Xbox fan change - needs 12V gets 6v...

[TaDa]

Hi!

I want to change the fan in my XBox (not a 360) to a more silent one.

Problem is that the current fan runs from 6v whereas the commonly available silent fans are 12v models.

The fan is controlled from the motherboard which outputs the driving 6V
but the hard discs run at 12v so I can get a 12v supply.

I'm wondering if I can run this through a transistor in some way.
Whereby the base is fed the 6v from the motherboard and the fan is in series with the collector/emitter.

I'm ok making circuits from diagrams but knowing what sort/power of transistor I would need in this scenario and whether a resistor would be needed from the 6v to base.

Could it be as simple as one small transistor and a resistor - or am I getting my hopes up (again)?

I'm assuming that if I get 3v at the base I want 6v across the fan (1v->2v, 5v->10v, 6v->12v etc)
So maybe I should be looking at some sort of voltage booster?

Cheers

 

[Reloadron]

Granted this is not the best answer to your question but a Google of "X box fan mod" will bring up about a dozen hits with some good tutorials on how to go about it, including adding a new 12 volt fan. Hope that helps...

Ron

 

[TaDa]

Cheers Ron.

I've seen all the mods but they do not answer my more techie requirement.

The fan in an xbox is a 6v fan - all the quiet 80mm fans out there are 12v

All the mods talk about undervoltage running the 12v fan by running it from the motherboard direct
or simply having the fan run all the time by having it wired to the 12v line.

I want something a little more clever - I want to run the 12v fan from the 12v supply but control it with the 6v motherboard.

I'm assuming that the motherbord outputs a varying voltage to better control the fan - say 3v to 6v
and I want to convert that to have a voltage over the fan of 6v to 12v

Hmm, I wonder, is the fan either on or off - if so, a simple relay would do what I want - anyone answer these questions?

If it was as easy as sticking a relay in the circuit I would have thought somone would have done that by now - so I'm thinking that the motherboard varies the fan speed by changing the voltage

 

[Reloadron]

This is where I get in trouble as I don't have a clue if the X-Box uses something like PWM to vary the fan speed based on heat or if it is a fixed 6 volt fan driven by a fixed 6 volts? Now if it is using PWM then you could use the PWM signal to possibly drive a MOSFET and let the MOSFET drive your 80 mm 12 volt fan. You would get the 12 volts from the HDD connector I would guess. However, since I don't have a X-Box to mess with I am not sure. Manual control of a 12 volt 80 mm fan would be as simple as using a 50 Ohm (or so) pot in series with the fan but I doubt a manual pot is what you want.

Maybe someone else has some thoughts or has hacked an X-Box?

Ron

 

[Dragon Tamer]

Does the old fan actually say 6V on it or is that what voltage you are reading? Even if an X-Box does use PWM, I'm sure that the voltmeter would display whatever "voltage" the fan would be running at. In any case, try using a charge pump to run your fan, just use it to double the voltage from your board. Just make sure the new fan doesn't exceed the current consumption of the old fan.

 

[TaDa]

Cheers Reloadron and Dragon Tamer.

I believe the XBox fan is controlled with PWM - So I'm not sure a charge pump would work.

When I take the xbox apart the next time I will have a better look around at the connections to see how I could fit a MOSFET solution into it.

Cheers again

 

[Reloadron]

Some time back there was a post in a computers forum I am active in. I haven't a clue why, but they wanted to drive several fans off the PWM signal to the processor fan. WE did come up with a simple circuit using a MOSFET that worked out fine. I remember the MOSFET was switching the low side of the fan to 12 volts. Anyway, it worked just fine. There wasn't much to it either.

Ron

 

[Reloadron]

I found the drawing.

Ron

 

[TaDa]

That looks great - thanks Ron