Slow down PWM fan at hardware (cable) level

ekerazha · Post by **ekerazha** » Sat Apr 25, 2009 1:13 am

Is there a way to slow down a PWM fan at "hardware" level?

Well... with a 3-pin fan we can undervolt it using resistors etc. is there a way to "slow down" a PWM-controlled fan adding something in the middle of the cable?

trident · Post by **trident** » Sat Apr 25, 2009 6:30 am

I am unsure what you want to accomplish. Do you want to set a maximum fan speed? Please describe your application and goals.
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trident

pcy · Post by **pcy** » Sat Apr 25, 2009 8:30 am

Hi,

I'm quite certain that if you simply reduced the voltage on the nominal 12v supply to a PWM fan by adding a resistor it would slow down.

I also suspect that the slow down would be in the same proportion at all fan speeds.

Peter

SebRad · Post by **SebRad** » Sat Apr 25, 2009 9:01 am

Hi, in this thread I talk about my experaince of adding a fanmate in the loop with a PWM fan to effectively move the working range.
I.E. change a 1300-2600rpm fan to a 1000-2000rpm fan. I think PWM fans can vary in how they respond to voltage changes, some will be very sensitive, other less so and more like "standard" 2/3 wire fans.
Seb

ekerazha · Post by **ekerazha** » Sat Apr 25, 2009 9:10 am

trident wrote:I am unsure what you want to accomplish. Do you want to set a maximum fan speed? Please describe your application and goals.
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trident

What SebRad said, correctly describes what I want to accomplish.

"I.E. change a 1300-2600rpm (PWM) fan to a 1000-2000rpm fan."

ekerazha · Post by **ekerazha** » Sat Apr 25, 2009 9:41 am

SebRad wrote:Hi, in this thread I talk about my experaince of adding a fanmate in the loop with a PWM fan to effectively move the working range.
I.E. change a 1300-2600rpm fan to a 1000-2000rpm fan. I think PWM fans can vary in how they respond to voltage changes, some will be very sensitive, other less so and more like "standard" 2/3 wire fans.
Seb

Thank you SebRad. With this method, is the fan speed correctly reported to the board?

SebRad · Post by **SebRad** » Sat Apr 25, 2009 10:38 am

Yes, the fan speed signal is in the 3rd wire and was reported fine by the motherboard.
Regards, Seb

ekerazha · Post by **ekerazha** » Sat Apr 25, 2009 10:54 am

SebRad wrote:Yes, the fan speed signal is in the 3rd wire and was reported fine by the motherboard.
Regards, Seb

So the idea would be to make an adapter in order to slow down the fan of a Sapphire 4870 Vapor-X video card

Because via software the minimum speed is

20% duty cycle = about 1100-1200 rpm

This video card is famous to be quiet, but this way it could be quieter

trident · Post by **trident** » Sun Apr 26, 2009 10:18 am

ekerazha as SebRad stated some PWM fans are more finicky than others so you will need to experiment with how much voltage drop your fan will tolerate. If you are handy with a soldering iron, a much smaller adapter could be constructed using rectifier diodes or a Zener diode. I have used them for fixed voltage drops on three wire fans with good results, but for an off the shelf solution the Fanmate is tough to beat. The crimp terminals and connector shells you will need are available from many electronics vendors. I recommend investing in a quality crimping tool for best results.
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trident

lodestar · Post by **lodestar** » Sun Apr 26, 2009 3:35 pm

So the idea would be to make an adapter in order to slow down the fan of a Sapphire 4870 Vapor-X video card

I appreciate you view that software control is not delivering enough of a reduction in fan speed, but you are using a graphics card with what can be a very hot running chip. Any hardware modification could put the card at serious risk.

The only off-the-shelf hardware I am aware of that could do what you want is the Cooler Master Wind Rider, which was a PWM fan hub which included a slider enabling the fan voltage to be varied from full to about half. I say was because I built a Core 2 Duo system using one, but that was last year and the Wind Rider no longer seems to be on the market.

So I still think that the best approach would be to use one of the utilities such as RivaTuner, and use either the manual or auto settings set to as low as you get away with. You have somewhat more capacity to do this because your particular graphics card incorporates an innovative cooling solution which drops the load temperature by around 14 degrees centingrade compared to the stock cooler.

ekerazha · Post by **ekerazha** » Tue Apr 28, 2009 12:54 am

lodestar wrote: So I still think that the best approach would be to use one of the utilities such as RivaTuner, and use either the manual or auto settings set to as low as you get away with.

Using software like these, you can't go lower than 20% (about 1100-1200 rpm for the Vapor-X), this is why I was thinking about this hardware mod.

However I still don't have this card... I'm wavered between a GTX 260 (with fan lowered to 25-30%, 900-1000 rpm, @ idle) and this Vapor-X (with that hardware mod).

lodestar · Post by **lodestar** » Tue Apr 28, 2009 1:58 am

You are likely to find that no model of gtx 260 will be as quiet as you would like it to be. Palit produce a model with a dual fan cooler which ought to produce less noise at idle, but manages to produce more due to the level at which the fans are set. This could be modified using software but it might still be no improvement over the ATI card.

This review of the Palit gtx 260 includes a chart of how much noise a range of graphics card produce, and might give you some other options to consider
http://www.techpowerup.com/reviews/Pali ... SP/28.html

ekerazha · Post by **ekerazha** » Tue Apr 28, 2009 2:23 am

I don't know, this SPCR review http://www.silentpcreview.com/article870-page1.html said the GTX 260 reference cooler was quite good (and that was with a 40% fan @ idle), so I thought a reference GTX 260 with fan lowered from 40% to 25% could be good