Treadmill motor speed control

I have come into possession of a surplus treadmill motor, including a
commercial PWM, high-current speed control board. Details of the
board can be found at
http://www.kbelectronics.com/catalog/gc115/kbwt.pdf

I'm looking to use a stamp (or maybe a PIC) to provide precise
control of motor RPM, using this control board. At the very end of
the PDF file linked above, it shows a suggested means of using a
microcontroller in place of a pot to provide control input to the
board.

Here's what I'm thinking of doing:
(1) using a keypad to enter desired RPM
(2) displaying actual RPM on an LCD
(3) sensing RPM via a hall-effect sensor, or maybe an opto-
interrupter on the motor shaft
(4) using the Stamp to adjust input to the control board to maintain
the desired RPM under varying motor loads. I am still unclear as to
exactly how to accomplish this - can anyone point me to the Stamp
commands that would be most helpful here?

This is my first attempt at anything approaching process control with
the Stamp, so I'm looking for any tips, hints, sample code, critiques
of my approach, etc.

Thanks in advance for your help.
David
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Comments

  • 2 Comments sorted by Votes Date Added
  • edited February 2001 Posts: 46,084Vote Up0Vote Down
    Hi David,

    You may be quite surprised at how good the speed regulation is with
    these DC motor controllers. I think you'll find it better than one
    percent from no load to full load at most rpm's. The specs will give
    you the story.

    So you just need to figure out the miles/hour or feet/minute or
    whatever versus applied voltage. Then you can write a PWM routine that
    can be calibrated in those kinds of units.

    The datasheet suggests the use of an optical isolator to connect the
    micro's PWM output to the controller input. This is a good safety
    procedure as it provides total electrical isolation that will protect
    your micro from possible damage. And it looks to me like you won't
    even have to filter the PWM output; that appears to be taken care of
    inside the controller.

    Someone more familiar than I with optical isolators can perhaps guide
    you to an off-the-shelf isolator that fills the bill. Or you can make
    one up from a bare isolator and the components they suggest.

    I hope this helps.

    Fred

    --- In basicstamps@y..., david@c... wrote:
    > I have come into possession of a surplus treadmill motor, including
    a
    > commercial PWM, high-current speed control board. Details of the
    > board can be found at
    > http://www.kbelectronics.com/catalog/gc115/kbwt.pdf
    >
    > I'm looking to use a stamp (or maybe a PIC) to provide precise
    > control of motor RPM, using this control board. At the very end of
    > the PDF file linked above, it shows a suggested means of using a
    > microcontroller in place of a pot to provide control input to the
    > board.
    >
    > Here's what I'm thinking of doing:
    > (1) using a keypad to enter desired RPM
    > (2) displaying actual RPM on an LCD
    > (3) sensing RPM via a hall-effect sensor, or maybe an opto-
    > interrupter on the motor shaft
    > (4) using the Stamp to adjust input to the control board to maintain
    > the desired RPM under varying motor loads. I am still unclear as to
    > exactly how to accomplish this - can anyone point me to the Stamp
    > commands that would be most helpful here?
    >
    > This is my first attempt at anything approaching process control
    with
    > the Stamp, so I'm looking for any tips, hints, sample code,
    critiques
    > of my approach, etc.
    >
    > Thanks in advance for your help.
    > David
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