RAMPS 1.4 / Marlin Firmware Modification

Hi All,

I'm working on a project where I'd like to have a constant 12V output from the extruder outputs on the RAMPS 1.4 board during extrusion events. I'm currently trying to sift through the Marlin firmware to determine how much work is going to be involved to modify for my needs, and it seems as though it may be easier to write "add-on" code in place of trying to modify the existing stepper functions to output a constant 12V during the extrusion events on only the E0 / E1 outputs.

Is there any firmware that exists that accomplishes this already?

Thanks,
zip

Edited 1 time(s). Last edit at 12/06/2013 11:41AM by zipfactor.

If you're driving an actual heater, this will lead to your plastic burning as you go.

I suspect however that you're not using a heater.

What's the project for, as someone may have tackled similar problems before in a completely different way.

eg: The local hackerspace I'm involved with uses Marlin to drive a laser cutter, with a few small mods. It doesn't use the extruder output at all, but instead drives one of the other outputs to do PWM to control the laser brightness.

The gcode that Slic3r generates is where the "extrusion events" (stepper motor movement instructions) come from. The are in the form of "move 10mm of filament". Do you still want to move the filament? Do you want the +12 signal to start before the move and finish after the move? Will there be retraction? What would you want to do in that case?

There's a lot of guessing we can do here. It would be helpful to know what the overall goal of the project is, not just how you think you might accomplish a sub-task.

Cefiar @zipfactor said .....
Re: RAMPS 1.4 / Marlin Firmware Modification
December 06, 2013 03:00PM Registered: 3 years ago
Posts: 895
If you're driving an actual heater, this will lead to your plastic burning as you go.

I suspect however that you're not using a heater.

What's the project for, as someone may have tackled similar problems before in a completely different way.

eg: The local hackerspace I'm involved with uses Marlin to drive a laser cutter, with a few small mods. It doesn't use the extruder output at all, but instead drives one of the other outputs to do PWM to control the laser brightness.


.....

So, Please, Cefiar,
could you tell me, in more datail, example (Gcode...?), how do you PWM control the laser?; In which pin ar you controling laser diode, and how is the wiring with it.

I am working with Prusa, Marlin and RAMPS 1.4, and my laser is controled with a driver board TTL capable,
As far as I know, RAMPS's fan wire could be used to send TTL signal, with a tension divider (2 resistor 7kohm+5kohm), to take 5v from 12 v fan output of RAMPS.
Then I shoul need to remap (in Gcode? firmware?) some pin for that laser control. ¿?
Could you help me explain it?

NOTE: I am trying to understand-explaining to myself the idea. I make a sketch (pdf file atached)

thanks
bobion

Edited 3 time(s). Last edit at 02/17/2014 05:16AM by bobion.

bobion: The github (for Firmware and Hardware) is at: [github.com]

While we did use RAMPS originally, we moved to a different (custom made) board, but it's still an Arduino at core.

You could simply map one of the Servo pins to the laser output. That will be TTL (max 5V) and should do PWM. I think that might be what we did, but it was a while ago.

Note: I was not involved in the actual doings of the project.

Cefiar:
thank you very much for your attention.
I am going to look at the github link you said.
great job.
regards
bobion

There are other m codes to do analog output on a pin.

See the reprap wiki about g codes.

hi, im planning to use a laser with my custom made printer, everything from the printed parts to the parts used are all custom made, except for the ramps board and marlin,

ok, so if u want to control ur laser, how abt u do this?
1. in the pins.h header file of marlin, change the extruder direction to some other pin use it to drive a transistor which in-turn controls the laser, the advantage is that the laser will be turned off when ever the head is moving along a non-prnting direction(I think this will work coz, from what I know extruder spins a bit in backward direction during no printing moves

2 another solutions is , if ur gona some CNC program to generate the G-code u need, then just removed the stepper driver or solder a wire to the direction pin of the stepper driver and feed it to a separate Arduino ( or a transistor or mosfet will do fine I guess but it wont be a good thing to do if ur still going to move z axis, but when using laser z is not actually needed so removing the stepper driver and using the direction pin to drive a transistor is the best option) and use it to determine when to turn off the laser. (since the z axis moves up every time the head positions itself the laser can be turned off and on using this output coming from ramps or which ever board ur using)

hope my concept is clear and correct