How do you under volt fans?

[Jordan]

a

[Metallurgico]

I have 5 fans in my system, each undervolted to 7V with resistors. Those fans are connected to a digital rheobus that undervolt them another bit. With this setup I can control the fan speed as I want, and if I use the auto mode on the rheobus the PC is not too loud either.

[ionbasa]

Running a PWM controllable fan designed for 12v may run OK at a lower voltage as long as you do not go too low. PWM controlled fans have an IC chip inside and a rotation sensor. When the voltage to the fan gets too low the IC chip will fail to operate correctly. I have found that I was able to get the fans to operate OK at voltages down to about 6.2 volts. Below that the fans would not start reliably and the fan motor lacks torque.

Basically I never try to run fans below 7v. So PWM adjusts rotation, Voltage would adjust torque. so by bumping it down to say 7v you will probably get less noise.

[Dragon_Cannon]

connecting a low speed adapter to the fans is the best way to do it.

If you start pulsing the fans, it can cause them to make sounds that wouldn't be there if you had just undervolted them. This could be caused by the motor that is in the fans doing funny things when you do that to them.

[Dragon_Cannon]

Another thing to add is be careful about the fans that you choose for this as some of them do not undervolt gracefully and sound horrible.

[ramzoHCR]

Definitive with resistors. The best and cheapest solution.

[ionbasa]

Or you could run the fan off the 12v and 5v rail for a delta of 7v.

See: http://www.overclockers.com/forums/s...d.php?t=372297

That way you dont need to buy anything.

[Ghost]

Resistors are far safer than the ghetto method.

[Tama]

Fan controller

[Guest]

I think Noctua make cables that have the resistors in them otherwise you could DIY it and insert your own resistors.

[LimeDk]

i use the ghetto method for my fan on my H50 they run on 5v so its very quiet (= and the rest of my fans in my case Haf X is running of my motherboard in silent mode so everything is very quiet but yeah get some resistors far better for safety

[Dragon_Cannon]

or if you want to run it a five volts just cut the 12v wire which is the yellow one and pray to high hell that you don't need it to run at twelve volts every again because it wont without a new wire.

[ramzoHCR]

You can buy such cables, I have 10 of them in my case they are most made by SHARKOON..

[Angelus]

this is linus' video on ghetto DYI undervolting to 7v

[orangecat]

Just use resistors or change your settings in your motherboard drivers or BIOS is just easy if you do it that way. But when it comes to building your own are you asking to build your own PWM circut?

[EYCEthebest003]

if you really are against using a resistor (they're really easy. If you can build a computer, you can do some simple wiring) then here.

http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=BESTMATCH&N=-1&isNodeId=1&Description=nzxt+sentry&x=0&y=0

NZXT makes some decent fan controllers. They're easy to use, you just plug in your fans to one of five connectors and away you go. A word of caution, the lowest they can output is 40% voltage so you can't go super low voltage. If you're not aiming for a voltage thats too low and you just want something thats horrifically simple, then this is probably what you should use.