Fan rpm question

[atsang]

Is there a way to make a fan have a slower rpm to make it quieter? Would this require some rewiring? I've got 3 120mm fans and they are just really too loud to bear. I can take the loss of cfm since I've got a pretty good setup already.

Thanks in advance

 

[KouklatheCat]

I have heard of people putting the fans on double pole switches. A double pole switch will esentially make the fan run at a slower speed when you want quitet but higher when you want more cooling. Run a search on fans, im sorry I cant remember more then that. Or check Virtual Hideout.

 

[atsang]

Oh yeah, the fans are the normal 4 pin power connector fans, not the fans with the 2 pin female connectors (whatever they call it). Is there a way to convert them from one to the other? Would splicing work? DO I even need to convert them?

Anyone else know?

 

[Viperoni]

Quickest and easiest way:

Take the +5v and +12v lines and wire them together.

That end will go to the "+" end on your fan (usually red)
The "-" end will still hookup to one (or both) of the black (ground) wires.

This will run your fans @ 7v (average of 12v and 5v linked together)

Very very easy to do, and it works

 

[fast_eddie]

C'mon Viperoni!

Are you really telling 'atsang' to SHORT the +5vdc and the +12vdc leads together? A very good way to kill the Power Supply.

I think the advice that you really intended to pass along is;

by connecting the +12vdc to the Red fan lead AND connecting +5vdc to the Black fan lead, you will be able to run the fan a 7vdc [the difference of potential], you will thus be running the fan at a slower speed.

KouklatheCat is suggesting a switching setup so a person could select between +12vdc and 7vdc for powering the fans, another suitable solution.

 

[atsang]

Is there something I would be able to buy so that I can hook the fans up and just be able to switch their voltages?

 

[Viperoni]

oh damm that's right!!!

*smacks self*

sorry about that

 

[Poof]

You may be in luck. Saw a link at Ars to a tutorial/faq on fan control. Looks like a cool site.

 

[groovy]

Wouldn't a variable rheostat work? Fan motors run on DC, so that seems feasible to me. A rheostat should give an infinitely variable selection.

 

[KouklatheCat]

My only experience with fans and reostats is with ceiling fans. I know that reostats are bad on most ceiling fans and usually make them noisier and wear on the motors heavily. I dont know if this applies to 12V DC fans or not.

 

[Usul]

Rehostats works perfect with me.
Also a 5W resistance is good for 120mm fans

 

[cockeyed]

Take the advice from Fast_Eddie and wire them up for +7 volts. This drops the RPM just enough to quiet them down. I've been using this trick for years and it works great without affecting the cooling very much. Just be sure your fans will always start at +7 volts. Most will, but some might not; test them before closing up the case. Just use your finger to stop them and see if they always re-start.