Is there any pin that indicates the extrusion is happening?

Hi, I'd like to know if there are any pins on the ramps board that will indicate whether or not extrusion is currently occurring. I suspect not, but does anyone know of a way to do this in the firmware? If someone could point me to where extrusion is controlled in the firmware, I could try to implement this myself.

The reason this would be nice is because I want to use the pin to control pneumatic extrusion (with a mosfet/solenoid) but without requiring modifying gcode. (to help with the pneumatic extrusion, the min and max speeds are set to a constant equal value.)

My experience is with teacup, but I imagine it's similar for all firmwares. There's no boolean logic that says extrusion is currently ongoing, there's just a periodic step when required. The steps could be several seconds apart (for a ridiculously slow extrusion rate) or 1/1000th of a second apart, and in both cases extrusion is "occurring". If you wanted to modify code to do this, you could use the step logic to set an unused pin high when the E axis steps and turn it off during the next 2ms clock tick (again, this is teacup specific), or you can just use the existing step pin and interpret it via some external circuitry with a 555 timer or another mcu without modifying the code at all. In both cases you'd obviously want to turn off reversal of the e axis during retraction moves.

You could also take a look at Grbl and consider that your pneumatic extruder is a tool.

What do you want? Can't really imaging what you want to reach. Something like a LED or something else should lightning when the extrusion motor is running?

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Most important Gcode.

I ended up writing code to modify the g-code to turn on and off an I/O pin when I needed it to because there was no pin that would indicate whether or not extrusion was happening or not. It would activate and h-bridge which would activate a solenoid to allow air pressure to push into material in a syringe (for paste extrusion). Works pretty well now.

Edited 1 time(s). Last edit at 03/28/2015 04:39PM by jessicabrenner.

FWIW, RepRapFirrmware for Duet electronics supports this feature as standard as of version 1.04. It's controlled by a gcode, which can also set the PWM factor on the pin. The pin is turned on with the specified PWM factor for every extruding move. I wondered why RepRapPro added this. Perhaps they are experimenting with paste extrusion too.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
FWIW, RepRapFirrmware for Duet electronics supports this feature as standard as of version 1.04. It's controlled by a gcode, which can also set the PWM factor on the pin. The pin is turned on with the specified PWM factor for every extruding move. I wondered why RepRapPro added this. Perhaps they are experimenting with paste extrusion too.

Oh, that's interesting.
I'm having weird problems with my Duet controlled Huxley and the ability to tell that it at least thought it was extruding would be really helpful. Could you expand on this please dc42?

[Details of my problem are here: [forums.reprap.org] ]

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csambrook
Oh, that's interesting.
I'm having weird problems with my Duet controlled Huxley and the ability to tell that it at least thought it was extruding would be really helpful. Could you expand on this please dc42?

If you send M571 S1.0 then the FAN0 output will be fully on when extrusion is taking place, and fully off when it isn't. There is a led near the FAN0 output that will light up when the fan is on.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].