How to control System_fan_2 with Easytune?

[vsloth]

Hi Lads,

I have x2 NB fans in a push/pull config. I've put em in respectively CPU_Fan, and System_fan_2 which should both be PWM controlled, and both have 4 pins!

The problem is, that CPU_Fan is working like a charm, but the system fan 2, is spinning away like a mad! I tried to work around in Easytune, but with no luck! Only thing I can, is to use Smartfan to decrease the speed - but then I lose the PWM feature.

So what I want, is the system_fan_2 to follow CPU_Fan in RPM, and stays in PWM mode! Is there any way to do this? Easytune appears not to be working, since it only affects CPU_Fan!

 

[o1die]

I use a zalman fan mate rpm adjuster, which costs about $7 at frys. It has a small knob that adjusts manually.

 

[bilbat]

This shows how to 'split' both PWM and standard 3 pins:

 

[vsloth]

So the only way to have them controlled simultanious, is by redo the wires??

 

[bilbat]

SYS_FAN2 is never PWM; how it works is that pin 4, which would normally be the PWM command, or 'gating' signal, is held at a constant +5V - thus 'locking on' the PWM switches in a PWM fan; the pin 2 +12V is then 'modulated' (they claim; I haven't seen it...); you want it 'slaved' to the CPU fan, split the CPU_FAN header...

 

[vsloth]

Allright, thanks!

Will it be safe to take the wires out of the fan plug, that intentionally should be in sys_fan2, and merge them into the CPU_FAN plug?

 

[bilbat]

Will it be safe to take the wires out of the fan plug, that intentionally should be in sys_fan2, and merge them into the CPU_FAN plug?

I'm not quite sure what you mean by that - the diagram on the right is the one you want... Tell me how many fans for what, and I'll 'customize' one for you - and give you a parts list... NE sells some PWM splitters that are almost right, but need surgery to a wire or two - for that I use cheap three pin fan extensions. The trick is, you want pins 1, 2, & 4 shared to all fans, but a seperate header for each fan carrying pin 3 - that one's the 'sense' pin, so your board can 'see' the individual fan speeds...

 

[vsloth]

Yeah sorry, a bit hard for me, to explain in english. Tried to illustrate it here, I hope you get the idea.


As seen on the picture, I ask if it's safe to simply take the wires from Fan2, and mash em' down into the Fan1 plug (as I did with some hustle electrical installations at home)

Illustration:

 

[bilbat]

That will not work as shown - but would be close. You need to leave out the second fan's pin three wire (usually yellow) from the 'mashing' - preferably, leave it in the original second fan's plug, and plug that into SYS_FAN2 - here's why: the fans have a little magnetic 'hall-effect switch' (well, actually, usually two) that 'fires' pin three twice per revolution; this is called the fan's 'feedback', as it 'feeds back' the information about how fast the fan is spinning to the chip (LPCIO - low pin count input/output) that's resposible for the fan control. If you give it two sets of pulses, it can't do speed control properly - as those tachometer pules will get scrambled...

 

[vsloth]

Thanks for that info!
If I do it like that, Bilbat - will the two fans still be controlled at simultanious speeds?

 

[bilbat]

That's kind of a 'yes and no' answer... If you 'split' the CPU_FAN power to more than one fan, both will be controlled 'simultaneously', but their speeds will only be the same if both fans are rated for the same top speed, as PWM control is done as a percentage of full speed. If you look at these fans, you will see that there are several physically identical fan types, which have different models with varying top speeds/maximum airflows... I have six case fans in my system, controlled by a five channel PWM controller; among them are two different 'types' (three 'cage type' exhausts, three 'tunnel type' intakes) with four different top speeds. I have one 'mighty blaster' cage exhaust on the rear panel; a pair of somewhat slower cages doing top exhaust duty; an extremely fast, high capacity tunnel for general bottom intake, and two slower tunnel types on the rear and top of my hard drive cage, just to keep air moving over the drives - the variety of speeds lets me 'tune' the tradeoff between airflow and noise, as well as adjust for varying ambient (I live near Milwaukee, WI, where our ambient varies between -25°C and +38°C!) temperatures.