Question on development, are new versions (multi-color) of the card planned?

[mrbi11]

E3d-online is developing a 4 color print hot end.
The rambo can handle 2 extruders. (colors)

So several questions,

1. Is anyone contemplating card versions that can handle 4 (or 6 or 8) colors?

2. The rambo has 2 z motor plugs, but apparently they are simply parallel connections for convenience? Not two independently controllable outputs?

I note that although one could implement 4 extruders by 4 motor controllers,
that never are more than one motor active.

If there were a way of selectively enabling/disabling motors in hardware, one could use a single motor controller for any number of extruders.
Software switching heads could output a different "selector" to say
2 pins to select 1 of 4 motors, all driven by 1 motor controller.

There are multiplexers to handle the logic, but...
3) Are there solid state switching devices (like mosfetts) able to handle current flowing either direction to use as switches (meaning able to also handle full current and no power drop).?

(I am unclear what mosfetts can do if they do not have a stable voltage at their source for the gate voltage to be relative to. Motor controllers I see seem to have mosfetts operate in pairs. Motor controller ic's may be as simple as a switching device get to connect or not to a motor. One could use external mechanical relays
but that seems inelegant.)

4. Are there any un-dedicated logic pins that could be used for selecting extruder?
   (2 pins for 4, 3 pins for 8, etc.)
   4a) Could the outputs driving the Rambo extruder 1 be re-purposed as multiplexer pins?

5. Is there a map of "unused" pins anywhere? Pins as yet not dedicated to
   other functions?

If the multiplexer selection of motor approach was taken, the primary issue is how to get enough extruder connectors. Little board rel estate and no need for more logic outputs for each motor.

Anyone interested in developing a new board with electronics design skills to do so, I would be happy to hear from you.

ps- by multi-color applies to filament, not the printed circuit board:-)

[RalphFerro]

ORD has a 5 extruded machine. I am not sure what electronics it uses.
I am not sure if their electronics are proprietary.

Sent from my iPhone

On Jan 6, 2014, at 2:23 PM, mrbi11 notifications@github.com wrote:

E3d-online is developing a 4 color print hot end.
The rambo can handle 2 extruders. (colors)

So several questions,

1. Is anyone contemplating card versions that can handle 4 (or 6 or 8) colors?

2. The rambo has 2 z motor plugs, but apparently they are simply parallel connections for convenience? Not two independently controllable outputs?

I note that although one could implement 4 extruders by 4 motor controllers,
that never are more than one motor active.

If there were a way of selectively enabling/disabling motors in hardware, one could use a single motor controller for any number of extruders.
Software switching heads could output a different "selector" to say
2 pins to select 1 of 4 motors, all driven by 1 motor controller.

There are multiplexers to handle the logic, but...
3) Are there solid state switching devices (like mosfetts) able to handle current flowing either direction to use as switches (meaning able to also handle full current and no power drop).?

(I am unclear what mosfetts can do if they do not have a stable voltage at their source for the gate voltage to be relative to. Motor controllers I see seem to have mosfetts operate in pairs. Motor controller ic's may be as simple as a switching device get to connect or not to a motor. One could use external mechanical relays
but that seems inelegant.)

4. Are there any un-dedicated logic pins that could be used for selecting extruder?
   (2 pins for 4, 3 pins for 8, etc.)
   4a) Could the outputs driving the Rambo extruder 1 be re-purposed as multiplexer pins?

5. Is there a map of "unused" pins anywhere? Pins as yet not dedicated to
   other functions?

If the multiplexer selection of motor approach was taken, the primary issue is how to get enough extruder connectors. Little board rel estate and no need for more logic outputs for each motor.

Anyone interested in developing a new board with electronics design skills to do so, I would be happy to hear from you.

ps- by multi-color applies to filament, not the printed circuit board:-)

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[kakaroto]

There are 3 extensions for motors in the Motor-Ext header : http://reprap.org/wiki/File:Rambo-conn-aux.jpg
The unused pins are explained here : http://reprap.org/wiki/Rambo_development
Along with the Motor Aux Power connector providing the +12V, someone could make an adapter that adds 3 extra motors to the RAMBo by connecting to the MX and Aux Power connectors and providing pins for three A4988 pololu stepper drivers. You could also use a breadboard for it, like in this page (it's in french though) http://mchobby.be/wiki/index.php?title=A4988
It would allow the board to support up to 5 extruder.

[mrbi11]

Thank you. That is extremely helpful.

I also investigated using relays (dpdt) to connect the same drive to
different extruder motors.
Two dpdt relays can switch to 4 motors, but requires 2 bits (pins) to
drive the selection.
Of course, this depends on the common fact that only 1 of multiple
extruders is active at any given time.
So the 2 on board extruder motor controllers could drive up to 8
extruders, but only one at a time.

I had hoped to use the rambo in a new 3d printer, but am pretty
disappointed in the 4 line 20 character displays it is often used with.
I was looking for a small color graphics display, which are quite
reasonably priced, but also need 16 bits to drive instead of 8.
So never having a definitive answer of which pins are free was pretty
stuck, so on the back burner it went.

Thank you for the pointer to unused pins, and for the excellent suggestions.

peace,
*Bill Kelley

• 512 266 1896

On 6/14/2014 3:59 PM, kakaroto wrote:

There are 3 extensions for motors in the Motor-Ext header :
http://reprap.org/wiki/File:Rambo-conn-aux.jpg
The unused pins are explained here :
http://reprap.org/wiki/Rambo_development
Along with the Motor Aux Power connector providing the +12V, someone
could make an adapter that adds 3 extra motors to the RAMBo by
connecting to the MX and Aux Power connectors and providing pins for
three A4988 pololu stepper drivers. You could also use a breadboard
for it, like in this page (it's in french though)
http://mchobby.be/wiki/index.php?title=A4988
It would allow the board to support up to 5 extruder.

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#22 (comment).

[kakaroto]

You're welcome. I think using relays would probably need changes to the firmware, and it would be an unusual setup, but I guess it could work if you use some of the free ext-2 pins.
I haven't tried the full graphics LCD, only the 4x20 Smart LCD, but it looks like the full graphic LCD uses the same EXT1+EXT2 ports than the 4x20 LCD, and the same adapter for RAMPS according to pictures from here : http://reprap.org/wiki/RepRapDiscount_Full_Graphic_Smart_Controller
So I would assume the full graphics LCD would work just the same with the RAMBo as the 4x20 LCD. You can see information about it here : http://reprap.org/wiki/RamboLCD although that wiki is outdated since there's an adapter for RAMBo now :
http://www.makerfarm.com/index.php/printer-electronics/lcd-adapter-for-rambo.html
https://ultimachine.com/content/lcd-smart-controller-adapter-board-kit-rambo
http://reprapelectro.com/product/rambo-smart-lcd-adapter/
(Note that reprapelectro website is not yet operational, we still need to add proper shipping costs to the website and we should be in business sometime this week).
You can actually see that the full graphic LCD works with RAMBo in one fo the pictures of MakerFarm's store : http://www.makerfarm.com/media/catalog/product/cache/1/image/e50596b62d4a48a983f848d3568a5b89/r/a/rambo_interface_6.jpg

[anderwm]

If you remove the motor connection to an A4988 while it is powered (by some sort of switching) it will very often damage the A4988. You would have to do a really good job with killing the voltage spikes that result from the switch(probably a bad idea though).

[kakaroto]

That's a good point, also add the fact that the motors would lose their holding torque which could cause the extruder to move due to the X movement and vibrations.

[mrbi11]

Thanks for the heads up.

I have noticed with power off, if I move my delta carriage down rapidly,
it generates enough power to light up the LCD!

So your point is well taken, I'd definitely need to suppress spikes. I'm
not sure if the extruders are always holding position like the other
motors, but it might require turning the extruder motor circuit off
completely before switching print heads, then switching it back on.
The hot end never switches during printing (extruding), so it should be
manageable.

*peace,
bill kelley
512 266 1896 *

On 6/16/2014 9:55 AM, anderwm wrote:

If you remove the motor connection to an A4988 while it is powered (by
some sort of switching) it will very often damage the A4988. You would
have to do a really good job with killing the voltage spikes that
result from the switch(probably a bad idea though).

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#22 (comment).