I-LPT & step/dir servo amps

I'm happy to see some discussion about Indexer LPT, even though it *is* a
for-profit product. I've been very interested in doing (and learning) some
of my own programming using I-LPT for motion control applications in
addition to the usual g-code/cnc applications that we discuss in this list.
Does anyone have other applications they've integrated I-LPT into? I'm
interested in hearing about different ways of utililizing it using different
software and mechanical systems.

Also, in a related topic: I've asked here before (with little response)
about step/direction-input servomotor amplifier systems such as the one
Camtronics sells.

What would it take to match the performance of a "standard" servo system,
using step/direction output? I've looked into this a little, and it seems
one issue is closing the loop with an equivalent, high-performance PID
algorithm. Another issue is resolution - you would need a fairly high
frequency step/direction source, I suppose. Would that frequency need to be
any faster than a good servo loop update rate (for an equivalent machine
resolution)?

I've got the itch about this topic because Texas Instruments is advertising
a low-cost DSP specifically targeted at motion control. Their TMS320LC2402
sells for $2.95 in higher quantities, and $7.95 for a flash version
(http://www.ti.com/sc/docs/products/dsp/tms320lc2402.html). (please, no
flames; I 'm not selling anything, and I don't own stock in TI!!) It has
A/D's, PWM outputs, counter/timers, and even direct encoder input (internal
quadrature encoder). AND they claim supports many standard microcontroller
functions. I wish I had the time to dig into it further. It would make a
simple (and cheap, if you don't count development time) step/dir input servo
amplifier.

Hope this sparks a little interest.

Carlos Guillermo

> -----Original Message-----
> From: batwings@... [mailto:batwings@...]
> Sent: Friday, October 15, 1999 4:09 AM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: [CAD_CAM_EDM_DRO] I-LPT
>
>
> From: batwings@...
>
> BTW, I forgot the last note on this, not to bore the easily
> distracted, but
> there's one more way to use the product ... part programs can be written
> directly in any of the ordinary programming languages, using file writes
> containing explicit commands for the indexer. The difference there is that
> they wouldn't take user inputs and do calculations nor generate commands
> using variables in the write functions; everything would be fixed specific
> to the part in question or perhaps family of parts (using only a few
> variables maybe for differences in length or diameter or locations where
> subs may be called). This gives the user great flexibility anyhow, as any
> programming language has loops and sub calls embedded in it as a matter of
> course. AS gives some programming language examples in Basic, C++ and
> Pascal, but any language you're familiar with will do if it can write to
> file pointers. And anybody that can write good scripts for machining or
> program a CNC control can write these same programs for PC; the only real
> difference is compiling them first. A side issue to this is once
> a user has
> written and compiled some parts in a programming language the task of
> programming more general motion software is a lot less intimidating.
>
> Best wishes,
>
> Hoyt McKagen
>
>
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