configuring a PWM 4 wire fan

Cassiopeia

so i have a duet 3 6hc board a just connected a 24v noctua PWM fan to it.

My problem is the Fan starts first spinning at 45% is this normal or connected to the configuration of the fan?

config is

M950 F2 C"!out6" Q25000
M106 P2 S0.0 H-1

only info i could find on the PWM settings was
noctua fq.JPG

https://noctua.at/pub/media/wysiwyg/Noctua_PWM_specifications_white_paper.pdf

which doesnt make much sense to me since the max RPM is 3.000 that would mean by that formula 100 Hz?
or are we talking about 100.000Hz so in config <M950 Q100000>

dc42

@cassiopeia said in configuring a PWM 4 wire fan:

M950 F2 C"!out6" Q25000

That is the correct configuration.

According to page 6 of the document you linked to, the fan should work down to 20% PWM or lower. The extract you posted refers to the tacho output signal, not the PWM input signal.

You said it is a 24V fan. Do you definitely have the VOUTLC jumper for that output block set to 24V not 12V?

Cassiopeia

@dc42 said in configuring a PWM 4 wire fan:

According to page 6 of the document you linked to, the fan should work down to 20% PWM or lower. The extract you posted refers to the tacho output signal, not the PWM input signal.
You said it is a 24V fan. Do you definitely have the VOUTLC jumper for that output block set to 24V not 12V?

yes the jumper is set on the left to VIN (24V)

the 20% in that document refers to some info from INTEL so i am not sure if it is ment in general.

so on Q25000 once i go over 40-45% i can go back down to 30% and its still spinning - it stops on 25% then

just FYI on Q500 it takes 85% to start - dont know if that info helps

i mean i will live with it just curious if i could improve someting in the settings

FYI thats the FAN
https://noctua.at/de/nf-a14-industrialppc-24v-3000-q100-ip67-pwm/specification

achrn

@cassiopeia

You shouldn't be altering the Q value. Q isn't the means of varying the speed, it's the frequency of the PWM and it stays at 25000 all the time. You vary the speed by varying the S parameter in the M106 command.

The equations you've quoted are nothing to do with controlling the fan - they are how the fan reports back the speed it's running at.

Intel's document is quite hard to find - lots of other documents refer to it, and it is a de facto standard but difficult to lay your hands on. However, here it is: Intel_4_Wire_PWM_Spec.pdf

In the Intel document, it basically says below 20% (i.e. if S is less than 0.2 in your M106) the behaviour is undefined (see diagram on P14) - the fan might run, or might stop.

Most manufacturers cite the Intel document, but also specify what happens below 20% - some fans run even with zero PWM (i.e. S0 in M106) and some come to a stop at or before zero. Nearly all Noctua fans stop at zero PWM, but not every one - P7 of the Noctua document lists some that run at a constant (minimum) speed below 20% PWM.

If you have M950 F2 C"!out6" Q25000 then if it follows normal noctua behaviour M106 P2 S0.0 H-1 shoudl cause the fan to stop (but if you have one of the rarities it might run at 20%).

Regardless, M106 P2 S0.2 H-1 should cause it to run at about 20% of full speed, and M106 P2 S1.0 H-1 should cause it to run at about full speed, and any intermediate value of S should run at a roughly proportional speed. Is it not doing that?

Cassiopeia

@achrn thanks for your detailed reply but as described above the fan starts spinning at M106 S0.4
if it would have started at M106 S0.2 I wouldnt have wondered.

I remember in klipper you could define some sort of starting current to give the fan some sort of "kick"

as you see by my language my knowledge in this area is very limited

Nevertheless even starting with M106 S.04 the lowest i can go afterwards is to M106 S0.3 but i cant start the fan with M106 S0.3

So i guess I will operate in the range of S0.4 - 1.0 which is fine for me. I just wanted to know if i can do something else in the configuration since the only thing i read about the fan PWM is that it should start at 20% (M106 S0.2)

dc42

@cassiopeia said in configuring a PWM 4 wire fan:

I remember in klipper you could define some sort of starting current to give the fan some sort of "kick"

See the B parameter of the M106 command in the RRF GCode documentation.