[mythtv-users] Fancontrol with replaced CPU fan

[Tortise]

----- Original Message ----- 
From: "Brian Wood" <beww at beww.org>
To: "Discussion about mythtv" <mythtv-users at mythtv.org>
Sent: Tuesday, October 13, 2009 11:33 AM
Subject: Re: [mythtv-users] Fancontrol with replaced CPU fan


Yes, simply varying the voltage isn't the best way to control a DC motor's
speed, but you can get away with it at the low currents most fans use. PWM is
in fact a more efficient way to control the speed, less power thrown away as
heat. The mobo may in fact be using a PWM variable voltage source, I'm not
sure.

I have a few little modules that can control a fan's speed using PWM, they can
be had cheaply, but use a manual potentiometer to set the speed. I use them
to set the maximum speed the mobo can run the fan(s) at.

=====================

Can you detail what you have?  One interest I have - I have been experimenting with water cooling my boxes.  I've been using 
Thermaltake T500 pumps which have good longevity bearing specs and seems reasonably made.  They proved to be noisy (that means 
audible) when run from the 12V rail, so I tried running it on the 5V rail and wallah, it still works!  (Pulled the molex pins out 
and plugged them in the other side to get 5V!)  Suspending them from the pipes (!) also reduced the noise as the noise to case 
conduction was largely eliminated.

These boxes run the CPU and NVIDIA chips at 39-42 degrees.  I figure this may be a benefit in longevity and maybe stability terms, 
however I do not know for sure.  There are times when I've found a CPU running at 100% for ages.....still 40 degrees gives one a 
degree of confidence the CPU can hack that.  (I am not overclocking, just seeking noise reduction)

As noted it might not be best for the motor in the long run and a PWM system might be better.  These motors draw upwards of 600mA, 
so they are not your average system fan drawing ~20mA.

Any suggestions on doing a PWM speed control for these, as well as the fans?

For system fan speed controls I've been trialling these http://www.overclockers.co.nz/product/casemod/controller/MFC-BK-B.jpg from 
http://www.overclockers.co.nz/product/casemod/controller/ocnz.shtml they can cut system fan noise in half however I am not sure how 
they work.  I suppose I could read their output voltage, I might get an idea however it might need more than a digital volt meter to 
confirm. Actually maybe I should pull one apart to see what chips are in it, that might be quicker!  I will also trial some of the 
other system fans mentioned on list, they "sound" promising.

Currently I have one box (Intel 3000 / PCI 9400GT) running with really the HDD's normal thrashing noise the most audible.  The box 
may become acceptable when I master diskless. (or solid state drives as I am not sure how long a network boot takes, I suspect it is 
some time longer...?)