Extra pins on mk3  

RE: Extra pins on mk3

or my idea could in fact be anything, it could be a huge fan to speed up the cooling of the bed once print is done

or it could be a high res DSLR camera to take better pictures

RE: Extra pins on mk3

It would be super useful if there were a way to use a GCode command to output an analog or even digital hi/lo signal on an extra pin on the main board.

If anyone happens to know how this could work please share!

RE: Extra pins on mk3

I can think of a way to do it that doesnt require any pins from the einsy board, or any board really.

Fit 2 microswitches to the printer frame.  One that is activated when the bed is fully forward, and the second that is activated when the extruder/x axis is at max height.  Wire them both in series.  When both are closed at the same time then that can be used to activate your external circuitry.

Then all you need to do is edit your end gcode in the slicer you use to move the bed fully forward (which is pretty much the prusa default anyway) and also move the extruder up to the top to activate the second switch.  Done.

You would need to design/modify and print a couple of brackets to hold the switches but there are hundreds on thingiverse designed to mount them to the slotted aluminium already.  Maybe a bit more difficult to do the one for the top but Id think a slight modification to one of the z screws holders would be possible.  Or a modification of the spool holder bracket so it can just be clipped over the top.

I would love to know the answer to the original question.

I would love to know the answer to the original question, so if anyone knows the answer that would be truly fantastic. 

M42 is supported according to the Prusa Knowledgebase

The Prusa documentation on supported gcode commands does list M42 with a link to the RepRap command description. I have not tested this myself.

pin to connect the relay

Thanks for the tip! Do you know how can I locate a free i/o pin so I could control the relay with 5V?  
Could I use one of the pins for the end stops? Well I am quite clueless so any help would be highly appreciated for a novice. 

1

" huge fan to speed up the cooling of the bed once print is done"

Could work, but this will help warping of the print.

OctoPrint?

Rather than burden your mainboard with additional works, there are many OctoPrint plugins that do that sort of thing.

Burden?

Well the additional burden is a 5v signal at the end of the print, I don’t see any problem with that. 

I don’t use a pi but a mini pc with linux, that’s where the octoprint is running. Anything happens with Octoprint or the pi/ minimpc and this functionality is gone. I would not think for a second about “burdening” the board and directly control the safety relay without placing additional hardware and software just to implement this dead simple solution. The only problem is my limited knowledge, that is the only reason why I bought a Sonoff smart plug and will control it with an octoprint plugin. This option is easy to implement and i gave up my initial plan after wasting  5-6 hours just trying to find out which pin I could connect the relay to on the board.  What I do not like about this is the fact that the relay is controlled wirelessly and it requires a network. 

.

You can take this example and use it for other purposes:

https://blog.prusaprinters.org/how-to-create-beautiful-3d-print-timelapse-videos_29743/

RE: Perfect!

Awesome thank you so much! 

Sorry

Sorry Bo I didn't read your original post. I take your points but if I may, using printer mainboard means that you need to recompile for every new revision from Prusa. I accept that it's a matter of opinion but I would not run OctoPrint on any hardware that was not running a RTOS, but thats just me

no need to tweak the firmware.

No worries mate! But I don't understand your point because m42 is supported by the original Prusa firmware as @bobstro pointed it out. So I don't really see any issue there, I don't think you would have to tweak the firmware. 

2¢

Posted by: @mate

No worries mate! But I don't understand your point because m42 is supported by the original Prusa firmware as @bobstro pointed it out. So I don't really see any issue there, I don't think you would have to tweak the firmware. 

That's my understanding as well. You can use M42 in gcode without any changes to the current firmware. However:

• I haven't actually tested this.
• Finding a free pin to use is a challenge.

My inclination would be to do this sort of thing with OctoPrint because of the ready availability of pins and no need to keep slicer profiles updated. I don't think there's anything wrong with using M42 though.

RE: the answer again.

@bobstro, I think you have missed @nikolai's answer:  https://blog.prusaprinters.org/how-to-create-beautiful-3d-print-timelapse-videos_29743/  

RE: no change to firmware

@Mate your correct, no need to change firmware, I didn't realise you set the GPIO pin in M42 I thought you'd need to define it.