In this Instructable I'll demonstrate how to install and configure Reprap Ramps1.4 RRD Fan Extender to make it possible to add a temperature controlled fan for your extruder (hotend) and a fan to cool your drivers on the Ramps board only when a driver is actually active. We will retain the ability to control the D9 fan using LCD or the M106 Gcode for the printer-bed as standard.
I am using the newest (As of 20th may 2015) iteration of Marlin firmware and run it on an Arduino Mega + Ramps board configured as EFB (Extruder D10, Fan D9, Bed D8).
I bought the extender and found it really hard to find some usefull information, where most of the information was old and dreprecated and also had various degrees of errenous info like wrong pin numbers. All info I found entailed using the extender in a two-extruder scenario meaning disabling the controllable D9 fan, which I did not want to do.
To compound the issues most "guides" assumped you were fluent in marlin firmware and gcodes, which I certainly am not!
You will obviously need the Reprap Ramps1.4 RRD Fan Extender, which can be found multiple Places. One of them is on ebay. There is really no money saved by buying in china, so buy locally if possible. Pay attention to the fans included if any. One of my fans didn't Work, so seller is sending a new one - just undelineing the need to buy locally!
According to the Ramps 1.4 schematics, the Fan Extender is placed over the Ramps servo-pins which has the pins D11, D6, D5 and D4, listed from the top left (with powerplug to the left). I'm mentioning this, as it seems different Fan Extenders are using different pins.
My version is White, and has no versioning numbers or text on it. I use Pin 4 and 6, but yours might be different.
Be sure to turn all power off your printer. That means remove both the power and usb cords.
Now take a close look at the small Extender board. There should be some tiny + and - symbols on it. I say this, as the image from Geetech is wrong - at least my extender board has the input pins in reverse.
The small extender goes on the grouping of pins right next to the reset button - this grouping is the Servos Aux-1 pins. It can only be installed in one direction - see images for details.
Now install the power-wire on the 12V-aux pins (see images for detail). When you have the green power-connector on the Ramps board to your left, the pins are oriented with 12v on top and Gnd beneath it. Ideally you want to verify this with a multiemeter.
When the extender board is installed on Ramps, and in same orientation as above, the 12v goes to the top pin on the extender board. There should be a tiny + to show it. The image from Geetech has this cable installed in reverse!
If you do not have all the pins needed on your Ramps board, you can solder them on yourself.
The power can be sourced from somewhere else. You can use 5v instead if you like.