What controls fan speed?

[V8Triker]

This may seem a crazy question, because the obvious answer would be temperature, but what controls the fan speed?

Firstly, my fan is set to "Smart fan". The unit is a F5-221

On average it is probably on low (nice and quiet) for about a total of 30 minutes each day. the rest of the time it is running at around 1500rpm.
Even in the middle of the night it is around 1500rpm. I'm old, so I get up

Here are some screenshots at 5 min intervals.

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fan_2.png (18.37 KiB) Viewed 4691 times

fan_3.png (18.19 KiB) Viewed 4691 times

30 minutes later.....

fan_4.png (18.59 KiB) Viewed 4691 times

I don't really want to force "Low speed", nor should I really need to.

Are speeds below 1500rpm unusual?

[TMS]

Hi,
We are improving the fan rotation mechanism, please be patient .

[V8Triker]

Hi,
We are improving the fan rotation mechanism, please be patient .

Many thanks

[V8Triker]

Today I will make an acoustic box to put the TNAS in.

The fan genuinely has a mind of its own. It peaked at 2100rpm.
This is with it set to "Low speed".

fan_5.png (18.2 KiB) Viewed 4642 times

[Tricky]

You could always fit a quieter fan.

[V8Triker]

You could always fit a quieter fan.

Acoustic box is cheaper, cos I have the materials in my workshop, but I will check out the thread on a quieter fan.

[Tricky]

Would a box not tend to increase temperatures?

Noctua fans are almost silent.

[V8Triker]

Would a box not tend to increase temperatures?

Noctua fans are almost silent.

It should be ok.
The idea is to line the box with acoustic form, which deadens the sound.
Leaving a slit in the back top of the box, and a slit at front bottom, should allow for adequate air flow.

Not gonna go over the top and double skin the box.

[justsimon]

Noctua NF-A8 PWM are quite reasonably priced on Newegg.
Approx AUD$51 for 2, which includes delivery. I think I paid AUD$32 each from a local store.

Just a shame that the fan speed control and detection don't work any more.

[justsimon]

Actually, a direct question for Terra-Master:
Have you adhered PWM standards with the fans?
Or have you implemented your own method of controlling and detecting fan speeds?