Re: [CAD_CAM_EDM_DRO] Re: Position counter stop updating....Still there....

[Babar <riet91-at-yahoo.com>]

Hi forum!

To make sure wether errornous count generation problem
stays with the STG-II card itself. I did a following
new test:

I turned on PC, ran EMC, ran stg2diag, turned on
Machine power which turned on drives, encoder's power
and power to relay board whcih at 
the moment doesnt connects to any relay. Now i gave
some motion to each
axis using tkEMC "testing" dialog box. And then :

I CUT OFF POWER TO MACHINE (drives and encoder power
set to off).
What I saw on dtg2diag was: " i still saw errornous
big jumps:
following is the response:
     +17994.000        +360.000          -2.000
   +4867658.000    +6816104.000      -65538.000
     +17994.000        +360.000          -2.000
     +17994.000        +360.000      -65538.000
     +17994.000        +360.000          -2.000
     +17994.000        +360.000      -65538.000
     +17994.000        +360.000          -2.000
     +17994.000        +360.000      -65538.000
     +17994.000        +360.000          -2.000

now while pc still turned on and machine off, i
detached P1 cable from STG-II P1 connector, Detached
LPT cable from lpt connector present on pc and last I
detached the P3 ribbon cable from the breakout board.
Even this time I saw the same errornous counts
although
the machine was all off, all the DAC, encoder
connections were open
nothing was turned on except computer but these
errornous count still
generate. This seems in my case this problem is
explicitly with 
the STG-II board itself. since there was no connection
of STG-II board
with external world this time, but still i saw the
errornous counts generated in stg2diag 

Do you think that this may be due to not very good
powersuply of
my computer itself? do you think that changing of
computer may result
in removal of this errornous count problem? anyways i
plan to do that
as a last effort.

cant the module that reads the 24 bit counters of
LS7166 coded
again to fix this bug? Isnt there possibility to
ignore these errornous
counts in software without depreciating the accuracy
of EMC system ?
If somobody can do that for us then me and my children
will say thanks,
thanks, thanks.... x 10E100 to that prince!

Please suggest!

babar

--- Les Watts <leswatts-at-alltel.net> wrote:
> Well if you have seen that before then it well could
> be it.
> I have never had that problem, but my computer and
> breakout boards are all in a well shielded case. As
> mentioned
> the ribbon cable to the card is a twisted pair type.
> My star ground
> point is right next to the breakout board and
> digital and analog
> ground is hooked there.
> 
> The servo amps are also in that box about a foot
> away. They are all
> bypassed right at the terminals with a couple
> hundred mf.
> 
> So filters on encoder lines would do nothing unless
> that was a noise
> path to the card internals.
> What about ferrite beads on the card grounds?
> 
> If the computer case was the star ground point that
> might help.
> It is earthed through the power plug. Or it is on
> mine.... hmmm
> I'll bet Babar is using something other than 120v 60
> Hz power.
> Actually on high power audio gear I have sometimes
> floated
> the units to remove hum from loops through rack
> panels.
> Not the best thing to do, but it did work well
> sometimes
> in desperate situations. Good way to get shocked.
> 
> Les
> Leslie Watts
> L M Watts Furniture
> Tiger, Georgia USA
>
http://www.alltel.net/~leswatts/wattsfurniturewp.html
> engineering page:
> http://www.alltel.net/~leswatts/shop.html
> 
> ----- Original Message -----
> From: "Jon Elson" <elson-at-pico-systems.com>
> To: <CAD_CAM_EDM_DRO-at-yahoogroups.com>
> Sent: Sunday, September 15, 2002 12:59 AM
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Position counter
> stop updating....Still
> there....
> 
> 
> > Babar wrote:
> >
> > > although the stg2diag shows big errornous values
> > > following is the respone of stg2diag utility:
> > >
> > > [root-at-localhost bin]# stg2diag
> > > Servo To Go Board IO address = 0x200
> > >          +1.000          +1.000          -2.000
> > >          +1.000          +1.000      -65538.000
> > >          +1.000          +1.000          -2.000
> > >          +1.000          +1.000      -65538.000
> > >          +1.000          +1.000          -2.000
> > >      +65537.000      +65537.000      -65538.000
> > >          +1.000          +1.000          -2.000
> > >      +65537.000      +65537.000      -65538.000
> > >          +1.000          +1.000          -2.000
> > >      +65537.000      +65537.000        -258.000
> >
> > Bingo!  This is the same horrible behavior seen
> with the STG-I
> > card!  This is not encoder noise, this is noise on
> the digital position
> > reading coming OUT of the 7166 encoder chips. 
> NIST put in a filtering
> > routine to throw away any samples that were too
> far away from the last
> > sample.  but, notice, these jumping values are
> almost always jumping ONE
> BIT
> > in the middle-most-significant byte!  The first
> bit of that middle byte is
> changing
> > from sample to sample, causing a jump of 65536
> counts in the total
> position
> > value.  Since the STG-II is a significant rework
> of the STG card, I
> suspect this
> > is an inherent defect in the 7166 chip, at least
> in the mode that STG and
> EMC
> > use it.
> >
> > Are these lines sequential samples recorded to
> memory, or does the
> computer only
> > print out a position reading whenever it detects a
> change from the
> previous one?
> > In other words, do these wildly jumping reading
> pour out of the computer,
> or do
> > they come out every now and then?
> >
> > I noteced the problem was most severe in the STG-I
> when the encoder
> position moved
> > acrosss the boundary from 0 to -1, ie. when all 24
> bits changed value at
> once.  This
> > could be expected to cause noise in the system.
> >
> > I don't know what to tell you about this, but from
> previous info you've
> supplied, it
> > is a problem of noise getting into the STG card,
> and upsetting its logic.
> If you have those
> > cable shields connected to terminals on your STG
> breakout board, try
> grounding them to
> > the computer's CASE, instead.  You don't want to
> force interference
> currents through the
> > board's logic, or through the logic's ground
> traces.
> >
> > But, this info you provide here makes it look very
> clear it is NOT,
> specifically, noisy
> > encoder signals causing false counts in the
> encoder counters.
> >
> > Jon
> >
> >
> > Addresses:
> > FAQ:  http://www.ktmarketing.com/faq.html
> > FILES:
> http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> >
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> >
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> 
> Addresses:  
> FAQ:  http://www.ktmarketing.com/faq.html 
> FILES:
> http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> 
> OFF Topic POSTS:  General Machining
> If you wish to post on unlimited OT subjects goto:  
> aol://5863:126/rec.crafts.metalworking or go thru
> Google.com to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html 
> 
> http://groups.yahoo.com/group/jobshophomeshop   I
> consider this as a sister site to the CCED group, as
> many of the same members are there, for OT subjects,
> that are not allowed on the CCED list.
> 
=== message truncated ===


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