• Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
    Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.

Undervolting fans using a resistor

N

nissanztt90

2[H]4U
Joined
Apr 13, 2007
Messages
3,858
Fan runs at 12v and 0.27a. That would put the resistance of the fan at ~45ohms. Id like it to run at 7-9v since its already a fairly slow speed fan. If i want it to run at 9v, i would put a ~33ohm resistor on the 12 volt line? Ive got a basic eletronics backround, just not sure if the fan motor is going to pull a constant current no matter what? Im really just not positive on how electric motors work other than the basic mechanics of magnets and AC current. Any input is appreciated, thanks.
 
Usually constant current, so a simple voltage divider will do the trick. So, 15-30 ohms depending on how slow you want it.
 
I wasnt thinking of a voltage divider, i thought ive seen some simple add-in 3pin-3pin connectors featuring a single resistor...definitely only had 1 resistor so it wasnt a voltage divider...but if these motors draw constant current then yeah 15-30ohm resistors would do what im looking for.

Pretty sure that little piggy-back type thing was at sidewinderpc.com...cant get that site to load up currently though.
 
The one single resistor will act as the voltage divider, as the fan itself also appears as a resistive component in the circuit.
 
Why not just 7 volt them the old fashioned way? Am I missing the benefit of using a resistor?
 
Its a 3 pin fan and id like to keep the cables nice and neat and use a motherboard fan header.
 
You must log in or register to reply here.
Back
Top