Add CONTROLLER_FAN_BED_HEATING option to control to run/not run the controller fan when the bed is heating

[rondlh]

Description

Add the option to run/not run the controller fan when bed heating is enabled, as this is often not needed.
This is done in Configuration_adv.h, by defining "CONTROLLER_FAN_BED_HEATING", which will run the controller fan when bed heating is enabled (the current default).
When the line is commented out the controller fan will not run anymore when the bed his eating, as this is often not needed, like for example when a main power bed heater is used or the controller fan does not affect the bed heating power supply.

Requirements

This PR does not require any specific boards. Obviously you need a controller fan, and a heated bed for this to be useful.

Benefits

Allow to have the bed heating, without running the controller fan, this will reduce noise, and can be useful when the bed is heating without the steppers being active. In my printer the bed is heated first, which takes some time, then homing starts. The controller fan does not need to run during the bed heating time. I also sometimes have the bed heating for some time without actually printing.

Configurations

Nothing special is needed, just at #define CONTROLLER_FAN_BED_HEATING to the Configuration_adv.h

Related Issues

No related issues.

[thisiskeithb]

Add the option to run/not run the controller fan when bed heating is enabled, as this is often not needed.

This is especially necessary for the bed mosfet since that will be the largest mosfet doing the most work.

[rondlh]

Add the option to run/not run the controller fan when bed heating is enabled, as this is often not needed.

This is especially necessary for the bed mosfet since that will be the largest mosfet doing the most work.

Agree, in some cases it's necessary and or useful to run the controller fan when the bed is heating, but in some cases it's not. I have seen several printers where the bed heating has nothing to do with the controller fan, often only the stepper drivers are targeted with the controller fan and even the power supply is not affected or has it's own independent fan.

In my experience mosfet bed driver should not get hot, especially the mains voltage ones. I run my bed at 12A 36V, and my basic MKS mini mos only gets slightly warmer than ambient. If the mosfet gets hot it's usually a sign that something is not configured correctly. If a mosfet is driven correctly then the resistance is only a few mOhms, and Marlin keeps the switching frequency quite low, so also there should not be an issue.

Anyway, the PR gives an option, if you need the controller fan during bed heating, then that's still the default.