autolevel and duet

good morning,
i'm considering buying a duet and extension to add to my home made (very) big prusa mendel . iI intend to use the kraken multi extruder from E3D so I need these multi extruder option

I would like to use as in marlin an servo output to automatise the auto level procedure at the beginning of each print.

is there servo output on the duet or extension card, and is there a way to do that in reprap firmware (ie a Mxxx command to command the servo move ?

thank you a lot

There is no specific support for servo-deployed Z probes in RepRapFirmware, because Duet owners nearly always use contactless Z probes, such as my own differential IR sensor (see [escher3d.com]). However, if your servo just needs a 3.3V control signal set either high or low, then you could add appropriate M42 commands in your bed.g file to deploy and retract the probe. But it may be that your servo needs a 5V pulse train instead.

Edited 1 time(s). Last edit at 01/08/2016 06:33AM by dc42.

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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].

Are there servo's out there which would work with a permanent control signal? In that case you could use some kind of SSR or optocoupler for the connection, but I only have found servos which needs some sort of control signal yet.

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Slicer: Simplify3D 4.0; sometimes CraftWare 1.14 or Cura 2.7
Delta with Duet-WiFi, FW: 1.20.1RC2; mini-sensor board by dc42 for auto-leveling
Ormerod common modifications: Mini-sensor board by dc42, aluminum X-arm, 0.4 mm nozzle E3D like, 2nd fan, Z stepper nut M5 x 15, Herringbone gears, Z-axis bearing at top, spring loaded extruder with pneumatic fitting, Y belt axis tensioner
Ormerod 2: FW: 1.19-dc42 on Duet-WiFi. own build, modifications: GT2-belts, silicone heat-bed, different motors and so on. Printed parts: bed support, (PSU holder) and Y-feet.
Ormerod 1: FW: 1.15c-dc42 on 1k Duet-Board. Modifications: Aluminium bed-support, (nearly) all parts reprinted in PLA/ ABS, and so on.

Most servos in this application are the R/C ones and the need a PWM signal. The width of the pulse between 0/2ms determines the position of the arm and the pulse is sent every 20ms in the most basic form. Some support faster refresh rates but are more expensive and complete overkill for deploying a probe.

the pb is : is there a pin available for a signal for a servo (ie pwm signal 20ms period 1-2ms width) i can easily adapt the level and most small rc servo can work with a 3.3V signal and use 5V for power

but I don't know if there is pin available when the extension board is plugged in, and if there is a servo primitive for the due as with tha arduino mega (if yes it is quite easy to add a command as Mxx Syy with YY from 0 = 1ms to 255 = 2ms

it could be a nice addition to the firmware to automatise some fonctions (open/close door for cooling for exemple, lower and retract probe, move a web cam for distant survey of the print process .....

thank you

It occurs to me that one option would be to use the 2nd fan output on the Duet 0.8.5 to control the servo. You could use a diode and pullup resistor to produce a 3.3V or 5V signal from it. The PWM duty cycle and frequency can both be set using the M106 command (with P1 parameter to select the second fan output), so you can deploy and retract the probe by putting appropriate M106 commands in the bed.g file. No firmware changes necessary.

Or you can use a contactless probe like the rest of us.

Edited 1 time(s). Last edit at 01/08/2016 10:59AM by dc42.

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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].

Quote
dc42
It occurs to me that one option would be to use the 2nd fan output on the Duet 0.8.5 to control the servo. You could use a diode and pullup resistor to produce a 3.3V or 5V signal from it. The PWM duty cycle and frequency can both be set using the M106 command (with P1 parameter to select the second fan output), so you can deploy and retract the probe by putting appropriate M106 commands in the bed.g file. No firmware changes necessary.

Or you can use a contactless probe like the rest of us.

you're right for the probe, but there is the other uses

and i still hav'nt got the answer : is there free pin for other output ? even an I2C connection ? there is a lot to expériment and the possibility to plug an small I2C card and use it for servo output could be useful (like the rolling bed to print lot of part one after the other, control of the enclosure temp, fan to cool the bed at the end of the print, .... lot of things I can't think of)

but before speaking of modifyin the firmware, is the hardware able ?

thank you

Yes, the I2C pins are brought out on the DueX4 expansion connector.

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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].