Use a servo controlled valve as the part cooling fan?

General Discussion
1

Greetings! I have an air pump that I use for remote hotend and part cooling on my high temp printer. Currently, the pump output is regulated by the part fan output.

I was wanting to use a servo controlled valve so that I can use an air tank. When the part cooling fan is at 0%, then the valve would be closed with the servo angle 0. When the fan is at 50% the servo angle would be 90, and with the fan at 100% the servo angle would be 180. This is just an example for reference.

Is this something that can be done in Klipper with the servo or PWM controls?

2

Try

Additional servos, LEDs, buttons, and other pins

https://www.klipper3d.org/Config_Reference.html

Btw, have you posted anywehere how you’re cooling the hot-end? I think compressed air is the way to go, but have not tried yet.

1 Like
3

Basically quite easy:

[servo myServo]
pin: myPin
initial_angle: 0
maximum_servo_angle = 90
minimum_pulse_width = 0.001
maximum_pulse_width = 0.002

Then control it with:

SET_SERVO SERVO=myServo ANGLE=90
1 Like
4

Thanks for the help. I am new to Klipper, coming from Marlin.

I understand for the most part what you described. How would I control the servo in Klipper as the part cooling fan?

5

Thanks! I dont have anything posted. I am just using a diaphragm pump (Berg style) mounted to the outside frame, with some silicone tubing going to a custom V6 hotend fan shroud I designed.

6

You could build a “delayed gcode macro” that referenced the fan speed (0-255) and convert it to the stepper angle (0-180), then modify the stepper angle automatically.

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7

Klipper reports the fan speed between 0.0 and 1.0.

Once you setup your servo like @Sineos posted, then you can use a combination of gcode_macro and delayed_gcode to automate the fan speed to servo angle with something like this:

[delayed_gcode set_stepper_angle_timer]
initial_duration: 1
gcode:
    # Delayed gcode will poll every second and update the servo angle
    SET_STEPPER_ANGLE
    UPDATE_DELAYED_GCODE ID=set_stepper_angle_timer DURATION=1

[gcode_macro SET_STEPPER_ANGLE]
gcode:
    # Set the servo angle based on the part cooling fan speed
    # Fan = 0.0, servo angle = 0
    # Fan = 0.5, servo angle = 90
    # Fan = 1.0, servo angle = 180
    SET_SERVO SERVO=myServo ANGLE={% printer.fan.speed * 180 %}

I might not have the Jinja2 syntax correct {% printer.fan.speed * 180 %}, and if you are not using the standard part cooling fan, that will need to be adjusted as well.

Hope this helps.

1 Like
8

Nice ideas @jjarosz
Another approach could be to define a custom M106 macro (no idea if this would work) or a completely new command and post-process your GCODE file to use the new command instead of the regular M106.

Quite specific requirement, so probably a lot tinkering.

9

@jjarosz Thanks for the help! I will try to get it working based on your suggestion. I am new to Klipper and havent tried any of the custom macro stuff yet so this should be a fun rabbit hole. Thanks again.

10

Hi, I am trying to understand the configuration syntax and whether it provides a way to tell Klipper that I am using a [fan] that is controlled like a [servo] rather than by PWM.

For example something like:

[servo myservo]
…

[fan myservo]
…

11

Hey AMV101!
How did this work? I had the same idea and just came across this in my search for answers. I have everything in place, just trying to get the config to work.

12

Yes I think it worked from my tests, but I moved on from that idea and cant remember if I had to change anything.

13

Hello everyone,
I’d like to revive this conversation as I am trying this avenue myself. Thanks to the previous posters who have helped.
I am having trouble with jjarosz answer as Klipper will not recognize the name seen at the bottom, printer.fan.speed
I tried removing printer and also putting fan in brackets to no avail. How do I reference the fan speed into the macro controlling the servo?
I have attached my printer.cfg file below
printer.cfg (3.6 KB)