Yours has this feature, mine does not. Exactly how common this feature is is unknown. Anecdotally, I would say not having the feature is very common -- I have read more reports of people being able to stop their PWM fans than those of people unable to do so.

[Klusu]

I think you are wrong. There is no On or Off. Rated speed 500 does not mean the fan certainly will not spin at 400. And it does not mean the fan will spin at 500 or 600 when old.
Old- I mean used for 5 years or so.
Much broader range with voltage control? No. And the same range exactly, if the MB's minimum output is low enough (you wrote:"I have read more reports of people being able to stop their PWM fans ")

Edit: most fans can not be PWM adjusted below min limit

[jessekopelman]

I think you are wrong. There is no On or Off. Rated speed 500 does not mean the fan certainly will not spin at 400. And it does not mean the fan will spin at 500 or 600 when old.

There is definitely on and off. The speed range is not so precise (usually specified by manufacture as +/- 100RPM), but using PWM control alone, there is no way to deviate broadly from it. Combine PWM with voltage control and you can achieve a much broader range of speeds. Not sure what you mean "when old" . . .

[frenchie]

using PWM control alone, there is no way to deviate broadly from it.

That's EXACTLY what I meant in the beginning !!! I just didn't phrase it quite like that.

Combine PWM with voltage control and you can achieve a much broader range of speeds.

interesting combinaison... never thought of that, but good to know !!!!!

[euimin]

However, if you use a 3 pin fan on another fan header on your mobo that speedfan can control, you can do just what you want.

I doubted what you wrote at first, but decided to try anyways. My mainboard has a total of 3 fan headers - CPU_FAN (4-pin), PWR_FAN (3-pin), and CHA_FAN (3-pin). As I mentioned earlier, I tried modulating 3-pin fans using CPU_FAN and PWR_FAN but not on CHA_FAN and concluded that my mainboard cannot control 3-pin fans. To my surprise, it turns out that only CHA_FAN is able to modulate the speeds of 3-pin fans. It was my fault for overlooking.

I am now able to make a 3-pin fan spin from a stopped state at a specified temperature threshold using SpeedFan.

I didn't even have to spend any money on PWM fans. Thanks for the tip on T-balancer, though. I am sure knowing this will help me some time down the road.

This makes me wonder why PWM fans even exist. I seems that 3-pin fans are capable of modulating themselves with the help of temperature sensors and software/BIOS. PWM fans also add that "PWM whine," which is annoying.

Thanks to everyone in this thread for your help!

[thejamppa]

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I didn't even have to spend any money on PWM fans. Thanks for the tip on T-balancer, though. I am sure knowing this will help me some time down the road.

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Thanks to everyone in this thread for your help!

You're welcome. T-balancer costs about you're average heatsink but it is unbelievably handy and versatile... It just needs more time and bigger learning curve than your average fan controller. Many also overlook it as they consider it as part of watercooling system.

[jessekopelman]

This makes me wonder why PWM fans even exist. I seems that 3-pin fans are capable of modulating themselves with the help of temperature sensors and software/BIOS. PWM fans also add that "PWM whine," which is annoying.

PWM fan control exists because it is less expensive to build PWM control into a MB than volatge control. Intel innovations like push-pin heatsink mounting and PWM fan control are all about the lowest cost good-enough standard solution, not the best standard solution. Not all PWM control/fans add any sort of whine. In its defense, PWM is actually more energy efficient than than voltage control, but given the energies involved in running fans that would really only be much of an issue for battery powered devices.