Variable Resistor Fan Control Mod

[DAnDan]

I was wondering if it is possible to cut the power wire going to a fan, add in a v. resistor, and use that to control the fan speed? Is there any reason why this shouldn't work?

The fans in my case are on 4 pin-molex cables, so finding a controller is proving tricky.

Getting hold of a few v.resistors shoudln't be hard, and will mean that I can turn the fans down when only doing simple taks, and then turn them up again when they're in need.

 

[Jokester]

Yes, but make sure the VR can handle the power.

 

[DAnDan]

I'm still on the learning curve with this, so it's probably a stupid question, but how much power is going through the cables? 12V?

 

[Jokester]

Depends on the fan you use, but you could be looking be looking at in the order of 1W for a quiet fan turned right down, and substantially more for a faster fan.

 

[DAnDan]

Okay thanks, what sort of resistance range am I going to need?
Sorry for the questions.

 

[Jokester]

Probably looking at something from 200Ohms and down I think.

 

[IAmATeaf]

Have you looked at doing the 7v mod to the fans? If you just want to quieten the fans and don't need to vary the speed then this is a no cost mod

 

[DAnDan]

7 Volt mod? Sorry, as I said, I'm new to this.

Realistically, I would like to be able to turn the fans down, and then back up when I need them.

 

[C4EVA]

100Ohm pot is best imho

 

[PhillyDee]

The 7 volt mod is attatching the 'ground' (Black) wire on the fan to the 5v supply (usually red) and the positive (red) wire to the 12v (usually yellow) on the molex. Difference of 7v. Just dont get it confused with the speed sensor wire if its a 3pin fan.

Something along the lines of 100-200ohms like suggested would so you fine.

Oh, you can buy a converter (If its not already supplied with the controller.
http://www.overclockers.co.uk/showproduct.php?prodid=CB-012-AK&groupid=701&catid=48&subcat=153

I think is the correct one. Converts a 4 pin fan to a 3pin header.