Re: [Emc-users] Grounding

[Chris Albertson]

On Fri, Jul 13, 2018 at 9:25 AM Roland Jollivet 
wrote:

>  > That's pretty much standard these days.
>
> I don't understand the desire to connect two lines together because they
> 'seem' to be of the same magnitude.  0VDC is Not equal to Gnd
> Many systems will have multiple 5V power lines, heavy, light, designated.
> Do you want to link all those up too?
>

Generally you want you power supply and logic nd safety grounds to be
separate.  But at ONE and one one point would you connect them.

What's happening here is that some "grounds" are carrying current exactly
equal to the power supply current and unless yu are using "super conductor"
cable cool with liqi=ud helium there *will* be a non-zero voltage on the
 "ground" cable.  That is the problem with interconnected grounds, all
those return currents and by Ohm's law "return voltages".   But if yu do
connect safety and return grounds at ONE point current can't flow.But
this is hard to do.  Really hard if there are multiple 3-prong power plugs.



>
>
> On 13 July 2018 at 18:05, andy pugh  wrote:
>
> > On 13 July 2018 at 16:52, Dave Cole  wrote:
> >
> > > That's pretty much standard these days.
> > >
> > > I'm not making this stuff up.   That's how its done.
> >
> > I think that there is still some confusion out there. I used to work
> > for a company making specialist test equipment (brake dynos, motor /
> > pump testers, that sort of thing).
> > Our electricians were convinced that everything needed an yellow/green
> > earth connection. Every panel for the control cabinet, the doors, the
> > individual devices bolted to the machine bed. We would spend ages
> > making things look nice and painting them, and then they would come
> > back festooned with stripy wires and with a hole drilled in every
> > separate metal part for the earth stud.
> >
> > --
> > atp
> > "A motorcycle is a bicycle with a pandemonium attachment and is
> > designed for the especial use of mechanical geniuses, daredevils and
> > lunatics."
> > — George Fitch, Atlanta Constitution Newspaper, 1916
> >
> > 
> > --
> > Check out the vibrant tech community on one of the world's most
> > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
>
> --
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>


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Re: [Emc-users] So, how's Ethernet?

[andy pugh]

On 14 July 2018 at 00:18, Peter C. Wallace  wrote:

> I believe you have the same advantages with the STMBL drives
>
> A basic step/dir drive would be easier to setup however...

STMBL can do step/dir too.

It's basically a servo drive with a HAL. You can freely combine motor
types, feedback types and control types.

But it works best of all as a Mesa Smart-Serial slave.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] So, how's Ethernet?

[Peter C. Wallace]

On Fri, 13 Jul 2018, Sven Wesley wrote:


Date: Fri, 13 Jul 2018 23:26:19 +0200
From: Sven Wesley 
Reply-To: "Enhanced Machine Controller (EMC)"

To: "Enhanced Machine Controller (EMC)" 
Subject: Re: [Emc-users] So, how's Ethernet?

Ok, friends. This is getting interesting (AKA I'm sort of lost).

Once upon a time there was a beautiful tutorial about choosing the right
setup with Mesa boards involved, but Internet is a living thing and that
page is gone. My entire Mesa knowledge was based on that page...

So, my retrofit is not progressing because I'm lost in the
what-to-choose-problem.

The machine has DC servos with optical disc encoders, I have no data on the
motors nor the encoders but the controller has a sign saying 5A fuse +/- 60
V. I hate when the encoders are crimped to the motor shaft and even though
they are sweet I am more than willing to rip them off and replace them with
capacitive encoders tomorrow.
https://www.flickr.com/photos/svenneduva/albums/72157698570971564

I need a few pins extra. The spindle is a HF air bearing (50 k RPM) with a
pneumatic tool changing mechanism. There goes a few extra pins. The tool
changer itself is fixed but has a motor driven cover with limit switches.
So two limit inputs, motor +/- direction and then signals for releasing the
tool.
The machine itself only has homing switches so three extra inputs, or one
if serial wired. I would like to add end switches though.

The easy way out would getting a Mesa 7i92 + 7i76 combo (no LPT) and some
step/dir servo drives. But I thought the nice thing with for example a 7i77
board is that it handles all the loop back and I only need some simple
amplifier drivers to run the servos and then feed the encoder signals to
the 7i77. But, all the drivers I find they want the encoder input? And I
though they were supposed to go to the 7i77? Even worse, I bought a 7i77
card to host a set of super fancy Omron drivers once upon a time and know I
don't even understand how I was thinking when I bought them. Correct, they
were never installed and are still collecting dust.

So, IF I am going with the Mesa boards, what on Earth is the driver I
should use, and what boards? Simply, I am lost on this one... I don't know
if I'm getting old and lack the googling skills, I can't find a decent
combo anymore. Step/dir is a breeze to setup compared to this jungle. I do
understand Mesa is supporting us and everything, I just don't understand
how little documentation there is to find _how_ to choose boards and to set
them up.

An alternative is Rene's STMBL driver which looks very nice but need
another breakout board as far as I understand. If I make it to the
Stuttgart meeting next weekend we might have a German solution to my
problem. Who knows...





If you have existing (good) analog drives, a 7I77 makes the most sense since 
it will read the encoder directly and control the analog drives.


If you have a newer drive that has encoder feedback to the drive itself you 
can still be able to get the to work well with a 7I77 if the drive has a 
analog velocity mode and has emulated encoder outputs to feed back to LinuxCNC


Both above systems have advantage of having feedback to LinuxCNC this means 
you can for example disable the drives and not lose position and the homing to 
index is easy to set-up, in addition linuxcnc "knows" the actual position so 
the drive tuning and performance (following error )can be monitored from 
LinuxCNC.


I believe you have the same advantages with the STMBL drives




A basic step/dir drive would be easier to setup however...








On Thu, Jul 12, 2018 at 10:25 PM Sven Wesley  wrote:


These little babies. I have a few of them already and my kids have the i7
version and they are fast. Linux just runs, no trouble. One Ethernet and
Wifi in the same box. Perfect.
https://www.dustin.se/product/5011010658/nuc-kaby-lake-wifi



On Wed, Jul 11, 2018 at 3:32 PM Eric Keller  wrote:


Which Intel NUC did you get?  A couple of years ago I got a zotac box with
dual ethernet ports thinking that I might use it as either a router or to
drive an ethernet mesa board.  I think it will end up as a router.
Eric Keller
Boalsburg, Pennsylvania

On Wed, Jul 11, 2018 at 4:05 AM Sven Wesley 
wrote:


Yes, looks like your email with the link went to me and not to the list.
Anyway, the Mesa card looks promising. Intel NUC and Mesa boards on the
way!

/S

On Tue, Jul 10, 2018 at 5:14 PM Les Newell 
wrote:


I beat you to it with the same link but it looks like my email went
directly to Sven, rather than to the list. For some reason when I

reply

to this list the replies usually end up going direct to the sender
rather than to the list.

Les

On 10/07/2018 13:38, andy pugh wrote:

On 10 July 2018 at 11:47, Sven Wesley 

wrote:

You too late, Andy. ;)

Too late in the sense that you have already bought the UC400 ?









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Re: [Emc-users] So, how's Ethernet?

[andy pugh]

On 13 July 2018 at 22:26, Sven Wesley  wrote:

> The easy way out would getting a Mesa 7i92 + 7i76 combo (no LPT) and some
> step/dir servo drives. But I thought the nice thing with for example a 7i77
> board is that it handles all the loop back and I only need some simple
> amplifier drivers to run the servos and then feed the encoder signals to
> the 7i77. But, all the drivers I find they want the encoder input?

Probably only the step-dir drives. And many of those that do want to
see the encoder also pass-through the encode signal for use by the
controller.


> Even worse, I bought a 7i77
> card to host a set of super fancy Omron drivers once upon a time and know I
> don't even understand how I was thinking when I bought them. Correct, they
> were never installed and are still collecting dust.

You have the drivers too? Do you have a link to the manual?
Are the servos you have brished-DC or brushless-DC?

> An alternative is Rene's STMBL driver which looks very nice but need
> another breakout board as far as I understand.

You would need a 7i74, yes, to connect to the (presumably) 5i25 that you have.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] So, how's Ethernet?

[Sven Wesley]

Ok, friends. This is getting interesting (AKA I'm sort of lost).

Once upon a time there was a beautiful tutorial about choosing the right
setup with Mesa boards involved, but Internet is a living thing and that
page is gone. My entire Mesa knowledge was based on that page...

So, my retrofit is not progressing because I'm lost in the
what-to-choose-problem.

The machine has DC servos with optical disc encoders, I have no data on the
motors nor the encoders but the controller has a sign saying 5A fuse +/- 60
V. I hate when the encoders are crimped to the motor shaft and even though
they are sweet I am more than willing to rip them off and replace them with
capacitive encoders tomorrow.
https://www.flickr.com/photos/svenneduva/albums/72157698570971564

I need a few pins extra. The spindle is a HF air bearing (50 k RPM) with a
pneumatic tool changing mechanism. There goes a few extra pins. The tool
changer itself is fixed but has a motor driven cover with limit switches.
So two limit inputs, motor +/- direction and then signals for releasing the
tool.
The machine itself only has homing switches so three extra inputs, or one
if serial wired. I would like to add end switches though.

The easy way out would getting a Mesa 7i92 + 7i76 combo (no LPT) and some
step/dir servo drives. But I thought the nice thing with for example a 7i77
board is that it handles all the loop back and I only need some simple
amplifier drivers to run the servos and then feed the encoder signals to
the 7i77. But, all the drivers I find they want the encoder input? And I
though they were supposed to go to the 7i77? Even worse, I bought a 7i77
card to host a set of super fancy Omron drivers once upon a time and know I
don't even understand how I was thinking when I bought them. Correct, they
were never installed and are still collecting dust.

So, IF I am going with the Mesa boards, what on Earth is the driver I
should use, and what boards? Simply, I am lost on this one... I don't know
if I'm getting old and lack the googling skills, I can't find a decent
combo anymore. Step/dir is a breeze to setup compared to this jungle. I do
understand Mesa is supporting us and everything, I just don't understand
how little documentation there is to find _how_ to choose boards and to set
them up.

An alternative is Rene's STMBL driver which looks very nice but need
another breakout board as far as I understand. If I make it to the
Stuttgart meeting next weekend we might have a German solution to my
problem. Who knows...








On Thu, Jul 12, 2018 at 10:25 PM Sven Wesley  wrote:

> These little babies. I have a few of them already and my kids have the i7
> version and they are fast. Linux just runs, no trouble. One Ethernet and
> Wifi in the same box. Perfect.
> https://www.dustin.se/product/5011010658/nuc-kaby-lake-wifi
>
>
>
> On Wed, Jul 11, 2018 at 3:32 PM Eric Keller  wrote:
>
>> Which Intel NUC did you get?  A couple of years ago I got a zotac box with
>> dual ethernet ports thinking that I might use it as either a router or to
>> drive an ethernet mesa board.  I think it will end up as a router.
>> Eric Keller
>> Boalsburg, Pennsylvania
>>
>> On Wed, Jul 11, 2018 at 4:05 AM Sven Wesley 
>> wrote:
>>
>> > Yes, looks like your email with the link went to me and not to the list.
>> > Anyway, the Mesa card looks promising. Intel NUC and Mesa boards on the
>> > way!
>> >
>> > /S
>> >
>> > On Tue, Jul 10, 2018 at 5:14 PM Les Newell 
>> > wrote:
>> >
>> > > I beat you to it with the same link but it looks like my email went
>> > > directly to Sven, rather than to the list. For some reason when I
>> reply
>> > > to this list the replies usually end up going direct to the sender
>> > > rather than to the list.
>> > >
>> > > Les
>> > >
>> > > On 10/07/2018 13:38, andy pugh wrote:
>> > > > On 10 July 2018 at 11:47, Sven Wesley 
>> wrote:
>> > > >> You too late, Andy. ;)
>> > > > Too late in the sense that you have already bought the UC400 ?
>> > > >
>> > >
>> > >
>> > >
>> > >
>> >
>> --
>> > > Check out the vibrant tech community on one of the world's most
>> > > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>> > > ___
>> > > Emc-users mailing list
>> > > Emc-users@lists.sourceforge.net
>> > > https://lists.sourceforge.net/lists/listinfo/emc-users
>> > >
>> >
>> >
>> --
>> > Check out the vibrant tech community on one of the world's most
>> > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>> > ___
>> > Emc-users mailing list
>> > Emc-users@lists.sourceforge.net
>> > https://lists.sourceforge.net/lists/listinfo/emc-users
>> >
>>
>> --
>> Check out the vibrant tech community on one of the world's most
>> engaging tech 

Re: [Emc-users] 7i92 bitfile programming problem

[Sebastian Kuzminsky]

On 13/07/2018 12:04, Les Newell wrote:
> I'm running a fairly recent Buildbot release and I built the latest Git
> version and still got the same error.

The version of mesaflash available in the linuxcnc.org debian archive,
3.3.0~pre0+dfsg-0, should work fine with the 7i92.

Note that mesaflash is in a separate package from linuxcnc, so
upgrading linuxcnc won't affect your version of mesaflash.


-- 
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Re: [Emc-users] Linuxcnc meeting Stuttgart, Germany 2018

[Sven Wesley]

Ah shoots, Maybe too tight. Will try to join, would be fun to meet everyone
again!

/S

On Fri, Jul 13, 2018 at 5:02 PM Rene Hopf via Emc-users <
emc-users@lists.sourceforge.net> wrote:

>
> > On 13. Jul 2018, at 15:14, Sven Wesley  wrote:
> >
> > Did this happen or will it happen? Would be nice to go to Stuttgart
> again!
>
> it will happen, from 20-22 this month.
>
> >
> > /S
> >
> >
> >
> > On Wed, May 2, 2018 at 6:41 PM andy pugh  wrote:
> >
> >> On 2 May 2018 at 17:14, Nicklas Karlsson 
> >> wrote:
> >>> I can't see the date, me be blind?
> >>
> >> At this point it is a survey to choose a date.
> >>
> >> --
> >> atp
> >> "A motorcycle is a bicycle with a pandemonium attachment and is
> >> designed for the especial use of mechanical geniuses, daredevils and
> >> lunatics."
> >> — George Fitch, Atlanta Constitution Newspaper, 1916
> >>
> >>
> >>
> --
> >> Check out the vibrant tech community on one of the world's most
> >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> >> ___
> >> Emc-users mailing list
> >> Emc-users@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/emc-users
> >>
> >
> --
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> > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
>
> --
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[Emc-users] Grounding

[Roland Jollivet]

 > That's pretty much standard these days.
>
> I'm not making this stuff up.   That's how its done.


So which is it? Connect Gnd to 0VDC, or not?

I've pulled apart quite a lot of industrial plotters, printers and I've
Never seen 0VDC connected to Gnd. Same with robots, Injection moulding
machines.
All frame metal parts are quite interconnected, sure, and Grounded, but all
electronics has it's own power system.

I don't understand the desire to connect two lines together because they
'seem' to be of the same magnitude.  0VDC is Not equal to Gnd
Many systems will have multiple 5V power lines, heavy, light, designated.
Do you want to link all those up too?



On 13 July 2018 at 18:05, andy pugh  wrote:

> On 13 July 2018 at 16:52, Dave Cole  wrote:
>
> > That's pretty much standard these days.
> >
> > I'm not making this stuff up.   That's how its done.
>
> I think that there is still some confusion out there. I used to work
> for a company making specialist test equipment (brake dynos, motor /
> pump testers, that sort of thing).
> Our electricians were convinced that everything needed an yellow/green
> earth connection. Every panel for the control cabinet, the doors, the
> individual devices bolted to the machine bed. We would spend ages
> making things look nice and painting them, and then they would come
> back festooned with stripy wires and with a hole drilled in every
> separate metal part for the earth stud.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1916
>
> 
> --
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> ___
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> https://lists.sourceforge.net/lists/listinfo/emc-users
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Re: [Emc-users] 7i92 bitfile programming problem

[Peter C. Wallace]

On Fri, 13 Jul 2018, Les Newell wrote:


Date: Fri, 13 Jul 2018 12:31:31 +0100
From: Les Newell 
Reply-To: "Enhanced Machine Controller (EMC)"

To: "Enhanced Machine Controller (EMC)" 
Subject: Re: [Emc-users] 7i92 bitfile programming problem

Looks like a must have messed up a path somewhere. Rebuilt mesaflash and it 
now works.


Les


Yeah you must have an old copy somewhere on your system (I remember this bug 
from a couple  of years ago...)




On 13/07/2018 12:04, Les Newell wrote:

Hi Peter,


I think that means you have a old version of mesaflash


I'm running a fairly recent Buildbot release and I built the latest Git 
version and still got the same error.


Les


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Peter Wallace
Mesa Electronics

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.


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Re: [Emc-users] Grounding

[andy pugh]

On 13 July 2018 at 16:52, Dave Cole  wrote:

> That's pretty much standard these days.
>
> I'm not making this stuff up.   That's how its done.

I think that there is still some confusion out there. I used to work
for a company making specialist test equipment (brake dynos, motor /
pump testers, that sort of thing).
Our electricians were convinced that everything needed an yellow/green
earth connection. Every panel for the control cabinet, the doors, the
individual devices bolted to the machine bed. We would spend ages
making things look nice and painting them, and then they would come
back festooned with stripy wires and with a hole drilled in every
separate metal part for the earth stud.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Grounding

[Dave Cole]

Each panel has its own star grounding setup, then panels are bonded 
between each other with a heavy cable.


That's pretty much standard these days.

I'm not making this stuff up.   That's how its done.

When we are talking about "modules", I am talking about industrial steel 
control panels.  Some are 7 feet tall, 2 feet deep and 4 feet wide.
Some of them are big enough that you can stand inside of them with the 
equipment installed in the panels.   Some are more like control closets 
than panels.   Sometimes they are bolted together as below, sometimes 
they are free standing and spread around a machine.  Sometimes they are 
much smaller.  But if they have large drives, the panels pretty much 
have to be large just to accommodate the large power cables and heat 
loads.  Some are air conditioned and some are not.


Similar to this:
http://www.elettronicalucense.com/portfolio/industrial-automation/

If you use decent equipment and follow their shielding recommendations, 
noise is typically not an issue.   But each device has undergone CE EMI 
noise testing as well.


Dave



On 7/13/2018 1:48 AM, Erik Christiansen wrote:

On 12.07.18 15:33, John Dammeyer wrote:

So what happens when the equipment with the 24V supply is 30m long in
multiple steel frames?  There would be a bonding wire from frame to
frame since you wouldn't want to bond one end to one AC ground outlet
and the other end to a different AC ground outlet.

Rather than chain a whole lot of modules on one long ground wire, where
each can interfere with the others by imposing HF noise on the common
ground impedance, thereby coupling it into the others, I'd wire them
individually back to the power supply. ("Star Earth", as Gene so rightly
points out.)

If there is internal DC connection to the equipment case, I'd provide
isolated mounts to defeat the earth loops which would most likely
otherwise cause problems.

If there's RF EMI into the equipment from a hostile environment, then
I'd be tempted to connect the metallic case to its internal equipment's
earth via a good RF bypass capacitor, to put the circuitry's Faraday
cage at earth potential.

...


What about if you have a vehicle instead.  Might have equipment
mounted on frames  that need to be bonded together.  If they run an
independent battery pack and/or genset then the DC ground doesn't need
to touch the frame.  But what if the vehicle 12V battery which does
have negative connected to the frame also provides some sort of
vehicle connection.  Say a radio that has a modem that connects to a
PC.

One connection, as at the battery would be fine. It's earth loops which
best radiate EMI, proportional to the area of the loop antenna.


Logic would dictate you want the DC ground of everything connected to
the frame with some bond wires even if just for lightning protection.
But now you run risk of ground loops on the 12V circuits interfering
with the system battery pack.

I'd put gaseous arrestors on external lines as primary protection,
followed by MOVs or transorbs further inboard, with some impedance
between, to further clamp the surge not entirely swallowed by the
arrestors. But I'd try to read up on that bit first. Grounded shielding
on external wiring has to help too.

Erik

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Re: [Emc-users] Grounding

[Dave Cole]

That is standard for 24 volt control panels.   I've done many of them 
and seen hundreds of them wired exactly that way.



On 7/13/2018 1:49 AM, Roland Jollivet wrote:

Definitely do not tie 0VDC to ground. It will often cause problems with the
switching power supply.




On 13 July 2018 at 04:55, Dave Cole  wrote:


Typically in a multi-panel control system setup there is a ground bar in
each panel.   The incoming AC power ground is tied to this and the 24 volt
power supply negative is tied to the local ground bar just as I described
before.  If all of these panels are on a common machine frame, the ground
bars are oftentimes linked together with a heavy bonding copper cable (like
a 4 gauge or heavier bare cable).

You don't want to rely on the machine frame to be the ground conductor.
The systems I used to work on way back when were all AC, 120 volts for the
controls and you could run control wire circuits for 1000 ft with only
occasional problems.  Way back when, a controls electrician typically
didn't carry a voltmeter with him.   He used a wiggy.
https://en.wikipedia.org/wiki/Solenoid_voltmeter

Now you just pull Ethernet cables between control panels.
Not much 120 VAC control wiring is being installed any longer.

Dave




On 7/12/2018 6:33 PM, John Dammeyer wrote:


So what happens when the equipment with the 24V supply is 30m long in
multiple steel frames?  There would be a bonding wire from frame to frame
since you wouldn't want to bond one end to one AC ground outlet and the
other end to a different AC ground outlet.

What if you have 30A, 24V supplies at each end of the machine or in each
module.If each 24V supply minus terminal is grounded to the frame and
you run a common ground bus through the machine you now have the frame and
the ground bus serving as the DC ground path.   You wouldn't want to run DC
ground on the frame.

I worked on a machine once that had I think 42 modules.  Each one was
independent and inserted two advertisement flyers into newspapers.  A
client would buy the number of modules they thought they would need for the
number of insertions.   I don't think they ran 24V from the front end all
the way through so probably AC to each module and a 24V supply for the
motors and relays (and air valves).   The entire set of modules was also
connected via CAN bus so we have the CAN signal ground in that match too.
It was a long time ago and I was brought in to solve CAN bus problems so I
never really looked closely at the power.

What about if you have a vehicle instead.  Might have equipment mounted
on frames  that need to be bonded together.  If they run an independent
battery pack and/or genset then the DC ground doesn't need to touch the
frame.  But what if the vehicle 12V battery which does have negative
connected to the frame also provides some sort of vehicle connection.  Say
a radio that has a modem that connects to a PC.

Logic would dictate you want the DC ground of everything connected to the
frame with some bond wires even if just for lightning protection.  But now
you run risk of ground loops on the 12V circuits interfering with the
system battery pack.

Do the hybrid electric cars connect the negative DC of the high voltage
battery pack to the frame?

I'm amazed at the can of worms this question raises.  We haven't even
discussed the electrical noise issues coupled through the lowest impedance
path.

John


-Original Message-

From: Dave Cole [mailto:linuxcncro...@gmail.com]
Sent: July-12-18 2:57 PM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Grounding

I think you need to define what you mean by "grounding".

If you have a 24 volt DC powered control system, like an industrial
control panel, typically the 24 volt DC power supply/s will tie the 0V
terminal on the power supply to frame/panel ground.�� These are the big
10, 20, 40 amp 24 volt DC power supplies that power the control panel
components.

There are some good reasons to do this.
Many industrial control components have loose ties frame ground
internally and if you don't tie 0V to frame ground they malfunction!
Many of these components have specifications for the number of volts
that the M, 0V terminal can be away from chassis ground.

The grounding is normally done by a single green wire from the power
supply 0V terminal to the ground bus bar.�� That way if there are
grounding/common issues you can lift that wire to aid in debugging the
system.

When you get into 5V systems, breakout boards, etc, I tend to keep those
isolated from frame/panel ground.��� I think there are only downsides to
connecting the 0V terminal of a 5 volt power supply to frame ground.

If you look at industrial drives, they always separate the frame/safety
ground from the signal "ground" or "reference" terminal.�� They are
usually two different terminals.� One is oftentimes a cable lug or
bolt-cable lug connection, and the other a small screw terminal.

FWIW, I am in the machine controls business.� PCs are 

Re: [Emc-users] Grounding

[Jon Elson]

On 07/12/2018 02:12 PM, John Dammeyer wrote:

Is it standard practice to connect the DC Servo and DC Instrumentation Bus
to the machine frame ground which is connected to power line earth?  Or is
it more normal practice to keep the DC isolated from the 'earth' ground.
  

The "DC Link" in a multi-axis servo system incurs large DC 
offsets when the drives are powering the motors.  This will 
shift constantly as motors accelerate and decelerate.  If 
the drives have complete isolation between the power stage 
and the control side, this should not be a problem.  But, 
you need to insure that the DC link is grounded at ONE POINT 
only to some other system ground.


If the drives are NOT fully isolated, then ground loops are 
guaranteed to occur, and everything else connected to ground 
needs to accommodate this.  If these are analog servo amps, 
then using differential amps on all inputs (especially tach 
and command) mostly solves it, as long as the DC link 
variation doesn't exceed the common mode rejection of the 
diff amps.  These DC shifts can be surprisingly large, even 
with beefy ground conductors.


And, of course, you CAN isolate the DC link, but have to 
consider the possible dangers when something goes wrong.  On 
the other hand, having the DC link minus grounded to case, 
and then somehow the DC link PLUS gets shorted to ground, 
can lead to massive damage as XX hundred Volts rushes around 
through the wall plug grounds and fries the CNC control, 
computer, etc.  I know because I have repaired some of my 
(Pico Systems) gear when this has happened to customers.


Jon

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Re: [Emc-users] Linuxcnc meeting Stuttgart, Germany 2018

[Rene Hopf via Emc-users]

> On 13. Jul 2018, at 15:14, Sven Wesley  wrote:
> 
> Did this happen or will it happen? Would be nice to go to Stuttgart again!

it will happen, from 20-22 this month.

> 
> /S
> 
> 
> 
> On Wed, May 2, 2018 at 6:41 PM andy pugh  wrote:
> 
>> On 2 May 2018 at 17:14, Nicklas Karlsson 
>> wrote:
>>> I can't see the date, me be blind?
>> 
>> At this point it is a survey to choose a date.
>> 
>> --
>> atp
>> "A motorcycle is a bicycle with a pandemonium attachment and is
>> designed for the especial use of mechanical geniuses, daredevils and
>> lunatics."
>> — George Fitch, Atlanta Constitution Newspaper, 1916
>> 
>> 
>> --
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Re: [Emc-users] Odd size Grub Screw

[andy pugh]

On 13 July 2018 at 13:13, Bengt Sjölund  wrote:

> I have a friend who has an old machine and needs to get hold of grub/set
> screws UNF 9/16" with a length of 3/4" 20mm with hex or torx head.
> Have been poking around for a while and cannot find any supplier.

https://www.allfix.co.uk/products/socket-set-screw-plain-cup-steel-self-colour-unf/spc0scf056x0075

Expensive, but I think that you can buy less than 100 at a time.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Linuxcnc meeting Stuttgart, Germany 2018

[andy pugh]

On 13 July 2018 at 14:14, Sven Wesley  wrote:
> Did this happen or will it happen? Would be nice to go to Stuttgart again!

Next weekend. (the next weekend that is not this weekend, to save confusion)

http://www.linuxcnc.org/2018/06/05/LinuxCNC-Meetup-in-Stuttgart/

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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[Emc-users] Odd size Grub Screw

[Roland Jollivet]

I am not in the UK but have bought from these guys, they should have it;

https://www.accu.co.uk/en/



On 13 July 2018 at 14:13, Bengt Sjölund  wrote:

> Hi,
>
> I have a friend who has an old machine and needs to get hold of grub/set
> screws UNF 9/16" with a length of 3/4" 20mm with hex or torx head.
> Have been poking around for a while and cannot find any supplier.
>
> Do you guys in UK have any secret supplier that can help out with this?
> 10-15 pcs would suffice a lifetime.
>
> Cheers
> Bengt
>
>
> 
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Re: [Emc-users] Odd size Grub Screw

[Gene Heskett]

On Friday 13 July 2018 08:13:23 Bengt Sjölund wrote:

> Hi,
>
> I have a friend who has an old machine and needs to get hold of
> grub/set screws UNF 9/16" with a length of 3/4" 20mm with hex or torx
> head. Have been poking around for a while and cannot find any
> supplier.
>
> Do you guys in UK have any secret supplier that can help out with
> this? 10-15 pcs would suffice a lifetime.
>
> Cheers
> Bengt
>
Thats quite a good size, I just checked MonsterBolts.com where I've been 
getting mine, but their stock stops at 10mm, so you might have to make 
them, but doing the socket is going to be fun. I have done that on The 
Little Monster, but much smaller stuff. It may actually be easier to do 
the torx, each "rib" is narrower, and would tend to concentrate the 
swaging force with fewer lbs from the tailstock. Start with say 1065, 
and harden them after forming. A2 as shipped might also be good, its 
easy to work before hardening, or has been for me.
>
> --
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Cheers, Gene Heskett
--
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Linuxcnc meeting Stuttgart, Germany 2018

[Sven Wesley]

Did this happen or will it happen? Would be nice to go to Stuttgart again!

/S



On Wed, May 2, 2018 at 6:41 PM andy pugh  wrote:

> On 2 May 2018 at 17:14, Nicklas Karlsson 
> wrote:
> > I can't see the date, me be blind?
>
> At this point it is a survey to choose a date.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1916
>
>
> --
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> ___
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> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>
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[Emc-users] Odd size Grub Screw

[Bengt Sjölund]

Hi,

I have a friend who has an old machine and needs to get hold of grub/set 
screws UNF 9/16" with a length of 3/4" 20mm with hex or torx head.

Have been poking around for a while and cannot find any supplier.

Do you guys in UK have any secret supplier that can help out with this? 
10-15 pcs would suffice a lifetime.


Cheers
Bengt


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Re: [Emc-users] 7i92 bitfile programming problem

[Les Newell]

Looks like a must have messed up a path somewhere. Rebuilt mesaflash and 
it now works.


Les

On 13/07/2018 12:04, Les Newell wrote:

Hi Peter,


I think that means you have a old version of mesaflash


I'm running a fairly recent Buildbot release and I built the latest 
Git version and still got the same error.


Les

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Re: [Emc-users] 7i92 bitfile programming problem

[Les Newell]

Hi Peter,


I think that means you have a old version of mesaflash


I'm running a fairly recent Buildbot release and I built the latest Git 
version and still got the same error.


Les

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Re: [Emc-users] Grounding

[Gene Heskett]

On Friday 13 July 2018 01:48:57 Erik Christiansen wrote:

> On 12.07.18 15:33, John Dammeyer wrote:
> > So what happens when the equipment with the 24V supply is 30m long
> > in multiple steel frames?  There would be a bonding wire from frame
> > to frame since you wouldn't want to bond one end to one AC ground
> > outlet and the other end to a different AC ground outlet.
>
> Rather than chain a whole lot of modules on one long ground wire,
> where each can interfere with the others by imposing HF noise on the
> common ground impedance, thereby coupling it into the others, I'd wire
> them individually back to the power supply. ("Star Earth", as Gene so
> rightly points out.)
>
> If there is internal DC connection to the equipment case, I'd provide
> isolated mounts to defeat the earth loops which would most likely
> otherwise cause problems.

As I describe in a clarifying post. And I'd delete the "most likely 
otherwise" above. This problem in my sheldon lathe build caused me to 
ditch the switching supplies for the motors in favor of some toroid 
transformers, bridge rectifiers and large filter caps, simply because I 
could much more easily ground the negative rails to that common point 
bolt w/o cause ground loops.  The switchers were injecting noise with a 
bandwidth exceeding my gigahertz sampling scope, at voltages (30 volts 
peak) sufficient to blow an unprotected 7i90HD instantly.

I changed the supplies to nice quiet discrete analog, and added the 
7i42TA's, giving me a much more easily wired interface, reducing that 
noise source to the drivers current regulation switching and under 200 
millivolts at the 7i42TA inputs. And modified the config to work around 
the blown gates in the last of 3 7i90's I had bought trying to make it 
work.  A year later its still running well on a half blown 7i90HD.

As I am a Certified Electronics Technician, I should have done the analog 
supplies in the first place, but I was in a hurry to make it move. 
Presumably I could have glued the switchers onto a couple strips of 
double sided pcb material, also glued to the mounting subplate in the 
motor driver box, but I like solid mounts. And that reminded me of the 
stupidity of short cuts. Not to mention that the pcb material used in 
that fashion would have represented a good sized capacitor coupling the 
switching noise they created into the chassis, not at all a good idea 
once the ramifications of that capacitance were considered.

I did hook up a breadboard I could drive with a function generator, with 
a common ground bolt hanging in the breeze. It worked to drive a 425oz 8 
wire motor to just over 3000 revs, but noise from the bolt to the case 
of the switcher sitting on wood with its ground terminal connected to 
that common bolt, was over 100 volts p-p on the scope, with rise and 
fall times equal to the scopes bandwidth. Theres 3 of those supplies in 
the G0704 power box, and one AC powered driver for the z motor and my 
portable phone is useless within 12 feet of it. They are that damned 
noisy. It rings raggedly, and if I want to talk on it, I have to be 12 
to 20 feet away. The sheldon's build does not bother the phone. I have 
another of those phones out in the shop building, but there the 
switchers are bolted down in closed metal boxes, so the phone works 
fine.

> If there's RF EMI into the equipment from a hostile environment, then
> I'd be tempted to connect the metallic case to its internal
> equipment's earth via a good RF bypass capacitor, to put the
> circuitry's Faraday cage at earth potential.

That capacitor is what the pcb material would have been had I used it for 
an isolation mount. If I were to do it again, I'd put the switchers in 
their own box, on isolated mounts, and make an expanded metal faraday 
cage around them so they could bounce w/o radiating that noise into the 
rest of the circuitry.  Hind sight, always 20-05.

> ...
>
> > What about if you have a vehicle instead.  Might have equipment
> > mounted on frames  that need to be bonded together.  If they run an
> > independent battery pack and/or genset then the DC ground doesn't
> > need to touch the frame.  But what if the vehicle 12V battery which
> > does have negative connected to the frame also provides some sort of
> > vehicle connection.  Say a radio that has a modem that connects to a
> > PC.
>
> One connection, as at the battery would be fine. It's earth loops
> which best radiate EMI, proportional to the area of the loop antenna.
>
> > Logic would dictate you want the DC ground of everything connected
> > to the frame with some bond wires even if just for lightning
> > protection. But now you run risk of ground loops on the 12V circuits
> > interfering with the system battery pack.
>
> I'd put gaseous arrestors on external lines as primary protection,
> followed by MOVs or transorbs further inboard, with some impedance
> between, to further clamp the surge not entirely swallowed by the
> arrestors. But I'd try to read