Re: [CAD_CAM_EDM_DRO] VEX CNC

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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