Treadmill motor speed control

Archiver

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

Archiver

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