Pairing PWM

Control: management of fans, temp/rpm monitoring via soft/hardware

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Juventas
Posts: 30
Joined: Wed Mar 07, 2007 10:25 pm
Location: Canada

Pairing PWM

Post by Juventas » Mon Jun 21, 2010 11:34 pm

I want to run two PWM fans at the exact same speed. I notice there are "PWM splitters", but I wonder what that does to the RPM and PWM signals. Obviously it can't give both RPMs, so is the result whichever is higher? An average of the two? And what happens with the PWM signal?

lodestar
Posts: 1683
Joined: Fri Aug 05, 2005 3:29 am
Location: UK

Post by lodestar » Tue Jun 22, 2010 12:31 am

PWM splitter cables have one socket wired with all four wires including fan speed sensing, and the other(s) with only three without fan speed sensing. So only one fan supplies information about its speed, which is normally the CPU fan. The PWM signal is based on duty cycle %, so for two identical fans they should both run at effectively the same speed.

cmthomson
Posts: 1266
Joined: Sun Oct 09, 2005 8:35 am
Location: Pleasanton, CA

Post by cmthomson » Tue Jun 22, 2010 5:22 pm

Take a look at the Arctic Cooler PWM fans. They come with all the cabling and connectors needed to daisy chain multiple fans off a single PWM motherboard 4-pin controller header, and attach the sense lines from each fan to any available 3-pin headers on the board.
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