Best way to power a 12vdc fan from 25vdc for an Aleph30

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I'm building an Aleph30 and wanted to include a low noise fan in the chassis.

The Aleph30 has a 25VDC powersupply and the fan is 12vdc at .06amps.

What is the best and easiest way to drop the voltage for the fan? Is a voltage divider needed or would a resister in series with the + slide of the fan work ok?

Thanks for the suggestions.

-David
 
Hi,

a simple series resistor will do. Normally 12V will be too much for really low noise. I would try 8 or 9V.
At ca. 45mA you will need a (25-9)/0,045=355ohm resistor. Power needed 0,045^2 x 355 = 0,72 Watt

You could try 330 or 390 Ohm resistors of 2 watts to be on the safe side.

William
 
from the secondary
a bridge of diode
C : 01µF
LM317
Rv 5K + 240R
C : 200µF
and one can regulate speed

or
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http://www.diyaudio.com/forums/showthread.php?s=&threadid=58073&perpage=10&pagenumber=1

Phill
 
simplest way -- without wasting any energy -- get yourself an LM3524 (SG3524) and PWM the fan circuit -- kind of an old circuit but National Semi has an application note which shows exactly how.

or if you are using a torroid -- just create another secondary by winding a few extra turns with #24 insulated wire around the core -- I did this with my LM4780 bridged amp which required a fan.
 
The one and only
Joined 2001
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In order to get silence, I try to run my fans as slow as possible,
which is usually a voltage so low that they won't start, and so
I think in terms of a higher start up voltage that then settles
into the sustained value.

Of course there are numerous ways of adjusting the fan speed
against sink temperature, which is what I did on the Adcom 5800.

:cool:
 
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