Easy way to match system fan speed to CPU fan speed?

[hadbeen]

I am trying to find an easy-ish way (whether it be a hardware or software based solution..the latter seems easier..) to match the speeds the two fans on my thermaltake frio heatsink. I know I could just get two PWM fans and have a PWM signal splitter and do it that way, but I'd rather not have to spend the money on them. I am wondering if any of you know a way to match the voltage variation of the CPU fan header to one of the sys_fan headers. right now I have the fan on the sys_fan header set to around 1800rpm via the potentiometer that comes with the fans. it's a bit loud and unnecessarily high when I'm not doing CPU intensive tasks (which is most of the time). I'm not totally sure how the mobo varies the voltage of the fan on the CPU header (whether it varies the +12v or varies the ground between 0 and higher) and I know that it is unwise to put strain on the headers. Any suggestions would be appreciated. Thanks! (By the way the fan on the CPU header is the same as the one on the sys_fan header. The one on the cpu_fan header has its potentiometer set to the "high" setting..not sure how that voltage control system actually works if it's an op amp in the fan circuitry or what)

MoBo: Gigabyte A75-UD4H
CPU Cooler: Thermaltake Frio
CPU: AMD A8-3870k
Memory: G.Skill Ripjaws X 1833 9-10-9-28
Case HAF-X (truly excessive for the components..got a good deal on it and waiting for haswell or ivybridge-E to come out to drop serious cash)

 

[airdeano]

if you are using a PWM (4-wire) fan, the motherboard uses the frequency on the PWM signal to
turn the fan on/off to regulate the speed. some motherboards can control the 3-pin variety of fans
by using voltage to turn the fan up or down in speed. most of the time, the speed is controlled by
heat sensors.

to match via a seperate controller will be a guess unless you have an propeller tachometer or can
monitor the voltage of the HSF fans.

airdeano

 

[hadbeen]

if you are using a PWM (4-wire) fan, the motherboard uses the frequency on the PWM signal to
turn the fan on/off to regulate the speed. some motherboards can control the 3-pin variety of fans
by using voltage to turn the fan up or down in speed. most of the time, the speed is controlled by
heat sensors.

to match via a seperate controller will be a guess unless you have an propeller tachometer or can
monitor the voltage of the HSF fans.

airdeano

the fans do have a propeller tachometer but are not PWM...I know that it would be an easy fix to just go PWM and have a PWM signal splitter from the cpu_fan header connected to the PSU and the two fans so no need for any additional software control. I am hesitant to go with the PWM fans because it's an economy system and although fans don't go bad, when I upgrade the internal components in a year or two, I'll probably go WC

 

[Lollipop]

Hook them up to the PSU wit fan speed reducers. Or get a y-splitter.

 

[hadbeen]

Hook them up to the PSU wit fan speed reducers. Or get a y-splitter.

should it be safe to have to 120mm fans connected to the cpu_fan header? I've heard it generally something to stay away from for fear of over amping the MoBo

 

[airdeano]

should it be safe to have to 120mm fans connected to the cpu_fan header? I've heard it generally something to stay away from for fear of over amping the MoBo

personally.. i dont use the mobo headers... buy the right fan or close and undervolt it
to the correct tolerance from the PSU molex power harness. stringing a gang of
fans from a mobo header is looking for issues. the traces on the boards are not
large (.010" or smaller or 30awg). some use a phoyba or gelid splitter that routes
power from the PSU , and the mobo header controls the PWM and tach function.

airdeano

 

[hadbeen]

unfortuntately the fans are not PWM and controlled by modding the +12v up and down..I was thinking maybe I could build a circuit with a BJT that takes the cpu_fan header voltage as input and regulates voltage from the PSU from 0 to +12v. I would think that it would be a fairly easy thing to build since we're not having to worry about being rated for high voltage/amperage and (it's been a while since I've used BJT's but..) I can't think of a reason why there'd be feedback from the PSU to the mobo header...well..that is as long as it's wired correctly...lol

 

[hadbeen]

Update:

I found that the voltage control of my sys_fan2 header wasn't working properly...using the sys_fan1 header instead and works fine. SpeedFan is doing it's job and my PC is at least 10dB quieter when idle.

 

[Reinforced.v2]

Hi would the hyper 212 evo fit with the corsair vengeance high profile and I have 2 of them plz advise ASAP

Thanks

 

[mattyb]

Hi hadbeen - I've had exactly the same issue with Sys_Fan1 header working fine, but Sys_Fan2 header not working. Have you managed to figure out why this is?

 

[airdeano]

Hi would the hyper 212 evo fit with the corsair vengeance high profile and I have 2 of them

you'd be better served to create a new thread, instead of starting a new topic in an older thread.

it can fit, but the limitations of the case come into play. the outer fan can be raised up
to clear RAM 'sinks, but may impeaded the case side-panel. if this is the case, simply
reverse the fan and install on opposite side.

airdeano

 

[hadbeen]

Hi hadbeen - I've had exactly the same issue with Sys_Fan1 header working fine, but Sys_Fan2 header not working. Have you managed to figure out why this is?

nope..no idea why this is..I've tried using the bios and speedfan to control Sys_Fan2...no luck. I'm curious..are you using the same board/brand as I am? maybe it's an issue with either gigabyte boards or this specific board/series. Currently I'm using speedfan and it works perfectly and is in sync with the cpu fan...sooo much quieter when I'm not maxing out the processor

 

[mattyb]

Yes, I'm using the Gigabyte GA-A75-UD4H as well - exactly the same.

I can also get the CPU fan and Sys_Fan1 running perfectly with Speedfan - just as you say.

I might try emailing Gigabyte and see if it's a known issue.

 

[hadbeen]

Yes, I'm using the Gigabyte GA-A75-UD4H as well - exactly the same.

I can also get the CPU fan and Sys_Fan1 running perfectly with Speedfan - just as you say.

I might try emailing Gigabyte and see if it's a known issue.

probably your best bet..I would prefer to use the sys_fan2 header because it looks cleaner than having a fan cable reach down from the second CPU heatsink fan.but whatever..if I really wanted to I'd go buy two or three high end practically silent PWM fans..two for the heatsink and one for the back and get a PWM splitter that will link the signal from the CPU header..but that's a lot of money..thought I might do that and just save the fans for whenever I upgrade my MoBo and processor for a WC radiator..imagine a few of these combined with a fast water pump

http://www.newegg.com/Product/Product.aspx?Item=N82E16835706015

it would be so loud..yet 5ghz on a WC setup would be a breeze (no pun intended)