[sci.electronics] smart fan

phil@amdcad.AMD.COM (Phil Ngai) (01/05/88)

I see that Rotron now has a great idea in fans. It's a DC operated fan
with an extra two wires. The resistance you provide between the wires
determines the speed of the fan, with the intention being that you use
a thermistor to regulate the amount of air moved based on the
temperature. The power supply voltage is not a factor (within limits
of course). This is all done with PWM type stuff so that efficiency is
very high. 

I hope Apple takes note of this!

-- 
"how long will the machine be down?"
"as long as you stand there and bother me"

Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.com

wtm@neoucom.UUCP (Bill Mayhew) (01/07/88)

My Tektronix 2445 'scope that I got 3 years ago has a fan whose
speed varies.  What is also a neat benefit is that it makes it
easier to maintain a semblance of *constant* rather than some
arbitrarily low temperature.  Quite a good thing for analog things
that drift in calibration with respect to temperature.  That scope
has taken some remarkably rough treatment and stays quite stable.

I agree; Apple should have learned about fans in, say about 1979 or
so.  I've replaced more Apple power packs in machines here than I
like to think about.  You'd at least think they could have put some
ventillation slots in those chintzy Apple ][ power packs.  I
suppose their lawyers advised them to seal the power pack to
prevent some kid from probing it with a paperclip or whatever.
Those Kensington System saver aftermarket fans help some, but
there still isn't any air circulation inside the power pack.