Servos as Axes
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Is it currently possible to configure a servo output as an axis within the firmware? I don't think it is, but if there was a way to do it I would certainly make use of it.
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@gizmotronx5000 no it is not i am afraid. can you let us know more about how you want to use this?
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Of course! I'm basically messing around with the idea of various accessories/tools that can come into and out of the print area on their own axes. They are currently controlled by servos, but if they behaved like axes I could track their position and incorporate them into the inverse kinematics model for the printer much more easily. I'm thinking about switching to steppers anyways, but the servos don't require any homing and are extremely light compared to steppers with similar holding torque.
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I have some more clarification for this concept. I am hoping to create a rotating build platform and the design so far seems to require a servo instead of a geared stepper motor just due to size, torque, and space constraints. Would it be possible to set up a rotational U-axis as a servo in addition to a linear delta printer?
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@gizmotronx5000 if its a large scale servo motor then you would need servo motor controller. The duex only supports hobby servos with limited current capacity on the servo ports.
If you are using a larger servo motor for this axis then you are probably best off using a controller that accepts step/direction pulses and translates them for the large servo movement.
what servo are you planning on using?
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Hi Tony,
It's actually a small hobby servo that I have had success running off of the Duet already. I don't know the brand off hand, but I have been running it using the PWM pins on the Duex5 with good results. It would be nice if I could move it using G1 though instead of M commands, since it is acting as a rotational axis. The problem I've run into using a stepper instead is just that this servo has a lot of torque for its size compared to a stepper, plus I don't have to worry as much about accuracy, because the servo won't skip steps like a stepper might do close to its peak holding torque.
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@gizmotronx5000 Ok i understand, well being able to use a servo PWM control as an axis is something for the firmware wishlist so this post is in the right place.
I am surprised that you are getting enough accuracy on the rotational axis for a hobby servo to be good enough.
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@t3p3tony Does this seem like something that is worth implementing? I'm also working on my own kinematics to go along with it, so it certainly wouldn't go unused by me if it was implemented. Only one axis will be a servo, but perhaps someone might want to build one using only servos at some point. I understand that it may be too niche of a request though. My next request will likely be to reserve a kinematics number in the firmware, but I'm not quite to that point yet.
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@gizmotronx5000 I will leave the decision on whether it is a good idea to implement to @dc42, he is away right now though.
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@t3p3tony Sounds good! Thanks.
