[Electronics] voltage adjusting

sorex

Expert
Licensed User
Howdy,

A few days ago I digged into an old server in our server room.

I recuperated a nice 210+CFM / 6500RPM / 65db / 35W 12x12x3.8cm fan out of it.

While this beast blows everything from my desk when feeding 12V to it I was wondering how I could adjust the voltage of this so that it operates about at half the speed/noise.

I know the oldskool potentio or fixed resistor method but then I don't know how to calculate which max K resistance value I need.

Are there electronic methods as mini boards aswell that can act as a stepper voltage relay kind of thing that can be triggered by a raspberry pi?

I tried to use one of the 2 USB ports on the solar controller but the limited amperage doesn't seem enough to let the fan spin at 5V.

Alternatively I could look for another fan aswell that does 120CFM or so at 30db
 

sorex

Expert
Licensed User
forgot to mention that the fan had a 4 wire connector so it's PWM based. that could be the reason why 5V fails since it needs 12V pulses to control the speed.

so I need a PWM controller board to get this working?
 
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Cableguy

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PWM is a bit over kill... A simple 3 component circuit using a 7806 should do the trick

I didn't see the 4wire post... So athe proposed circuit should do the job
 
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sorex

Expert
Licensed User
I'm not good with electronics so something ready made would be the best I guess. :)

There are PWM boards on aliexpress for 1 to 5 euros but most of them have 2 leads going to the 'motor'.
Not sure if that is enough for this PWM fan tho. one extra pin is for the tacho/rpm and one for PWM.
not sure what the PWM on is needed for tho if you could do it on the main 2 pins aswell.
 
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