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ASCII commands

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  • ASCII commands

    Good Morning,
    We are new to stepper motor control but are seeing where they could be very useful in upgrading many pieces of equipment in our plant. The first few areas unfortunately are tied into AB systems. Switching them over to an automation direct product at this time just isnt in the budget (do to interlocks with HMI's and output cards)

    I can get the drive running smooth and fast using the surestep pro SCL program. And I can get it running "ok" with the AB PTO command, but im not 100% satisfied with the movement. Heres an overview of the operation:

    home the unit
    press start
    set speed low (think 25 inches per minute)
    End prox is triggered
    set reverse
    set high speed (think 600 inches per minute)
    Home prox is triggered
    set low speed
    press start

    Now for the issue, I cant seem to set the high speed fast enough if I want to hold the low speed. I'm not sure if its a setting in my PTO thats off or a configured error in surestep pro.

    So what about ASCII commands to the driver? Has anyone done this from a ML1100? I'm having some issues setting up.
    Any assistance would be appreciated

  • #2
    I'm only familiar with a few of the PLC's sold through Automation Direct, but I have played with ASCII commands quite a bit. Here are some pointers I can offer you:

    - Regardless of which PLC you use to communicate, make sure that you have asynchronous capabilities if you plan on sending AND receiving information from step drive (e.g. obtain current step count, receive acknowledgement that command was sent, etc.). Click does not have asynchronous capabilities, and DL series will need the use of a co-processor. Do-More CAN do this!

    - You can send multiple commands in one string to the step drive. For example, if you want to send accel, decel, and velocity, you can send it altogether with <CR> (I think that can be called out as $0D, but I'm not sure off the top of my head) in between: AC10<CR>DE15<CR>VE4.2<CR>.

    - Take a close look at the surestep SCL command guide. FC command may be useful, but you know your application best.

    The sequence you laid out sounds like something that can be done using ASCII. Try simple jogging commands through the AB PTO. If it's different than what you are seeing through the SCL program, you may be setting some parameters either differently or wrong, resulting in it running 'ok'.


    • #3
      In an industrial application I would recommend a servo drive and motor using the Positioning mod. Basically you are using the servo in stepper mode. You get more reliable positioning, as the servo is tracking a count and staying with that position. Steppers lose torque with speed and the servos are happy with speed.