Basic case fan questions

[sleonard]

I really want some 120mm case fans w/ 3 pin connectors that fit my motherboard headers and whose speed can be controlled by the motherboard.

I thought this would be easy to find but it seems that all the case fans I see (@ NewEgg) have either a static speed or, if they are variable, have thier own speed control that is set and forget (i.e., 3-speed switch)

Will the motherboard vary the speed of those fans that have a static speed listed (such as this for example)?

S

[Taddeusz]

AFAIK, most motherboards are not capable of varying the speed of chassis fans. Generally only the CPU fan. And usually it's only one of the chassis fans.

What I would recommend is either get a power supply that has "fan only" connectors that automatically vary the speed or get a fan bus controller that allows you to do it manually from the outside of the case.

[PLUCKYHD]

DOn't quote me on this but an adjustment to fan speed only requires an udjust of the power been sent to it and I believe that is what I motherboard does when it adjust the fans it adjust the power going to the fan.

[toony]

What mobo do you have?

[Taddeusz]

Originally Posted by PLUCKYHD

DOn't quote me on this but an adjustment to fan speed only requires an udjust of the power been sent to it and I believe that is what I motherboard does when it adjust the fans it adjust the power going to the fan.

Yes, but not all motherboards do that. I think only the most expensive enthusiast motherboards or name brand computer motherboards can.

[CarlR]

Originally Posted by sleonard

I really want some 120mm case fans w/ 3 pin connectors that fit my motherboard headers and whose speed can be controlled by the motherboard.

I thought this would be easy to find but it seems that all the case fans I see (@ NewEgg) have either a static speed or, if they are variable, have their own speed control that is set and forget (i.e., 3-speed switch)

Will the motherboard vary the speed of those fans that have a static speed listed (such as this for example)?

S

The fan speed of any "static speed" case fan will vary if you change the voltage supplied to the fan - so while I didn't actually look at the fan you linked, I would say that you should be able to adjust the fan speed if your MB has that capability. It is implemented as a PWM (pulse width modulation) circuit to step the voltage down to a lower level.

Check the "speedfan" site for a list of MBs that are verified to have the capability.

[sleonard]

Originally Posted by PLUCKYHD

DOn't quote me on this but an adjustment to fan speed only requires an udjust of the power been sent to it and I believe that is what I motherboard does when it adjust the fans it adjust the power going to the fan.

That is what I thought and also here is what the motherboard manual states:

It is an Intel DG45ID.

Fan Headers
The function/operation of the fans is as follows:
• The fans are on when the computer is in the ACPI S0 state.
• The fans are off when the computer is in the ACPI S3, S4, or S5 state.
• All fan headers support closed-loop fan control that can adjust the fan speed
according to thermal conditions.
• All fan headers have a +12 V DC connection.
The Desktop Board has a 4-pin processor fan header and two 3-pin chassis fan
headers.

It's just when I started browsing case fans at newegg and noticed that all the fans were either static or had their own speed switch that doubts started to creep in.

BTW, does "closed-loop fan control" mean the motherboard varies the fan voltage and thus the fan speed or does it require fans with a special feature?

S

[Taddeusz]

In that case it should be able to control both case fans. Any three pin fan should work. The third wire sends a pulse back to the computer every time the fan rotates. This tells the computer how fast the fan is spinning. That motherboard can control the voltage to each fan to control the speed.

[toony]

The manual for your mobo states;

Hardware monitor with:
• Three fan sensing inputs used to monitor fan activity
• Intel® Quiet System Technology (Intel® QST) fan speed control

you need a fan like this the Anitec Tricool 120

The fan must be thermistor based if you wish to only use a 3-pin fan. Make sure that you have PWM enabled in BIOS for the CPU fan, and see if there is this option for the case fans as well, if so turn it on.

[Striker:WG]

Check out the program SpeedFan, it should give you alot of control over your system fans:

http://www.almico.com/speedfan.php

-Striker-

[wayner]

Speedfan doesn't always work - I have it running on my Sage server (WHS) in an Antec 300 case and it only let's me control one of the three case fans.

[Striker:WG]

i'm no expert on SpeedFan, i just know its worked for me in the past.

your probably running into a limitation of your motherboard and the fan headers ability to monitor/control the fan connected to it. SpeedFan is supposed to detect all the fans it can control.

-Striker-

[sleonard]

Originally Posted by Taddeusz

In that case it should be able to control both case fans. Any three pin fan should work. The third wire sends a pulse back to the computer every time the fan rotates. This tells the computer how fast the fan is spinning. That motherboard can control the voltage to each fan to control the speed.

After some more research and actual testing I have verified that you are correct. Just need a plain 3-pin fan. The advertised speed will be the max and the motherboard will reduce it as needed (varies the voltage from 12V to 5V)

Pin 1 is ground, pin 2 is 5 - 12V, and pin 3 is PWM. PWM monitors the speed.

Intel QST closed loop fan control moitors the fan speed via PWM on pin 3 and varies the voltage on pin 2 to change the fan speed.

I tested this by installing the Intel Desktop Utility and noting the idle temps and fan speed. The I ran a dbPoweramp conversion utilizing all the cores. As the temps increase so did the fan speed.

Originally Posted by toony

The manual for your mobo states;

Hardware monitor with:
• Three fan sensing inputs used to monitor fan activity
• Intel® Quiet System Technology (Intel® QST) fan speed control

you need a fan like this the Anitec Tricool 120

The fan must be thermistor based if you wish to only use a 3-pin fan. Make sure that you have PWM enabled in BIOS for the CPU fan, and see if there is this option for the case fans as well, if so turn it on.

The fan you linked to has its speed set by a 3-position switch. Probably not ideal for use with a variable controller like on my motherboard.

Also, a thermistor both measures the temp and varies the voltage to the fan without any input from the motherboard controller. Definately not suited for use with any other fan speed controller like on newer Intel boards with QST closed loop fan control.

Thanks all,

S

[toony]

Well you seem to know more than I do about this, good luck