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Any suggestions for controlling a KB motor drive?

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  • Any suggestions for controlling a KB motor drive?

    Hi all,

    I currently have a KBCC-125 DC motor control running an old treadmill motor. Instructions say it needs a 0-9v analog input for speed control. I tried setting it up with an optocoupler, 9v dc regulator and a filter circuit to provide the analog voltage from the pwm signal.

    When I tried that, I blew both rectifying diodes on the KB controller and the pc that was connected. The KB instructions says it needs to be an isolated voltage signal.

    I'm using one of the cheap mach3 5-axis breakout boards. It has it's own 0-10v output for motor control built in. Would that work? Or am I at risk of blowing everything again?

  • #2
    There be monsters behind that door! You need a KBSI 240D signal isolation board (or the like). I do not understand the isolation elec-trickery well enough to explain it myself. A knowledgeable member here told me that I must have one between the 0-10V analogue output of my CNC controls and my KB speed controls.. I have one on a Mach3 system and a Centroid Acorn. They both work great with no fireworks .
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

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    • #3
      Originally posted by DICKEYBIRD View Post
      There be monsters behind that door! You need a KBSI 240D signal isolation board (or the like).
      Thanks. That's what I figured. I blew a couple PCs and 2 motor drivers, so ice pretty much given up attempting something unless I know its gonna work

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      • #4
        Many of the KB drives do not have the control voltage isolated internally, so they are connected to the power line more-or-less directly. Obviously a problem for a regular computer output.

        Isolation boards have no direct connection between the input and output. The signal is typically converted to a light beam (by an LED), or a magnetic field, and then either an optical pickup or coil picks up the signal on the other side of a physical gap.

        There are various methods to keep the isolator producing an accurate reproduction of the input, but you don't need to worry about that except to know that the cheapest methods are not nearly as good as the better ones. The cheap ones may not be "linear" in terms of producing the same output as they got for input. It can be tricky to do well for an analog signal. Pretty easy for a digital signal.
        1601 2137 5683 1002 1437

        Keep eye on ball.
        Hashim Khan

        If you look closely at a digital signal, you find out it is really analog......

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        • #5
          What Dickybird said. We use a lot of KB drives with PLCs at work. It requires you use KBs interface board.

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          • #6
            Some years ago i picked up some KB drives and accessories in an auction, among them was a box of Isolator boards, they were designed to plug directly over the top of the Smaller KB boards for signal isolation, I imagine the circuit is the same as all they are mains transformer operated isolation with analogue in/out SI-5 boards.
            Max.

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            • #7
              A cheat smart relay with the right i/o should do the job
              https://www.flickr.com/photos/csprecision

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