RE: [CAD_CAM_EDM_DRO] Re: EMC stg2mod.o and problem with homing

Hi Asim and Jon

It is beginning to look like the index latching bug.

To explain:

With your version and some others homing would not work
with ANY of those modules (including newstgmod.o) with the
Servo to go II 8 axis card. Only newstgmod worked with the
Servo to go II 4 axis card.

Asim, I still need to know if you SPECIFICALLY have the
SERVO TO GO MODEL II 8 AXIS card to be able to help you.

When Paul Corner was visiting last year I hunted up the address
of the STG registers IDLEN (0x409 offset) and SELDI (0x40b offset)
that respectively enables index operation and uses the encoder rather
than an external signal.

Paul did a hack by directly writing a 1 to IDLEN and 0 to SELDI
somewhere in newstgmod. I still use this on my machine, but Paul did
a little more structured fix on later versions I think.
I need to get to Paul about this so you can get the right version.
Are you on the emc list?

As for the ini variables...

HOME_SWITCH_POLARITY depends on the logic of the switch... I use
normally closed switches and set it to 1.

HOMING_POLARITY is the DIRECTION the axis travels to seek the
home switch. 1 is positive direction, 0 is negative. It can be either way,
but I have the home switch at minimum count, so I use a value
of 0.

So here is a typical sequence:

command home

axis moves in the negative direction (HOMING_POLARITY=0)

when limit switch is opened by the axis motion direction
reverses, speed doubles. This is due to (if I am remembering right)
JOGGING_POLARITY=1 (the positive direction). The speed doubling is hard
coded.

The first index pulse detected
will be defined as home. It will stop there and axis numbers
will zero and turn green.

In my case the motion continues past this to the axis center
of travel because I have a non-zero HOME_OFFSET. In that case
the axis travels to the HOME_OFFSET value, zeros, and goes green.

Many other homing sequences can be done by alterations of these
parameters.

An example of a known to work ini file using stg II 8 axis and
normally closed switches is on my engineering website
below. Follow the cnc links.

Les



Leslie M.Watts
L M Watts Furniture
Tiger Georgia USA
(706) 212-0242
http://www.lmwatts.com
Engineering page:
http://www.lmwatts.com/shop.html
CNC surplus for sale:
http://www.lmwatts.com/forsale.html
CNC carved signs:
http://www.lmwatts.com/signwp.html




-----Original Message-----
From: Jon Elson [mailto:elson@...]
Sent: Monday, September 22, 2003 2:08 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: EMC stg2mod.o and problem with homing




Asim Khan wrote:

>Hi Les, Jon and the group!
>I was on holidays so i coundnt experiment with the HOMING_POLARITY
>I changed the HOMING_POLARITY to 0 and 1 but it has no effect!
>i also changed the motion control modules, i had experimented with
>newstgmod.o stgmod.o, stg2mod.o and stg8mod.o but each had same result
>that is, the axis donot home! donot turn green.
>I'had setup EMC on two machines,
>My machine's encoders support index pulse outputs.
>the encoder resolution at one machine with servo2go card has
>800 CPR and the otrher machine has 2500 CPR resolution. but both of
>machines are unable to home.
>please suggest where this trouble lies and what might be solution to
>this problem? are there any working systems with Servotogo cards on
>EMC? and those have no homing problems?
>
>

OOps, I think you have to change the sign of HOMING_VEL!
Actually, I don't know what the difference between HOMING_VEL
and HOMING_POLARITY is? Maybe HOMING_POLARITY
is the polarity of the index signal from the encoder! I think it is, so
my original info was wrong (But, I was within 4 lines of the problem!)

I know this worked on exactly the same situation at my client's.

Jon


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