Question Help with PWM Splitters

Sep 6, 2020
5
0
10
0
I am finishing up my first pc build.
I have a b450M gaming MoBo, that has only 2 system fan headers and a cpu fan header.
I guess the cpu fan header will be used by the cpu cooler (wraith prism), so that leaves me with 2 open spots
And I need to connect :
2x140mm front fans
1x120mm back fan that came with case, which is connected to a rgb hub. So really, I need to connect the hub to a 4 pin in the motherboard
Last, connect the wraith prism rgb, either via 4pin or USB.
___
So, I was thinking that I needed a fan splitter for the front fans and connect them both to sys_fan1,
and connect the hub to sys_fan2.
And lastly connect the wraith prism to a usb2.

So I have 3 questions.
1)Is this correct?
  1. Related to 1, should I connect the wraith prism rgb to the HUB. even though the hub inputs are 3 pin?
  2. Lastly, what is the fan splitter that I need? Should it have 4 pin entry connection, and 4 pins on both of the split ends?
Or is it 4 pin on the entry connection and on the split end, one 3 pin and one 4 pin?
Or is it 4 pin on the entry connection and on the split end, both 3 pin?

Thanks for reading, been learning about pcs for the last couple of weeks so I'm not really acquainted with the terminology or the correct translation to spanish, which is why I made the questions so long.
 

jojesa

Illustrious
I have a b450M gaming MoBo, that has only 2 system fan headers and a cpu fan header.
I guess the cpu fan header will be used by the cpu cooler (wraith prism), so that leaves me with 2 open spots

Last, connect the wraith prism rgb, either via 4pin or USB.
Which PC case model do you have?
Could you post a picture of the RGB hub?

The isn't either or....the CPU cooler must be connected to the motherboard CPU fan header.
The RGB and USB are optional.
The RGB cable could be connected to the 4-pin RGB header or hub if you want RGB lighting.... and the USB cable to a USB header on the motherboard.
The Wraith Prism LED lighting is divide in two sections and to have both you will need the 4-pin RGB cable and USB cable.

Related to 1, should I connect the wraith prism rgb to the HUB. even though the hub inputs are 3 pin?
The Wraith Prism should be connected to a 4-pin RGB header or hub.

Lastly, what is the fan splitter that I need? Should it have 4 pin entry connection, and 4 pins on both of the split ends?
You could get a 4-pin to 3-pin fan splitter like the one on this link
 

Paperdoc

Glorious
Ambassador
To start with, like many others, you have been confused by the way the labels "3-pin" and "4-pin" are used.

Today's RGB Fans really are two devices in one unit - a fan motor, and some RGB lights in the fan frame. Each has its own separate power cable. One cable for the fan MOTOR ends in a female (with holes) standard fan connector about ½" wide, with two ridges running down one side. The ridges slip around a plastic tongue sticking up beside Pins 1-3 on the male mobo fan header. Fans come in two different designs that require different methods of speed control by the host header. The older Voltage Control Mode fans use a 3-pin connection; the newer PWM fans use a 4-pin connection. So the MOTORS are often called 3-pin or 4-pin fans.

The other cable is solely for the LIGHTS in the frame, and these also come in two forms. the plain RGB lighting system uses a wider 4-pin connector that carries a common 12 VDC power supply line and three separate Ground lines for the three colours of LED's in the lights. The control system allows many light colours and changes of them, but at any one moment the entire strip of lights is all one colour. When using these type, note carefully that the connector and the header each have the hole (or pin) on one end marked for the +12 VDC power line. At every connection point these MUST be matched up. The second type of lighting is called Addressable RGB or ADDR RGB or ARGB or Digital RGB. It uses a THREE-pin connector that looks just like the 4-pin one, but with one pin (or hole) missing. This supplies common +5 VDC and Ground lines, and a Digital Control Line. This system can set different colours all along the light strip, so you can get complex displays like rainbows, even moving ones. Because both the power supply and the method of display control are quite different between these two, you can NOT mix the two types in one circuit. So now the two LIGHT systems also are labelled as "3-pin" (ADDR RGB with 5 VDC) and "4-pin" (plain RGB and 12 VDC), and that has NOTHING to do with the fan MOTOR type, even though they have used the same labels!

An additional note on lighted fans. An earlier design called LED FANS had some LED's (usually only one colour) in the frame that were merely connected in parallel with the motor, and light up whenever the motor is running, This type has only ONE cable that feeds both motor and LED's, and you have no control over the lights. IF you have that type we need to be a bit cautious, because the LED's add power needs to take into account in where to plug the fan in.

Now we get to connecting several devices to one mobo header. You can get both Splitters and Hubs for fan MOTORS, and which type if device you use depends on whether the motors are 3-pin or 4-pin, and on how many fans you are connecting to a single mobo fan header. The label "PWM" specifically refers to one type of FAN MOTOR design and control system. Similarly, you can get Splitters and Hubs for RGB LIGHTS of either type, but these are NOT the same as the devices used to connect MOTORS to headers.

OP, I can tell you something important about your Wraith Prism cooler. It contains the ARGB type of lights (3-pin 5 VDC), but the mobo LED_CPU header you have is for the OTHER type of lights - that is, it is a 4-pin plain RGB header you can NOT use with the Wraith Prism. That is why it has a USB cable. You do NOT connect the 3-pin ARGB cable from it to any mob header. Instead you connect the USB cable from a socket on the side of the Prism unit to a mobo USB2 header. Then you download and install the software tool from AMD's Prism web page and use that to configure the lights in the Prism cooler unit.

Regarding the rest, you need to tell us what case you have. If possible tell us the maker and exact model number of the fans you have, both the one included with the case and the others you have bought separately. We need to look up the specs for the MOTOR power requirements and the design type, and for the LIGHTS in the frame of at least one of those fans. Then we can advise where and how to connect them.
 
Last edited:
Sep 6, 2020
5
0
10
0
Thanks for the help so far, My case is the Rockstar 2 (gamemax) https://gamemaxpc.com/productkkk/1012-en.html

So, in very simple terms.
Connect the wraith prism via usb (done)
Connect the front fans with a 4pin splitter to sys_fan1 ? ( Model: Bequiet PureWings 2 140mm x2)
Connect the hub to the sys_fan2 ?

And I can finally turn on my cute beast of a pc?
 

Paperdoc

Glorious
Ambassador
Please look closely at all the fans. You have one pre-mounted on the back with the case, and I believe it has TWO cables. One is for the fan MOTOR and ends in a 3-hole standard fan connector that fits onto a mobo fan header. The other is a wider 3-hole connector (looks like it had 4 holes with one blocked off) and that goes to a LIGHTING header.

Then you have two beQuiet Pure Wings 2 140mm fans for the front with NO lights in them, so they have only ONE cable from them. Those also, I believe, have THREE-hole connectors on the ends.

For the moment, focus on the FAN MOTOR connectors. As I said, I think they all are 3-hole ones. Is that right? If so, most fan HUBS cannot control fan speed for them. But a fan SPLITTER can. HOWEVER, the HUB that has been included with your case MAY be able to control fan speed even on 3-pin fans. It appears to have been designed that way, but I cannot find any manual to tell us for sure. To do that, a Hub needs to "translate" from the PWM Mode control signals a mobo header provides into the older Voltage Control Mode that 3-pin fans use, which is not the way most Hubs operate. BUT your Hub is designed to accept that PWM signal from the mobo, and has THREE-pin outputs for the fan motors, consistent with the 3-pin fan provided with the case. So maybe it does include that "translation" feature.

So, the first option will be to assume that you have those three fans with 3-pin motor connectors, and that the Hub that came with your case CAN control those 3-pin fans. So, connect all three fans' motor connectors to the 3-pin fan output ports of your Hub. Connect to the Hub the power supply cable from a SATA power output from the PSU, and the cable from the mobo SYS_FAN1 header to the Hub's PWM input port. Ensure that, in BIOS Setup, the SYS_FAN1 header is set to use the PWM Mode of control. That should get ALL three fans' speeds under automatic control. If this works, you will not need a Splitter, and not need to use SYS_FAN2 for anything.

Now to the lights. The case has ARGB lights in the front and side panels, plus the ones in the rear fan. Each of those three, I expect, has its own 3-pin ARGB cable that needs to connect to the ARGB output ports of the Hub included with the case. Since you have no ARGB header on your mobo, you do NOT connect any cable from the Hub's "Aura Sync" port to the mobo. ALL control of the case lights will be done with the manual-button remote control box that came with your case. Control of the lights in the Wraith Prism unit will be done separately using the software tool provided for that.

With those connections made, go ahead and start up your system. To get the lights working on case panels and rear fan, you may have to use an On / Off button on the remote control. For the Wraith Prism unit, use the software utility. See how all those work.

Regarding FAN speeds, you need to watch carefully to detect whether their speeds are under control. Before starting up, open the case side and get ready to watch all three fans as soon as you start it up. The NORMAL start-up sequences is this: As soon as you push the On button, all fans atart up at full speed. After a few seconds, all of them will slow down to some reduced speed, because the case is still cold and does not need much cooling. If you do a bunch of work and things heat up, all the fans may speed up a little. SO, if you DO see the fans start fast and then slow down, the automatic fan speed control system IS working.

IF you find that the case fans are NOT under speed control and only run full speed all the time, post back here for alternatives.
 

jojesa

Illustrious
Thanks for the help so far, My case is the Rockstar 2 (gamemax) https://gamemaxpc.com/productkkk/1012-en.html

So, in very simple terms.
Connect the wraith prism via usb (done)
Connect the front fans with a 4pin splitter to sys_fan1 ? ( Model: Bequiet PureWings 2 140mm x2)
Connect the hub to the sys_fan2 ?

And I can finally turn on my cute beast of a pc?
Pretty much so.
Besides connecting the Wraith Prism via USB, connect its fan cable to the CPU fan header.
 

ASK THE COMMUNITY