A while ago I received my Rumba board which is going to control my MendelMax2, and not only is it a pretty nice little board, it also got some extra handy features.
I have in other blog posts written about the functions I made to turn a fan on and off when the hotend got over a defined temperature or if any of the drivers were on, and the rumba is almost perfect for this!
Let’s have a look at the pcb…
Bottom in the center of the pcb you find HE2, FAN0 and FAN1. These are the ones we are interested in.
Since it is not marked on the pcb I will here bring the pin numbers.
HE2 = 6
FAN0 = 7
FAN1 = 8
As default the fan cooling the extruded plastic is set to pin 7 (FAN0), and we will leave it like that to (hopefully) make it less confusing.
Before continuing you need to have a look at what power supply you have connected to MAIN-PWR, if it isn’t 12V and your fans are 12V, you need to connect the pin-header between the center pin and PWR next to each of the three outputs. If you are using a 24V power supply, which are getting more and more common, you set it to 12V-Select instead. This sets the outputs to use the power from the on-board voltage regulator, which is 12V.
With the default fan on pin 7 we got HE2 and FAN1 left to play with, and that is exactly what we are going to do!
To the HE2 we will connect the fan cooling the barrel of the hotend, and to FAN1 we connect a fan which cools the stepper drivers.
Next step, which is also the last, is to configure the firmware.
These functions should be in both Sprinter and Marlin, but they are in different files. In Sprinter you will find them in Configuration.h, and in Marlin Configuration_adv.h
#define CONTROLLERFAN_PIN 8 //Pin used for the fan to cool controller, comment out to disable this function
#define CONTROLLERFAN_SEC 60 //How many seconds, after all motors were disabled, the fan should run
//This is for controlling a fan that will keep the extruder cool.
#define EXTRUDERFAN_PIN 6 //Pin used to control the fan, comment out to disable this function
#define EXTRUDERFAN_DEC 80 //Hotend temperature from where the fan will be turned on
This will turn FAN1 on when any stepper driver is activated, and leave it on for 60 seconds after the last has been turned off. It also makes HE2 turn on when the hotend temperature is above 80C and leave it on until it is below again.