Question Can i connect fan hub to cpu fan header?

Feb 19, 2020
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Hi guys,
Sorry for my bad English, but the thing is that i just bought a case with 3 fans included. They have 4 pin connectors but i have 3 pin connector on my motherboard. My question is - can i connect all the 3 fans + the cpu cooler to a fan hub (deepcool fh-10) to the cpu fan header instead of the cha header? (My mobo is h61m-vg3)
 
Last edited:

korv

Notable
Dec 26, 2018
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You'll still be able to power the fans but you'll lose some functionality. And of course you can still have their speed adjusted by the mobo or a dedicated fan controller.
 
Sorry, but there's a bunch of wrong information above.

The speed of 3-pin fans is achieved by varying the VOLTAGE supplied to the fan on Pin #2. (The wiring on a 3-pin fan is: Pin #1 (Black) Ground; Pin #2 (Red) +DCV supply; Pin #3 (Yellow) speed signal sent from fan to mobo.)

4-pin fans work differently. (Wire colours are different too but pins are very similar.) For them the power supplied on Pin #2 is always the full 12 VDC. Then Pin #4 sends the new PWM signal to the fan. Inside the fan a small chip uses that PWM signal to modify the flow of current from the fixed 12 VDC power supply line through the motor windings, thus altering its speed.

Now let's consider the specific mis-match that OP has - that is, plugging 4-pin fans into a mobo 3-pin fan header. This uses a backwards compatibility feature of this new design. That header can ONLY use the older Voltage Control Mode - that is, it WILL vary the voltage supplied on Pin #2 from 12 VDC (full speed) down to about 5 VDC. It will not take voltage lower because that might cause the fan to stall. This header can NOT supply any PWM signal from its non-existent Pin #4. The 4-pin fan receives NO PWM signal, so its special chip cannot modify current flow from the power on Pin #2. HOWEVER, the VOLTAGE on that power line IS already being altered by the mobo, so that DOES control the speed of the 4-pin fan. Technically, this method of speed control is not quite as good as proper PWM Control, but the differences are very small and not worth worrying about. Realistically, OP, you do NOT lose any important function of your fan this way.

On your mobo, the CPU_FAN header does its automatic fan speed control work by using the actual TEMPERATURE inside the CPU chip, based on a sensor in there built in by the CPU maker. Elsewhere on your mobo is one 3-pin CHA_FAN header that uses the older Voltage Control Mode, AND uses for actual temperature measurement a different sensor built into the mobo. THIS is the right way to control your CASE ventilation fans, no matter whether those fans are 3-pin or 4-pin models. But how to connect three fans to one header? Specifically because there is NO PWM signal available from that CHA_FAN header, you cannot use a HUB, and that is what the Deepcool FH-10 unit is. A HUB gets power for all its fans directly from a fixed 12 VDC line of the PSU and sends that out to all its fans. It does NOT send out to its fans whatever it receives from the mobo header's Pin #2. BUT it DOES send out to all its fans the PWM signal it gets, and thus it DEPENDS on having only 4-pin fans connected to it. It ALSO DEPENDS on getting that PWM signal from the mobo header, and your 3-pin CHA_FAN header does NOT have that!

The right device fo you to use is a SPLITTER. This device has NO source of power from the PSU. It merely connects all its fans in parallel to the three lines of mobo header, so they all get the same varying Voltage supplied to them. Since all the power for those fans must come from that one header, you need to pay attention to a limit. Most mobo fan headers can supply up to 1.0 A total current to all fans connected to it, and most simple fans today consume 0.1 to 0.25 A max each, so you should have no problem with this. You could use a 3-output Splitter like this

https://www.newegg.com/p/N82E16812423163?Description=coboc fan splitter&cm_re=coboc_fan_splitter-_-12-423-163-_-Product&quicklink=true

Or, buy three common 2-output Splitters like this

https://www.newegg.com/p/N82E16812423160?Description=coboc fan splitter&cm_re=coboc_fan_splitter-_-9SIA85VAXC2570-_-Product

and make a "stack" by plugging two of them into the outputs of the third. This gives you four outputs from one header.

Just a small note when using Splitters (also applies to Hubs). Any mobo fan header can handle the speed signal coming back to it from only ONE fan - two or more overlapping signals cause errors and trouble. So a Splitter will only send back to the header the speed signal from ONE fan and will ignore the other(s). If you look closely at those Splitters, you will see that, among the male output arms only one has all four pins, while the other(s) are missing Pin #3 so it can NOT capture the speed signal from the fan on that output. This is NOT a problem for fan speed control - the header actually does NOT use that speed signal for contrlol.
 

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