On Sun, 12 Sep 2004 18:57:56 +0000, raden wrote:

In message , Martin Warby
writes
On Sun, 12 Sep 2004 16:34:52 +0100, Set Square wrote:

In an earlier contribution to this discussion,
Martin Warby wrote:

On Sun, 12 Sep 2004 15:10:06 +0100, Set Square wrote:


Works a treat - *except* that it's a bit (audible) noisy, and doesn't
actually *need* to run all the time. Now it just so happens that I
have a spare Danfoss TWP room stat after fitting a programmable stat
on the central heating. So I've mounted this TWP inside the computer
case, and wired it to switch the fan on when the temperature is
above the set value.


why not use a pot (potential devider) to slow the fan down ?

Martin Warby

Do you mean insert a resistor in series with the fan - so that it *always*
runs at at least low speed - and use the stat to by-pass the resistor when
max cooling is required?

Would that work with this type of motor?

Wouldn't contact noise from the stat still get into the system?

I was thinking of a pot (a variable resistor looks like
http://www.maplin.co.uk/media/largeimages/2203i0.jpg).Set it up as a
potential devider as below

connect outer 2 tags to supply
connect inner tag to +ve lead of fan
connect -ve led of fan to -ve lead on outer 2 tags

Simply turn the pot till the desired speed is obtained

Until you see smoke and smell burning

Have you looked at the power rating of a normal pot?

1Watt IIRC

see my earlier post I had not realised it was a mains fan (I presumed it
was running from the 12V DC line).

Martin Warby