Re: Fw: Stg2, 2- problems

[Will Shackleford <shackle-at-cme.nist.gov>]

> Date: Fri, 17 Mar 2000 15:38:40 -0500 (EST)
> Originator: emc-at-nist.gov
> From: Fred Proctor <proctor-at-cme.nist.gov>
> To: Multiple recipients of list <emc-at-nist.gov>
> Subject: Re: Fw: Stg2, 2- problems
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> X-To: Jan <postmaster-at-chocolateworld.be>
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> 
> Jan,
> 
> I manually added you to the emc-at-nist.gov mailing list. Sorry, I should
> have done this long ago. Your name won't appear on the published list of
> subscribers for about a day, but you can begin to post immediately.
> 
> You wrote:
> 
> > Input_scale left to 1000 so 1count=0,001mm. (with units set to mm or
> > inch it always gives the same result?)
> 
> If you set UNITS = 1.0 for the [TRAJ] and [AXIS_#] sections, this makes
> your user units millimeters. Then, for INPUT_SCALE, the first value
> should be whatever encoder counts equal 1 mm. The second should be 0,
> since it's not used in the .ini file for servo machines.
> 
> I think I tested this and it worked, but I'm not sure so you should try
> it and let me know what your symptoms are.
> 
> Also:
> 
> > Encoder 1,3 and I presume 5 and 7 gives out, flipping values between
> > the exact counts and counts * 65537. So a movement of 0,001mm gives
> > out the value of 1 and 65537, a movement of 0,002 gives out 2 and
> > 131074... This can be seen on the original STG-module and with
> > stg2diag. The latter gives whit every flip a linefeed so the values
> > can be easily read. The value 65537 can be interesting; as 2 to the
> > power of 16 + 1 = 65537. I don't know of this problem is only
> > encountered with my board but I will ask STG if they know this problem
> > yet.
> 
> I've never seen this. You need to be sure that the power supply that
> powers the encoders shares its ground with the Servo To Go digital
> ground. Otherwise, ground loop problems will cause noise and
> unpredictable feedback. If you're sure of the elcctrical hookup then the
> STG folks may be able to give you some pointers. Let me know what they
> say. Post to the emc-at-nist.gov mail list so others can see; I'm always
> surprised at the experts in the field who know more than I do about my
> software.
> 

My 2 cents:

I occasionaly see some flipping back and forth if you run stg2diag at the 
same time as the real-time emc controller. If the motion contoller latches the
encoder while stg2diag is reading it stg2diag can get some wierd results. 

--- Will



---------------------------------------------------------------
William Penn Shackleford III			shackle-at-nist.gov
National Institute of Standards & Technology	Tel:	(301) 975-4286
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