Re: [Emc-users] Rewiring the BP Again

[Mark]

We had about 10" of snow on the ground before the short melt hit, making 
things a bit soggy.  Then the temps dropped again and we got another 3 - 
4 inches over the last couple of days.  Hopefully, they'll have the 
roads cleared by the time I set out.

Mark

On 01/11/2016 08:14 AM, Peter Blodow wrote:
> Mark, it surely was interesting, when I drove to Traverse City last
> time, some 50 years ago, when I was temporarily a Michigander. Was a
> nice skiing weekend.
>
> Peter
>
> Am 11.01.2016 13:34, schrieb Mark:
>> 8 Degrees and snowing here in Grayling, MI this morning. I have to
>> drive over to Traverse City this morning. Should be interesting. Mark


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Re: [Emc-users] Rewiring the BP Again

[Mark]

On 01/10/2016 04:23 PM, Dave Cole wrote:
> I understand.I'm working out of town and just came back for the
> weekend.
>
> For me this is a good time to be distracted with too much work.
>
> It helps me ignore the wind gusts to 30 mph, the snow, and the temps
> headed to 8 degrees F for tonight.
> Except that I need to drive a long ways in this crap tomorrow morning.
>
> Dave

8 Degrees and snowing here in Grayling, MI this morning.  I have to 
drive over to Traverse City this morning.  Should be interesting.

Mark

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Re: [Emc-users] Rewiring the BP Again

[Peter Blodow]

Mark, it surely was interesting, when I drove to Traverse City last 
time, some 50 years ago, when I was temporarily a Michigander. Was a 
nice skiing weekend.

Peter

Am 11.01.2016 13:34, schrieb Mark:
> 8 Degrees and snowing here in Grayling, MI this morning. I have to 
> drive over to Traverse City this morning. Should be interesting. Mark


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Re: [Emc-users] Rewiring the BP Again

[Gene Heskett]

On Monday 11 January 2016 08:35:59 Mark wrote:

> We had about 10" of snow on the ground before the short melt hit,
> making things a bit soggy.  Then the temps dropped again and we got
> another 3 - 4 inches over the last couple of days.  Hopefully, they'll
> have the roads cleared by the time I set out.
>
> Mark
>
Positively balmy down here in WV, 18 degrees this morning, 1/4" of snow 
in the shade.

Winds were high & gusty yesterday though, my 7000 lb WV Cadillac got 
moved sideways about 2 feet at 75 mph, taking me over the right hand 
white line on I-79 as I was approaching the AnnMore turnoff ramp, then 
out of the south when I turned around & went back south to home, 
normally a top gear 75mph trip, it blew the automatic into passing gear 
5 times in that 15 miles to the Jane Lew exit.  Keeps one up on his 
tippy toes for sure. 

OTOH, I learned to drive 66+ years ago in Iowa, and that winter was 
legendary, still remembered by us oldtimers.  Same in Nebraska.  When I 
moved there from Rapid City where I had seen -39F on a tree in front of 
my house in South Canyon back in the middle 60's, the first time I went 
to get a hair cut in a little square block building, grandfathered into 
one edge of a block square city park, the first thing I noticed on the 
wall was a picture taken in 1950, of a smoking stovepipe sticking up out 
of a snowdrift.

Taken from an angle that did not show the front had a shoveled path to 
the front door, it was that barbershop. The stove was by then, in 1971 
propane gas, but it was a coal burning, pot bellied "Warm Morning" in 
1950.  He said he brought 2 buckets with him from his home coal shed 
when he opened up, and again after lunch in those days.

So yeah, WV is balmy.  I think I'll stay till the rapture.:)

> On 01/11/2016 08:14 AM, Peter Blodow wrote:
> > Mark, it surely was interesting, when I drove to Traverse City last
> > time, some 50 years ago, when I was temporarily a Michigander. Was a
> > nice skiing weekend.
> >
> > Peter
> >
> > Am 11.01.2016 13:34, schrieb Mark:
> >> 8 Degrees and snowing here in Grayling, MI this morning. I have to
> >> drive over to Traverse City this morning. Should be interesting.
> >> Mark
>
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Cheers, Gene Heskett
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Genes Web page 

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Re: [Emc-users] Rewiring the BP Again

[Bertho Stultiens]

On 01/10/2016 12:44 PM, John Thornton wrote:
> Well none of the suggestions about star grounding did any good. In
> fact they made the problem worse than before, so bad I could not even
> get 2.6 to run.

That may suggest a couple of things being wrong simultaneously:
1) you may still have loops in the 0VDC which are crossing power
domains. These /are/ hard to detect with many devices connected together;
2) there are impedance mismatches in the signal wiring (this one often
works together with 1);
3) shields may pick up noise they should reject.

The question is how to reduce the practical problems, not how to
eliminate all theoretical problems. That is the hard part.


> Off this list I was sent the AB servo best wiring practices pdf 
> which explained how to reduce noise in a servo drive enclosure. I 
> followed the advise as much as possible and after removing all my ground 
> wire antennas I was back running with an occasional sserial error. The 
> short explanation is to terminate the shields to a ground plane as close 
> as possible to the point where you take the shield/drain wire from the 
> cable. I still have a cable bundle running to my switch box that is 
> parallel wires and I might replace that with some twisted pairs. Photos 
> at 11.

You refer to this document?
http://literature.rockwellautomation.com/idc/groups/literature/documents/at/motion-at004_-en-p.pdf

That doc explains very well how to separate into different power zones.
Also, it makes a good case of shielding and how to do it properly. BTW,
note that it uses protective ground as shield potential and _not_ 0VDC.
That is also why the argument of two-sided termination of the shield is
appropriate (see page 21).

But all this does not save you from impedance problems. The sserial
errors are interesting because it is probably something you actually can
measure with an oscilloscope.

You should be able to see the signal integrity and whether you have
reflections of the signal at either end of the cable.

The sserial connection has a great potential for a loop. See attached
image for illustration. The image has a shielded connection between two
devices, which is good. However, the 0VDC connection (aka GND), which is
embedded in the shielded connection is shorted outside the cable via a
protective ground connection through the PSUs. This means that part of
the signal return may circumvent the constraints of the signal cable and
that creates an unbalanced path. Effectively, it means that the shield
is now part of the cable's impedance, and that is guaranteed to be off
by a factor.

You can check for this scenario by disconnecting the sserial connector
at one side and measure 0VDC vs protective ground on the connector on
the other side (and the other way around). You are in trouble when
measurements on both sides indicate a connection between 0VDC and
protective ground.

If you only have one PSU for both devices, then you are potentially also
in trouble. The PSU will then act as the loop facilitator (through two
distinct 0VDC connections). However, the effects are more subtle and
depend on coupling effects.

The rule for a shielded cable is that all energy must be contained
within the cable to be effective. In other words, the sum of all
currents in the cable's wires must be zero. Bypassing some of it may
cause impedance and therefore signal integrity problems.

-- 
Greetings Bertho

(disclaimers are disclaimed)
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Re: [Emc-users] Rewiring the BP Again

[Dave Cole]

Do you have filters just prior to the input power on the AB Servo drives?

I've also had problems with Teco servo drives backfeeding noise into the 
AC line and messing with Mesa boards.
An input filter from AD fixed that problem as well.

Dave

On 1/10/2016 6:44 AM, John Thornton wrote:
> Well none of the suggestions about star grounding did any good. In fact
> they made the problem worse than before, so bad I could not even get 2.6
> to run. Off this list I was sent the AB servo best wiring practices pdf
> which explained how to reduce noise in a servo drive enclosure. I
> followed the advise as much as possible and after removing all my ground
> wire antennas I was back running with an occasional sserial error. The
> short explanation is to terminate the shields to a ground plane as close
> as possible to the point where you take the shield/drain wire from the
> cable. I still have a cable bundle running to my switch box that is
> parallel wires and I might replace that with some twisted pairs. Photos
> at 11.
>
> JT
>
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Re: [Emc-users] Rewiring the BP Again

[Bertho Stultiens]

On 01/10/2016 02:48 PM, Bertho Stultiens wrote:
> The sserial connection has a great potential for a loop. See attached
> image for illustration. The image has a shielded connection between two
> devices, which is good. However, the 0VDC connection (aka GND), which is
> embedded in the shielded connection is shorted outside the cable via a
> protective ground connection through the PSUs. This means that part of
> the signal return may circumvent the constraints of the signal cable and
> that creates an unbalanced path. Effectively, it means that the shield
> is now part of the cable's impedance, and that is guaranteed to be off
> by a factor.

The sserial connection is a differential line (like rs422 afaik). See
for example http://focus.ti.com/lit/an/slla070d/slla070d.pdf chapter
4.5. Scenario 4.5.2 will get you into trouble in noisy environments.


-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Rewiring the BP Again

[John Thornton]

I don't have AB drives... I have a filter on my GS2 and another one 
after the control transformer.

JT

On 1/10/2016 11:40 AM, Dave Cole wrote:
> Do you have filters just prior to the input power on the AB Servo drives?
>
> I've also had problems with Teco servo drives backfeeding noise into the
> AC line and messing with Mesa boards.
> An input filter from AD fixed that problem as well.
>
> Dave
>
> On 1/10/2016 6:44 AM, John Thornton wrote:
>> Well none of the suggestions about star grounding did any good. In fact
>> they made the problem worse than before, so bad I could not even get 2.6
>> to run. Off this list I was sent the AB servo best wiring practices pdf
>> which explained how to reduce noise in a servo drive enclosure. I
>> followed the advise as much as possible and after removing all my ground
>> wire antennas I was back running with an occasional sserial error. The
>> short explanation is to terminate the shields to a ground plane as close
>> as possible to the point where you take the shield/drain wire from the
>> cable. I still have a cable bundle running to my switch box that is
>> parallel wires and I might replace that with some twisted pairs. Photos
>> at 11.
>>
>> JT
>>
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Re: [Emc-users] Rewiring the BP Again

[Rafael]

I tried to find the original message in previous monster thread to have 
a better understanding of the problem but could not find it. I can't 
remember seeing what is connecting to VFD and few other things. I assume 
it's a Mesa board but which one? [1]

We all seem to keep running in circles here. Grounding had been 
mentioned many times, other theories abound, yet the system still shows 
"occasional sserial error". Occasional error is unlikely happening with 
good grounding solution unless you have a heavy load that pulls huge 
current through the ground exactly at that time or a high voltage spike 
somewhere.

In my last post in previous thread I suggested to go back to the 
beginning and check HW around the data line, both visual and electrical:
- cable, connectors including soldered or crimped connections,
- metal dust and corrosion on PCB traces, ICs, capacitors, (but I see 
your box is very clean)

I checked one of your pictures and see that you have a PC like power 
supply mounted on the door. PSU would be better mounted on the main 
panel, possibly eliminating need for undesirable DC cable extension. How 
good is the PSU?

Are the door and the box grounded to the common ground on the panel? 
Can't see that in the picture. I see wires at the bottom corners of the 
analog servo board, one black (left) and three black with yellow shrink 
tube (right). They are connected to the panel but not together in a star 
configuration. Where do they go? I don't see one (copper) bus bar for 
use as a common ground for everything.

More close up pictures from different angles would be helpful.

Additional questions related to "occasional sserial error" pop up in mind:
* what does it mean "occasional"? One error per 100 characters sent, one 
per 1k, etc.?
* what about parity or error correction?
* what kind of a command is issued when this happens?
* what happens before and after "sserial error" occurs?
* what are DC levels on serial connection?
* what is the noise level on DC power lines in idle mode and under the load?
* does it happen when the door is closed or open? See PSU notes above.
* is it always the same sequence of bits/bytes when this happens?
* what about mechanical vibration at the time?
* is it HW issue at all? What about the software? Are you doing 
something else on the same system while the CNC code is executing?
* Is there firmware in IO interface you need to deal with?
* where do you see "sserial error"? Log files or screen popup message? I 
think it's dmesg but I'm not familiar with this obviously. If log files 
what else is there before and after?

[1] http://www.linuxcnc.org/docs/devel/html/man/man9/sserial.9.html

On 01/10/2016 03:44 AM, John Thornton wrote:
> Well none of the suggestions about star grounding did any good. In fact
> they made the problem worse than before, so bad I could not even get 2.6
> to run. Off this list I was sent the AB servo best wiring practices pdf
> which explained how to reduce noise in a servo drive enclosure. I
> followed the advise as much as possible and after removing all my ground
> wire antennas I was back running with an occasional sserial error. The
> short explanation is to terminate the shields to a ground plane as close
> as possible to the point where you take the shield/drain wire from the
> cable. I still have a cable bundle running to my switch box that is
> parallel wires and I might replace that with some twisted pairs. Photos
> at 11.
>
> JT

Everybody please trim advertising and other noise at the bottom or other 
parts that are not relevant in the replies.

-- 
Rafael

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Re: [Emc-users] Rewiring the BP Again

[Dave Cole]

I understand.I'm working out of town and just came back for the 
weekend.

For me this is a good time to be distracted with too much work.

It helps me ignore the wind gusts to 30 mph, the snow, and the temps 
headed to 8 degrees F for tonight.
Except that I need to drive a long ways in this crap tomorrow morning.

Dave

On 1/10/2016 3:59 PM, John Thornton wrote:
> Still trying to digest this in between working...
>
> On 1/10/2016 7:48 AM, Bertho Stultiens wrote:
>> On 01/10/2016 12:44 PM, John Thornton wrote:
>>> Well none of the suggestions about star grounding did any good. In
>>> fact they made the problem worse than before, so bad I could not even
>>> get 2.6 to run.
>> That may suggest a couple of things being wrong simultaneously:
>> 1) you may still have loops in the 0VDC which are crossing power
>> domains. These /are/ hard to detect with many devices connected together;
>> 2) there are impedance mismatches in the signal wiring (this one often
>> works together with 1);
>> 3) shields may pick up noise they should reject.
>>
>> The question is how to reduce the practical problems, not how to
>> eliminate all theoretical problems. That is the hard part.
>>
>>
>>> Off this list I was sent the AB servo best wiring practices pdf
>>> which explained how to reduce noise in a servo drive enclosure. I
>>> followed the advise as much as possible and after removing all my ground
>>> wire antennas I was back running with an occasional sserial error. The
>>> short explanation is to terminate the shields to a ground plane as close
>>> as possible to the point where you take the shield/drain wire from the
>>> cable. I still have a cable bundle running to my switch box that is
>>> parallel wires and I might replace that with some twisted pairs. Photos
>>> at 11.
>> You refer to this document?
>> http://literature.rockwellautomation.com/idc/groups/literature/documents/at/motion-at004_-en-p.pdf
>>
>> That doc explains very well how to separate into different power zones.
>> Also, it makes a good case of shielding and how to do it properly. BTW,
>> note that it uses protective ground as shield potential and _not_ 0VDC.
>> That is also why the argument of two-sided termination of the shield is
>> appropriate (see page 21).
>>
>> But all this does not save you from impedance problems. The sserial
>> errors are interesting because it is probably something you actually can
>> measure with an oscilloscope.
>>
>> You should be able to see the signal integrity and whether you have
>> reflections of the signal at either end of the cable.
>>
>> The sserial connection has a great potential for a loop. See attached
>> image for illustration. The image has a shielded connection between two
>> devices, which is good. However, the 0VDC connection (aka GND), which is
>> embedded in the shielded connection is shorted outside the cable via a
>> protective ground connection through the PSUs. This means that part of
>> the signal return may circumvent the constraints of the signal cable and
>> that creates an unbalanced path. Effectively, it means that the shield
>> is now part of the cable's impedance, and that is guaranteed to be off
>> by a factor.
>>
>> You can check for this scenario by disconnecting the sserial connector
>> at one side and measure 0VDC vs protective ground on the connector on
>> the other side (and the other way around). You are in trouble when
>> measurements on both sides indicate a connection between 0VDC and
>> protective ground.
>>
>> If you only have one PSU for both devices, then you are potentially also
>> in trouble. The PSU will then act as the loop facilitator (through two
>> distinct 0VDC connections). However, the effects are more subtle and
>> depend on coupling effects.
>>
>> The rule for a shielded cable is that all energy must be contained
>> within the cable to be effective. In other words, the sum of all
>> currents in the cable's wires must be zero. Bypassing some of it may
>> cause impedance and therefore signal integrity problems.
>>
>>
>>
>> --
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Re: [Emc-users] Rewiring the BP Again

[Dave Cole]

My mistake, gotta clean my glasses apparently.

What are you using for axes drives?

Dave

On 1/10/2016 3:35 PM, John Thornton wrote:
> I don't have AB drives... I have a filter on my GS2 and another one
> after the control transformer.
>
> JT
>
> On 1/10/2016 11:40 AM, Dave Cole wrote:
>> Do you have filters just prior to the input power on the AB Servo drives?
>>
>> I've also had problems with Teco servo drives backfeeding noise into the
>> AC line and messing with Mesa boards.
>> An input filter from AD fixed that problem as well.
>>
>> Dave
>>
>> On 1/10/2016 6:44 AM, John Thornton wrote:
>>> Well none of the suggestions about star grounding did any good. In fact
>>> they made the problem worse than before, so bad I could not even get 2.6
>>> to run. Off this list I was sent the AB servo best wiring practices pdf
>>> which explained how to reduce noise in a servo drive enclosure. I
>>> followed the advise as much as possible and after removing all my ground
>>> wire antennas I was back running with an occasional sserial error. The
>>> short explanation is to terminate the shields to a ground plane as close
>>> as possible to the point where you take the shield/drain wire from the
>>> cable. I still have a cable bundle running to my switch box that is
>>> parallel wires and I might replace that with some twisted pairs. Photos
>>> at 11.
>>>
>>> JT
>>>
>>> --
>>> Site24x7 APM Insight: Get Deep Visibility into Application Performance
>>> APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month
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Re: [Emc-users] Rewiring the BP Again

[John Thornton]

The original Anliam drives and power supply.

JT

On 1/10/2016 2:41 PM, Dave Cole wrote:
> My mistake, gotta clean my glasses apparently.
>
> What are you using for axes drives?
>
> Dave
>
> On 1/10/2016 3:35 PM, John Thornton wrote:
>> I don't have AB drives... I have a filter on my GS2 and another one
>> after the control transformer.
>>
>> JT
>>
>> On 1/10/2016 11:40 AM, Dave Cole wrote:
>>> Do you have filters just prior to the input power on the AB Servo drives?
>>>
>>> I've also had problems with Teco servo drives backfeeding noise into the
>>> AC line and messing with Mesa boards.
>>> An input filter from AD fixed that problem as well.
>>>
>>> Dave
>>>
>>> On 1/10/2016 6:44 AM, John Thornton wrote:
 Well none of the suggestions about star grounding did any good. In fact
 they made the problem worse than before, so bad I could not even get 2.6
 to run. Off this list I was sent the AB servo best wiring practices pdf
 which explained how to reduce noise in a servo drive enclosure. I
 followed the advise as much as possible and after removing all my ground
 wire antennas I was back running with an occasional sserial error. The
 short explanation is to terminate the shields to a ground plane as close
 as possible to the point where you take the shield/drain wire from the
 cable. I still have a cable bundle running to my switch box that is
 parallel wires and I might replace that with some twisted pairs. Photos
 at 11.

 JT

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Re: [Emc-users] Rewiring the BP Again

[John Thornton]

Still trying to digest this in between working...

On 1/10/2016 7:48 AM, Bertho Stultiens wrote:
> On 01/10/2016 12:44 PM, John Thornton wrote:
>> Well none of the suggestions about star grounding did any good. In
>> fact they made the problem worse than before, so bad I could not even
>> get 2.6 to run.
> That may suggest a couple of things being wrong simultaneously:
> 1) you may still have loops in the 0VDC which are crossing power
> domains. These /are/ hard to detect with many devices connected together;
> 2) there are impedance mismatches in the signal wiring (this one often
> works together with 1);
> 3) shields may pick up noise they should reject.
>
> The question is how to reduce the practical problems, not how to
> eliminate all theoretical problems. That is the hard part.
>
>
>> Off this list I was sent the AB servo best wiring practices pdf
>> which explained how to reduce noise in a servo drive enclosure. I
>> followed the advise as much as possible and after removing all my ground
>> wire antennas I was back running with an occasional sserial error. The
>> short explanation is to terminate the shields to a ground plane as close
>> as possible to the point where you take the shield/drain wire from the
>> cable. I still have a cable bundle running to my switch box that is
>> parallel wires and I might replace that with some twisted pairs. Photos
>> at 11.
> You refer to this document?
> http://literature.rockwellautomation.com/idc/groups/literature/documents/at/motion-at004_-en-p.pdf
>
> That doc explains very well how to separate into different power zones.
> Also, it makes a good case of shielding and how to do it properly. BTW,
> note that it uses protective ground as shield potential and _not_ 0VDC.
> That is also why the argument of two-sided termination of the shield is
> appropriate (see page 21).
>
> But all this does not save you from impedance problems. The sserial
> errors are interesting because it is probably something you actually can
> measure with an oscilloscope.
>
> You should be able to see the signal integrity and whether you have
> reflections of the signal at either end of the cable.
>
> The sserial connection has a great potential for a loop. See attached
> image for illustration. The image has a shielded connection between two
> devices, which is good. However, the 0VDC connection (aka GND), which is
> embedded in the shielded connection is shorted outside the cable via a
> protective ground connection through the PSUs. This means that part of
> the signal return may circumvent the constraints of the signal cable and
> that creates an unbalanced path. Effectively, it means that the shield
> is now part of the cable's impedance, and that is guaranteed to be off
> by a factor.
>
> You can check for this scenario by disconnecting the sserial connector
> at one side and measure 0VDC vs protective ground on the connector on
> the other side (and the other way around). You are in trouble when
> measurements on both sides indicate a connection between 0VDC and
> protective ground.
>
> If you only have one PSU for both devices, then you are potentially also
> in trouble. The PSU will then act as the loop facilitator (through two
> distinct 0VDC connections). However, the effects are more subtle and
> depend on coupling effects.
>
> The rule for a shielded cable is that all energy must be contained
> within the cable to be effective. In other words, the sum of all
> currents in the cable's wires must be zero. Bypassing some of it may
> cause impedance and therefore signal integrity problems.
>
>
>
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Re: [Emc-users] Rewiring the BP Again

[Dave Cole]

Hmm.. perhaps you should tell Peter that Missouri is wonderful this time 
of year.

Perhaps he will schedule a flight to the "show me state".  :-)

Dave

On 1/10/2016 3:35 PM, John Thornton wrote:
> I don't have AB drives... I have a filter on my GS2 and another one
> after the control transformer.
>
> JT
>
>

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