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Path: utzoo!attcan!utgpu!watmath!uunet!shelby!apple!bbn!csd4.milw.wisc.edu!leah!rpi!crdgw1!ge-dab!ge-rtp!edison!toylnd!dca
From: dca@toylnd.UUCP (David C. Albrecht)
Newsgroups: comp.sys.att,unix-pc.general
Subject: Re: Fan Recommendation
Message-ID: <265@toylnd.UUCP>
Date: 9 May 89 21:56:56 GMT
References: <1567@jhunix.HCF.JHU.EDU> <485@limbic.UUCP> <664@devildog.UUCP> <1611@neoucom.UUCP>
Organization: Dave & Anne, Charlottesville VA.
Lines: 33

In article <1611@neoucom.UUCP>, wtm@neoucom.UUCP (Bill Mayhew) writes:
> 
> I've thought about either using a thermistor probe or an air flow
> switch and an external controller to cut power when things get out
> of hand.  A termistor would be fairly simple to implent.  The
> termistor could be placed in series with a latch-up relay that
> would prevent power cycling.  It might be possible to select a
> thermistor and relay that wouldn't need any transistors, etc to
> drive the relay.  If I get anywhere with the project, I'll post the
> results.  I don't think there is enough of a static pressure drop
> in the Unix PC case to make using an *inexpensive* commercially
> available pressure sensor practical; one might be able to use a
> vane air flow switch mounted outside the case with the fan blowing
> on it.
> 
I considered replacing the DC fan in my 3b1 with an AC one until I did a
conversion job on my girlfriends 7300 to full height and at the same time
did a refit of the two DC fans two one AC fan for additional 12v capability.
The AC fan was not only louder it also had louder vibration modes in the
case which I wasn't really able to figure out how to completely damp.
I'm not too keen on loud fans to begin with, buzzing cases are right out.
I figured if I really want to protect my 3b1 from melting down what might
do the trick is a thermal fuse in line with the AC supply (Radio Shack has
a 139 degree C and 226 degree C model).  Now, 139 degrees C is pretty hot
but if I can mount it somewhere appropriate it would probably do the trick.
The only other problem other than choice of mounting location is how to
attach to it since it comes with wire leads and it might be difficult to solder
to without blowing it.  However it gets done, though, its likely it will
require case disassembly and a little replacement work should it blow.
Since this should be a fail safe device an awkward to replace component doesn't
seem to be as bad an idea as it might be otherwise.

David Albrecht