Re: VEX CNC

her is a pdf on linear and circular interpolation that may be of some use

<http://www.ieor.berkeley.edu/~goldberg/pubs/XY-Interpolation-Algorithms.pdf>

chris

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Wreno Wynne <wrenow@...> wrote:
>
> Hi Chuck,
>
> " Am I getting from you that the controller and C might not fit CNC
use?"
>
> Not at all. I am glad you asked, so I can clarify. If you are happy
> with programming in C, that is /*by far */the way to go (based on my
> admittedly slim understanding). Myself, C is a foreign language, as I
> grew up in BASICland, rather than across the C. ;-)
>
> I think programming in curves, circles, etc. are going to be
> "interesting" whatever language you use. However, with all the gantry
> style XY robots out there, there surely must be lots of algorithms
> available to do so. You are, frankly, more likely to find them in C
> than BASIC, I would imagine, though the math part is math.
>
> I know of no specific tools in BASIC for this, and plead ignorance in
> toto on C tools.
>
> However, I would caution you against expecting machining type accuracy,
> as I do not believe the servos are capable. If you can get 1024
> distinct steps, with a fair amount of slop from the deadzone, I
would be
> surprised as all getout. But, for some simple drawing with a pen,
> probably enough accuracy to do some fun stuff.
>
> As for the rest, I was just trying to point out some additional
tools in
> case you liked BASIC better than C and also to let you know that the
Vex
> servos and motors are compatible with regular hobby RC equipment (but
> for the plugs). This means you can use Vex servos with RC stuff, and
> RC servos with Vex (with an adapter for the plug - and the parallax
> cable mentioned gives you one of each adapters).
>
> Cheers,
>
> Wreno
>
> Chuck Merja wrote:
> >
> > Thanks for the comments. It looks like I am trying to fit a round
peg in a
> > square hole, maybe?? I'm interested in VEX stuff because we have
it and we
> > have a little expertise in programming it. The controller has a
Microchip
> > PICmicroR PIC18F8520 and uses PIC C, and we use EasyC to do the
> > programming.
> >
> > Am I getting from you that the controller and C might not fit CNC
use? I
> > didn't see a way to interpret shapes, especially without a fair
amount of
> > programming, which isn't the goal. The goal was to find yet another
> > use for
> > use the VEX platforms we have (or understand why they aren't the best
> > fit) -
> > I just added the part in parentheses, cuz that looks to be where
we are
> > headed:o))
> >
> > I get how I could do straight lines in X or Y, but I'm wondering
how to do
> > anything complex, and thus wondering if I am trying to apply the
wrong
> > tool
> > to this job.
> >
> > Thanks, Chuck
> >
> > Wreno said:
> > Hmmm. In'n you want to use C, that ought to work If, however, you
> > prefer BASIC instead of C, you might want to know about the Picaxe
> > series of microcontrollers. Only takes a serial cable and 2 resistors
> > to program them, and they are very flexible and simple (they are
> > intended for the education market, and are based on PIC
> > microcontrollers). The IDE (aka the Programming Editor) is free and
> > allows for in-circuit programming, etc. There is also a native Servo
> > command They are manufactured by http://www.rev-
> > <http://www.rev-ed.co.uk/picaxe/ <http://www.rev-ed.co.uk/picaxe/>>
> > ed.co.uk/picaxe/
> >
> > There is also a very active and helpful forum on the Rev Ed site.
> >
> > There are several distributors in the US in the $3 - $12 range
depending
> > on the chip (8 pin to 40). They make a nice 3 servo controller board
> > for about $12-15 that runs off the 08M that might be just the
ticket for
> > you to play with. Note the Vex servos are wonderful for plugging into
> > breadboards, but do not plug in to regular R/C type equipment.
However,
> > the serial LCD display cable
> > http://www.parallax
> >
<http://www.parallax.com/Store/Accessories/CablesConverters/tabid/166/Catego

> >
<http://www.parallax.com/Store/Accessories/CablesConverters/tabid/166/Catego>
> >
ryID/40/List/0/Level/a/ProductID/385/Default.aspx?SortField=ProductName%2cPr
> > oductName>
> >
.com/Store/Accessories/CablesConverters/tabid/166/CategoryID/40/List/0/Level
> > /a/ProductID/385/Default.aspx?SortField=ProductName%2cProductName
> > will adapt it to standard hobby RC equipment.
> >
> > Drawing circles might be "interesting.", though straight X/Y lines
would
> > be pretty straightforward. Do not expect incredibly high accuracy with
> > the servos, though.
> >
> > Cheers,
> >
> > Wreno
> >
> > ebiz_59 wrote:
> > >
> > > My highschool science club is the proud owner of a couple VEX kits -
> > > erector sets with brains. We are thinking of making a CNC project
> > > with this VEX - more as a learning exercise than functional. We
would
> > > probably just use a Sharpie pen on paper, or something like
that. The
> > > motors are controlled by a servo PWM signal as we understand it, and
> > > we can create autonomous functions. However, that programming is
done
> > > in C, and I can see where we could make a square, or even a slanted
> > > line, maybe, but I'm puzzled as to how to make, say a circle or
> > > something more complex than a straight line. Are we going to have
> > > more problems than it is worth, and learn mostly that we need to
> > > finish our stepper controller, and use a CAD/CAM program to do this,
> > > or mgiht this be an interesting project, if the mentor just knew
what
> > > he was doing?? Thanks, Chuck
> > >
> > >
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