[mythtv-users] latest svn and pwm to voltage conversion for fans

Marius Schrecker marius at schrecker.org
Tue Dec 6 11:44:32 EST 2005

Hi again,

two questions:
1. What is the state of the latest svn? Anything I should be avoiding

2. More like train of thought than a question, but here goes:
Still on the quest for a quieter mythbox. I'm swapping my 2 pin 92mm
SilenX fan for an updated 3 pin version with rpm monitoring. I happened to
mention to the supplier that I'd be using pwm to control it, and he said
that pwm wasn't supported because of the extra vibration caused by the
pulsing, and pointed me to a statement by the manufacturer which
identified pwm contacts as being 4 pin. My contacts are 3 pin, but
fancontrol identifies the pwm interface in sys and slows down my other
fans. Question is if anyone can think of a way (other than connecting up
an oscilloscope) to identify what's coming out of the contacts. It could
be that as they are 3 pin the pwm signal is filtered onboard to produce a
variable voltage...or not, in which case I could connect up a simple
filter network myself, I might lose a couple of extra dB by running the
fans from smooth dc rather than pwm. I'd need to know the frequency in
order to get the low pass filter right.

Has anyone done anything similar?

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