Thermostatic controler for PSU fan?

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Despite getting a "quiet" PSU for my almost silent PC, I can still
hear the fan.

Does anyone make a thermostatic controller for a PSU fan?

Failing that, has anyone seen a circuit diagram for one?

Nigel M

Re: Thermostatic controler for PSU fan?

Nigel Molesworth wrote:
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You can buy temperature controlled case fans. Then unplug the fan
and install the new one.

But I don't recommend that. If the power supply is a cheap design
(not a high efficiency unit), the high fan speed may be necessary
to keep the unit cool. The difference between a low efficiency
power supply and a high efficiency one, could be 50W of heat
output versus 100W. The high fan speed may be used to get
rid of that 100W of heat. If you put in a slower fan, you
don't know if the fan curve cuts in at the right temperature.
In fact, a computer case fan will likely run at full speed,
when it encounters the heat from a cheap power supply. So
while it would be fun to experiment, there is no guarantee
you will "out-engineer" the people who made the supply.

Another alternative, is if your motherboard has a thermistor
input, and has a hardware monitor chip, then a program like
Speedfan could be used. You would need a 10K NTC thermistor
on the end of a twisted pair cable (and you need to select
one with the right "beta" value, as there is a defacto standard
for 10K computer thermistors). But then, you must have
Speedfan loaded at all times, to ensure your PSU is cooled properly.
If you left the room, and Speedfan exited for any reason,
the PSU could overheat. It has been about four years, since
the last thermistor input motherboard.

There are also separate fan controller products like that, with
thermistor heat detection, for controlling fans, but they probably
cost more than a decent power supply. And you still have to
investigate whether they need software running, to do their
job properly.

The safest thing to do, is spend a few bucks on a decent supply.
There are some (I believe certain Enermax models) that have
a knob on the back to set minimum fan speed. There are also
high efficiency 80%+ models (Seasonic and a few others), where
they don't need to exhaust a lot of heat in the first place.
Even PCP&C recognizes the need for quiet supplies, and makes
the loud Turbocool and the quieter Silencer product lines.
It should not be difficult to find a nice supply.

A Seasonic at up to 85% efficiency operation:

There are even supplies that are fanless. But unless your
computer has a minimal hardware configuration (i.e. a low
end video card with 64 bit memory interface to the GPU, maybe an
Athlon64 single core), a fanless supply could well overheat.

Also, from your description, it sounds like you may not have
much of a fan on the back of the computer, to exhaust the
computer case air. If you use a fanless power supply, and
did not have a rear fan on the computer, the computer case
air will become very hot. The component most affected by
heat, is a disk drive. Make sure your disk drive has a
good working environment - for a long life, try to keep the
air around the drive at 35C or less. With no case ventilation,
or if the hard drive is sitting in a "dead spot", the drive
can be needlessly tortured by the heat.


Re: Thermostatic controler for PSU fan?

On Sat, 04 Nov 2006 15:26:44 -0500, Paul wrote:

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It isn't, it's a ThermalTake TR2 500W Black Silent. It seems this does
have a speed control based on the load:

I've since discovered that it isn't the PSU making the noise (I turned
on with a pen stuck in the fan), it's my bank of three hard drives
(400Gb SAMSUNG HD401LJ). These are supposed to be quiet, but I guess
that three of them are going to vibrate a bit.

Would rubber washers between the drives and the chassis help? If so,
where can I get some?

Nigel M

Re: Thermostatic controler for PSU fan?

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You can get them at any hardware store that has a large selection of screws,
bolts and washers etc. Take a HDD screw with you to get the right size. Soft
vinyl grommets came with my old Lian Li case I still use. They fit in the
HDD rack holes......Most newer HDDs, especially the non-Raptor WD drives are
pretty quiet and shouldn't need them as long as the HDD is firmly (not
overtight) tightened down. Any of the 10,000rpm drives are noisy compared to
7200rpm ones. I have heard that the Samsungs should be quieter than the WD


Re: Thermostatic controler for PSU fan?

Nigel Molesworth wrote:

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Dear Nigel,

depending on which power supply you purchased, there is a pretty good
chance it already has a thermostatic controller built into it--several
power supplies use variable fans to spin up when needed, and then run
more quietly when the PC is not using as much power.

You are probably familiar with Silent PC Review, but, just in case you
are not, here is their write up on quiet power supplies:

Their recommended units:

 > Failing that, has anyone seen a circuit diagram for one?

Hmm, the phrase "playing with fire" comes to mind here--changing the
cooling solution that came with a certain power supply, and working
inside it might be the first turn on the road to least I
would prefer to pay a bit extra for a power supply that comes from the
factory running cool and quiet....I am a big fan (!) of PC Power and
Cooling PSUs: /

And, depending on what you use your machine for, consider a Mac Mini:
  silent.  I use it for email/word processing in office, cannot hear
it at all, ever.

I have had good luck building quiet (not silent) PCs with Antec Sonata
cases, and, I have read their P180 can be very quiet.



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