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  1. #1
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    Snapamp and linear glass scale

    I am running snapamp with 3 dc brush servos with shaft encoders. I hooked the glass scale to channel 3. Input encoder snapamp 11. No output. It will be driving channel 0. Snapamp channel 8 input and output DC motor and encoder. Channel 0 is tuned great and has worked for years.

    I have checked that the scale reads and tracks correctly. I then tried to link it with channel 0 using the dual feedback loop c program. I ran a test move on the step response for channel 0 to initialize and enable it. I then ran the dual loop c. After that I made a move on the channel 3 step response screen. The first time I tried I had p set to .01. No I or d gain. It took off really fast like a run away and faulted after a inch of movement. I tried again with p at .0001. It took off very slowly then ramped up speed in spurts till it hit a hard stop. I don't want to keep crashing so I figured it was time to see if I can get some advice about what's going wrong or settings I may have missed but need. I will take pictures of the screen and post them shortly.

    Thanks
    Ben

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  2. #2
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    Re: Snapamp and linear glass scale

    Here are the screen pics

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  3. #3
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    Re: Snapamp and linear glass scale

    Just giving this a bump and adding a few things.

    Do I need to change the input gain on channel 3?
    How would I add this to the initialization program once it's working? Do I just add the program code to link the channels in a forever loop and add in my channel 3 parameters but still initialize (0,1,2,-1) similar to the spindle.

    I am pulling my hair out so any help would be much appreciated.

    Thanks
    Ben

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  4. #4
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    Re: Snapamp and linear glass scale

    Also how will this effect limits and soft limits?

    Thanks
    Ben

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  5. #5
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    Re: Snapamp and linear glass scale

    Before I go any further with the dual loop I have a bigger issue.

    My snapamp blows the breaker for DC power instantly if power is applied to side 1. Side 2 seems to still be working. I don't know if it was a crash or a short or anything else that caused it. The encoders still work on those 2 motors but like I said if you apply DC to the amp it blows the breaker. I will order another snapamp but I will be afraid to install it not knowing if it could be wiring or a motor. Any help tracing the cause would be great.

    Thanks
    Ben

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  6. #6
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    Re: Snapamp and linear glass scale

    Hi Ben,

    Sorry somehow I missed this Thread.


    It took off really fast like a run away and faulted after a inch of movement. I tried again with p at .0001. It took off very slowly then ramped up speed in spurts till it hit a hard stop.
    It sounds like you have positive instead of negative feedback causing a runaway. You could either change the direction of the Axis #3 encoder input using InputGain0. Or reverse the direction it commands Axis 0 with:

    ch0->Dest -= ch3->Output;

    Which one depends on whether you wish to change the direction the encoder counts or not.


    How would I add this to the initialization program once it's working? Do I just add the program code to link the channels in a forever loop and add in my channel 3 parameters
    yes

    but still initialize (0,1,2,-1) similar to the spindle.
    No. The GCode X Axis would now drive the Axis 3 Encoder position loop which would then internally drive Axis #0's velocity. So it would be (3,1,2,-1).


    Also how will this effect limits?
    I think you should configure both Axes for the same Limit inputs so if they are tripped both axes disable. Axis #0 to stop the motors and Axis 3 so KMotionCNC knows X is disabled.


    and soft limits?
    Soft Limits should be applied to the Position Loop Axis #3.


    My snapamp blows the breaker for DC power instantly if power is applied to side 1. Side 2 seems to still be working. I don't know if it was a crash or a short or anything else that caused it. The encoders still work on those 2 motors but like I said if you apply DC to the amp it blows the breaker. I will order another snapamp but I will be afraid to install it not knowing if it could be wiring or a motor. Any help tracing the cause would be great.
    Sorry to hear that. An Axis Crash should not have caused that. Regenerative Braking (stopping quickly) with the motors can cause the supply voltage to shoot up and cause damage if the Voltage clamping was not enabled. You might ohm out your motor wiring looking for the expected motor resistance as well as any shorts to GND.
    TK
    http://dynomotion.com

  7. #7
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    Re: Snapamp and linear glass scale

    Thank you for your advice Tom that took care of most of my issues. I have 3 rutex rt990h drives sitting around and was wanting to hook them up to k-flop for testing. Once again and sorry wiring the step direction and appropriate mode are my issue. I attached the pdf for the drives. If you can recommend how to wire to them I would really appreciate it.

    Thanks
    BenAttachment 475170

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  8. #8
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    Re: Snapamp and linear glass scale

    Hi Ben,

    The Spec is not very clear, but it shows connecting to a PC Printer Port so most likely will work connected to KFLOP in LVTTL Mode.

    Wire KFLOP GND to J1 External power supply 0V (Note these drive's inputs are not opto-isolated from motor power)

    Then Connect KFLOP's Step and Direction pins to J1 pins 4 an 5

    Configure Step/Dir as LVTTL (Add 8 to the channel number)

    HTH
    TK
    http://dynomotion.com

  9. #9
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    1022

    Re: Snapamp and linear glass scale

    Thank you Tom. I will give it a try and report back in case anyone else has the same drives.


    Ben

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