What actually does the extruder controller do?

Hello All

In respect to the G3 electronics...

I was wondering what the extruder controller actually does.

If using a stepper motor to drive the extruder that is controlled from the motherboard and if using a pololu driver then what does the controller do?

I can think of the following

- extruder temperature reading
- extruder temperature control
- heated bed temp reading
- heated bed temp control
- switch valve on or off.

What else? Can this not all actually be done by the motherboard itself? Does the communications from the motherboard to the extruder controller not take just as much time as it would to directly control and read the relevant temperatures? Especially if one uses bang-bang temp control (I assume bang-bang is too hot switch off, too cold switch on, perhaps with a 1 degree leeway)

The reason I am asking is my extruder controller seems to have broken for some reason and I am wondering what I can do to recover. see here

My plan was always to move on to an external controller for the extruder motor, probably a pololu, so I need to know what a replacement for the extruder controller needs to do.

Yea thats about it, apart from a fan/mosfet output that you don't really need.

You can remove the need for it as you only really need the temp reading and two mosfet outputs. This is exactly what Mendel-Parts did with Gen6 electronics, it's esentially just Gen 3 all in the single micro so you dont use the second micro (extruder controller)

But my advice would be get an Atmel MEGA for about 25 Pounds as Adrian has done the Firmware for you it's just a compile switch or you can use the RAMPS pinouts - But esentially they are the same. (Mega+pololu) and everything else like the extruder and heatbed outputs can be connected to the Mega with a very small number of extra components.

Don't give up you are almost there.

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[richrap.blogspot.com]

Hi Rich

Thing about using another controller is the communications interface which is where I am having my current problem.

Anyway, it is worth looking into. Do you have any links I can look at for the reworked controller? Also, is this using the regular reprap firmware with a switch set?

PS - my investment is too much in time and funds (over £600) for me to give up. The despondency is just temporary and I am actually having a lot of fun and learning loads with this project. It is just that reaching the milestone of actually printing would have been really good.

Malesh - one soldiers on.

Hi

[reprap.org]

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Regards

Ian

Hi Ian

Thanks for that, but I am looking for a slot in solution just for the extruder controller to work with my existing G3 electronics, not a complete solution.

Looking at the extruder controller v2.2 schematic it looks like it would be substantially simplified if it is not used to control the extruder stepper.

AgeingHippy Wrote:
-------------------------------------------------------
> Hi Ian
>
> Thanks for that, but I am looking for a slot in
> solution just for the extruder controller to work
> with my existing G3 electronics, not a complete
> solution.
>
> Looking at the extruder controller v2.2 schematic
> it looks like it would be substantially simplified
> if it is not used to control the extruder stepper.

the "i2c" lines to the motherboard carry step and dir signals, you can simply hook another pololu to these and many have done exactly that

using the A3949 chips on the extruder board to control a stepper is a nasty hack that works rather poorly, they're simply not designed for it

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Wooden Mendel
Teacup Firmware

Quote
Triffid_hunter
the "i2c" lines to the motherboard carry step and
dir signals, you can simply hook another pololu to
these and many have done exactly that

using the A3949 chips on the extruder board to
control a stepper is a nasty hack that works
rather poorly, they're simply not designed for it

Yes, the point is getting the other stuff like reading temperatures and turning the heaters on and off that I am looking at.

As my father always said before I wrote an exam 'Read the question'

cheers

Hi AH,

The MEGA board is very similar to the Gen3 but it has more pins so it's usually configured to do all the work that the Gen3+Slave Extruder does.

If the Firmware you just need to set the motherboard type to be for the MEGA, I think it's '3' then make sure you have connected the seppers as per Adrian's drawing or the RAMPS design.

Take a look here, you will see all you need to add is a few Caps and resistors and some Mosfets - MEGA Based - Pololu Electronics

You don't need to do a fancy Shield, just borrow the pinouts and schematic - RAMPS

If you want to go for a MEGA, I got hold of a few from this seller on Ebay, very good price (£26 delivered) - MEGA clone

If you buy from somewhere else, just make sure you buy the ATmega1280 version. - and watch out some places sell them for over £67 each!

Then all you need to do is program the firmware (the MEGA has a built-in FTDI RS232 converter) so you just need a normal USB A->B cable. Just select the MEGA target board before compile and program.

I now have three MEGA based electronics sets working with different sets of stepper electronics, they all give me much less hassle than my first set of GEN3.

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[richrap.blogspot.com]

Thanks for that Rich

My next iteration most certainly will not be a commercial solution (other than using the pololu drivers). I will probably even build an Arduino clone from components as well...

Fortunately the problem that inspired this investigation turned out to be software (firmware) rather than hardware so I need not rebuild the extruder controller just yet.

Thanks for the pointers though