Re: PWM vs Constant current and G-rex

<huge snip>

> There is absolutely nothing wrong with parallel port systems. I'm

running three of them: 2 Bridgeports and a JVM 836. The 2 Bridgeports
have 120 ipm rapids and the JVM has 140 ipm rapids reliably. All three
are close loop position monitored. I asked someone that was ranting
about how great it was going to be: "What would this new system do for
me?"and never got a reply.

>
>
> Ron
>

OK, I really have to agree here. The Toyota Prius is the new hybred
that will probably in all of our futures, but... My "old technology"
car is still running and doing a very fine job.

I would venture to guess that only about 1-3% of the peoples running
machines would swap out what they have for the new technology.

Why ? more in's and out's I needed more extra stuff to make things
work. I finally figured a way to hobble together enough components to
make the machine work, but if I was in that building stage again, I
would have opted for the higher I/O counts.

Analogue I/O there are features that would be nice, air compressor
pressure, coolant tank level, oil lube level ? who knows. if there
was not enought of something to compelte a run, the software could
alarm or some such.

Some shops considder one bad part to be much more expensive than an
upgrade. Not many though.

And, there are home builders who have the $$ to get the newest things.

With the hundreds or maybe thousands of installations, and the fact
that there are many people that chose the high end breakout cards over
the much lower cost stuff indicates, to me, that there are people who
will spend the bux.

As to the perceived need for the faster or more capable drives ?

I think part of the answer is in Mariss's anti-lost step stepper
driver. That bit of magic will be another, very desirable unit.

But, I really have to agree with you on what to buy today.

A breakout board (I have not heard of a bad one) that extends the
parallel port to the motors is very common.

the limitation is on frequency of steps or output pulses.

I ran the math on some pulleys for a plasma or router table and there
is a limitation on encoder count and motor speed and software output
speed.

It is not hard to get around that one way or another.

For steppers it is a mute point as steppers cannot spin faster than
the software can drive them. Not and stay in a useable power range
anyway.

sorry if this reads a little disjointed, I'm Mr. Mom today and the
baby is all over.


Dave