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  1. #13
    Member Joey2point0's Avatar
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    Default Re: Usability of Encoder on DC Motor,

    You wiz machinists are loosing me, appreciate all the good info though. Certainly learning a lot through this process!



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    Default Re: Usability of Encoder on DC Motor,

    Quote Originally Posted by Joey2point0 View Post
    Doing a retrofit of D&M 5 Lathe, adding Acorn CNC controller. It has the stock 90 vdc motor.

    Is it worth it to add a rotary encoder? Wondering if this will allow me to do threading?

    Also, any encoder recommendations would be appreciated.

    Thanks, Joey
    Yes that will work fine as long as you have the right Encoder, a lot seem to be using this Encoder which is on the low side but seems to work with the Acorn Control Omron E6B2-CWZ1X, they can be had for around $30 to $40

    Mactec54


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    Default Re: Usability of Encoder on DC Motor,

    Quote Originally Posted by hfjbuis View Post
    @mactec54 I am sorry if I wasn't clear
    • Not the gearing of the encoder is important but the final pulses per spindle revolution is what counts
    • By design, threads have a lot of clearance. Trying to get this few hundreds of a mm clearance within 0.001 mm accurate will not make a better thread.
    • Even so, according to the measured accuracy, even using this low resolution encoder, the result is accurate, not a waist of time but a learning experience.
    • I agree on the X or Z axis, a decent encoder resolution is a must because it is used for positioning.



    By the way, for accurate threading, meaning even the last winding (deceleration of the Z-axis) is in spec, I use a stepper on the spindle.
    If you are only working at Hobby level then anything can work even just a single index pulse, it just the control he is using has a requirement which has to be met or it will not work

    Mactec54


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    Default Re: Usability of Encoder on DC Motor,

    Sounds like acorn have a problem with the index, in that can't be more than once per spindle rev, which would rule out fooling it with just the total pulses per spindle rev as calculated at the motor.
    Bummer, I would think thats something they could fix easily enough.
    You could still do it with an encoder on the motor, and an index pulse once per rev from the spindle, just more parts...



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    Default Re: Usability of Encoder on DC Motor,

    Quote Originally Posted by ninefinger View Post
    Sounds like acorn have a problem with the index, in that can't be more than once per spindle rev, which would rule out fooling it with just the total pulses per spindle rev as calculated at the motor.
    Bummer, I would think thats something they could fix easily enough.
    You could still do it with an encoder on the motor, and an index pulse once per rev from the spindle, just more parts...
    There is nothing to fix

    Acorn does not have a problem with anything to do with Encoder input, the Encoder only needs to be on the spindle it can of cause be on both but is not needed unless you are using servos motors that need the own Encoder

    Mactec54


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    Member Joey2point0's Avatar
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    Default Re: Usability of Encoder on DC Motor,

    With all this being said can someone tell me if the way I plan on setting this up genuinely wont work.

    The encoder is driven by the motor at the same rate as the spindle. (see the photo)

    Attached Thumbnails Attached Thumbnails Usability of Encoder on DC Motor,-20190921_082140-jpg  


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    Default Re: Usability of Encoder on DC Motor,

    I have looked at this acorn video (and some others) for connecting an encoder to the spindle. In this video, they require one encoder revolution for one spindle revolution and use an encoder with a lot of wires. On some forums there is a request for an index pulse, others talk about quadrature differential inputs. For me, as an electronics/software guy, I read the requirements as a quadrature encoder and index pulse and one index pulse per spindle revolution. This fulfills the "one encoder revolution for one spindle revolution"requirement and also a requirement for rigid tapping.

    Your encoder is a 5 Volt quadrature encoder (A/B outputs) with index pulse (Z output) . For me, this should work.

    You have to check the manual for your controller to be sure or ask acorn (centric)



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    Default Re: Usability of Encoder on DC Motor,

    Quote Originally Posted by hfjbuis View Post
    I have looked at this acorn video (and some others) for connecting an encoder to the spindle. In this video, they require one encoder revolution for one spindle revolution and use an encoder with a lot of wires. On some forums there is a request for an index pulse, others talk about quadrature differential inputs. For me, as an electronics/software guy, I read the requirements as a quadrature encoder and index pulse and one index pulse per spindle revolution. This fulfills the "one encoder revolution for one spindle revolution"requirement and also a requirement for rigid tapping.

    Your encoder is a 5 Volt quadrature encoder (A/B outputs) with index pulse (Z output) . For me, this should work.

    You have to check the manual for your controller to be sure or ask acorn (centric)
    If you have a reasonable Encoder and index pulse /Z pulse is not needed or used, it makes for a slow and jerk operation, the whole objective is to have a synchronized spindle and X axes to operate as smooth as possible

    An index pules / Z pulse are normally used for homing a machine, and does not perform that well for synchronizing 2 axes

    Mactec54


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    Default Re: Usability of Encoder on DC Motor,

    Quote Originally Posted by Joey2point0 View Post
    With all this being said can someone tell me if the way I plan on setting this up genuinely wont work.

    The encoder is driven by the motor at the same rate as the spindle. (see the photo)
    Should work fine as long as your wiring and Encoder is setup in the software is correct, you will be good to go

    Mactec54


  10. #22
    Member WayneHill's Avatar
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    Default Re: Usability of Encoder on DC Motor,

    I use AMT102 encoders instead of US Digital.

    https://www.digikey.com/product-deta...1307-ND/827015

    The PPR can be set on the chip. They have been trouble free since installing them over 10 years ago.

    Wayne Hill


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    Default Re: Usability of Encoder on DC Motor,

    I've heard that there is a little bit of delay in those AMT102 encoders... supposedly it works OK for spindle because that just results in a little bit of rotational skew of where the thread ends up; but supposedly it can cause some issues when you try to use it as the shaft encoder on a servo motor???



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    Default Re: Usability of Encoder on DC Motor,

    The AMT102 are used on the shaft of a DC motor. I do not see any delays. It runs five start acme threads reduced down 1:2 at the motor. Anti-backlash nuts. It's fast.

    Wayne Hill


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