Re: Home switches.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "David Micklethwaite"
<d.micklethwaite@o...> wrote:

> At the moment my mill uses microswitches for homing the X and Y

axes. This

> sort of works but does not allow exactly reproducible positioning.

The axes

> are driven by servos with encoders. I would like to combine the

index pulse

> from the encoder with the microswitch to get a more accurate

indication of

> the home position. Can anyone give me some advice, preferably with a

circuit

> diagram, on the electronics needed to achieve this.
>
> The microswitch operates with 5 volts as do the encoders and the

combined

> signal has to go into a PMDX-120 breakout board.
>
> Thanks in advance,
>
> Dave Micklethwaite

Are you asking to use the existing end or home switch in combination
with an encoder ?

As I understand, some encoders have a 3rd channel. a single point per
revolution.

It would appear that one could run the axis to the end switch and then
until that encoder point changed state.

That would represent the motor being in one exact location, and not
necessarly the screw or table. But, it does eleminate a chip or dirt
from influencing the home point.

Dave