PWM Fan question

Cobra26

E.M.I.
Hi guy's,

Is it possible to use PWM fans since the lian li 4 x fans provided with the Lian li Tyr PCX-500 case are not realy silent. I ask this because the PWM fans i have in mind are the Noiseblocker NB-Blacksilent XLP - PWM. But it uses a 4-pin, while the lian li fans use 3-pin. Is it possible to connect the 4-pin noiseblocker to the fan controller wich use 3-pin connectors (see link below 5th picture) of the case and still adjust the speed? Hope this is not a silly question i already have the case.

I'm not planning to connect the pwm fans onto the motherboard or get my self a 3th party fan controller wich most of it use 3-pin connectors anyway.

http://techreport.com/articles.x/16258/2

Is there a solution for this? Perhaps some cables....
Or can the included fan controller of the case adjust the speed of any "normal" 3-pin fan? This seems logical since the lian li fans use 3-pin. If i buy some 3-pin 1500rpm fans i can lower the speed but never increase the speed above 1500rpm...

Thanks in advance
 
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crowTrobot

E.M.I.
AFAIK, 4-pin PWM fans are backwards compatible although if its going to be connected to a 3-pin or 2-pin connector, you will lose the ability to control the speed.

The pinout for 4-pin PWM afaik usually is: RED(or sometimes YELLOW)=12v, BLACK=GND, the last two are speed control and pulse modulation (color varies with brand, usually white or yellow, intel uses blue for the pwm and green for the sensor)
 

Tharic-Nar

Senior Editor
Staff member
Moderator
While backwards compatible, it's usually a case of, will the 3 pin have room for a 4 pin. Quick Diagram to show you....

3pin.jpg

If the 3 pin connector has a supporting boarder (like with extension cables or drive bay mounted fan controllers), you'll need to remove the right edge for the 4 pin to fit.

If you have the connectors mounted on a PCB, then you can only fit the 4 pin PWM if the PCB connectors are mounted a certain way or with suffecient space between each connector.
 

2Tired2Tango

Tech Monkey
While backwards compatible, it's usually a case of, will the 3 pin have room for a 4 pin. Quick Diagram to show you....

Found this detail on the fans themselves. It seems to support what everyone's saying...

http://pavouk.org/hw/fan/en_fan4wire.html

I'd want to test the setup on an old motherboard first, just in case. I'd also want to test with 9 or 7 volts to be shure the fan starts and spins reliably, since most speed controllers work by reducing the supply voltage to the fan.

Personally I'd just look for some standard 2 or 3 wire fans that are quiet enough for your job... Try to find PanaFlo fans... all I ever hear from them is airflow.
 
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Tharic-Nar

Senior Editor
Staff member
Moderator
4 pin fans will work in a 3 pin connector (as long as it fits), even fan controlled (yes, i have used 3/4pin combo's in the past), since as you state, most controllers change the voltage via a rheostat - which, while effective, is inefficient. PWM doesn't change the voltage, but the DC pulse frequency (it rapidly switches between on and off), thus power loss is minimized compared to a rheostat (always on). So the PWM channel is like a plugin, it can be used if you want, but not required since standard speed control can be done through voltage changes with a rheostat. The third pin is purely for monitoring revs like a speed counter and does not have any effect on the other pins (the motherboard/controller changes voltage based on the interpreted speed and thermal conditions).

It is also worth noting as Tango said, to check the fan if your going to use a controller. Many slow Rev fans (800rpm), have difficulty starting when the rheostat is turned all the way down - which usually results in 7 volts. Since they are low speed fans, they are designed to run at full rpm at 12 volt, but if you decide to drop the voltage further, then they may not have enough power to overcome the magnetic resistance + friction (problems usually occur at 600-700 rpm).
 
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Cobra26

E.M.I.
Thank you guy's for the reply's

Ok i generaly understand the issue of the pwm fans, it does take some work to figure it out especialy when u want it to work. And also could not find a fan controller with 4 pins.
So i abandon the idea of PWM fans it seems these are ment to connect directly into the motherboard.

As previous mentioned by me this should also work with 1500rpm fans...see below

Can i connect any 3-pin fan on a fan controller wich is provided with my case Lian LI Tyr PCX500. The 3-pin 1500rpm fans provided with the case are not realy silent even when i adjust the speed to 1000rpm, and want to swap them. The fans have 3-pin so does the fancontroller socket. So in my opinion all 3-pin fans should work with the fan controller. All the fancontroller does is lowering the voltage (decrease of rpm) and thus lowering the noise. This should work right thats the purpose of the fan controller. Altough this is effective but not realy healthy for a fan but this apply's to 800rpm fans not 1500rpm right?

Thanks in advance
 

2Tired2Tango

Tech Monkey
Altough this is effective but not realy healthy for a fan but this apply's to 800rpm fans not 1500rpm right?

Any fan you're going to run undervoltage is going to dislike it in some way. The problem is the series resistance of the rheostat doesn't just turn down the voltage, it also limits the current, which reduces the fan motor's torque, in turn preventing it from starting reliably.

Of course lowering the RPM of a fan also reduces it's airflow, rather substantially. At some point the whole gambit of having bigger fans becomes self-defeating if you turn them down to silence them.

If your only concern is noise (not airflow) then you really should look into non-ballbearing fans like those made with the Panaflo mechanism. It's a nylon sleeve bearing that carries a small amount of oil through grooves in the bearing. These fans run virtually silent, even at 2700rpm and you can safely take them down to about 8 volts (1200 rpm) with no problem.

http://www.newegg.com/Product/Produ...ctory=11626&SubCategory=573&SpeTabStoreType=1

Look for the "hydro wave" fans...
 

Kougar

Techgage Staff
Staff member
Thank you guy's for the reply's

Ok i generaly understand the issue of the pwm fans, it does take some work to figure it out especialy when u want it to work. And also could not find a fan controller with 4 pins.
So i abandon the idea of PWM fans it seems these are ment to connect directly into the motherboard.

As previous mentioned by me this should also work with 1500rpm fans...see below

Can i connect any 3-pin fan on a fan controller wich is provided with my case Lian LI Tyr PCX500. The 3-pin 1500rpm fans provided with the case are not realy silent even when i adjust the speed to 1000rpm, and want to swap them. The fans have 3-pin so does the fancontroller socket. So in my opinion all 3-pin fans should work with the fan controller. All the fancontroller does is lowering the voltage (decrease of rpm) and thus lowering the noise. This should work right thats the purpose of the fan controller. Altough this is effective but not realy healthy for a fan but this apply's to 800rpm fans not 1500rpm right?

Thanks in advance

PWM and voltage are two common methods for reducing the speed of computer fans. Undervolting them isn't as precise and it depends on the type of fan controller (They can use different methods to reduce voltage/current) as well as the fan for how well it will work. Different fans respond differently to undervolting, but some fans are designed for it as well. Typically some fans can start generating low level buzzes or growling when undervolted, but don't when at their full speed. So I'd recommend ya should test out any fans you plan to use before committing to buying a bunch of them.

You can always plug a 4-pin fan into a 3-pin socket if it is open-ended (like it is in that photo), just make sure the blue PWM wire is the one hanging off the end and not making contact. Otherwise the fan just won't run at all. Of course doing this means you can't use PWM to control the fan speeds... it's usually easier to just buy fans tested and you will know that will run silent at their full speed... this is why most fans are sold in 2-3 models with the only difference being stock RPMs. For me 1200-1500RPM is about the range for a silent 120mm fan, but it does depend on the fan... 2Tired's fan suggestions are a good place to start too. ;)
 

Cobra26

E.M.I.
Thanks for the help/advise people,

I think il go with the fan that tango recommended me because well if i understand it correctly its somehow stronger to resist voltage changes.

My first bet was buying 2 1500rpm fans for intake in the case and change the speed whenever i need to hence the question pwm and regular fan to change the voltage.

But i'm not sure i already have 7 Noiseblocker NB-Blacksilent XL1 Rev.3 (41CFM) 4 for the rad XSPC 480 rad these are 1000rpm fans its good enough since the rad is suitable for low rpm fans because of the greater distance between the fins of the rad. And 3 (1 i need to buy...) for the case well ....i'm not sure if 4 fans with 41cfm is good enough to cool the case inside. See below for my setup and the case. Then again the lian li fans all run at 1000rpm lowest setting from 1 to 3 i use 1. Its kind of a waste if il not use the noiceblocker fans. If they arent that good il buy the Panaflo mechanism fans as mentioned earlier. All it takes is money money, wich i do not have at the moment swapping 4 fans with new ones.

Review of the noiseblocker:

http://tech-reviews.co.uk/reviews/noiseblocker-blacksilent-fans/

Thanks again for the help
 

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Kougar

Techgage Staff
Staff member
Ah, well since you already have those, then obviously only replace the fans if you aren't happy with them. If you undervolt them and they start making noise or lose too much performance at acceptable volume levels then that's when you should pick up new fans.
 
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