Re: [CAD_CAM_EDM_DRO] Low cost limit switch suggestions

Jon Elson wrote:

> Robert Allen & Marsha Camp wrote:
>
> > If I already have max. travel limits do I need any thing but
> > a home switch?
>
> Probably not. EMC, at least, has software limits that are referenced
> from the home switch position. The software-sensed limit switches
> would be pretty redundant.

What happens when you home the machine, then move to some other position on
the table and reset the axes to zero? Will the software realize that you do
not have full x or y travel from this point? The machine I have now ain't
that smart, I've always wondered why but it is a 1983 control.

>
>
> > What are the reasons for having limits the computer can see?
>
> Reall not much use. About the only time they might be tripped under
> normal use is when a home search goes the wrong way.

Does this happen?

> You could
> probably come up with a way that the limit switches could both
> give individual signals to the computer and provide an E-stop
> signal too. That is really an or-gate type function.

True, but it would still shut off the motor power losing the last position. I
think I need limits that operate sequentially, first the computer is told to
stop and if I have a drive failure then the power is cut.

Bob KB1FRW