Re: gEDA-dev: fans?

["John Luciani" <jluciani-at-NOSPAMgmail_dot_com>]

On 2/7/07, Dan McMahill <dan@mcmahill.net> wrote:
> anyone have a good source for DC fans?  I need to replace a Delta
> ASB0912H which is a DC brushless fan, 12V, 0.30A.  There is also a
> "-FOO" on the label.  It has 3 wires so my guess is one is maybe a speed
>   sensor.
>
I replaced the fans in two of my servers with the Scythe SFF21F that I
puchased from newegg.com ($14.95 in 2006). The fans are quiet and I
believe they are ballbearing. You could also try zipzoomfly.com

Model #        Dimensions    Speed     Noise   Air Flow Rated Current
-------------  ------------  -------- -------  -------- -------------
Scythe SFF21D  120x120x25mm    800rpm  8.7dBA  33.5CFM  0.10A
Scythe SFF21E  120x120x25mm  1,200rpm 20.1dBA  49.0CFM  0.15A
Scythe SFF21F  120x120x25mm  1,600rpm 28.0dBA  63.7CFM  0.20A

Here  are some notes on fan speed control that I found
on the internet

(1) Tachometer Wire:

A tachometer is a is an electronic sensor that measures how fast
something turns. Just like a car has a tachometer to tell you how fast
the motor is running, some fans have one to tell the motherboard how
fast the fan is running. The motherboard can't guess at how fast a fan
is running so it needs this tachometer to tell it this
information. The tachometer wire is used to pass this speed
information from the fan to the motherboard.

(2) Controlling Fan Speed

The tachometer wire does not control a fan's speed. It will only read
it and pass the information to the motherboard. The fan's speed is
controlled by how much voltage is provided on the fan's other two
wires - the closer to 12 volts that is supplied, the faster the fan
turns. This can be controlled by some software programs when the fan
is connected to the motherboard, or physically using a knob when the
fan is connected to an add-on fan controller.

(3)4-pin fans vs 3-pin fans

You cannot monitor the speed of a fan that has only 2 wires (usually
red or yellow & black) because it does not have that magic tachometer
wire. Most often these days when you buy a fan you will get a 3 wire
fan that has a 3-pin plug and an adapter to allow you to attach it to
a 4-pin connector. In this case you can remove the adapter and connect
to the motherboard if the fan is not too powerful. BUT if a fan only
has a 4-pin connector the fan really is only a two-wire fan and only 2
of those pins used for the fan. You can not monitor the speed of this
type of fan.

(* jcl *)

-- 
http://www.luciani.org


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