Re: Position counter stop updating....



Babar,
This may have been mentioned before but I have
had problems long ago with SINGLE ENDED encoders.
These have 3 TTL outputs and of course a +5 and return.

Since then I have always used DIFFERENTIAL encoders-
there are a total of 8 wires... a pair for each of the three
channels , +5, and return. This type of encoder has very
much higher noise immunity and the stg card IS 
set up to take them. I am using this type and do long
(8 ft+) runs back to the computer/stgII with no problem.

If your encoders are single ended you can convert them
with a small circuit placed very near the encoder body.
I have a simple little circuit that uses a SN75174 quad
differential line driver. It costs about a dollar.

Oh, one other note... stg says to limit total current
for the +5 output to 500 milliamps. If the current draw
is high a series polymer PTC thermistor will drop the
voltage. Many encoders use 200 ma each. Something
to check. I use a separate supply.

If the machine is running smoothly and controllably
but just with a locked up display it is prob something else
though; I would expect a servo setup with noisy encoders
would have a bad case of "st vitus dance".

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: "Babar" <riet91-at-yahoo.com>
To: "Multiple recipients of list" <emc-at-nist.gov>
Sent: Monday, September 02, 2002 7:34 AM
Subject: Re: Position counter stop updating....


> 
> Hi Forum
> 
> We are still in trouble with this counter stuck/hang
> problem. now this problem has become a headache and
> soon it'll become a nightmare for us. I guess i wont
> be able to sleep well soon!!
> 
> We are using STG-II board the latest version of stg.
> Does these still have this noise problem with their
> Position counters??
> 
> After reading Jon's mail I got into my ini and looked
> for CYCLE_TIME variable. It was found that this
> variable is present
> in many sections: 
> [DISPLAY]
> [TASK]
> [TRAJ]
> [AXIS_X]
> [EMC_IO]
> 
> I had set this to .001 to task, traj, and to all three
> AXIS_X but still having the same problem.
> 
> We have connected the Encoder connections to STG-II
> board without any filteration using RIBBON cable.
> Although the connections of encoder from DC-Motors are
> made using a shielded cable.
> Encoders of all the three DC-Motors are powered (+5V &
> GND) from STG-II.
> 
> Our PC body as well as the Machine body is connected
> to earth.
> 
> One more thing that I've obsereved is when I run the
> diagnostic utility found on the harddrive "STG2DIAG"
> (which comes from BDIEMC209-01.img)
> When I run it with following parameters:
> 
> stg2diag index x where x = 0-2
> or
> stg2diag latch x where x = 0-2
> 
> then for x = 0-1 i see such kind of pulse stream:
>  11100010100001111001010
> 
> for x = 2
>  i see a continous stream of '0' zeroes
> 
> This hapens even when there is no motion in these
> three axis May be this information is helpful for
> forum members to diagnose the problem we are having
> with our EMC & STGII
> 
> Looking for suggestions
> 
> Thanks and best regards
> 
> Babar
> 
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