Re: know your limits

["Ian Wright" <Ian-at-iw63.freeserve.co.uk>]

Hi Bill,

Can you tell me a bit more about your home switches please? I have tried
putting a +5v supply onto pin 12 via a 5K6 current limiting resistor and
then connecting the home switch from this to ground but I can't get any
response from EMC. If I set the 'homing switch polarity' to '0' in the .ini
file, pressing the 'home' button turns the relevant axis display green but
there is no movement from the machine. If I set it to '1', then pressing the
'home' button sends the machine off in a positive direction along the axis
but it never stops - the switch has no effect whatsoever. What am I doing
wrong?

Ian
--
Ian W. Wright
Sheffield  UK
www.iw63.freeserve.co.uk
----- Original Message -----
From: "William Scalione" <wscalione-at-nc.rr.com>
To: "Multiple recipients of list" <emc-at-nist.gov>
Sent: 12 March 2001 23:09
Subject: Re: know your limits


>
> Ian,
>
> I had the same question about this when I first hooked up my home switches
>
> When you home in EMC each axis is homed separately, and yes, you must
> either use the offset function or move that axis off the switch to home
any
> other
> axis. I believe you can also use one of the limit switches as a home
switch
> although I have not done this.
>
> Once an axis is homed, then the software limits work well. Suppose you
> set up an axis with 10" of total travel, with zero at one end of that
> travel.
>  If you now move to 5" and set that point to zero you will be able to move
> -5" to +5". It will not let you move to +6"
>
> Bill
>
>
>
> > Hi,
> >
> > Having now got bits of mechanism moving back and forth under EMC
control,
> I
> > am turning my attention to adding switches to the axes etc.
> >
> > What use are home and limit switches using the EMC program? I can't work
> out
> > in my own mind how three home or limit switches in series can possibly
> give
> > any usable output. Presumably the first to trip will just bring the
> machine
> > to a complete stop and, since it would be physically impossible to get
all
> > three to trip at the same instant, this would mean that two axes will be
> at
> > an unpredicatable position. If you use the 'home offset' feature, does
> this
> > mean that the first axis will close its switch, back off by the offset
> > amount and then stop, and that the second axis will then continue to
move
> > until its switch closes and then back off and stop to allow the third to
> do
> > likewise? I had considered just relying on the software 'maximum
distance'
> > option to limit travel but, if you reset zero along the way, this
> presumably
> > becomes ineffective. Any advice would be appreciated. Thanks,
> >
> > Ian
> > --
> > Ian W. Wright
> > Sheffield  UK
> > www.iw63.freeserve.co.uk
> >
> >
>
>
>