ARRRRRRRGH!!!!
Folks,
This won't work. I don't care what the resistance of the LED is, I don't
care what the voltage drop is, I don't care what the short lead is.
You are testing for the wrong &*^$#(*& thing. You are testing that the MB
is supplying power to the fan. I could take the fan and ____* it, and the
LED would glow. Ajit wants to know if the fan is working. Stop thinking
like a engineer, and think like a consultant.
What is Ajit's problem (family aside)? That he is not sure of the heat
buildup in his cabinet. Not being a techie (he is an Arts graduate, man),
he tries to use words like CPU FAN. Ignore him. He is actually asking
about sufficient cooling. Solve that problem.
Coming back to the point, a slightly better solution would be to put the
monitoring device in series, then we could test that at least the fan still
exists, and is drawing current.
* Insert graphical image. Due to Neil being on the list, I moderate my
language.
--
Ghane "baby sitting two engineers to become consultants".
----- Original Message -----
From: Vipul Mathur <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>; Ajit Ranade <[EMAIL PROTECTED]>
Sent: Tuesday, May 09, 2000 5:03 PM
Subject: Re: [linux-delhi] temperature
> Well here is how you can implement the LED indicator being talked about
> here:
> (ascii art follows)
>
> +V (Red Wire) o--------+-------------------------------o
> | ..
> +--/\/\/\/----->|-----+
> >From Motherboard Resistor LED | TO CPU FAN
> R |
> |
> GND (Black Wire) o---------------------------+---------o
>
>
> Now the value of the resistor can be derived as:
>
> R = (V - 1.5) / (25 * 10^(-3))
>
> V is the voltage being supplied to the CPU fan, wither 12v or 8v
>
> For most LEDs 1.5v is the voltage drop across the LED when it is lit-up.
And
> the current throught the LED is 25*10^(-3) A = 25mA for maximum
birghtness.
>
> For V=12v, the value of R = 420 ohms
> For V=5v, the value of R = 140 ohms
>
> Any nearby value of the resistor may be used. Be careful about the
polarity
> of the LED as it won't work if connected the wrong way. In the diagram the
> end with the | is the -ve terminal (usually marked by a shorter lead).
>
> HTH
>
> Cheerio!
> ,_,
> (O,O) Vipul Mathur <[EMAIL PROTECTED]>
> ( ) http://www.crosswinds.net/~vipul/
> +---"-"------------------------------------------------------------------+
> | 'The most exciting phrase to hear in science, the one that heralds new |
> | discoveries, is not "Eureka!" but "Hmm. That's funny..."'-Isaac Asimov |
> +------------------------------------------------------------------------+
> A good programmer makes all the right mistakes
>
>
> Durga Prasad Allada <[EMAIL PROTECTED]> wrote:
> > Soldering an LED is a goiod idea and it will not drain much current nor
> > effect the Fan performance.BUt must make sure the power to Fan is driven
> > by AC or DC..and if DC is it at 12 V or 5 Vand select a
> > right LED matching this power input..
> > - durga
> >
> > Raju Mathur wrote:
> > > Solder an LED there yourself :-)
> > >
> > > Warning: I don't know if this will affect the fan speed.
> > >
> > > >>>>> "Ajit" == Ajit Ranade <[EMAIL PROTECTED]> writes:
> > >
> > > Ajit> raju-
> > >
> > > Ajit> i did check the bios, and it has a setting for turning off
> > > Ajit> the cpu fan during "suspend" state. but otherwise there was
> > > Ajit> nothing about sensing whether cpu fan is on or
> > > Ajit> not. shouldn't oem's put a led or something, or will that
> > > Ajit> consume too much power, relative to its utility.
>
>
>
> --------------------------------------------------------------------
> The mailing list archives are available at
> http://lists.linux-india.org/cgi-bin/linux-delhi
>
>
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