Noctua fan PWM issue
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Are these actual 4 wire PWM fans? What is the Noctua model number?
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Yep, they're 4-wire PWM fans. Noctua NF-A4x10 PWM.
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Yes - this is the guide I followed to connect them. They're connected as specified in the guide, but not working as expected.
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Which Duet are you using?
The FAN- connection is an open drain output with a flyback diode connected to VFAN. The leakage in the flyback diode is very small, so it should be safe to connect the FAN- pin directly to the PWM input. However, if you are worried about the leakage then you cold connect a 1N4148 or similar diode between the FAN- pin and the fan PWM lean (cathode to the FAN- pin). I am running two Noctua 4-wire fans on Duet 3 in this way.
Did you remember to set the fan PWM to be inverted, and to increase the pWM frequency to 25000 ?
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I had my Smart Effector off to change out some other components yesterday, and took the opportunity to re-make all the fan connectors and test some things.
I tested both fans with a known good 12V supply - both were working. I reassembled everything, and haven't had an issue with it since...
It seems that there was a dry(ish) joint somewhere between the Duet and the fans, and the voltage wasn't quite high enough on the fans for them to start reliably (apparently Noctua fans are known to need a high voltage to start - i.e. if there is too much droop on the 12V, they won't work).
Everything seems to be working now, so I think this can be considered closed - thank you very much @Phaedrux and @dc42 for your help!
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You didn't say in your original post that you were using a Smart Effector. The magnetic joints on the effector prevent some makes of fan from starting, especially if you haven't alternated the rod directions so that they go N-S-N-S-N-S around the effector. I suspect that may have been the problem.
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If this helps you or anyone else this is how I have my 2 Noctua 4pin fans:
NF-A6x25
NF-A4x10; Fans M950 F0 C"!out4" Q25000 ; create fan 0 on pin out4 and set its frequency M106 P0 C"Extruder" S0.2 L0.2:1.0 X1.0 H1 T60:180 ; set fan 0 name and value. Thermostatic control is turned On, low low speed at 60c max speed at 180c+ M950 F1 C"!out5" Q25000 ; create fan 1 on pin out5 and set its frequency M106 P1 C"Part" S0.2 L0.2:1.0 X1.0 H2 T25:80 ; set fan 1 name and value. Thermostatic control is turned on low speed at 25c and max speed at 80c -
Thanks so much for all of this it helped me a lot. Question: How do I view the rpms if I connect it to the PB6 via a diode?
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@devpeeps said in Noctua fan PWM issue:
How do I view the rpms if I connect it to the PB6 via a diode?
The RPMs should show up in the DWC dashboard.
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If you are running RRF3.x then you will need to declare the tacho input in your M950 command. There is an example at https://duet3d.dozuki.com/Wiki/RepRapFirmware_3_overview#Section_M950_Create_heater_fan_or_GPIO_servo_port.
