Re: motor interface wiring

[mooney@oxygen.aps1.anl.gov (Tim Mooney)]

Mark Rivers writes:

> > Tim Mooney writes:
> > I think this is overkill, but I see no point in excluding it.
> > It's the driver's responsibility to stop on an open limit switch.
> > Sending the controller an unsolicited message that the driver screwed
> > up is not a robust way of getting the motor stopped.  (If you don't
> > trust the driver hardware to respond to the limit switch, why would you
> > trust it to tell you it didn't?)
> 
> Actually it is generally the CONTROLLER'S responsibility to stop sending pulses
> on an open limit switch. This is certainly the way the current Step-Pak
> drivers work - they don't look at the limit lines at all, they only pass them
> back the controller.

You're right of course, thanks.  (I had some kind of brain cramp when I wrote that,
I guess.)
The point I wanted to make was that limit switches are honored by hardware, and
the entity listening to the overtravel signal would have to be software, since
the hardware thinks limit-switch inputs are sufficient assurance.

> > This signal will probably not be delivered by name from the Step Pack
> > interface, since it gets only one home signal from the motor
> > connector.  However, Leo Bric plans to use DB-9 connectors for the
> > encoder inputs, and since only eight signals are currently specified,
> 
> I want to second Gerd's recommendation. Klinger/Newport stages with encoders 
> and origin signals use the following signals:
>     Phase A
>     Phase B
>     Index (also called Top 0)
>     Origin (Home)
> 
> Home can be established to within 1 step by looking for the 0-1 transition on
> Origin and then looking for the next Index pulse. This is 0.1 micron on their
> best stages.
> 
> Note that their stages also require a +5V input to drive the origin and
> encoder electronics. Leo must provide us with an option for this. It should
> not be constrained to be the same voltage as the motor drive.

Ok, so the home input from the motor-drive cable could be Gerd's coarse home,
and the home input from the encoder cable would then be his fine home.  I'll
get this and a separately-derived user voltage on the encoder-connector
pinout to Leo.

Thanks for your help and quick response.

Tim