controlling fan speeds with fan splitter

[Peterthecat1]

I have a fan splitter that has a 4pin to MB and 3 peripheral fan connection one is 4 pin the others are 3 pin and has one molex that I assume is for power only....I have five case fans and am trying to keep them quiet... not sure how this device will work I think that all fans connected to this device thru the fan headers will be controlled by the MB and MB software(MSI 970 Krait)...what exactly does the molex connector do??? can I have 2 addition splitters here to accommodate the five fans?? what if I leave the molex unplugged can one MB header control 5 fans??

 

[Paperdoc]

Last question first: no. Most mobo fan outputs appear to be able to supply up to two fans, but not more. So you can't connect 5 to one mobo SYS_FAN port.

The splitter you describe is an odd one I have not seen, for two reasons. One is that you say it has one 4-pin "input" connector to go to a mobo port and then four "outputs", of which only one is 4-pin. No 4-pin PWM Mode port can control 3-pin fans. Moreover, as I said, you can't connect 4 fans to one mobo port. Secondly, you say there's also a Molex connector, and such a thing can only pick up 12 VDC power for fans - it cannot control anything.

Now, there is a way to use mobo control of multiple fans from ONE mono SYS_FAN port, but only on condition that ALL the fans AND the mobo port MUST be of the 4-pin variety, and the mobo port must actually be operating in PWM Mode. The unit needed is a 4-pin fan Hub. That device also will have one 4-pin Molex connector, or possibly a connector for a SATA power output instead. It gets power for all its fans from the PSU via that last power connector. It picks up the PWM signal only from one SYS_FAN mobo port. It then shares the PWM control signal to all its fans, but supplies the actual power to the fans from the PSU source.

I have seen one similar device with a significant difference, the Phanteks PWM Hub. It looks similar, except that all its output ports (six of them) have three pins, and operate only in Voltage Control Mode. This Hub apparently uses the PWM control signal from one SYS_FAN port and internally creates six 3-pin Voltage Control Mode ports for its fans. Any 3-pin fan con be connected to its ports and will run under control of that mobo SYS_FAN port. Even 4-pin fans can be connected to this Hub, because a 4-pin fan has a backwards compatibility feature that allows it to be controlled by a 3-pin Voltage Control Mode port.

 

[Peterthecat1]

Last question first: no. Most mobo fan outputs appear to be able to supply up to two fans, but not more. So you can't connect 5 to one mobo SYS_FAN port.

The splitter you describe is an odd one I have not seen, for two reasons. One is that you say it has one 4-pin "input" connector to go to a mobo port and then four "outputs", of which only one is 4-pin. No 4-pin PWM Mode port can control 3-pin fans. Moreover, as I said, you can't connect 4 fans to one mobo port. Secondly, you say there's also a Molex connector, and such a thing can only pick up 12 VDC power for fans - it cannot control anything.

Now, there is a way to use mobo control of multiple fans from ONE mono SYS_FAN port, but only on condition that ALL the fans AND the mobo port MUST be of the 4-pin variety, and the mobo port must actually be operating in PWM Mode. The unit needed is a 4-pin fan Hub. That device also will have one 4-pin Molex connector, or possibly a connector for a SATA power output instead. It gets power for all its fans from the PSU via that last power connector. It picks up the PWM signal only from one SYS_FAN mobo port. It then shares the PWM control signal to all its fans, but supplies the actual power to the fans from the PSU source.

I have seen one similar device with a significant difference, the Phanteks PWM Hub. It looks similar, except that all its output ports (six of them) have three pins, and operate only in Voltage Control Mode. This Hub apparently uses the PWM control signal from one SYS_FAN port and internally creates six 3-pin Voltage Control Mode ports for its fans. Any 3-pin fan con be connected to its ports and will run under control of that mobo SYS_FAN port. Even 4-pin fans can be connected to this Hub, because a 4-pin fan has a backwards compatibility feature that allows it to be controlled by a 3-pin Voltage Control Mode port.

this is the item http://www.newegg.com/Product/Product.aspx?Item=N82E16812423164

looking at the reviews on this i see most are not getting adjustments using PWM for their fans and originally i got this just to add more fans and control wiring for fans that come stock with a 3pin conn and have a large wire cluster to adapt to molex... the MB doesnt appear to have an alternative to PWM on the bios... it does have software called command center tho i usually dont install much extra stuff on a build... any body use this software for fan control ie voltage reg

anybody ever make their own speed control for multiple fans from a single control knob... saw some tutorials and videos and none really the same...looked like a potentiometer from an electronics store and a long molex extension should do it????

 

[Paperdoc]

The item you linked really is the common "4-pin fan hub" I described. It just does not have a central block of connectors. It gets fan power from one 4-pin Molex male connector that picks up only the Ground and 12VDC lines from the PSU. It uses one 4-pin fan female connector to a single mobo SYS_FAN port to connect to the fan speed (Pin #3) and PWM Signal (Pin #4). It has three output connectors of the 4-pin male design, but only one of those has all four pins. The other two, which I think you called 3-pin connectors, are just missing their Pin #3. This is to ensure that, of the three 4-pin (PWM) fans you connect, only ONE will actually send its speed signal back to the mobo port, and that is the correct way to do this. Each fan generates a speed pulse signal (2 pulses per revolution) and sends it back to the mobo on Pin #3 for counting. If you connect more than one fan to a mobo fan port, you must NOT send to the port more that one fan's speed pulse signal. Otherwise the port's pulse counting solftware would be very confused with many pulses at random timings.

So, that splitter is for use ONLY with 4-pin fans and a 4-pin mobo header, BOTH truly operating in PWM Mode.You must understand that what it does is send to its three fans a constant 12 VDC power supply on Pins 1 and 2, and a PWM signal on Pin 4. If you connect a 3-pin fan to an output, that fan will not receive the PWM signal and could not use it anyway, so it will always tun at full speed. Another way this plan can "fail" is if the mobo SYS_FAN port is really a 3-pin port operating in Voltage Control Mode. In this situation the varying voltage on mobo port Pin #2 is NOT passed on to the fans because the fans' power is coming from the PSU source via the Molex connector. Even if the mobo port has 4 pins, there are two possible ways for this to not work. One is that SOME mobos allow you to set the way the 4-pin port operates, either as PWM Mode or Voltage Control Mode. If you do NOT set it to PWM Mode, there will be no PWM signal to pick up and share with the three fans. The other possibility for "failure" is that SOME mobos provide "fake" 4-pin mobo SYS_FAN ports that really are only 3-pin ports with a fourth useless pin, and that operate only in Voltage Control Mode and fail to provide the PWM signal required.

OP, you hope was to use automatic control by one mobo SYS_FAN port of several fans via this splitter / hub. However, that cannot work for 3-pin fans that cannot use the shared PWM signal. Using this unit, all your 3-pin fans WILL work with proper power from the PSU (not overloading the single mobo fan port) BUT they will not be under control - they will all run full speed all the time. You could get that result without this splitter by merely connecting all the fans via adapters directly to a PSU 4-pin Molex output.

For your situation, you CAN control multiple 3-pin (Voltage Control Mode) fans from ONE mobo SYS_FAN 4-pin header IF you buy and use the Phateks PWM Hub I mentioned. Instead of simply sharing the PWM signal to its fans (as the splitter you linked does) the Phanteks unit uses that PWM signal to create six of its own 3-pin fan ports that do operate in Voltage Control Mode to run your 3-pin fans under proper control.

Hypothetically you could just connect all the 3-pin fans to a single PSU 4-pin Molex output using only the Ground and +12VDC lines, and inserting into the voltage line a variable resistor (wired as a series resistor, and not a true potentiometer). You'd need to do a bunch of calculations to figure out the proper resistance and the power rating of that resistor. You also would need to figure out how to deal with two significant issues for such a circuit: the fans cannot reliably start up from stop unless their voltage is at least 7 VDC, and at some slightly lower voltage (maybe 5 to 6 VDC) even a running fan with good bearings will stall and not re-start. Properly-designed third-party "fan controller" modules take care of these issues for you by designing circuits containing much more that a mere series variable resistor. Then you still have to understand that any manually-controlled fan speed control system makes YOU the "brains" of the control. That is, YOU must decide what speed the fans need to be running to keep your system cooled properly, AND you must monitor your system and change the fan settings as your workload changes. If you want your fans to be automatically controlled according to actual temperatures measured by properly-placed sensors calibrated for your system, that can't be done with third-party fan controllers. It CAN be done by the mobo automatic controllers IF you use the correct tools to connect fans to the mobo ports.

 

[Peterthecat1]

The item you linked really is the common "4-pin fan hub" I described. It just does not have a central block of connectors. It gets fan power from one 4-pin Molex male connector that picks up only the Ground and 12VDC lines from the PSU. It uses one 4-pin fan female connector to a single mobo SYS_FAN port to connect to the fan speed (Pin #3) and PWM Signal (Pin #4). It has three output connectors of the 4-pin male design, but only one of those has all four pins. The other two, which I think you called 3-pin connectors, are just missing their Pin #3. This is to ensure that, of the three 4-pin (PWM) fans you connect, only ONE will actually send its speed signal back to the mobo port, and that is the correct way to do this. Each fan generates a speed pulse signal (2 pulses per revolution) and sends it back to the mobo on Pin #3 for counting. If you connect more than one fan to a mobo fan port, you must NOT send to the port more that one fan's speed pulse signal. Otherwise the port's pulse counting solftware would be very confused with many pulses at random timings.

So, that splitter is for use ONLY with 4-pin fans and a 4-pin mobo header, BOTH truly operating in PWM Mode.You must understand that what it does is send to its three fans a constant 12 VDC power supply on Pins 1 and 2, and a PWM signal on Pin 4. If you connect a 3-pin fan to an output, that fan will not receive the PWM signal and could not use it anyway, so it will always tun at full speed. Another way this plan can "fail" is if the mobo SYS_FAN port is really a 3-pin port operating in Voltage Control Mode. In this situation the varying voltage on mobo port Pin #2 is NOT passed on to the fans because the fans' power is coming from the PSU source via the Molex connector. Even if the mobo port has 4 pins, there are two possible ways for this to not work. One is that SOME mobos allow you to set the way the 4-pin port operates, either as PWM Mode or Voltage Control Mode. If you do NOT set it to PWM Mode, there will be no PWM signal to pick up and share with the three fans. The other possibility for "failure" is that SOME mobos provide "fake" 4-pin mobo SYS_FAN ports that really are only 3-pin ports with a fourth useless pin, and that operate only in Voltage Control Mode and fail to provide the PWM signal required.

OP, you hope was to use automatic control by one mobo SYS_FAN port of several fans via this splitter / hub. However, that cannot work for 3-pin fans that cannot use the shared PWM signal. Using this unit, all your 3-pin fans WILL work with proper power from the PSU (not overloading the single mobo fan port) BUT they will not be under control - they will all run full speed all the time. You could get that result without this splitter by merely connecting all the fans via adapters directly to a PSU 4-pin Molex output.

For your situation, you CAN control multiple 3-pin (Voltage Control Mode) fans from ONE mobo SYS_FAN 4-pin header IF you buy and use the Phateks PWM Hub I mentioned. Instead of simply sharing the PWM signal to its fans (as the splitter you linked does) the Phanteks unit uses that PWM signal to create six of its own 3-pin fan ports that do operate in Voltage Control Mode to run your 3-pin fans under proper control.

Hypothetically you could just connect all the 3-pin fans to a single PSU 4-pin Molex output using only the Ground and +12VDC lines, and inserting into the voltage line a variable resistor (wired as a series resistor, and not a true potentiometer). You'd need to do a bunch of calculations to figure out the proper resistance and the power rating of that resistor. You also would need to figure out how to deal with two significant issues for such a circuit: the fans cannot reliably start up from stop unless their voltage is at least 7 VDC, and at some slightly lower voltage (maybe 5 to 6 VDC) even a running fan with good bearings will stall and not re-start. Properly-designed third-party "fan controller" modules take care of these issues for you by designing circuits containing much more that a mere series variable resistor. Then you still have to understand that any manually-controlled fan speed control system makes YOU the "brains" of the control. That is, YOU must decide what speed the fans need to be running to keep your system cooled properly, AND you must monitor your system and change the fan settings as your workload changes. If you want your fans to be automatically controlled according to actual temperatures measured by properly-placed sensors calibrated for your system, that can't be done with third-party fan controllers. It CAN be done by the mobo automatic controllers IF you use the correct tools to connect fans to the mobo ports.

Thanks for the very well explained reply... probably will go with Phantex item as its prob more fool proof
what about this ? same thing?
http://www.amazon.com/SMAKN%C2%AE-temperature-controlled-supports-Ports-SATA-port/dp/B015BZ6FHA/ref=sr_1_5?ie=UTF8&qid=1452708712&sr=8-5&keywords=fan+hubs

 

[Paperdoc]

No, not the same. That SMAKN unit appears to be only a common 4-pin hub. It is intended to control only multiple 4-pin PWM Mode fans from one mobo SYS_FAN port, and says it does NOT exercise speed control over any 3-pin fan connected to it. Such a 3-pin fan will only run full speed.

 

[Peterthecat1]

No, not the same. That SMAKN unit appears to be only a common 4-pin hub. It is intended to control only multiple 4-pin PWM Mode fans from one mobo SYS_FAN port, and says it does NOT exercise speed control over any 3-pin fan connected to it. Such a 3-pin fan will only run full speed.

ok great looks like the Phanteks or bust!!!