PWM Fan splitter

[UberCanuber]

I am buying three 4 pin PWM fans all exactly the same and was wondering if I can run them and control them from a single 4 pin output off my motherboard by using something like this.

Thanks for the help!

 

[bgunner]

Yes you can. That will work just fine for what you want to do.

 

[nikoli707]

damn, i learn something every day, i need one of those.

awesome find ubercanuber

whats the power limit though??? on most modern motherboards, can a single pwm fan header feed the wattage split across up to 4 pwm fans for them to spin up to whatever their max rpm is?

 

[bgunner]

this will depend on how much voltage and wattage the fan requires. Yes it is possible to overload the Fan header and But usually only causes the fans not to get to full speed.

Some fan need more wattage to spin at full speed, a set of 4 of these high wattage fans can cause issues. 3 should be fine but 4 is pushing it in my opinion. I can look up some reference material if you would like.

 

[UberCanuber]

Thanks bgunner!!

nikoli707 I am not sure on the power limit, I am using a single molex to power 4 fans at the moment (non pwm) and they are running at 12 volts at full rpm. Just doing an upgrade!

 

[nikoli707]

yeah ive used cheap resistors to run fans at 5 or 7 volts to slow them down until their inaudible. ive always wanted a fan controller but never jumped on it. this option is cheap and im more than fine with the noise of the fans if the system needs airflow but not at idle.... for $7 shipped im probably going to try it. if i dont like it or its not working i will just revert back to what im doing now, or just use it to power one extra fan.

 

[UberCanuber]

How about I tell you how it goes nikoli707 ... Although I asked one of the PCCasegear guys today whether it would take tbe perfect for controlling multiple fans from a single PWM fan and he said as long as they are all the same it will take the readings from one fan and give them all the same RPM.

 

[AndreyT]

I am buying three 4 pin PWM fans all exactly the same and was wondering if I can run them and control them from a single 4 pin output off my motherboard by using something like this

Well, yes, you can. There's one little detail though.

Since one of the wires in a standard fan connector is a RPM feedback wire, you cannot just connect RPM wires from all four fans back to the motherboard. This will completely screw up the RPM feedback and make it meaningless.

For this reason, as you can see yourself in the zoomed picture, the splitter takes RPM feedback from only one fan of the four. That means that you will have one "master" fan, whose RPM feedback signal will govern the motherboard's speed control logic (and PWM signal) for all four fans. With four identical fans this should not be an issue. Although it might be a good idea to think carefully where you place the "master" fan inside the case.

A failure of "master" fan will typically ruin the operation of all other fans sitting on the same connector, since the RPM feedback will cease. (Depends on how the motherboard will react to missing RPM signal, besides raising an alarm)

And if one day you decide to replace some of these fans with different kind (probably not a very good idea, since all fans will receive the same PWM signal, but might work), you have to choose the "master" fan with care.

 

[UberCanuber]

Although it might be a good idea to think carefully where you place the "master" fan inside the case.

A failure of "master" fan will typically ruin the operation of all other fans sitting on the same connector, since the RPM feedback will cease. (Depends on how the motherboard will react to missing RPM signal, besides raising an alarm)

Where would you recommend I put the master fan?

I will be using two as front intakes and one as an exhaust either at the top or rear, not sure yet.