fan layer choice and wiring
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I need to change the layer fan and I don't know which one to get for my 24Volt powered Duet 2 WiFi.
To premise that I currently only print PLA and the 4020 axial fan I have has started to make a bad noise. I need to change it as soon as possible and would like to replace it with something that can be efficient, quiet and durable.
With the filaments I am using, I hardly have to send it over 50%, so which of the 3 possible alternatives is best? ....con 2, 3 or 4 wires?
Any recommendations?
Consider that it is currently connected to the “duex.fan3” connector and is configured as follows:
M950 F0 C"duex.fan3" Q200 M106 P0 S0 L90 C"Layer Fan" H-1 
NF-A4x10 24V PWMalthough it is more subtle, I really like this one.
my layer conveyor is set up for both 1 and 2 fans.
I might start by trying 1 fan.... -
By the way, I happened to watch this video.
https://www.youtube.com/watch?v=v7Fc8p8aaxc
what do you think of it?
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@bernardomattiucci If you can, use a 4-wire fan. The PWM control from the Duet is used to modulate the voltage internally, so 4-wire fans are powered by variable voltage, not PWM-chopped voltage. 4-wire fans should meet the Intel PC specification. See the 4-wire tab here: https://docs.duet3d.com/en/User_manual/Connecting_hardware/Fans_connecting#connecting-fans-to-duet-fan-pins
I think that Noctua fan should work. With a 4-wire fan, you also get tachometer readings. They are slightly more complex to connect to Duet 2, but it is covered in the above link.There's not much advantage of a 3-wire fan vs 2-wire; the 3-wire has a tachometer output, but it will only show the correct speed when the fan is at 100%.
You should be able to get 2-wire fans that work nicely with PWM. I have 2-wire 50x50x10 blower fans, and 40x40x10 standard fans, that don't whine. Playing with the PWM frequency (M950 Q parameter) may help.
The video shows a simple circuit to convert PWM to voltage. That's fine, but these circuits generate heat. There's a few threads on the forum discussing circuits to convert PWM to voltage, for example:
https://forum.duet3d.com/topic/21680/designing-a-pwm-to-analog-mini-board-for-fans
https://forum.duet3d.com/topic/23080/pwm-to-constant-dc-voltage-for-fan-controlIan