Question Fan hub, different type and size fans.

[maraxion]

Hi.

So iv got a few pwm fans laying around. They are of different size and rated at different DC voltage.
Iv now ordered a hub, in my case the"Artic case fans hub". This has outputs for 10 fans that relay on the input on fan in port 1.

So if I now connect these different fans, should I connect the one with lowest DC to port 1?
Or does this only take into factor relative % speed of the fan connected in port 1 and then extends that % to all other fans?
But does that mean if fan number 1 runs on 50%, wil all fans run on their own 50%? Or wil they all run on 50% rpm of fan 1?

 

[Eximo]

Just PWM or voltage control. Each fan will react to that as they are built. No way for them to match RPM in any way.

Even the same model fans will have different RPMs in the end, there will be an acceptable manufacturing tolerance so they will be similar, but not exact.

 

[maraxion]

Just PWM or voltage control. Each fan will react to that as they are built. No way for them to match RPM in any way.

Even the same model fans will have different RPMs in the end, there will be an acceptable manufacturing tolerance so they will be similar, but not exact.

So all fans wil reach their own individual % and in that it does not matter which fan is connected to the controlling port as long as all are pwm fans?

 

[Eximo]

The control port goes into your motherboard if I take your meaning. You use one fan header to control all the additional ports connected to the hub. You aren't using a fan to control other fans, that wouldn't work.

 

[maraxion]

The control port goes into your motherboard if I take your meaning. You use one fan header to control all the additional ports connected to the hub. You aren't using a fan to control other fans, that wouldn't work.

Correct. The controll port goes from motherboard and identify the fan in port 1. The other fans on the hub wil then receive the same signal as the one in port 1, even if other size and speed rating.
So what I want to know if that matters at all, or if a pwm signal only is %, and thus all fans wil run at their specs since all get a % signal. Or if they are all locked into the speed of fan 1 and wil follow that.

 

[Eximo]

Not sure I can explain it better.

The fan doesn't know what percentage you have set. It is getting a PWM signal or DC voltage from the motherboard. Now the PWM at 50% may indeed be a 50% duty cycle so the fans would operate at 50% power. 50% power is not a set speed. That will be entirely dependent on the fan.

If you have a 3000rpm fan and 1700rpm fan and a 1300rpm fan, 50% power is going to be very different between all of them. And not even necessarily half the RPM, it is half POWER. It takes more power to move faster so it isn't a linear curve.

DC fans are more linear as the voltage is really controlling speed, but there is some diminishing returns on voltage/speed as you go faster. Coils get saturated and stop increasing in speed.

 

[Paperdoc]

IF all your fans really are the 4-pin PWM type, then that makes things easier. Despite what you say, ALL PWM fans require a power supply at 12 VDC from header Pin #2, and their speed is controlled by the PWM signal from Pin #4. IF you have ANY fan that claims to use 5 VDC power instead, do NOT attempt to use that in a mix with others.

That Hub you bought is a standard case fan Hub with 10 output ports. It has TWO input sockets - one wide one for a SATA power output connector from your PSU, and on the opposite end a smaller port for a cable that goes to a mobo SYS_FAN or CHA_FAN header to get the PWM control signal. ONE of your fans must be plugged into output Port #1, and the speed of that fan only will be sent back to the host header for display. You will never "see" the speed of fans on other ports.

The PWM signal all fans get is basically a "% of Full Speed" kind of signal. Different fan models will run at different speeds given the SAME PWM signal, but that does not matter. The important thing from a fan is air flow, not speed. In fact, the mobo header does not use or care what its fan's speed is. It just manipulates the PWM signal to get whatever air flow is required to meet a TEMPERATURE target at a mobo sensor.