Turn off part cooling fans when klipper is booting / offline

Hi guys,
I have V-Core 4.0 with IDEX and can not figure out, how to turn off the two part cooling fans (4028) until the klipper boots up. They go on full blast for a minute or two in the beginning, when klipper is offline (no PWM signal). There is this guide in the documentation https://os.ratrig.com/docs/guides/4028/#my-fan-runs-at-100-until-klipper-boots, but I can not make it work in the current setup. Klipper neither accepts "shutdown_value" in fan section, nor "enable_pin" works due to it being used multiple times. I have a standard IDEX setup/kit.
Is there a way to turn these fans off in configuration, until klipper boots up or do I have to rewire the fans (GND) to do so with Octopus board?

message.txt23.36KB

message.txt8.21KB

Connecting a 4028 fan | RatOS

4028 server fans are becoming a popular option for part cooling because of their light weight and great pressure and flow rates. In this guide we'll go over how to connect one and use it for part cooling. 4-pin fans usually aren't used in 3d printers, and many boards only provide 2-pin ports, but fear not! There's always a way.

Solution

it should be similar to

[fan]
pin: !fan_part_cooling_pin
cycle_time: 0.01
enable_pin: PA3

[fan]
pin: !fan_part_cooling_pin
cycle_time: 0.01
enable_pin: PA3

with

PA3

PA3

being this one marked in RED

Jump to solution

TheTik•12/31/24, 6:49 PM

The 4028 fans are "smart", in that if they don't get a PWM signal, then they will run 100%.
In order to get them to stop, you need to only allow them to consume power once the PWM signal is available. So just like you realized, you'll need to remove power or ground to the fan, and that guide shows using the heater port gnd to do that.

TheTik•12/31/24, 6:50 PM

I haven't investigated if/how to do that via the toolboards. I also son't have the my printer in the same room, nor do I turn it on/off very often so the inital noise doesn't bother me

AAndrii Hi guys, I have V-Core 4.0 with IDEX and can not figure out, how to turn off the...

blacksmithforlife•12/31/24, 7:12 PM

I don't see the edits you tried to make in your printer.cfg (ratos.cfg should NOT be modified). Please upload the one that gave you an error

Solution

blacksmithforlife•12/31/24, 7:16 PM

it should be similar to

[fan]
pin: !fan_part_cooling_pin
cycle_time: 0.01
enable_pin: PA3

[fan]
pin: !fan_part_cooling_pin
cycle_time: 0.01
enable_pin: PA3

with

PA3

PA3

being this one marked in RED

AndriiOP•1/2/25, 9:03 PM

Hi blacksmithforlife,
thank you for your reply.
I have understood now, that rewiring the part cooling fans (connecting ther black (GND) wires to the PA3 pin ("-" of HE1) ) is the only way not to have them on full blast, when klipper is offline.
So I rewired everything as you and the documentation described (both fan GND wires to PA3) and now I get "Sensor 'heater_bed' temperature -59.500 not in range" error message. Do you have any idea, regarding what I have done wrong?

klippy.log1.06MB

printer.cfg8.27KB

blacksmithforlife•1/2/25, 9:06 PM

probably bumped something and connection came loose

blacksmithforlife•1/2/25, 9:06 PM

check your thermistor wiring for your bed since that is the one that is complaining

AndriiOP•1/2/25, 9:14 PM

You are right. Sorry for the dumb question. I have indeed unplugged the bed thermistor cable...
Thank you for your help and patience. (:

Turn off part cooling fans when klipper is booting / offline

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