# what size resistor?



## Deleted member 24505 (Mar 20, 2006)

just a quickie,what size resistor do i need in line to drop the fan voltage to 7v?,without doing the yellow+/red- thing?.i dont really want or have room for a controller.
thanks guys


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## Yin (Mar 25, 2006)

well it might be a 5v resistor.......
12v - 5v = 7v
im not a totally sure thats what their measured in but if you ask whereever your buying it from they should help


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## mikechinym (Mar 25, 2006)

if i am not mistaken,
volt=ohm x ampere...
to reduce the voltage,it must know both the resistor and your fan voltage resistance...


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## Yin (Mar 25, 2006)

ahh yeh thats right
v/ir 
v = voltage (volts)
i = current (amps)
r = resistance (ohms)
Im pretty sure if you look on your psu
it will tell you the amps on your 12volt rail. normally its about 20amps i think, but it varies from psu to psu.
im a physic student but im pretty sure thats right


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## ferynov (Apr 13, 2006)

*volt*

Volt = i (ampere) / R (resistor)
then 

7 = 5 Ampere (approx) / R

7 / 5 = R  R=1.4 Ohm ... check the ring colour ..or ask mr.google


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