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Ok very simple right? how do I change from 12vdc to 10vdc

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New Member
All I want to do is lower dc volts from 12vdc to 10vdc or 8vdc
this is to quiet fans in an computer. All site that sell fan controls allow U to vary voltage
using a rheostat at a substantial cost. I would like to do this foe vary cheap,
I do not need to vary voltages I just want constant volts of 10vdc or 8vdc.
can I just splice in an resistor in + line and if this is possible what resistor should I use?
I would like to do this with several fans so I need something that will work with different fans.
About the max I've seen is 6watts.

Thank you


Active Member
You can use LM317 voltage regulator IC. The circuit will consist of one 3-pin IC and 2 resistors.
Using only a resistor or two resistors in potential divider will not work as it won't be able to supply enough current to run those fans.

To remind you, doing this will reduce the air circulation inside your PC cabinet and may cause your CPU to overheat after a long run.


New Member
well from what i know the lm317 reg. needs a 3V droput minimum, so it wouldnt wotk for 10V, but perfectly for 8 V.
but there is another thing, some fans from teh computers have internal regulators, switching usually, so lowering the voltage will not always help.
and a suggestion for getting 10V. just use 3 rectifiing diodes(1N4001-4007) in series. considering that a diode has a voltage drop around 0.6-0.7V you will get something like 10.2 to 9.9 volts, wich is good
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