[SOLVED] Cant control the speed of case fans

[skearly13]

I have a gigabyte x570 gaming x with 4 case fans that are all corsair sp120 fans that are have 3 pins. They are connected to a Deepcool FH-10 which is the fan hub and that is connected to the sys fan 1 port on my motherboard. But when I try to change the speed of the fans in the bios, the fans don't change speed. I was wondering if it was possible to be able to control the 3 pin fans connected to the hub.

 

[Nemesia]

Are they set as PWM or DC?

 

[skearly13]

Are they set as PWM or DC?

I tried both and neither of them worked

 

[Paperdoc]

The problem is they are 3-pin fans. The ONLY way to control their speeds is by having the mobo header they are connected to configured to use the older Voltage Control Mode, and not PWM Mode. FURTHER, you can NOT control their speeds using a fan HUB, and that is what the Deepcool FH10 is. That device can only control the speed of the new 4-pin PWM type fans.

There is a good way to do this, but there's a limit we need to take into account. A mobo fan header can supply up to 1.0 A max current to the total load on that header. So to do this using a SPLITTER rather than a Hub, we need to know the max current spec of your fans. You have four, and tell us they are Corsair SP120's. Right now there are three fans like that with different names, and there are others before now that are discontinued. The Corsair SP120 RGB LED High Performance pulls 0.30A max. The Air Series SP120 LED Red High Static Pressure pulls 0.26A max. The iCue SP120 RGB Pro Performance pulls 0.30A max. Older models with NO LED's in them used less. So, exactly which do you have? Do they tell you a max current on the label?

What you need is a pair of Splitters, which are different from Hubs. Here's an example of a 2-pack of 4-pin Splitters, but you CAN use these with 3-pin fans.

https://www.amazon.com/JBtek-Black-...1&keywords=fan+splitter&qid=1609561880&sr=8-3

Note that these devices have only two types of "arms" / connections. There is one input for the mobo header, two outputs (male) for the fans, and no others. On the other hand, that Hub you have also has a third "arm' to connect to a SATA power output from the PSU. That's the easy difference to spot. The Splitter gets ALL its power from the host header, so the header's current limit is important.

I will assume that your fans are ones with max current specs over 0.25 A each, so you can NOT connect 4 of them to one header. You do have two SYS_FAN headers to use, however, so two Splitters to connect two fan to each solves the problem. Once you get them and hook them all up, go into BIOS Setup (see manual p. 25) and for EACH of those two headers, configure Fan Control Mode to use Voltage, not PWM. Remember to SAVE and EXIT. You will not be using the Hub for this any more.

This will allow the mobo headers to control the speed of your 3-pin SP120 fans.

 

[M3rKn]

That device can only control the speed of the new 4-pin PWM type fans.

It can control 3 pin fans. So long as the header the hub is connected to is set to auto or voltage.

But the user needs to connect at least one fan to the correct port on the hub or the fans will operate at one speed as the user is experiencing.

The hub has one port with a barely visible "dial" that is "fan port 1."

The user likely misunderstood the directions and connected the hub's 4 pin connection to Fan Header 1 on the motherboard, but it doesn't matter which header on the motherboard it is connected to. What matters is the fan port on the hub, because that is the only port that can be identified by the system.

With that said... Since the user only has 4 fans I would prefer to populate the mobo headers before using a hub. It is cleaner than a hub IMO & you have more control of individual fans. T

 

[Paperdoc]

M3rKn, you and I may be using two terms differently. I have complained before that sellers often use the terms "Splitter"and "Hub" interchangeably, and they are different devices.

I use the term "Splitter" for the simple device that merely connects all the outputs to the input in parallel, so that all the power for the fans comes from the host header. Now, not quite "all": Only ONE output connector should be set up to return the speed signal it gets on Pin #3 of its fan to the host header, because that header can deal with only one fan's speed signal pulse train. All other outputs must not send back the speed signal, and often this is done merely by omitting Pin #3 of all but one of the male output connectors. When you use a Splitter, the Ground (Pin #1) and +VDC line (Pin #2) are fed to all outputs. IF you are using a 4-pin Splitter, then also the PWM signal from host header Pin #4 is sent out to all fans. So, whether you configure the host header to use Voltage Control Mode (aka DC Mode) or to use PWM Mode, those signals are sent to all fans.

I use the term "Hub" for the device that changes significantly the +VDC line. In a Hub, there is NO connection from the host header's Pin #2 to the output connectors for the fans. Instead, the Hub has a third "arm" to connect to a power source from the PSU (either 4-pin Molex or SATA), and it feeds the fixed +12 VDC supply from there to all of the Pin #2 points. So ALL fans on a Hub get a fixed +12 VDC supply at all times from the Hub, and the normal 1.0 A limit on the max current a mobo header can supply is avoided.

Now review the difference between the two methods (or MODE setting) of how fan motor speed is controlled. For a 3-pin fan, the method is to alter the VOLTAGE sent out on Pin #2, from 12 VDC (full speed) to about 5 VDC (minimum speed without danger of stalling). For a new 4-pin PWM style fan, the voltage sent out on Pin #2 is ALWAYS 12 VDC, and the new PWM signal in on Pin #4. Inside the 4-pin fan is a small chip that uses that PWM signal to modify the flow of current from that fixed 12 VDC line though the motor windings to change the motor speed.

If you match motor type to the header MODE, it all works. But what about mis-matching? If you plug a 3-pin fan into a header using PWM Mode, it gets a constant 12 VDC power supply from Pin #2, and it does NOT receive the PWM signal from Pin #4 (no connection) but it could not use that, anyway, because it has no special chip. So that fan always runs full speed. That is why I said you cannot control the speed of a 3-pin fan from a HUB designed for use with 4-pin fans. In fact, if you read the fine print on many, the Hub maker will say it "supports" 3-pin fans but WITHOUT control of speed. If you plug a 4-pin fan into a header using Voltage Control Mode, it gets no PWM signal and so it cannot alter the flow of current from the power line. BUT that line (Pin #2) supplies a VARYING voltage, so the motor speed IS under control by the mobo. Technically this is not quite as good as using the "proper" PWM Mode for such a motor, but it does work. This is one of the backwards compatibility features of the PWM fan system design.

By far the majority of Hubs (as I label them) sold today require that they receive the PWM signal from the host header and the fixed +12 VDC supply from the PSU, and simply distribute those two signals (plus Ground) to all their fans. Hence they can ONLY be used to control the speed of 4-pin fans. There are a very few models out that do it differently. A few do a conversion for SOME of their output ports, thus creating Voltage Control Mode ports for 3-pin fans as well as providing other unchanged PWM Mode ports for 4-pin fans. They still require a PWM signal from a mobo header using PWM Mode. The most recent Phanteks Universal Fan Controller goes one step further. I has both 3-pin Voltage Control Mode ports and 4-pin PWM Mode ports, but it can accept as inputs from the host header either Voltage Control Mode or PWM Mode signal sets.

By the way, a mobo fan header does NOT need or use the speed signal for speed control. It DOES use it for another function: fan FAILURE detection. If the speed signal fails (or, in some mobos, if it falls below some value you MAY be able to set), that is recognized as a fan failure and generates an alarm and possibly other protective actions. But when you use a Splitter or a Hub, only ONE fan on each such device can have its speed monitored that way. Hence, the user should check from time to time that all fans are operating.