Journeyman 325 retrofit


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Thread: Journeyman 325 retrofit

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    Default Journeyman 325 retrofit

    Gentlemen,

    I have been working for a week or so on converting my Tree Journeyman 325 Mill with Kflop / Kanalog.
    So far everything is going well, I have all of the functions working with the relay outputs and switches detected by the opto inputs.
    The DAC outputs seem to work fine and correctly operate the servo and spindle inputs.

    I have connected my differential 5v encoders X, Y, Z, Spindle to the Kanalog channels 0, 1, 2, 3 respectively.
    I have the A+, A-, B+, and B- terminals on the corresponding terminals of Kanalog.
    On the X axis, the Axis screen count would not change, until I reversed the polarity of the encoder inputs.
    - is tied to + on the board and vice versa. The X axis did not read otherwise.

    On performing the same test with the Y axis, I have tried it both ways and still it does not work.
    Some configurations will count 4x greater in one direction, and 1/4 as much in the opposite direction.
    I have connected an oscilloscope to both channels of the encoder wires alone, and can see a 5v quadrature signal with the polarity I expected.

    I'm not sure how to proceed here. Are the gain and offset settings necessary?

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    Default Re: Journeyman 325 retrofit

    Reversing the polarity shouldn't have any effect other than reversing the count direction, depending on if you swapped a single or both pairs.

    Have you configured the channel inputs on the Config&Flash screen, and uploaded the settings to the KFlop?
    I don't think encoder inputs will show on the Axis screen until the Channel has been configured to tell the KFlop there is an encoder linked to that channel.

    In Analog output, I don't think the gain setting is needed, as I'm sure it's only for step/dir outputs where you may need a ratio between input/output steps.
    Offset may be needed, however as long as you're servos don't move at 0V, then you shouldn't, as the closed loop should handle things.



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    Default Re: Journeyman 325 retrofit

    m_c

    Thanks for the reply,

    I agree with you about the direction. The X encoder would not read, so I reversed the polarity of both pairs. This way it worked, the other way did not. I don't know why.
    It would seem that the switching threshold in Kanalog must be slightly negative, so that reversing the polarity crossed it.

    Doing this for the Y channel however, did not make it work.

    Yes, I did configure each channel in the config screen and download to the Kflop board.

    It seems to me that an offset of 0 would be best, as the signals swing from +5 to -5.
    I was referring to the input gain and offset, not the output.
    Not sure if the offset is in volts, or percentage, or what. It doesn't say V on the screen.

    Thanks,
    Rick



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    Default Re: Journeyman 325 retrofit

    After thinking about this a bit more, It occurred to me that the signals on the scope did not look differential.
    They did not swing from +5 to -5, but from +5 to ground, although the encoder signals do have a pair for each channel.

    Is there a way to use this with the Kanalog inputs, or should I build a differential conversion circuit?

    Rick



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    Default Re: Journeyman 325 retrofit

    Encoder differential signals don't actually drop below 0V. Referenced to 0V, they should switch from roughly 0.5V to over 2.5V. 2.5V is the minimum, but a 5V encoder should manage around 4V unless there's a long cable and/or the receiver end is drawing more current.
    The only time you'd get a negative voltage is if you are measuring between the main and compliment on each channel (would show as a mirrored square wave on a scope).

    What kind of waveform do you get if you scope each pair?
    I'd try scoping each wire with them attached to the Kanalog, and make sure you have the correct pairs (differential waveform) together, and you're getting a quadrature signal between the A and B wires (it shouldn't matter what A or B wire you scope, you should still get the same pattern, just possibly reversed).



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    Default Re: Journeyman 325 retrofit

    I measured the signals relative to each - encoder output, not DC gnd.
    Relative to DC ground, the + output goes from gnd to +5. The - output stays at gnd relative to gnd.
    Therefore I think the outputs are single ended even though they do have a + and - for each channel.

    I would expect a differential output to swing from +5 to -5 on the scope, relative to the - differential output.
    It's not negative with respect to DC GND, but the negative and positive terminals should change polarity.

    Rick



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    Default Re: Journeyman 325 retrofit

    Certainly sounds like you've not got the compliment signals.

    Depending on the encoder, it may be possible to dismantle it and add the compliment signals. I know from past experience, some encoder manufacturers just cut/don't connect the compliment signals internally, with the actual hardware being identical between single ended/line driven output encoders.



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    Default Re: Journeyman 325 retrofit

    Hi Rick,

    I agree both the + and - signals need to be driven from 0.5V to 2.0v (or more) for it to be a differential signals.


    Another option might be to add a differential line driver module at the encoder. Such as:

    https://cnc4pc.com/differential-line-driver.html

    Regards

    TK
    http://dynomotion.com


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    Default Re: Journeyman 325 retrofit

    I built a board to use a 74hc14 to invert the + side of each channel to generate the - side. It looks like this works fine with the differential inputs.

    Couple of other questions:

    1. I have an external MPG that I would like to connect. The outputs of this are differential, so that will be channel 3 on the KANALOG board. The MPG also has 7 other outputs which indicate the scale and axis. These signals are switch contacts, so they can be any voltage. Where do you recommend I connect these?

    2. I also have 4 pushbutton switches mounted to my new front panel. These will duplicate the on screen buttons for start, reset, stop, and motion stop. I was considering using an arduino board to have these emulate a USB keyboard with the appropriate keys, but would there be an advantage to wiring them directly to KFLOP or KANALOG? My KANALOG opto inputs are already used up.

    Thanks,
    Rick



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    Default Re: Journeyman 325 retrofit

    Hi Rick,

    1. I have an external MPG that I would like to connect. The outputs of this are differential, so that will be channel 3 on the KANALOG board. The MPG also has 7 other outputs which indicate the scale and axis. These signals are switch contacts, so they can be any voltage. Where do you recommend I connect these?
    KFLOP JP4 and JP5 have 3.3V I/O with 150ohm pull down resistors. Switching those to 3.3V is one possibility.

    2. I also have 4 pushbutton switches mounted to my new front panel. These will duplicate the on screen buttons for start, reset, stop, and motion stop. I was considering using an arduino board to have these emulate a USB keyboard with the appropriate keys, but would there be an advantage to wiring them directly to KFLOP or KANALOG? My KANALOG opto inputs are already used up.
    I think it is better to connect directly to KFLOP/Kanalog for things like feedhold. In that case any PC/Windows/USB delays can be eliminated.

    HTH
    Regards

    TK
    http://dynomotion.com


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    Default Re: Journeyman 325 retrofit

    I think I have a handle on the axis tuning now.
    The encoders yield 20,000 counts per inch on the X axis.
    The maximum velocity looks good at 60,000 counts per second.
    Maximum Velocity, acceleration, and Jerk are set.

    I'm not too clear on how to set the following error.
    Is this error per unit time, per move, or cumulative?

    Does anyone have suggestions on tuning a bit more?

    I have no filters set up, but the output curve doesn't seem to need it.

    Thanks,
    Rick


    Attachment 341568
    Attachment 341570
    Attachment 341572
    Attachment 341568



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    Default Re: Journeyman 325 retrofit

    Hi Rick,

    To set the Max Following Error use the Step Response Screen to Plot Following Error for all your normal move types, sizes, and speeds. Then set the Max Following Error to a number slightly larger than the largest Following Error the occurs normally. The units are Encoder Counts. If the difference between the target Destination and the actual Position ever differs by more than that amount for even an instant the Axis will be disabled.

    For some reason your attachments didn't post properly. Please try attaching them again.

    Regards

    TK
    http://dynomotion.com


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