Encoder for stepper motor


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Thread: Encoder for stepper motor

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    Default Encoder for stepper motor

    Hi. I have recently purchased the KFLOP board. I have a 3 axis milling with stepper motor nema34 size and the driver DQ860M controlled by mach3. I want to configure it as closed loop. My question for the moment is; the following encoder model can work with KFLOP, mach3 and my motor?
    https://mall.industry.siemens.com/mall/en/WW/Catalog/Product/6FX2001-3EB02
    Thank you very much for your help.

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    Member TomKerekes's Avatar
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    Default Re: Encoder for stepper motor

    No. That Encoder outputs 1V analog sine/cosine signals. KFLOP requires digital quadrature signals. See:

    Dynomotion Motion Control Boards for CNC Manufacturing and Robotics Applications


    Regards

    Regards
    TK http://dynomotion.com


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    Hi Tom. Thank you for your answer. I been searching in the web. I found a lot of models with many prices. But I'm not sure if they can work with KFLOP because most of them dont say explicit like you explain in your webpage. As I understand the encoder is "Two phase AB quadrature incremental encoder 5-12V" or "analog TTL quadrature incremental encoder 5-12v" but most of the vendors omits the word "quadrature" or "single ended". It means that it is not correct?

    In the case of the encoders that say quadrature with voltage output and ABZ output (differential), as I understand, they can be connected to Kanalog? Or to kflop with a low cost cable converter?



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    Community Moderator Al_The_Man's Avatar
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    Default Re: Encoder for stepper motor

    If you post details of the encoder you are thinking of buying it would help.
    Here is a typical TTL/differential output .
    Al.

    Attached Thumbnails Attached Thumbnails Encoder for stepper motor-quadencoder-jpg  
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    The encoders should be 5V not 12V.

    I recommend purchasing differential encoders where possible as these can be connected to single ended inputs (just don't connect the complementary signals) or to differential inputs.

    USDigital.com is one reasonable source.

    HTH
    Regards

    Regards
    TK http://dynomotion.com


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    Default

    Quote Originally Posted by Al_The_Man View Post
    If you post details of the encoder you are thinking of buying it would help.
    Here is a typical TTL/differential output .
    Al.
    What do you think about this:
    The model that is available in mexico is CWZ6C. Can it work?

    http://www.mouser.com/ds/2/307/e6b2-c_ds_csm491-25665.pdf

    The z signal can be used for homing? Just like as limit switch?

    Best regards



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    Community Moderator Al_The_Man's Avatar
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    Default Re: Encoder for stepper motor

    You want the line driver version, If using a Z for homing, generally a home switch is also used where the routine is to rapid to the switch, stop, then move off the switch in slow until the marker is seen and immediately use it for home position.
    Tom may confirm if this is correct for Kflop.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    As Al points out the Line Driver option would be the best E6B2-CWZ1X. Line Driver = 5V Differential Signals.

    If you interface the Z index pulse it can help to make homing more accurate. But it can't work all by itself because it occurs every revolution of the encoder at multiple places over the entire travel range. So you need some other indication of approximately where you are so the index pulse for the same revolution is always found. A additional Home Switch is often used for this. Homing is performed in a User C Program so you have the freedom to do things however you want. The example SimpleHomeIndexFunctionTest.c which calls SimpleHomeIndexFunction.c will perform the sequence Al describes.

    HTH
    Regards

    Regards
    TK http://dynomotion.com


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    Default Re: Encoder for stepper motor

    Quote Originally Posted by TomKerekes View Post
    Hi ssjantonio,

    As Al points out the Line Driver option would be the best E6B2-CWZ1X. Line Driver = 5V Differential Signals.

    If you interface the Z index pulse it can help to make homing more accurate. But it can't work all by itself because it occurs every revolution of the encoder at multiple places over the entire travel range. So you need some other indication of approximately where you are so the index pulse for the same revolution is always found. A additional Home Switch is often used for this. Homing is performed in a User C Program so you have the freedom to do things however you want. The example SimpleHomeIndexFunctionTest.c which calls SimpleHomeIndexFunction.c will perform the sequence Al describes.

    HTH
    Regards
    Thank your for your help. I have already ordered the model from china. I understand about the Z phase, I will try to do my best for make it work.
    Another question, it is possible to make rigid tapping using an encoder in the spindle and a VFD driver?, and what about spindle orientation using a mark in the spindle with an optical sensor, it is posible? is necessary the encoder for this function ?



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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    Rigid Tapping is possible if you have spindle position feedback (an encoder) and the VFD is capable of being controlled well enough to move at a reasonably controlled speed, then stop, and reverse at a reasonably well determined position.

    Indexing with a VFD is probably more difficult. It depends on how quickly the VFD can reverse speed/torque in order to operate like a servo to hold position as well as your accuracy requirements. An encoder would most likely be needed so that the speed and distance to target can be known for better control.

    HTH
    Regards

    Regards
    TK http://dynomotion.com


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    Hi Tom. there is a way to change the pins used for step/dir and encoder?. For example Axis0 step/dir with IO0 and IO2. Encoder0 A/B with IO1 and IO3. This is only for make easier the connections in a printed board.
    Thank you for your help!

    Best Regards



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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    Encoder counters and Step/Dir Generators are basically hardware devices hard wired to fixed pins. There is a mux option to move them to different connectors (so you basically have two options). But they can not be arbitrarily assigned to any pin like that. Sorry.

    Regards

    Regards
    TK http://dynomotion.com


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    Default

    Than you. It was only a curiosity. I have already read all the documentation and I understand now.
    I have a confusion. If I use JP7 bit 8 to bit 15 for Step Dir(CL step) and bit 0 to 7 for encoder, Any other LVTL 3.3v can be used for home and limits? (I will use an opticall isolated board with filter for the connection of the endstop).

    Thank you very much!



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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    Limits, Home Sensors, and Index Pulses are handled in software so they can be connected to any spare input. Those listed are only suggestions.

    HTH
    Regards

    Regards
    TK http://dynomotion.com


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    Hi Tom. I'm testing my encoders but I'm doing something wrong because the curve of position is displaced from the command curve. I have attached an image. The gain is ok. Do you know why happend that?. Is the same in the 4 axes. The displacement depends on the position of the motors.
    Thank you for your help!

    Attached Thumbnails Attached Thumbnails Encoder for stepper motor-20161003_110502-640x480-jpg  


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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    You need to initialize in a way that matches the Commanded Destination and the Measured Position.

    One way to do that is to Zero(X); the axis That will set them both to zero. (There is also a Zero button on the Step Response Screen).

    Another approach that allows re-initialization without loss of position is to Enable the Axis and set the Destination to the Measured Position. With (for Axis 0):

    EnableAxisDest(0,ch0->Position);

    Regards

    Regards
    TK http://dynomotion.com


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    Quote Originally Posted by TomKerekes View Post
    Hi ssjantonio,

    You need to initialize in a way that matches the Commanded Destination and the Measured Position.

    One way to do that is to Zero(X); the axis That will set them both to zero. (There is also a Zero button on the Step Response Screen).

    Another approach that allows re-initialization without loss of position is to Enable the Axis and set the Destination to the Measured Position. With (for Axis 0):

    EnableAxisDest(0,ch0->Position);

    Regards
    I have tried the zero button in the step response screen, but nothing happend. My motors are steppers, is the same history?. Tomorrow I will to try with EnableAxisDest. Thank you!!



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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    Strange the Zero button wouldn't Zero the Destination and Position. It should for any Axis type. Check the KMotion Axis Screen to see what they do. You may have noise or miscounting so they drift apart.

    What do you mean by: "The displacement depends on the position of the motors"

    Also post a screen shot of your Config Screen.

    Instead of taking a photo please use Alt-Print-Screen to capture the Window and paste to a *.png file to upload.

    Regards

    Regards
    TK http://dynomotion.com


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    Default

    Hi Tom. It is working now, I was wrong because the zero button is working fine, thank you very much.
    I have another question. I have a siemens VFD with ansyc motor. The vfd is controled by a plc with modbus and the pwm output from kflop is connected to the PLC, everthing is workin fine, the question is; with this configuration is possible to make a closed loop with the encoder connected to the spindle? I have read about CL with Kanalog ADC output, but I cant found information about pwm directly from kflop. My intention is implement rigid tapping.



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    Member TomKerekes's Avatar
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    Default Re: Encoder for stepper motor

    Hi ssjantonio,

    Closed loop Spindle Control may be possible. Performance will depend on how quickly the PLC and VFD respond to speed and direction changes. Can the PLC drive the spindle both directions? There isn't any direct PWM Output Type. You must use a small C Program to write the Servo Output to the PWM in the appropriate manner for your device. Set the Axis Output Type to "No Output" as the C Program will be doing the Output. I've attached an example.

    HTH
    Regards

    Attached Files Attached Files
    Regards
    TK http://dynomotion.com


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