Need help with dual extruder setup

Hi guys,

I am currently in the process of upgrading my Prusa i3 to have dual extruders and need some guidance from fellow reprappers. So I am using Ramps 1.4 / Marlin with the extruders connecting to D9 and D10, I have 2 fans that cool the hotends and 2 fan that cool the print, now these fans can be either 5v or 12v as I have both, what I would like to do is have the fans that cool the hotends to only come on when the hotend temperature rises above 50 degrees C and I would like the 2 fans that cool the print to be controlled by the slicing software (by that I mean comes on when bridging etc). I have looked at some other peoples examples of their wiring setup but they have the fans connected to the 12v rail and permanently on, is there a way to connect the fans to the ramps board and perhaps change something in marlin to allow me to have the fans as I would like them?

Thanks,
Chris

I´m clueless about the hotend fans, but
the print-fans could be controlled by the 5V servo pins, if you have a decent 5V supply ( not the arduino regulator ) and remove D1 on the Ramps.

The 5V source could either be a simple 7805 or a RC-BEC-circuit or a red wire from a PC-PSU. ( see other threads for details )

You´d have to change the pins.h settings to route the print fan-PWM control to the desired servo-pins.
-Olaf

@ Chris

I would suggest you try to use one of the unused Arduino PWM ports available on the RAMPS to control an extra MOSFET for the layer fan(s) (which you have mentioned above as the "fans that cool the print"). Wiring an extra MOSFET to the RAMPS shouldn't be too hard and it's an inexpensive solution (< $1).

Then of course you'll have to patch/edit some of Marlin's configuration files, as Olaf mentioned.

Edited 1 time(s). Last edit at 06/26/2015 04:01AM by AndrewBCN.

Thanks for the suggestions guys,

I never thought of using the servo pins, i'm surprised that the mega wont be powerful enough to power the fans, are there any instructions anywhere that show to how to wire the extra circuit needed? also, i have never had to re-assign pins in marlin, what exactly do i have to change?

I used one of these LINK to power the fans, its just as a safety measure the Ramps might be able to handle them, but I wasn't sure.

What version of Marlin are you using the older one has all them in the pins.h newer version has the pins spit up in seperate files for each board which is allot easier. So in the new one pins_RAMPS_13.h if you scroll down look for
#define FAN_PIN 8

There is an else statement for each value as well, if not sure just make all them match so assign the Fan pin to the value you want in each section. You will want to go through the file and look if the pin you want to use is assigned for another function and remove that by changing to -1.

Edit the value to the pin you want to use on RAMPS board here is a LINK to pinout.