preferred fan speed control methods?

[David Ecklein]

Consider the following folk remedies and notions- may not apply to your
case - may also be open to criticism or additions from others on this list:

I tend to throw extra fans in any computer I put together.  But sometimes
people complain about the noise.  Especially when compared to some of the
brand-name boxes that use devious means to cut sound (like making the power
supply fan double for cpu cooler - dangerous I think!).  I feel the computer
should be operable, or at least safe, when any one fan is out to lunch.  And
a dead fan does not emit noise!

One simple trick that I have used with the 12v 3"x3" box fans is to run them
at 7 volts.  Connect the black to the +5v bus and the red to the +12v bus.
Fan will still spin, but not quite so energetically.  Two fans run this way
make less noise than one fully powered, so you could add a fan if the volume
of air moved is a concern.

I have also used some bigger fans (approx. 5"x5") - rated at 24v, they seem
to run fine and with less noise on the +12v bus.  A big fan running slowly
is not as noisy as a small fan trying to push the same amount of air.

It is probable that these fans will last longer (and thus postpone
end-of-life bearing noise) when run on less than the design voltage.

Of course, one could also use a thermostat or thermistor approach, but the
turning on and off (or spinning up and down) of a full-blast fan may be
worse than a steady low-level ambient sound.

Sleeve bearing fans tend to be quieter, although they do not last as long as
ball bearing fans, other things being equal.  Bearings can be noisy, they do
run dry.  I use an automotive oil additive containing molybdenum disulfide
to lubricate (sparingly!) noisy bearings when fan replacement is precluded
for some reason.

Dust getting into fan bearings (and probably even that adhering to fan
blades) may result in noise and shorter fan life.  A free-flowing filter
over the fan intake in dirty environments might be worth considering.  Once
I reversed the direction of the power supply and case fans so I could
install such filters externally.  Why the convention is that these fans draw
air into the case rather than expel it has been a puzzle to me.

If you want to spend money, I have seen Peltier coolers for sale, but have
never tried them.  Likewise, water cooling seems to be the rage with extreme
gamers, but the thought of it leaves me cold.  Which is probably the object!

Dave Ecklein
Diacad Associates


----- Original Message ----- 
From: "Bill McGonigle" <bill at bfccomputing.com>
To: "GNHLUG Group" <gnhlug-discuss at mail.gnhlug.org>
Sent: Wednesday, November 29, 2006 5:34 PM
Subject: preferred fan speed control methods?


> Googling around a bit I see there are a few different ways to go
> about fan speed control under linux.  I've got a couple very noisy
> servers that are well under operating range for their components and
> I'd like to slow down the fans a bit so the people sitting near them
> suffer less hearing loss.
>
> Does anybody have preferred tools?
>
> -Bill
> -----
> Bill McGonigle, Owner           Work: 603.448.4440
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