Simple fan question

[bgeiger]

I have 2 Noctura NF S12B FLX fans for my Noctura cooler, to be set up in push pull. The fans come with 2 inline resistors, which can be used to slow (and quiet) the fans to your liking. Is it OK to use a fan controller with these fans, in lieu of using the resistors, so I can have real time control of my fan speeds? I know some fans do not work well with variable resistors, which is how the fan controllers presumably control the fan speeds.

[Crazy_Nate]

There are two ways to control fan speed that I've seen.

 

Voltage or PWM.

 

Voltage is pretty simple with a fixed voltage divider (resistors, etc), or rheostats (potentiometers), or simply instead of running it off of 12V, run it off of 7V (12V minus 5V) or 5V.

 

PWM is pulse width modulation. It's a way of using a less than 100% duty cycle (at high frequency) and simple filters (sometimes not even needed) to reduce the 'effective' voltage. Think of it as having an off/on switch and flipping it reallly fast.

 

I wouldn't hesitate to use either in place of the other - the fans probably have enough inertia to not care either way. The only time I would hesitate is if there was some internal circuitry that required a specific voltage. The S12B-FLX lists 12V as the input voltage, however, some other fans on their website list an operating range of 4V - 13V (like this one). This sets of my warning flag. Noctua doesn't beat around the bush...I'd probably see what those inline resistors are doing before I try it with a fan controller.

 

OTOH, it probably wouldn't hurt it to run off of less voltage. You could try a 9V (or 6V battery if you have one on hand) with a couple wires and see how they run. The fan connector pin-outs are, most likely, online.

[bgeiger]

Thanks for your input. The specific 12v input voltage worries me as well. I sent support at Nocture a question about this, and will reply back here when Ifind out.