Re: [CAD_CAM_EDM_DRO] Home /limit switches

Robert Allen & Marsha Camp wrote:

> > > I think the encoder has an index mark (ch. A, ch. B and I) but I don't think
> > > CNCpro can use it.
> >
> > Well, of course, EMC can use it!
>
> It was the $800 board plus servo drivers that stopped me.

You don't need the Servo-to-Go card. I have a $500 set (should be ~$600
with the digital I/O) of boards to operate servos with EMC. But, you don't
even need that. The Kulaga/Mauch DRO card can also do this if
you are using encoders for closed-loop steppers. If you are using
Open-Loop steppers, you can STILL use the high resolution home
qualifier, but you will have to build the sensor disc yourself.

> I think that the program just stops at the limit change of state then backs away
> so the limit isn't the home position, probably the backup distance should change
> the limit back to its normal state.

That's what I thought you described.>

> > > I would have to set the back up distance to go further than the index mark
> > > and stop the gekko input, how, a transistor shorting the input from the
> > > software high or low as needed. This might be accurate if the homing speed
> > > was slow enough. I see this getting a lot more complicated than I thought it
> > > would be.
> >
> > This sounds dangerous. (Not physically, just that it could cause lost
> > steps, sometime.)
>
> Why, especially if this is done very slowly?

Your circuit to take home switch and fine sensor signals and hook them up to
the step signal sounded like unnecessary stuff. You'd have to have a mode
switch that put this circuit in home or normal modes. The concept I proposed
would not need such things, as it only would modify the way the home signal
appeared to the control software.

Jon