Fans on full blast during startup using PWM converter board

p8blr

I setup a large fan for forced convection on my chamber heaters and I used a PWM converter board to signal the motor controller that needs 0-5V for speed control. It works, other than the fact that the fan jumps to full speed when you turn on the printer, which I want to avoid because it's a large mechanical jolt to the system and I use a macro to turn on the fan slowly with gcode. What can I change in my code/wiring to prevent this from happening?

fan setup in config.g

M950 F1 C"!5.out3"                        ; create chamber fan 1 
M106 P1 S0 H-1 C"Chamber Fan"             ; set fan 1 value

gloomyandy

@p8blr What do you have that pwm board connected to? It looks like you are using some sort of Duet3 expansion board, is that the case? If so what board is it?

p8blr

@gloomyandy The duet board is a 3HC

gloomyandy

@p8blr I think that the fan outputs like out3 on the 3HC are initially turned "off" by the firmware, but it looks like your config (which will not be applied until the 3HC has synced with the mainboard), is setting the output to be inverted. I think that this will mean that until the 3HC has synced and received the output pin configuration from the main board it may in effect be "on" as far as your hardware is concerned.

If your pwm converter can operate from a 3.3V logic level signal you may be able to connect it to one of the io pins (like io_0 etc.). But you would need to check if that is possible and probably remove the 1K pullup resistor (or perhaps connect that to 3.3V instean of 5v)? But I'm getting beyond my knowledge of the Duet3D hardware at this point, so perhaps someone like @T3P3Tony could comment!

dc42

@p8blr as Andy says, you may be able to drive the PWM input port directly from an io_out pin and only take fan power and ground from the out port.

Which type of PWM converter do you have? Depending on the type there may be another option too.

p8blr

@dc42 I will try using an io_out pin for PWM and report back.

I'm using this board:
https://www.amazon.com/gp/product/B0BG2G5FMX

p8blr

@dc42 @gloomyandy Thanks for your suggestions, that fixed the issue!

M950 F1 C"5.io1.out"                      ; create chamber fan 1
M106 P1 S0 H-1 C"Chamber Fan"             ; set fan 1 value, thermostatic control off