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
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
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
http://www.diyaudio.com/forums/showthread.php?s=&threadid=58073&perpage=10&pagenumber=1
Phill
a bridge of diode
C : 01µF
LM317
Rv 5K + 240R
C : 200µF
and one can regulate speed
or
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.
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.
I use a circuit like this one..
An externally hosted image should be here but it was not working when we last tested it.
Sure that works... they are common amongst amateur radio people for obvious reasons.. But personally i would'nt use it, ive seen too many broken direct zener regulator circuits on old circuit boards at work..
Since aleph30 seems to be classA i'll agree that temperature regulation is of very little use..
Since aleph30 seems to be classA i'll agree that temperature regulation is of very little use..
dw8083 said:How important is the zener in making this work verses having a just a resister in series to reduce the voltage?
Thanks!
-David
it regulates voltage.15v zener 'gives' 15v regulated,12v 'gives' 12v.etc etc.i used 12v in my smps.
there is an old thread for low noise fan and covers many aspects of low noise fan design
http://www.diyaudio.com/forums/showthread.php?s=&threadid=26237&highlight=
http://www.diyaudio.com/forums/showthread.php?s=&threadid=26237&highlight=
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.
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.
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