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Need Help with converting 12V to 3V.

post #1 of 3
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So, what you see in picture is me trying to do PS3 fan mod, but need to bring 12v down to 3V so I can use Potentiometer to control speed of the fan since it uses 0.6V for slow RPM and 3V for max RPM.

What I want to do is get rid of that third wire and use 12v lead for this.

I am lost about resistor. PS3 fan is 12V 2.2a so 12/2.2=5.45 correct?

As you can see in this link this fan is rated at 12v 2.6 just a bit more that stock PS3 fan so that where I got info.


ske-1.jpg
Edited by DraganUS - 12/28/10 at 5:27pm
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post #2 of 3
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Anyone with electronics exp.
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post #3 of 3
Based on what you've said, and a few things I saw off google, you are thinking about this all wrong. It looks like the 2.2A spec is rated on the 12V rail, and has nothing to do with the 3.3V rail. It look like the fan changes the speed based on the voltage at the 3.3V rail, and the PS3 uses a thermistor or similar device to change the resistance of a voltage divider to change the voltage on that rail. This would then assume that the RPM wire draws very little (~0A) current.

Assuming these assumptions are correct, then your circuit needs to look like this: (see pic). This circuit will produce voltages of 3V and .6V on the green wire.

I don't have the spec sheet of the fan, so I can't say for sure if this will work. Nor an I familiar with a PS3 fan mod. Where exactly do you know the voltage need to be changed from 3V to .6V?
Edited by just_nuke_em - 1/5/11 at 2:14am
    
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