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PWM wiring for case fans - can I do this?

post #1 of 3
Thread Starter 
Let's say I have 4 case fans, all PWM, and I wanted to control them but only have 1 PWM header on my motherboard left (this is just hypothetical, yes I know my mobo has 2). Tell me if this would work:

Ground/power etc connected to the PSU via molex, while the blue wire (which is for the PWM signal) for all 4 of the fans gets connected onto a single PWM header on the motherboard. Is that something that would A) work and B) not overload the motherboard?

I know if you use Y splitters and connect too many fans to one header, that you can overload it because its not able to provide that much power. But is that also true for the PWM connector?

ty guys smile.gif
    
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post #2 of 3
Quote:
Ground/power etc connected to the PSU via molex, while the blue wire (which is for the PWM signal) for all 4 of the fans gets connected onto a single PWM header on the motherboard. Is that something that would A) work and B) not overload the motherboard?
YES

wire up like is. - exactly like you had it.

AK-CB002_f00.png

Only 1 fan gets the RPM connected
Edited by andrewmchugh - 8/8/11 at 2:15am
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post #3 of 3
Thread Starter 
EDIT: Andrew thanks, yeah I feel like I've seen that cable before, I didn't realize it had all the blue wires into a single PWM header.

I guess it works then... smile.gif

==========

Just came across a random thread, where someone posted a really handy PWM pdf file.......
Quote:
If driving multiple fans with a single PWM output, an open-drain / open collector output
buffer circuit is required. Consult your Hardware Monitor vendor for layout suggestions.

http://www.formfactors.org/developer%5Cspecs%5C4_Wire_PWM_Spec.pdf

Hmm... sounds like one of those things where I'm gonna have to scour the internet for some random person that's done it. I read on another forum "you may need a PWM amplifier because the signal gets weakened with additional fans". I'm not sure why it would though, in this PDF I read that it uses .025A for the signal. How can it get weakened? Is it via some other mechanism than current?

I also am hearing that a lot of mobos can actually handle the current draw of as many as 4-5 PWM fans (because fans draw like .3A, and the header can handle around 1.5A or more for newer boards - not sure for mine atm).

If that's the case I cant wait to get 4 more blademasters lol...
Edited by donkrx - 8/8/11 at 2:23am
    
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