how to lower fan speed?

  • Thread starter Thread starter GEO
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GEO

I have a 120mm case fan that's too loud. Is there some kind of inline switch
to lower the voltage to the fan that would lower the rpm?
 
how are you powering the fan, from the mb header?
if you power a 12v fan through the PSU drives power pigtails you could use
the 5v side to slow it down or the ground(black) of the 5v(red) and
12v(yellow usually) to get 7v.
 
I have a 120mm case fan that's too loud. Is there some kind of inline switch
to lower the voltage to the fan that would lower the rpm?
Click to expand...


There are lots of ways to do it, so how did you "want" to do
it?

Have any misc. electronic parts lying about? Some
resistors, diodes, linear regulator, rheostats?

Does it need to be *fancy*?
Are you critical of having an exact RPM or would having it
in a reasonable range work? In other words, suppose you
targeted 2000RPM, is it ok if a quick method were off by a
few % and you ended up with 1850RPM?

Does it need to be adjustable, either from inside the case
or out?

What specific fan? What is that fan's RPM rating, current,
nominal voltage (or we assume 12V?), and how much do you
expect to be able to reduce the fan speed while still
retaining suitable airflow from it? Some of these fan specs
are probably on the fan label, and might be enough to get
the job done. As for determining suitable airflow rate, we
are in the dark here as only you can see the system.

The quick/easy/generic answer is to get a (roughly) 47-120
Ohm 1W-2W resistor and put it in series on the fan's power
lead, heat shrinking each end to electrically isolate them.
The value of resistor you will need varies per fan.
Paradoxically a fan that starts out with higher RPM,
"usually" needs a lower Ohm value resistor than one that
starts with lower RPM. RPM being relative, a large fan with
low RPM might still be loud so above mentioned details could
be helpful but the safest bet is to have a few resistors so
you can try different values till you find the best one. A
good selection might include values like 47, 68, 82, 100,
120, 150 Ohm. Such resistors are about 10 cents each, maybe
a little more if buying only a few. A local electroics shop
like Radio Shack might have them, but many tend to stock
more lower wattage resistors than the 1-2W size.

There are ready-made fan controllers, either the type that
sits in a front bay with a control knob or the entirely
internal type. They're relatively cheap and worthwhile for
some who don't know where to being with fan speed control as
they can often be found online for about $10 though you'll
have to find one compatible with whichever fan plug and
socket type you have at each end. For example,
http://froogle.google.com/froogle?q=fan+speed+controller&scoring=p
 
I have a 120mm case fan that's too loud. Is there some kind of inline switch
to lower the voltage to the fan that would lower the rpm?
Click to expand...

Slowing down the fan may cause the processor to overheat. You might want to
look into a quieter fan.

Brad H
 
Slowing down the fan may cause the processor to overheat. You might want to
look into a quieter fan.

Brad H
Click to expand...

it's essentially the same difference, unless the fan was
defective it's expected that a quieter fan will have a
similar reduction in airflow if the same size and (general
type, which it would have to be).
 
Do your self a favour and google for an
adjustable 120mm case fan, thats if you have
no experience with electronics. If you do try
some of the suggestions. job done
 
GEO said:
I have a 120mm case fan that's too loud. Is there some kind of inline switch
to lower the voltage to the fan that would lower the rpm?
Click to expand...

If you don't use the 7V trick (www.7volts.com -- lots of fan control
info), try either a variable resistor (potentiometer) or a thermistor
in series with the read lead. The variable resistor or thermistor
should be about 50-100 ohms, or roughly 12V divided by the fan's amp
rating. These should probably be rated for at least 3-5 watts.
 
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