Re: [Emc-users] Grounding

[John Dammeyer]

I think we should also be more clear on our nomenclature.  We have DC GROUND 
which can be as simple as 3.3V or +5V and ground.  We can have 24V and 12V 
relays and valves that also have a DC ground.  And we have Stepper/Servo motors 
with high voltages from 24V to 300VDC.  The high voltage ground may or may not 
be connected to the low voltage DC ground.   The symbol is normally a triangle 
with the point downward and wire into the middle of the opposite horizontal 
part of the triangle.

The AC side should more correctly be referred to as EARTH or if the word ground 
is used EARTH GROUND.  That's the symbol with the tapering horizontal lines.

The metal case is CHASSIS GROUND and is often drawn as a horizontal line with 4 
or 5 short lines coming off at an angle on the bottom while the connection 
again is in the center of the horizontal line.  

The CHASSIS GROUND should be connected to EARTH GROUND at only one location; 
generally where power comes into the equipment.   So when we're talking about 
bonding all our metal case bits together we're really talking about CHASSIS 
GROUND.

https://www.clarionsafety.com/content/Featured_Articles/InCompliance-January-2012-Grounding-Symbols.pdf


John


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Re: [Emc-users] Grounding

[Chris Albertson]

By code you only have the Earth ground the parts that are used to enclose
the high voltage electronics.  So handles and carrages are not grounded.
The motor case would be if the motor used high voltage.  But in the case of
a small CNC mill or lathe like what I have the motors are running off 36
volts so a ground is not needed.   But a bigger machine might have 270V
inside.



On Mon, Jul 16, 2018 at 12:04 PM andy pugh  wrote:

> On 16 July 2018 at 19:24, Chris Albertson 
> wrote:
>
> > Those grounds are best thought of as part of the mechanical enclosure.
> > Those safety grounds do nothing at all until one day there is a fire and
> > some insulation melts
>
> One of my machines was a lot like a lathe, with a cast iron bed.
> Bolted to that bed was an electric motor, a torque meter, an angular
> encoder, something I have forgotten and then the pump under test.
>
> There were earth wires run to each item bolted to the bed.
>
> If that is necessary then a CNC lathe needs an earth wire to the
> carriage, the toolpost, the top-slide, each handle..
>
> They had read that a fixing bolt can not be used to conduct protective
> ground. (Which might well be true) and saw that as an instruction to
> earth every separate metal part. (which is the logical conclusion from
> the prior statement)
>
> --
> 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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> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
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Re: [Emc-users] Grounding

[Dave Cole]

 not all in a box
is different.

John




-Original Message-
From: Jon Elson [mailto:el...@pico-systems.com]
Sent: July-14-18 8:57 AM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Grounding

On 07/14/2018 02:37 AM, Gene Heskett wrote:

Not exactly 100% correct John. High frequencies are
generally carried only by current flow at the skin of a
conductor. And the large conductor, while having some rise
in impedance, is still the better conductor because the
smaller wire has far less surface skin area, raising both
its impedance and its ohmic effects faster than the big wire.

There's also loops.  Bundling the power supply and ground
return close together minimizes inductance.  Having the
supply and return form a big loop increases inductance, and
can cause greater noise as well as radiation of EMI.  So, in
general, you want the return wires to follow the supply
wires closely.

Jon




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Re: [Emc-users] Grounding

[andy pugh]

On 16 July 2018 at 19:24, Chris Albertson  wrote:

> Those grounds are best thought of as part of the mechanical enclosure.
> Those safety grounds do nothing at all until one day there is a fire and
> some insulation melts

One of my machines was a lot like a lathe, with a cast iron bed.
Bolted to that bed was an electric motor, a torque meter, an angular
encoder, something I have forgotten and then the pump under test.

There were earth wires run to each item bolted to the bed.

If that is necessary then a CNC lathe needs an earth wire to the
carriage, the toolpost, the top-slide, each handle..

They had read that a fixing bolt can not be used to conduct protective
ground. (Which might well be true) and saw that as an instruction to
earth every separate metal part. (which is the logical conclusion from
the prior statement)

-- 
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

[Chris Albertson]

The safety grounds like that, those wires bolted to cover plates, Are
important if there is mains power inside the device.But they do nothing
with regards to the operation of the device or noise on the data lines.
Those grounds are best thought of as part of the mechanical enclosure.
Those safety grounds do nothing at all until one day there is a fire and
some insulation melts.

On Mon, Jul 16, 2018 at 9:39 AM Dave Cole  wrote:

> On 7/13/2018 12:05 PM, 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.
> I know exactly what you are talking about.   This can certainly be
> overdone.
>
> I think the problem is that people are afraid of what will happen if
> they don't run ground wires.
> The question is always;   If I don't run a ground wire to it will it
> make it unsafe.
> Most electricians (who are oftentimes paid by the hour) are happy to
> make the system "really safe" by running more ground wires.
>
> Dave
>
>
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Re: [Emc-users] Grounding

[Dave Cole]

This is the problem:

Many industrial devices powered by 24 volts DC; PLCs computers, etc have 
specifications which limit the number of volts which DC Negative,"M" 
common, can be away from frame ground.   If you don't tie the 0V 
terminal on the DC power supply to frame ground, you have no idea how 
far "M" is from frame ground since it is floating.


I would not tie the 0V terminal of a 5 volt power supply to frame ground 
unless it is required.


For instance, a 5 volt power supply powering Mesa cards.   I would leave 
that off frame ground unless you find that it must be referenced to 
frame ground via debugging.


I once blew a comm port on a USB to RS232 converter when I was 
programming an ungrounded 24 volt PLC system.   The 0V terminal on the 
PLC was not close to absolute ground so the signal ground on the PLC 
RS232 connector was also not near absolute ground.   My laptop was 
connected via a grounded power supply.   When I plugged into the PLC 
with the RS232 port cable, current flowed from the control systems 
ground into the RS232 to USB adapter, through the shielded USB cable and 
into the frame ground on the PC which was of course was connected to the 
AC power ground.   Fortunately the RS232 to USB adapter took the hit and 
my laptop was ok.   It wasn't hard to figure out what happened as the 
computer rebooted when I plugged in the cable.  A bad sign for sure!


I obtained another RS232 to USB adapter and programmed the PLC with the 
laptop while running off battery power (the Laptop was isolated from 
absolute ground) since it was not plugged in via the AC power supply.


Here are some things to read:
https://control.com/thread/1026164262
http://forums.mrplc.com/index.php?/topic/15175-ground-the-24vdc-power-supply-common/

Dave

On 7/13/2018 12:24 PM, Roland Jollivet wrote:

  > 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


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Re: [Emc-users] Grounding

[Dave Cole]

On 7/13/2018 12:05 PM, 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.
I know exactly what you are talking about.   This can certainly be 
overdone.


I think the problem is that people are afraid of what will happen if 
they don't run ground wires.
The question is always;   If I don't run a ground wire to it will it 
make it unsafe.
Most electricians (who are oftentimes paid by the hour) are happy to 
make the system "really safe" by running more ground wires.


Dave

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Re: [Emc-users] Grounding

[Chris Albertson]

Yes the effect is 100% symmetric.  It works the same for receive and
transmitted noise

On Sat, Jul 14, 2018 at 3:49 PM John Dammeyer 
wrote:

> I believe twisted cables are more immune to externally induced
> interference.
> The twists result in the noise canceled out at the receiving ends.
>

Chris Albertson
Redondo Beach, California
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Re: [Emc-users] Grounding

[John Dammeyer]

What follows is a  long story about how the ground in a DC system moves
around.

This isn't the first time I've run into an issue on DC bus power systems.
Almost 10 years ago I was responsible for the electronics design and
software for this project.
http://www.autoartisans.com/rings/Barge1a.jpg
Each ring is a separate CAN network with a bridge splitting the 150 lights
into sets of 50 each with the longest length about 37m.
The software that ran on a laptop PC, connected to each side by a USB port,
could not only run light shows but logged the data reported from each lamp
to tell us temperature and status.  Mapped out in these screen shots blue is
colder than green and if they were red they'd be above 60C.
http://www.autoartisans.com/rings/BargeRingsTemperatures.JPG

Each light drew about 4.25W max with all 36 LEDs on.   The math is about
3kW, 48V, 66A total.  About 13A per ring resulting in about 4.5A per
segment.  The set at the YVR airport ran on a 24VDC toroid driven
bridge/capacitor and was closer to 8A per segment.  The thick DeviceNet
cable was rated at no more than 7A for the red/black power pair.

For the barge set of rings the power was from a bank of batteries (48V) at
the far end of the barge.  Power was run through some very thick cables in a
trough to the center of the barge.   Because the cable was so expensive the
installers decided to coil the leftover part at the base of the cabinet
before running it into the cabinet.

Now picture all lights on and around 66A running through those cables split
up onto the 5 rings.  Then imagine sending the command All Lights Off.  The
3 turns about 2' in diameter of both the ground and power at the base of the
cabinet was enough of an inductor to cause a voltage spike as the current
was stopped; a spike that was well over 100V.  The voltage regulators on the
lamps were max 70V in.  That event took out more than 200 lamps.  It wasn't
until the trip home that the engineer mentioned the coiled cable below the
cabinet and wondered if that was important.  We cut it to the exact length,
repaired the lamps and the problem was gone.

So what's the point of all this?  The lights were run with CAN bus
messaging.  CAN uses a 3 wire system; CAN High, CAN Low and CAN Ground.
Contrary to what may be on the internet here and there, the ground is
important.The two wires for CAN High and Low expect to have a cable as a
transmission line with a 120 ohm impedance and therefore terminated at each
end with a 120 Ohm resistor.  During the bus passive state, when no one is
sending, the CAN H and CAN L have effectively 60 ohms between them and are
biased to 2.5V relative to ground.   Hence the need for the ground wire.  No
significant current flows through the ground.The devices also tend to
have a Max/Min voltage on the CAN signal pins, again relative to ground of
about -7V and up to as high as 42V.  If you are running CAN devices with a
24V power supply you can have a cable error with 24V connected to the CAN
pins and not destroy the device.  Not so with 48V which on the Barge took
out a segment of 50 lights due to a badly manufactured cable.

The 50 lights occupied the last 10m or so of cable and the other 25m or so
was the feed to those 50 lights. That's because the rings were 10m in
diameter and that gives about 31.4m circumference.   Needless to say there
was a slight voltage drop from lamp to lamp with the far end showing the
highest drop.  So at the cabinet the battery voltage, when the genset was
running and charging the batteries, the voltage would measure 56V.  At the
far end across the last lamp the voltage might be 48V.  But that's not 8V
across the red wire.  That's 4V across the black one (ground) and 4 volts
across the red (supply). 

Relative to the CAN H and CAN L signals at the lamp, measured at the lamp,
the signals were still 2.5V relative to the local ground.  With at most 60mA
flowing through the CAN signal lines the voltage drop from 2.5V at one end
is pretty well 0V at the other end.   But now it depends on where you put
that ground lead on the meter.   It starts getting close to the -7V min
value.Add the scenario where the lights are flickering on and off
running a light show and that ground signal is all over the place and
inductance can cause even more ground bounce.

The lights in plastic boxes and so were isolated.  I don't recall if we ever
connected the DC to the barge or the ring frame.  I hesitate to think about
what kind of problems would have happened had we connected the other end of
the 35m cable ground to the frame.  The shields on the cables were connected
to the cabinet and thereby the frame inside the cabinet.  The other end of
the shield was left floating.

The point of all this is for a system like this there was never any need to
connect the DC to the frame.  The shields yes.  But DC  ground to the
cabinet could cause interesting transients on a frame that was over 15m high
and about 40m wide.

The Batteries were 

Re: [Emc-users] Grounding

[John Dammeyer]

I believe twisted cables are more immune to externally induced interference.
The twists result in the noise canceled out at the receiving ends.  
John

> 
> Yes of course this is true.  But it is true if the wires are twisted 1, 4
> or 16 times per inch.   Why does twist help?
> 
> OK I just figured it out.  if you look at the e-feild at a point some
> distance from the wire pair and the pair is twisted you can integrate the
> field in the direction of the wire (in a plane parallel to the cable and
> e-feild at d is truly zero.  It is way hard to symbolically but way easy
> using numeric integration.  The results are pretty dramatic.   I can see
> why every new kind of data cable uses this.
> 
> 
> Chris Albertson
> Redondo Beach, California
>

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Re: [Emc-users] Grounding

[John Dammeyer]

For reducing interference DC grounds are often connected to the metal
cabinet with capacitors.  The path of HF noise is often not what you think
compared to DC. Sometimes also done with, as you suggest, a high value
resistor in parallel with a capacitor.

But I agree.  Following the rules is generally the best approach.

John

> -Original Message-
> From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> Sent: July-14-18 12:16 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding
> 
> From a safety point of view.  It is best to follow rules from local safety
> labs be it in the US or EU.   Basically if you have a metal cabinet with
AC
> power inside The cabinet MUST be grounded to the earth pin on the power
> socket and there are rules about using a dedicated screw (not used for
> other purposes) and close to the power entrance.
> 
> If you don't like the this then the other option is "double insulated"
> design which mostly means a non-conductive cabinet made from perhaps
> ABS
> plastic.
> 
> There is good reason to tie you DC ground to safety ground at one point,
> even if you use a 1M resister to do this.   Many times (especially with
> vacuum tube circuits but in other cases too) there are leakage paths and a
> ground left floating can float up to a high voltage.  So many times we
find
> some kind of RC circuit used, but more commonly a simpl wire inside the
> power supply.
> 
> The idea is that is must remain safe even AFTER is major failure such as
> insulation melting off an overloaded wire because of a fire.
> 
> You will NEVER think of everything yourself, so just follow the rules.
> They are the result of 100 years of world-wide experience.
> 
> Most consumer products we buy today use double insulation.  But if you are
> using a metal external housing, double insulation is complex
> 
> The best plan is to pretend you are actually going to SELL the machines
you
> are wiring up.  Keep is "legal" in both the US and EU and you are OK.
>  There is a strong temptation to say "It is just my own toys in my own
> house and I never plan to apply for a UL Lab sticker so way bother with
> their rules?"
> 
> 
> 
> On Sat, Jul 14, 2018 at 11:05 AM John Dammeyer 
> wrote:
> 
> > The power supply cabinet I'm putting together for my Mill has a terminal
> > strip with ground and 105VDC power (1500W) with one pair of terminals
> for
> > each axis.   From that strip I run one pair to each Servo Drive.  From
each
> > Servo Drive a pair to the motor.  The encoder cables enter the Servo
Drives
> > on a different side of the board and will be not be run in parallel with
> > the
> > motor cables.  Stepper motor for the knee has its'  own power supply and
> it
> > too runs separately  (power and ground) to the Gecko.  These high power
> > supplies are all run with 220VAC through a separate contactor controlled
> by
> > the ESTOP.
> >
> > The PMDX-126, the 24VDC and the PC/Monitor are also on a 220VAC circuit
> > that
> > is live from the Mill Master Switch.  The 24VDC supply is what I'd refer
to
> > as the instrument bus and it's used for a variety of controls like the
> > control side of the STMBL Servo drive and 12V supply for the DRO..  It
will
> > share the DC ground with the PMDX-126 breakout board, PC USB and
> ultimately
> > a series of CAN bus based controls for tool changer etc.
> >
> > I wanted to also run the 24V into a 15V regulator to provide power for
the
> > control side of the HP-UHU servo drives but here is where that pesky
> ground
> > sneaks in again.  Connecting a 15V supply sourced from the instrument
> power
> > that then runs the HP_UHU connects the Instrument power to the Servo
> Power
> > ground.  The step/dir/error from the HP_UHU is optically isolated so I
> > don't
> > have to worry there.
> >
> > The Servo Power Transformer has a 12VAC winding which through a bridge
> > gives
> > me roughly 16V which is the better source for the 15V that not only is
> > regulated down to 5V for the HP_UHU but also supplies the gate bias
> voltage
> > for the FETs.  I'll only know if it works well enough once I put a scope
on
> > the running system.
> >
> > This is an example of where I'm not sure I see any value in ever
connecting
> > the two DC grounds together.  As long as there isn't a return path for
the
> > high voltage DC through any part of the instrument bus DC circuit it
> > doesn't
> > matter if the high voltage DC ground became completely disconnected.
> But
> > connect both of those DC grounds to Earth (metal cabinet etc) and now
the

Re: [Emc-users] Grounding

[Chris Albertson]

On Sat, Jul 14, 2018 at 1:14 PM Gene Heskett  wrote:

>
> Nope, and any current flowing out is matched by a current coming back,
> and when they add at a distance, they are essentially canceling because
> one matches the other but has an opposite sign.
>

Yes of course this is true.  But it is true if the wires are twisted 1, 4
or 16 times per inch.   Why does twist help?

OK I just figured it out.  if you look at the e-feild at a point some
distance from the wire pair and the pair is twisted you can integrate the
field in the direction of the wire (in a plane parallel to the cable and
e-feild at d is truly zero.  It is way hard to symbolically but way easy
using numeric integration.  The results are pretty dramatic.   I can see
why every new kind of data cable uses this.


Chris Albertson
Redondo Beach, California
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Re: [Emc-users] Grounding

[Gene Heskett]

On Saturday 14 July 2018 14:40:24 Chris Albertson wrote:

> On Sat, Jul 14, 2018 at 10:26 AM Gene Heskett  
wrote:
> > On Saturday 14 July 2018 11:57:10 Jon Elson wrote:
> >
> > Preferably as a twisted pair so the radiation of noise largely
> > cancels at 2x the twist rate distance or more. A tight twist = less
> > radiated noise.
>
> No doubt twisting helps, but I have not seen a derivation of the above
> 2X the twist rule.
>
You could say thats a rule derived from my own observations on a scope, 
noise coupling is usually less than 10% of that measured when the two 
twisted pairs cross each other at right angles when the separation is 
about 2x the twist rate, and should not be observable without very 
careful scope trigger settings by the time the separation is 5x the 
twist rate.

> On the other hand if you simply use zip cord, with parallel conductors
> the equation for the electric field on the plane perpendicular to the
> current is easy to derive. (Note that zip cord and a tightly waisted
> pair are identical if you look only on the "cut plane")  The 2D
> electric field  is simply the field created by one wire (simple
> inverse square law)  added on the other and it basically goes to near
> zero after 8X the center to center distance of the wires.  I always
> figured that twisting was just a good way to minimize the center to
> center distance.

It does better than that since the current going out is matched by the 
opposing current coming back (if there are no loops), and they rather 
quickly cancel each other out.
> But it could work out that 2X the twist pitch work
> s out the same 
> because small wires have both a higher twist and smaller center to
> center distance.
>
>
> I wonder if the twist actually does anything other then just hold the
> pair of wires closer together?I think  it might but I have never
> seen a mathematical derivation.   The 2D slice case is easy using only
> high school level math but a full analysis of the 3D cable might be
> much harder.

I think the old ARRL "Ham Book" has a formula for that. I was going to 
see about it, but looking up at the shelves above me, all I see ATM is 
an old ITT #5, and I can't recall if its in there someplace in its 1k+ 
pages or not.

> It might be that the twisting is just a mechanical thing and a way to
> ensure that wire pairs in a cable bundle are never parallel with each
> other and can't capacitively couple.
>
> Has anyone tried to measure the inductance of a twisted pair.   Then
> twist it more and re-measure.   I don't find any difference at all. 
> But perhaps My measurement technique is wrong.
>
> My conclusion is that we twist wires only for two reasons (1) to keep
> then closely spaced and (2) to make the path "bumpy" so it is
> impossible to lay parallel with anything else.   So the effect is
> mechanical not electrical.
>
> I could be wrong, but I've never seen mathematical proof.
>
> Also when you think about voltages on the grounded return wires, some
> people do forget that impedance is a complex number, we are not
> dealing with a special case of a constant DC voltage and a resistive
> load.

Nope, and any current flowing out is matched by a current coming back, 
and when they add at a distance, they are essentially canceling because 
one matches the other but has an opposite sign.

> You do either want to run all grounds to one and only one common point
> or galvanically isolated the systems that you interconnect. In the
> machine tool world many systems choose Galvanic isolation using either
> opt-iolators or transformers.  For a large distributed system
> isolation is easier.

And both methods insert bandwidth limitations that can muck up the 
feedback, playing hell with the Nyquist charts and subsequent stability 
margins.

-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Grounding

[Chris Albertson]

>From a safety point of view.  It is best to follow rules from local safety
labs be it in the US or EU.   Basically if you have a metal cabinet with AC
power inside The cabinet MUST be grounded to the earth pin on the power
socket and there are rules about using a dedicated screw (not used for
other purposes) and close to the power entrance.

If you don't like the this then the other option is "double insulated"
design which mostly means a non-conductive cabinet made from perhaps ABS
plastic.

There is good reason to tie you DC ground to safety ground at one point,
even if you use a 1M resister to do this.   Many times (especially with
vacuum tube circuits but in other cases too) there are leakage paths and a
ground left floating can float up to a high voltage.  So many times we find
some kind of RC circuit used, but more commonly a simpl wire inside the
power supply.

The idea is that is must remain safe even AFTER is major failure such as
insulation melting off an overloaded wire because of a fire.

You will NEVER think of everything yourself, so just follow the rules.
They are the result of 100 years of world-wide experience.

Most consumer products we buy today use double insulation.  But if you are
using a metal external housing, double insulation is complex

The best plan is to pretend you are actually going to SELL the machines you
are wiring up.  Keep is "legal" in both the US and EU and you are OK.
 There is a strong temptation to say "It is just my own toys in my own
house and I never plan to apply for a UL Lab sticker so way bother with
their rules?"



On Sat, Jul 14, 2018 at 11:05 AM John Dammeyer 
wrote:

> The power supply cabinet I'm putting together for my Mill has a terminal
> strip with ground and 105VDC power (1500W) with one pair of terminals for
> each axis.   From that strip I run one pair to each Servo Drive.  From each
> Servo Drive a pair to the motor.  The encoder cables enter the Servo Drives
> on a different side of the board and will be not be run in parallel with
> the
> motor cables.  Stepper motor for the knee has its'  own power supply and it
> too runs separately  (power and ground) to the Gecko.  These high power
> supplies are all run with 220VAC through a separate contactor controlled by
> the ESTOP.
>
> The PMDX-126, the 24VDC and the PC/Monitor are also on a 220VAC circuit
> that
> is live from the Mill Master Switch.  The 24VDC supply is what I'd refer to
> as the instrument bus and it's used for a variety of controls like the
> control side of the STMBL Servo drive and 12V supply for the DRO..  It will
> share the DC ground with the PMDX-126 breakout board, PC USB and ultimately
> a series of CAN bus based controls for tool changer etc.
>
> I wanted to also run the 24V into a 15V regulator to provide power for the
> control side of the HP-UHU servo drives but here is where that pesky ground
> sneaks in again.  Connecting a 15V supply sourced from the instrument power
> that then runs the HP_UHU connects the Instrument power to the Servo Power
> ground.  The step/dir/error from the HP_UHU is optically isolated so I
> don't
> have to worry there.
>
> The Servo Power Transformer has a 12VAC winding which through a bridge
> gives
> me roughly 16V which is the better source for the 15V that not only is
> regulated down to 5V for the HP_UHU but also supplies the gate bias voltage
> for the FETs.  I'll only know if it works well enough once I put a scope on
> the running system.
>
> This is an example of where I'm not sure I see any value in ever connecting
> the two DC grounds together.  As long as there isn't a return path for the
> high voltage DC through any part of the instrument bus DC circuit it
> doesn't
> matter if the high voltage DC ground became completely disconnected.  But
> connect both of those DC grounds to Earth (metal cabinet etc) and now the
> potential for high voltage, through component failure running through the
> instrument circuit, to instrument ground to earth back up into high voltage
> ground is more likely.  And touching that high voltage now ungrounded
> section and perhaps the metal frame puts the body into the circuit.
>
> And yet if you have, say an audio amplifier or radio transmitter with both
> 48V and 5V that share a common ground a circuit failure usually smokes
> things.  But those are all usually in a sealed metal cabinet.A system
> where the various devices are placed around the equipment, not all in a box
> is different.
>
> John
>
>
>
> > -Original Message-
> > From: Jon Elson [mailto:el...@pico-systems.com]
> > Sent: July-14-18 8:57 AM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] Grounding
> >
> > On 07/14/2018 02:37 AM, Gene Heskett wrote:
&g

Re: [Emc-users] Grounding

[Chris Albertson]

On Sat, Jul 14, 2018 at 10:26 AM Gene Heskett  wrote:

> On Saturday 14 July 2018 11:57:10 Jon Elson wrote:
>
> Preferably as a twisted pair so the radiation of noise largely cancels at
> 2x the twist rate distance or more. A tight twist = less radiated noise.
>


No doubt twisting helps, but I have not seen a derivation of the above 2X
the twist rule.

On the other hand if you simply use zip cord, with parallel conductors the
equation for the electric field on the plane perpendicular to the current
is easy to derive. (Note that zip cord and a tightly waisted pair are
identical if you look only on the "cut plane")  The 2D electric field  is
simply the field created by one wire (simple inverse square law)  added on
the other and it basically goes to near zero after 8X the center to center
distance of the wires.  I always figured that twisting was just a good way
to minimize the center to center distance.

But it could work out that 2X the twist pitch works out the same because
small wires have both a higher twist and smaller center to center distance.


I wonder if the twist actually does anything other then just hold the pair
of wires closer together?I think  it might but I have never seen a
mathematical derivation.   The 2D slice case is easy using only high school
level math but a full analysis of the 3D cable might be much harder.

It might be that the twisting is just a mechanical thing and a way to
ensure that wire pairs in a cable bundle are never parallel with each other
and can't capacitively couple.

Has anyone tried to measure the inductance of a twisted pair.   Then twist
it more and re-measure.   I don't find any difference at all.  But perhaps
My measurement technique is wrong.

My conclusion is that we twist wires only for two reasons (1) to keep then
closely spaced and (2) to make the path "bumpy" so it is impossible to lay
parallel with anything else.   So the effect is mechanical not electrical.

I could be wrong, but I've never seen mathematical proof.

Also when you think about voltages on the grounded return wires, some
people do forget that impedance is a complex number, we are not dealing
with a special case of a constant DC voltage and a resistive load.

You do either want to run all grounds to one and only one common point or
galvanically isolated the systems that you interconnect. In the machine
tool world many systems choose Galvanic isolation using either opt-iolators
or transformers.  For a large distributed system isolation is easier.



-- 

Chris Albertson
Redondo Beach, California
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Re: [Emc-users] Grounding

[John Dammeyer]

The power supply cabinet I'm putting together for my Mill has a terminal
strip with ground and 105VDC power (1500W) with one pair of terminals for
each axis.   From that strip I run one pair to each Servo Drive.  From each
Servo Drive a pair to the motor.  The encoder cables enter the Servo Drives
on a different side of the board and will be not be run in parallel with the
motor cables.  Stepper motor for the knee has its'  own power supply and it
too runs separately  (power and ground) to the Gecko.  These high power
supplies are all run with 220VAC through a separate contactor controlled by
the ESTOP.

The PMDX-126, the 24VDC and the PC/Monitor are also on a 220VAC circuit that
is live from the Mill Master Switch.  The 24VDC supply is what I'd refer to
as the instrument bus and it's used for a variety of controls like the
control side of the STMBL Servo drive and 12V supply for the DRO..  It will
share the DC ground with the PMDX-126 breakout board, PC USB and ultimately
a series of CAN bus based controls for tool changer etc.

I wanted to also run the 24V into a 15V regulator to provide power for the
control side of the HP-UHU servo drives but here is where that pesky ground
sneaks in again.  Connecting a 15V supply sourced from the instrument power
that then runs the HP_UHU connects the Instrument power to the Servo Power
ground.  The step/dir/error from the HP_UHU is optically isolated so I don't
have to worry there.  

The Servo Power Transformer has a 12VAC winding which through a bridge gives
me roughly 16V which is the better source for the 15V that not only is
regulated down to 5V for the HP_UHU but also supplies the gate bias voltage
for the FETs.  I'll only know if it works well enough once I put a scope on
the running system.

This is an example of where I'm not sure I see any value in ever connecting
the two DC grounds together.  As long as there isn't a return path for the
high voltage DC through any part of the instrument bus DC circuit it doesn't
matter if the high voltage DC ground became completely disconnected.  But
connect both of those DC grounds to Earth (metal cabinet etc) and now the
potential for high voltage, through component failure running through the
instrument circuit, to instrument ground to earth back up into high voltage
ground is more likely.  And touching that high voltage now ungrounded
section and perhaps the metal frame puts the body into the circuit.

And yet if you have, say an audio amplifier or radio transmitter with both
48V and 5V that share a common ground a circuit failure usually smokes
things.  But those are all usually in a sealed metal cabinet.A system
where the various devices are placed around the equipment, not all in a box
is different.

John



> -Original Message-
> From: Jon Elson [mailto:el...@pico-systems.com]
> Sent: July-14-18 8:57 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding
> 
> On 07/14/2018 02:37 AM, Gene Heskett wrote:
> > Not exactly 100% correct John. High frequencies are
> > generally carried only by current flow at the skin of a
> > conductor. And the large conductor, while having some rise
> > in impedance, is still the better conductor because the
> > smaller wire has far less surface skin area, raising both
> > its impedance and its ohmic effects faster than the big wire.
> There's also loops.  Bundling the power supply and ground
> return close together minimizes inductance.  Having the
> supply and return form a big loop increases inductance, and
> can cause greater noise as well as radiation of EMI.  So, in
> general, you want the return wires to follow the supply
> wires closely.
> 
> Jon
> 
>

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Re: [Emc-users] Grounding

[Gene Heskett]

On Saturday 14 July 2018 11:57:10 Jon Elson wrote:

> On 07/14/2018 02:37 AM, Gene Heskett wrote:
> > Not exactly 100% correct John. High frequencies are
> > generally carried only by current flow at the skin of a
> > conductor. And the large conductor, while having some rise
> > in impedance, is still the better conductor because the
> > smaller wire has far less surface skin area, raising both
> > its impedance and its ohmic effects faster than the big wire.
>
> There's also loops.  Bundling the power supply and ground
> return close together minimizes inductance.  Having the
> supply and return form a big loop increases inductance, and
> can cause greater noise as well as radiation of EMI.  So, in
> general, you want the return wires to follow the supply
> wires closely.
>
> Jon
>
Preferably as a twisted pair so the radiation of noise largely cancels at 
2x the twist rate distance or more. A tight twist = less radiated noise.

-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Grounding

[Jon Elson]

On 07/14/2018 02:37 AM, Gene Heskett wrote:
Not exactly 100% correct John. High frequencies are 
generally carried only by current flow at the skin of a 
conductor. And the large conductor, while having some rise 
in impedance, is still the better conductor because the 
smaller wire has far less surface skin area, raising both 
its impedance and its ohmic effects faster than the big wire.
There's also loops.  Bundling the power supply and ground 
return close together minimizes inductance.  Having the 
supply and return form a big loop increases inductance, and 
can cause greater noise as well as radiation of EMI.  So, in 
general, you want the return wires to follow the supply 
wires closely.


Jon

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Re: [Emc-users] Grounding

[Gene Heskett]

On Saturday 14 July 2018 03:13:49 John Dammeyer 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.
>
> And then there's impedance.  That thick conductor that measure almost
> zero ohms with a meter compared to 0.5 ohms of the thin one suddenly
> has a very high impendence to high frequency noise bursts.   So the
> high current spikes don't go through the thick but instead through the
> thin.
>
> John
>
Not exactly 100% correct John. High frequencies are generally carried 
only by current flow at the skin of a conductor.  And the large 
conductor, while having some rise in impedance, is still the better 
conductor because the smaller wire has far less surface skin area, 
raising both its impedance and its ohmic effects faster than the big 
wire.

>
> --
> 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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-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Grounding

[Gene Heskett]

On Saturday 14 July 2018 01:22:12 Chris Albertson wrote:

> 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.
>
Just one of the reasons I've incorporated a power strip in the AC wiring 
of one of my later builds. That way I have both a common power switch, 
and just one 3rd pin connecting back to the common-ized point in the the 
electrical service via the 4 plex on the wall

With care, and cheap two wire extension cords cut up for power wiring, I 
can stop 99% of the ground loops. I've taken a somewhat different tack 
with power switching on the Sheldon, which has a separate 250 volt 
single phase service cable, possible since I have a surplus of gpio's in 
the 7i90, I've used 2 gpio's to switch a couple 40 amp SSR's controlled 
by the F2 button, so if F2 is not enabled, only the pi and the 
interfaces and a 4000 lumen led lamp above the lathe bed are left on. 
All motor power including the spindle vfd are shut down.  The lamp draws 
maybe 18 watts, so it and the pi is on unless I kill that 125 volt leg 
with a toggle switch in a 4 plex mounted on the stick that used to hold 
the drum switch.  Makes a good night light. :-)

> > 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
> >
> > 
> >-- 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



-- 
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] Grounding

[John Dammeyer]

> >  > 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.
> 

And then there's impedance.  That thick conductor that measure almost zero ohms 
with a meter compared to 0.5 ohms of the thin one suddenly has a very high 
impendence to high frequency noise bursts.   So the high current spikes don't 
go through the thick but instead through the thin.

John



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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
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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
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designed for the especial use of mechanical geniuses, daredevils and
lunatics."
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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 m

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] 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 

Re: [Emc-users] Grounding

[Erik Christiansen]

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]

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 common
components
in machine controls.

Dave


On 7/12/2018 4:31 PM, John Dammeyer wrote:

Thanks,
I'm not concerned about the AC ground side of things.

Internet searches on this subject generally seem to agree that DC ground
doesn't and shouldn't be conn

Re: [Emc-users] Grounding

[Gene Heskett]

On Thursday 12 July 2018 17:31:17 andy pugh wrote:

> On 12 July 2018 at 20:12, 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.
>
> I think it might be a good idea to keep the high voltage DC bus
> separated from Signal Ground. I don't know this for a fact and I am
> only mentioning it because the other replies seem to be glossing over
> that part of the question.

So I did Andy, but the connection there cannot be opened if you are using 
one of Jon's pwm-servo amps to drive the spindle, which I am. In that 
driver, ground, the negative end of a 126 volt multi-amp (around 20) 
supply, and the common of the pwm signal that controls it are one and 
the same terminal on that driver. I too would like to see some isolation 
there, but it does in fact work well if the rest of the grounding is 
solid. Twice, as thats essentially the same circuit in The Little 
Monster 7x12.

-- 
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] Grounding

[John Dammeyer]

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 common
> components
> in machine controls.
> 
> Dave
> 
> 
> On 7/12/2018 4:31 PM, John Dammeyer wrote:
> > Thanks,
> > I'm not concerned about the AC ground side of things.
> >
> > Internet searches on this subject generally seem to agree that DC ground
> > doesn't and shouldn't be connected to the metal frame earth ground at
> any
> > point.  If it is either through a capacitor  or a 100 ohm resistor.
> >
> > I remember many years ago working on Trim & Form Equipment in The
> > Netherlands we ran into problems with the PCs used for the User interface
> > (Pentium 386) had the power supply internally connect the DC ground to
> the
> > frame.  Caused all sorts of havoc.  I don't remember what the solution was.
> >
> > Jeff Birt also suggests not connecting DC ground to the frame on one
> group's
> > posting.   Obviously there may be Break Out Boards that break this rule but
> > then they may also be made by hobbiests who h

Re: [Emc-users] Grounding

[Dave Cole]

Agreed, I have never seen a high voltage DC drive bus leg connected to 
ground.  That could cause all kinds of problems!


Dave

On 7/12/2018 5:31 PM, andy pugh wrote:

On 12 July 2018 at 20:12, 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.

I think it might be a good idea to keep the high voltage DC bus
separated from Signal Ground. I don't know this for a fact and I am
only mentioning it because the other replies seem to be glossing over
that part of the question.



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Re: [Emc-users] Grounding

[Dave Cole]

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 common components 
in machine controls.


Dave


On 7/12/2018 4:31 PM, John Dammeyer wrote:

Thanks,
I'm not concerned about the AC ground side of things.

Internet searches on this subject generally seem to agree that DC ground
doesn't and shouldn't be connected to the metal frame earth ground at any
point.  If it is either through a capacitor  or a 100 ohm resistor.

I remember many years ago working on Trim & Form Equipment in The
Netherlands we ran into problems with the PCs used for the User interface
(Pentium 386) had the power supply internally connect the DC ground to the
frame.  Caused all sorts of havoc.  I don't remember what the solution was.

Jeff Birt also suggests not connecting DC ground to the frame on one group's
posting.   Obviously there may be Break Out Boards that break this rule but
then they may also be made by hobbiests who have gone into the machine
controls business and don't really know.

John


-Original Message-
From: Gene Heskett [mailto:ghesk...@shentel.net]
Sent: July-12-18 1:16 PM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Grounding

On Thursday 12 July 2018 15:12:40 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.

John

Generally speaking its a good idea to have then all come together at a
common  bolt, also called a star ground.  The bolt is the star center
point and all other ground circuits radiate from it..  The machines
frame ground should connect to this common point, and it should be
ohm-meter verified that there is not another connection between that
bolt and the machine frame if the frame grounding wire is disconnected.

This means that its good practice to have shielded motor and sensor
cables, but the shield is cut short, not connected at the frame end of
the run.  If there is another connection, then you have a ground loop
which can inject several tens of volts of noise back into the interface
card, potentially damaging it. Or worse, inject noise into a stepper
drive resulting in a gradual drift of the homed point which=wrecked, out
of spec parts.

IOW, the motor power supplies should be the only circuit that connects to
the 3rd pin of the power cord, and that 3rd pin should be connected only
to that common bolt. Do not connect this 3rd wire to the supplies, but
to this bolt, and take a separate wire from the bolt back to the ground
symbol on the PSU's. And if that ground has continuity to the shell of
the PSU, mount it insulated to open that ground loop. A piece of pcb
material, glued to the chassis, and the PSU's glued to the pcb should do
it nicely.

IHTH.

--
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
  soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>




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Re: [Emc-users] Grounding

[andy pugh]

On 12 July 2018 at 20:12, 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.

I think it might be a good idea to keep the high voltage DC bus
separated from Signal Ground. I don't know this for a fact and I am
only mentioning it because the other replies seem to be glossing over
that part of the question.

-- 
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

[John Dammeyer]

HI Dave,
The problem comes in when some devices ground the DC to the frame internally.  
I don't see an issue with grounding the DC bus bar to earth ground at one 
point.  
I'm just looking at "standard practices" which all suggest no connection or at 
only one spot.
Thanks
John


> -Original Message-
> From: Dave Cole [mailto:linuxcncro...@gmail.com]
> Sent: July-12-18 1:26 PM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Grounding
> 
> Normally, a single ground point is established in the cabinet and all of
> the grounds tie to that one point.
> 
> The same point is also tied power line ground.
> 
> The multi hole bus bars they sell for use in a AC power breaker boxes
> work well for this.
> Every big box home store will have a selection of them.
> 
> I screw that to the panel back plane and run all of the ground wires to
> that block.� That grounds the steel panel, backplane, and everything in it.
> The incoming power ground wire is also connected to the same bus bar.
> 
> Dave
> 
> On 7/12/2018 3:12 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.
> >
> > John
> >
> >
> >
> > --
> > 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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> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
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Re: [Emc-users] Grounding

[John Dammeyer]

Thanks,
I'm not concerned about the AC ground side of things.  

Internet searches on this subject generally seem to agree that DC ground
doesn't and shouldn't be connected to the metal frame earth ground at any
point.  If it is either through a capacitor  or a 100 ohm resistor.

I remember many years ago working on Trim & Form Equipment in The
Netherlands we ran into problems with the PCs used for the User interface
(Pentium 386) had the power supply internally connect the DC ground to the
frame.  Caused all sorts of havoc.  I don't remember what the solution was.

Jeff Birt also suggests not connecting DC ground to the frame on one group's
posting.   Obviously there may be Break Out Boards that break this rule but
then they may also be made by hobbiests who have gone into the machine
controls business and don't really know.

John

> -Original Message-
> From: Gene Heskett [mailto:ghesk...@shentel.net]
> Sent: July-12-18 1:16 PM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Grounding
> 
> On Thursday 12 July 2018 15:12:40 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.
> >
> > John
> 
> Generally speaking its a good idea to have then all come together at a
> common  bolt, also called a star ground.  The bolt is the star center
> point and all other ground circuits radiate from it..  The machines
> frame ground should connect to this common point, and it should be
> ohm-meter verified that there is not another connection between that
> bolt and the machine frame if the frame grounding wire is disconnected.
> 
> This means that its good practice to have shielded motor and sensor
> cables, but the shield is cut short, not connected at the frame end of
> the run.  If there is another connection, then you have a ground loop
> which can inject several tens of volts of noise back into the interface
> card, potentially damaging it. Or worse, inject noise into a stepper
> drive resulting in a gradual drift of the homed point which=wrecked, out
> of spec parts.
> 
> IOW, the motor power supplies should be the only circuit that connects to
> the 3rd pin of the power cord, and that 3rd pin should be connected only
> to that common bolt. Do not connect this 3rd wire to the supplies, but
> to this bolt, and take a separate wire from the bolt back to the ground
> symbol on the PSU's. And if that ground has continuity to the shell of
> the PSU, mount it insulated to open that ground loop. A piece of pcb
> material, glued to the chassis, and the PSU's glued to the pcb should do
> it nicely.
> 
> IHTH.
> 
> --
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page <http://geneslinuxbox.net:6309/gene>
> 
>

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Re: [Emc-users] Grounding

[Dave Cole]

Normally, a single ground point is established in the cabinet and all of 
the grounds tie to that one point.


The same point is also tied power line ground.

The multi hole bus bars they sell for use in a AC power breaker boxes 
work well for this.

Every big box home store will have a selection of them.

I screw that to the panel back plane and run all of the ground wires to 
that block.  That grounds the steel panel, backplane, and everything in it.

The incoming power ground wire is also connected to the same bus bar.

Dave

On 7/12/2018 3:12 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.
  
John
  
  
  
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Re: [Emc-users] Grounding

[Gene Heskett]

On Thursday 12 July 2018 15:12:40 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.
>
> John

Generally speaking its a good idea to have then all come together at a 
common  bolt, also called a star ground.  The bolt is the star center 
point and all other ground circuits radiate from it..  The machines 
frame ground should connect to this common point, and it should be 
ohm-meter verified that there is not another connection between that 
bolt and the machine frame if the frame grounding wire is disconnected.

This means that its good practice to have shielded motor and sensor 
cables, but the shield is cut short, not connected at the frame end of 
the run.  If there is another connection, then you have a ground loop 
which can inject several tens of volts of noise back into the interface 
card, potentially damaging it. Or worse, inject noise into a stepper 
drive resulting in a gradual drift of the homed point which=wrecked, out 
of spec parts.

IOW, the motor power supplies should be the only circuit that connects to 
the 3rd pin of the power cord, and that 3rd pin should be connected only 
to that common bolt. Do not connect this 3rd wire to the supplies, but 
to this bolt, and take a separate wire from the bolt back to the ground 
symbol on the PSU's. And if that ground has continuity to the shell of 
the PSU, mount it insulated to open that ground loop. A piece of pcb 
material, glued to the chassis, and the PSU's glued to the pcb should do 
it nicely.

IHTH.

-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Grounding Issues

[John Thornton]

Just looking through my supplies and I find a Hevi-Duty 240v -120v 
0.95KVA transformer... gotta make room for it in the VFD cabinet and get 
rid if the 120v plug in.

JT

On 12/25/2015 10:51 AM, Ed wrote:
> On 12/25/2015 04:59 AM, John Thornton wrote:
>> Dave, the AD filter came in yesterday and I'm fitting it to the machine
>> now. I had to relocate the VFD to the side of the cabinet due to the
>> additional height. I also ordered a smaller filter for the DC power
>> supply. I wonder if I should put that filter at the beginning of the AC
>> circuit or just ahead of the bridge rectifier? I'm still thinking of
>> changing to a 4 wire system and pull the 120 off of one leg of the 240
>> so I have a single power source for the whole machine.
>>
>> JT
>>
> On my CHNC I have a 500VA control transformer to drop 240V to 120V for
> the computer and the monitor. That way I do not have to worry if I have
> pick the wild phase or not.
>
> Ed.
>
>
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Re: [Emc-users] Grounding Issues

[Stephen Dubovsky]

I run my pc and monitor off the 240. Almost all are universal input
nowadays (some pcs require a switch) and have isolated supplies.

On Dec 25, 2015 12:18 PM, "Ed"  wrote:
> On my CHNC I have a 500VA control transformer to drop 240V to 120V for
> the computer and the monitor. That way I do not have to worry if I have
> pick the wild phase or not.
>
> Ed.
>
>
>
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Re: [Emc-users] Grounding Issues

[John Thornton]

I just realized that putting the control transformer in and I would not 
need to pull a neutral for my 120v side! Now to get off $40 for fuses 
for the dang thing.

JT

On 12/25/2015 12:45 PM, John Thornton wrote:
> Just looking through my supplies and I find a Hevi-Duty 240v -120v
> 0.95KVA transformer... gotta make room for it in the VFD cabinet and get
> rid if the 120v plug in.
>
> JT
>
> On 12/25/2015 10:51 AM, Ed wrote:
>> On 12/25/2015 04:59 AM, John Thornton wrote:
>>> Dave, the AD filter came in yesterday and I'm fitting it to the machine
>>> now. I had to relocate the VFD to the side of the cabinet due to the
>>> additional height. I also ordered a smaller filter for the DC power
>>> supply. I wonder if I should put that filter at the beginning of the AC
>>> circuit or just ahead of the bridge rectifier? I'm still thinking of
>>> changing to a 4 wire system and pull the 120 off of one leg of the 240
>>> so I have a single power source for the whole machine.
>>>
>>> JT
>>>
>> On my CHNC I have a 500VA control transformer to drop 240V to 120V for
>> the computer and the monitor. That way I do not have to worry if I have
>> pick the wild phase or not.
>>
>> Ed.
>>
>>
>> --
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Re: [Emc-users] Grounding Issues

[Dave Cole]

On 12/25/2015 5:59 AM, John Thornton wrote:
> I wonder if I should put that filter at the beginning of the AC
> circuit or just ahead of the bridge rectifier?

I think I would put it prior to the transformer that feeds the bridge 
rectifier, if that makes sense.

That AD VFDs tend to broadcast serious noise back into the AC line.   
I've seen the VFD noise go right through AC to DC power supplies.

Dave



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Re: [Emc-users] Grounding Issues

[John Thornton]

The bridge rectifier is connected to 120v so no transformer is there... 
not sure how it gets 190vdc out of 120vac but it does. Now to find some 
fuses for it... may be Tuesday before I can use that.

JT

On 12/25/2015 12:34 PM, Dave Cole wrote:
> On 12/25/2015 5:59 AM, John Thornton wrote:
>> I wonder if I should put that filter at the beginning of the AC
>> circuit or just ahead of the bridge rectifier?
> I think I would put it prior to the transformer that feeds the bridge
> rectifier, if that makes sense.
>
> That AD VFDs tend to broadcast serious noise back into the AC line.
> I've seen the VFD noise go right through AC to DC power supplies.
>
> Dave
>
>
>
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Re: [Emc-users] Grounding Issues

[Ed]

On 12/25/2015 04:59 AM, John Thornton wrote:
> Dave, the AD filter came in yesterday and I'm fitting it to the machine
> now. I had to relocate the VFD to the side of the cabinet due to the
> additional height. I also ordered a smaller filter for the DC power
> supply. I wonder if I should put that filter at the beginning of the AC
> circuit or just ahead of the bridge rectifier? I'm still thinking of
> changing to a 4 wire system and pull the 120 off of one leg of the 240
> so I have a single power source for the whole machine.
>
> JT
>
On my CHNC I have a 500VA control transformer to drop 240V to 120V for 
the computer and the monitor. That way I do not have to worry if I have 
pick the wild phase or not.

Ed.


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Re: [Emc-users] Grounding Issues

[John Thornton]

Dave, the AD filter came in yesterday and I'm fitting it to the machine 
now. I had to relocate the VFD to the side of the cabinet due to the 
additional height. I also ordered a smaller filter for the DC power 
supply. I wonder if I should put that filter at the beginning of the AC 
circuit or just ahead of the bridge rectifier? I'm still thinking of 
changing to a 4 wire system and pull the 120 off of one leg of the 240 
so I have a single power source for the whole machine.

JT

On 12/25/2015 12:53 AM, Dave Cole wrote:
> John,
>
> Do you have an AC filter on the power lines feeding the GS2 drive?
>
> If not, go to Automation Direct and buy the filter they specify for that
> drive.   You will not regret the purchase.
>
> Don't buy a cheap filter.   The ones that AD has now are good filters.
> I've had similar issues.
>
> Dave
>
> On 12/20/2015 8:20 AM, John Thornton wrote:
>> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>> all the Anilam controls a while back. I've retained the drives and power
>> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>>From the get go I've had problems with the electronics on this machine.
>> The VFD is controlled by modbus via the gs2 component. The VFD gets
>> reset to default parameters all the time from noise on the modbus. the
>> 5i25 get sserial errors. The sserial errors are so bad now it won't even
>> move an axis. The spindle works ok. The power supply is a simple bridge
>> rectifier with a huge blue cap and a large power resistor across the cap.
>>
>> Peter keeps telling me it's a grounding issue so where do I start
>> looking and what do I need to do?
>>
>> Thanks
>> JT
>>
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Re: [Emc-users] Grounding Issues

[Bertho Stultiens]

On 12/25/2015 11:25 PM, John Thornton wrote:
> There is no transformer in there...

Ah, sorry about that...
The second variable should then be considered, mains tolerance.

The usual tolerance of the mains line is between +20% and -30%. If that
seems large, it is. If you ask the company what you may expect, they
will be very reluctant to give you an answer. The point is that the
mains is geared to deliver a resonably constant frequency at the cost of
voltage accuracy.

The tolerance depends on topology and differs from where you are located
from the nearest transformer, how many connections are shared on the
transformer(s) and how the line is loaded along the way when it gets
home to you.


I actually measured the mains line at work once over a period of 7 days
(15s interval) because we were having trouble with a mercury lamp that
was not constant in intensity. The delivery company did not wish to be
bound to any "hard" values and said that there is no guarantee for the
actual voltage. They try to keep it within +/-15%, but cannot guarantee
it due to line topology.

The measurements I took showed very nicely how the grid "wakes up" in
the morning and "enters sleep" in the evening. The voltage starts high
early and starts to drop and jumps up whenever the delivery company adds
a generator to compensate. The opposite happens late in the evening. The
variability was arround the +/-15%.

-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Grounding Issues

[Ed]

On 12/25/2015 12:59 PM, John Thornton wrote:
> I just realized that putting the control transformer in and I would not
> need to pull a neutral for my 120v side! Now to get off $40 for fuses
> for the dang thing.
>
> JT
>
That is the main reason in industry, fewer wires and mains isolation.

I cut off the plug on a power strip and wired that directly to the 
control transformer.

Ed.


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Re: [Emc-users] Grounding Issues

[Gene Heskett]

On Friday 25 December 2015 13:48:52 John Thornton wrote:

> The bridge rectifier is connected to 120v so no transformer is
> there... not sure how it gets 190vdc out of 120vac but it does. Now to
> find some fuses for it... may be Tuesday before I can use that.
>
> JT

That is a puzzle John, the best DC I can get out of that with kcalc, 
assuming a perfect bridge rectifier feeding a capacitor input filter is 
179 volts & change.  Assuming a 127 volt, more or less standard AC input 
that is.

> On 12/25/2015 12:34 PM, Dave Cole wrote:
> > On 12/25/2015 5:59 AM, John Thornton wrote:
> >> I wonder if I should put that filter at the beginning of the AC
> >> circuit or just ahead of the bridge rectifier?
> >
> > I think I would put it prior to the transformer that feeds the
> > bridge rectifier, if that makes sense.
> >
> > That AD VFDs tend to broadcast serious noise back into the AC line.
> > I've seen the VFD noise go right through AC to DC power supplies.
> >
> > Dave
> >
> >
> >
> > 
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 soap, ballot, jury, and ammo. Please use in that order."
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Re: [Emc-users] Grounding Issues

[John Thornton]

There is no transformer in there...

On 12/25/2015 4:19 PM, Bertho Stultiens wrote:
> On 12/25/2015 11:05 PM, Gene Heskett wrote:
>>> The bridge rectifier is connected to 120v so no transformer is
>>> there... not sure how it gets 190vdc out of 120vac but it does. Now to
>>> find some fuses for it... may be Tuesday before I can use that.
>> That is a puzzle John, the best DC I can get out of that with kcalc,
>> assuming a perfect bridge rectifier feeding a capacitor input filter is
>> 179 volts & change.  Assuming a 127 volt, more or less standard AC input
>> that is.
> A transformer's output voltage is rated at the rated load. If you are
> not loading the transformer at the rated power, then you will usually
> see between 10% and 30% higher output voltage. The amount of increase
> depends on the quality of the transformer.
>
> So, the DC conversion at (almost) no load will be between 120 * sqrt(2)
> * 1.1 = 186V and 120 * sqrt(2) * 1.3 = 220V. Taking account for a 2..3V
> droop at the bridge-rectifier would mean anything between 183...217V
> would be quite normal at 120V AC input.
>
>


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Re: [Emc-users] Grounding Issues

[John Dammeyer]

The AC voltage we talk about is called an RMS or Root Mean Square voltage.  

For example 10VDC across a 10 Ohm resistor results in 1A DC current.  The
resistor will dissipate 10W  (IxV).

The RMS AC voltage is the equivalent to the DC voltage for power
calculations.  So 10VAC across the 10 Ohm resistor will also result in 1A
RMS.  But the power will be 10W.  Really handy to know that for choosing the
wattage of the power resistor.

But because the AC varies, it's both below, down to 0 and above, up to the
peak value.  The peak is calculated by multiplying the RMS value by the
square root of 2 or 1.414;  120V x 1.414 = 170V peak.  Given that the AC
line can surge up as high as 135V you have to design for 135 x 1.414 = 190V.

John Dammeyer


> -Original Message-
> From: John Thornton [mailto:j...@gnipsel.com]
> Sent: December-25-15 10:49 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding Issues
> 
> 
> The bridge rectifier is connected to 120v so no transformer is there...
> not sure how it gets 190vdc out of 120vac but it does. Now to find some
> fuses for it... may be Tuesday before I can use that.
> 
> JT
> 
> On 12/25/2015 12:34 PM, Dave Cole wrote:
> > On 12/25/2015 5:59 AM, John Thornton wrote:
> >> I wonder if I should put that filter at the beginning of the AC
> >> circuit or just ahead of the bridge rectifier?
> > I think I would put it prior to the transformer that feeds the bridge
> > rectifier, if that makes sense.
> >
> > That AD VFDs tend to broadcast serious noise back into the AC line.
> > I've seen the VFD noise go right through AC to DC power supplies.
> >
> > Dave
> >
> >
> >
> >

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> 
>

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Re: [Emc-users] Grounding Issues

[John Thornton]

I have my own personal pad mounted transformer, all underground wire 
back in the woods. My memory might be wrong about the voltage... can't 
check it now because I can't get the 5i25 to come on line.

JT

On 12/25/2015 4:48 PM, Bertho Stultiens wrote:
> On 12/25/2015 11:25 PM, John Thornton wrote:
>> There is no transformer in there...
> Ah, sorry about that...
> The second variable should then be considered, mains tolerance.
>
> The usual tolerance of the mains line is between +20% and -30%. If that
> seems large, it is. If you ask the company what you may expect, they
> will be very reluctant to give you an answer. The point is that the
> mains is geared to deliver a resonably constant frequency at the cost of
> voltage accuracy.
>
> The tolerance depends on topology and differs from where you are located
> from the nearest transformer, how many connections are shared on the
> transformer(s) and how the line is loaded along the way when it gets
> home to you.
>
>
> I actually measured the mains line at work once over a period of 7 days
> (15s interval) because we were having trouble with a mercury lamp that
> was not constant in intensity. The delivery company did not wish to be
> bound to any "hard" values and said that there is no guarantee for the
> actual voltage. They try to keep it within +/-15%, but cannot guarantee
> it due to line topology.
>
> The measurements I took showed very nicely how the grid "wakes up" in
> the morning and "enters sleep" in the evening. The voltage starts high
> early and starts to drop and jumps up whenever the delivery company adds
> a generator to compensate. The opposite happens late in the evening. The
> variability was arround the +/-15%.
>


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Re: [Emc-users] Grounding Issues

[Gene Heskett]

On Friday 25 December 2015 13:59:32 John Thornton wrote:

> I just realized that putting the control transformer in and I would
> not need to pull a neutral for my 120v side! Now to get off $40 for
> fuses for the dang thing.
>
> JT

Correct, you can use either side as neutral, or even, if it has a 
centertap on that winding, ground it to earth and feed a 63.5 volt AC 
from the ends of the winding up to each side of the monitor and 
computers duplex socket.  Thats still 127 volts AC across the cpu & 
monitor. If the supplies in both are clean as far as ground leakage, 
you'll be, as we used to say when putting Titan rockets together, fat, 
dumb and happy.  The fat actually stood for factory acceptance tested.
>
> On 12/25/2015 12:45 PM, John Thornton wrote:
> > Just looking through my supplies and I find a Hevi-Duty 240v -120v
> > 0.95KVA transformer... gotta make room for it in the VFD cabinet and
> > get rid if the 120v plug in.
> >
> > JT
> >
> > On 12/25/2015 10:51 AM, Ed wrote:
> >> On 12/25/2015 04:59 AM, John Thornton wrote:
> >>> Dave, the AD filter came in yesterday and I'm fitting it to the
> >>> machine now. I had to relocate the VFD to the side of the cabinet
> >>> due to the additional height. I also ordered a smaller filter for
> >>> the DC power supply. I wonder if I should put that filter at the
> >>> beginning of the AC circuit or just ahead of the bridge rectifier?
> >>> I'm still thinking of changing to a 4 wire system and pull the 120
> >>> off of one leg of the 240 so I have a single power source for the
> >>> whole machine.
> >>>
> >>> JT
> >>
> >> On my CHNC I have a 500VA control transformer to drop 240V to 120V
> >> for the computer and the monitor. That way I do not have to worry
> >> if I have pick the wild phase or not.
> >>
> >> Ed.
> >>
> >>
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Re: [Emc-users] Grounding Issues

[Bertho Stultiens]

On 12/25/2015 11:05 PM, Gene Heskett wrote:
>> The bridge rectifier is connected to 120v so no transformer is
>> there... not sure how it gets 190vdc out of 120vac but it does. Now to
>> find some fuses for it... may be Tuesday before I can use that.
> That is a puzzle John, the best DC I can get out of that with kcalc, 
> assuming a perfect bridge rectifier feeding a capacitor input filter is 
> 179 volts & change.  Assuming a 127 volt, more or less standard AC input 
> that is.

A transformer's output voltage is rated at the rated load. If you are
not loading the transformer at the rated power, then you will usually
see between 10% and 30% higher output voltage. The amount of increase
depends on the quality of the transformer.

So, the DC conversion at (almost) no load will be between 120 * sqrt(2)
* 1.1 = 186V and 120 * sqrt(2) * 1.3 = 220V. Taking account for a 2..3V
droop at the bridge-rectifier would mean anything between 183...217V
would be quite normal at 120V AC input.


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Re: [Emc-users] Grounding Issues

[Dave Cole]

John,

Do you have an AC filter on the power lines feeding the GS2 drive?

If not, go to Automation Direct and buy the filter they specify for that 
drive.   You will not regret the purchase.

Don't buy a cheap filter.   The ones that AD has now are good filters.   
I've had similar issues.

Dave

On 12/20/2015 8:20 AM, John Thornton wrote:
> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> all the Anilam controls a while back. I've retained the drives and power
> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>   From the get go I've had problems with the electronics on this machine.
> The VFD is controlled by modbus via the gs2 component. The VFD gets
> reset to default parameters all the time from noise on the modbus. the
> 5i25 get sserial errors. The sserial errors are so bad now it won't even
> move an axis. The spindle works ok. The power supply is a simple bridge
> rectifier with a huge blue cap and a large power resistor across the cap.
>
> Peter keeps telling me it's a grounding issue so where do I start
> looking and what do I need to do?
>
> Thanks
> JT
>
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Re: [Emc-users] Grounding Issues

[MC Cason]

   Those carbon fiber sections must have a conductive layer added, for 
lightning protection.  The Dreamliner uses a combination of wire meshes, 
and metal foils for grounding it's carbon fiber sections.



On 12/20/2015 08:50 PM, R.L. Wurdack wrote:
> Some of them tubes are Carbon fiber composite these days. Makes grounding
> more fun.
>> Don't get too carried away with Earth as the most important part of
>> grounding.  After all those big metal tubes that fly through the sky
>> aren't
>> connected to ground and they have all sorts of power systems from DC to AC
>> (if you can afford business class).
>




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github.com/mcason/Eagle3D



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Re: [Emc-users] Grounding Issues

[Bertho Stultiens]

On 12/21/2015 02:48 PM, andy pugh wrote:
>> Where did you get the filter from?
> search eBay for "Rasmi filter" and find one with the right number of
> phases and current rating for your system.
> 
> The suggestion from Bertho sounded to be worth a try too.

Yes, to expand slightly with all the filters being installed...

You must ensure that all mains power input is in phase when it goes
through separate filters (see below). Mains filters use T and Pi
constructs where a (capacitively coupled) common goes to earth.

If the filters are not connected with the phase-polarity in mind, then
you will have an earth point that will conduct current, due to the
phase-shift between the filters.

The same happens when you use transformers. The capacitive coupling in
your system may induce (large) currents if the power lines are not
entirely in phase.


The classic example is the computer with a printer. Touching the
computer and the printer-cable (when they are not connected) can have a
differential between them, and you get zapped. This happens when the
devices are not on the common earth. However, connecting the earth will
mean that there is an induced current in the earth between the devices,
which still may wreak havoc.

The "wisdom" people said in that case was: "put the plug in reversed".
That simple swapping of phase and neutral often solves this particular
common-mode problem because it will put both devices in phase.


Now, using multiple mains-filters can be a huge problem because the
common point (earth) of these filters may still be off due to load
imbalances (cos(phi) differences) and therefore carry current.

The best way to handle mains noise is to use one mains-filter, which
must be rated for the total load. Internal wiring and loads should be
carefully planned to prevent local phase-imbalances. Most local noise
sources are (relatively) high-frequency and are dampened with shielding
and ferrites on the wires.

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Re: [Emc-users] Grounding Issues

[andy pugh]

On 21 December 2015 at 13:15, John Thornton  wrote:

> Where did you get the filter from?

search eBay for "Rasmi filter" and find one with the right number of
phases and current rating for your system.

The suggestion from Bertho sounded to be worth a try too.

-- 
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Re: [Emc-users] Grounding Issues

[andy pugh]

On 21 December 2015 at 14:26, Bertho Stultiens  wrote:
>
> The "wisdom" people said in that case was: "put the plug in reversed".

Not possible with the infinitely superior[1] BS 1363 plugs and sockets.

[1] Apart from being very large, very ugly, and really bad to stand on
in bare feet.

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Re: [Emc-users] Grounding Issues

[Bertho Stultiens]

On 12/21/2015 03:34 PM, andy pugh wrote:
>> The "wisdom" people said in that case was: "put the plug in reversed".
> Not possible with the infinitely superior[1] BS 1363 plugs and sockets.

Agreed.

However, how many people have been able to connect the wires wrong? (not
counting the sealed cables)


> [1] Apart from being very large, very ugly, and really bad to stand on
> in bare feet.

Well, large, yes; ugly, yes; but bare feet?

I guess that working in the shop is a no-go on bare feet...

Then again, I'd prefer to use something more sturdy like
http://dk.rs-online.com/largeimages/R7249088-01.jpg which I actually may
stand on with bare feet without being afraid ;-)

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Re: [Emc-users] Grounding Issues

[John Thornton]

After sleeping on this for a bit my question is if I change the 220v to 
two hots and a neutral then string a ground wire across the floor (for 
testing) and wire the left cabinet to split out one phase and a neutral 
to run the 120v part do you think this would be worth the effort to try 
out? I'd rather try an experiment like that prior to trying to walk 
across my attic to string a ground to the 220v outlet. I have 12" of 
insulation  on top of 3.5" so walking is very difficult... actually 
finding a place to step is rather fun.

JT

On 12/20/2015 11:55 PM, Jon Elson wrote:
> On 12/20/2015 05:06 PM, John Thornton wrote:
>> Well it works fine till I plug in the VFD so I guess I'll have to rewire
>> the machine and my shop again :(
>>
>>
> Well, that is now very important information!  Just plugging
> in the VFD, without having it start the spindle motor causes
> the problem? Then you are probably right.  If you only had
> problems when the spindle was running, then the line
> reactors might help.
>
> I put a commercial line filter box on the VFD on my mill, I
> was having interference in a couple units, but only when the
> VFD was running the spindle.  The filter fixed it.
>
> Jon
>
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Re: [Emc-users] Grounding Issues

[John Thornton]

By robust, what do you mean?

JT

On 12/20/2015 6:44 PM, John Dammeyer wrote:
> John,
> I'd still take a close look at your existing system to see if it is robust.
>
>


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Re: [Emc-users] Grounding Issues

[John Thornton]

Kirk,

Where did you get the filter from?

JT

On 12/20/2015 11:44 AM, Kirk Wallace wrote:
> On 12/20/2015 05:20 AM, John Thornton wrote:
>> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>> all the Anilam controls a while back. I've retained the drives and power
>> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>>From the get go I've had problems with the electronics on this machine.
> I have had good results (noise on encoder lines) by adding mains filters
> to my VFD power inputs.
>
> The shiny box here:
> http://www.wallacecompany.com/cnc_lathe/HNC/00024-1a.jpg
>
> I suspect any switching power circuit might benefit from installing an
> input filter.
>


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Re: [Emc-users] Grounding Issues

[John Thornton]

Another update, Automation Direct has an EMI input filter designed for 
that drive that mounts under it so that is on order as well as a ferrite 
bracelet... Peter said it was a bracelet not a bead. At least knowing 
it's the VFD and not an unknown issue is a big relief for me. In any 
case I have a well grounded machine now :)

JT

On 12/20/2015 7:20 AM, John Thornton wrote:
> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> all the Anilam controls a while back. I've retained the drives and power
> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>   From the get go I've had problems with the electronics on this machine.
> The VFD is controlled by modbus via the gs2 component. The VFD gets
> reset to default parameters all the time from noise on the modbus. the
> 5i25 get sserial errors. The sserial errors are so bad now it won't even
> move an axis. The spindle works ok. The power supply is a simple bridge
> rectifier with a huge blue cap and a large power resistor across the cap.
>
> Peter keeps telling me it's a grounding issue so where do I start
> looking and what do I need to do?
>
> Thanks
> JT
>
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Re: [Emc-users] Grounding Issues

[John Dammeyer]

The addition of the VFD might just put an system that is on the edge of
being unstable over the edge.
John Dammeyer


> -Original Message-
> From: John Thornton [mailto:j...@gnipsel.com]
> Sent: December-21-15 3:15 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding Issues
> 
> 
> By robust, what do you mean?
> 
> JT
> 
> On 12/20/2015 6:44 PM, John Dammeyer wrote:
> > John,
> > I'd still take a close look at your existing system to see if it is
robust.
> >
> >
> 
> 
>

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Re: [Emc-users] Grounding Issues

[andy pugh]

On 21 December 2015 at 14:49, Bertho Stultiens  wrote:

[BS1363 Plugs]
>> [1] Apart from being very large, very ugly, and really bad to stand on
>> in bare feet.
>
> Well, large, yes; ugly, yes; but bare feet?

They seem well designed  lie on the ground with the pins poking upwards.
This tends to mainly cause problems in bedrooms with hairdriers.

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Re: [Emc-users] Grounding Issues

[John Thornton]

The VFD has been on that machine since the original conversion from 
Anilam to LinuxCNC. Hm2 has reported errors from time to time all along 
but never quit. Upgrading to 2.7 was the reason it now won't run when 
the VFD is plugged in due to a change in 2.7 that's a bit over reactive 
at this time. If I can get it to run even with the overly sensitive 
software then I'm good. I upgraded to 2.7 to use my new probe with an 
encoder input.

JT

On 12/21/2015 10:54 AM, John Dammeyer wrote:
> The addition of the VFD might just put an system that is on the edge of
> being unstable over the edge.
> John Dammeyer
>
>
>> -Original Message-
>> From: John Thornton [mailto:j...@gnipsel.com]
>> Sent: December-21-15 3:15 AM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Grounding Issues
>>
>>
>> By robust, what do you mean?
>>
>> JT
>>
>> On 12/20/2015 6:44 PM, John Dammeyer wrote:
>>> John,
>>> I'd still take a close look at your existing system to see if it is
> robust.
>>>
>>
>>
> 
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Re: [Emc-users] Grounding Issues

[Gregg Eshelman]

On 12/20/2015 4:06 PM, John Thornton wrote:
> Well it works fine till I plug in the VFD so I guess I'll have to rewire
> the machine and my shop again :(

VFD output directly to motor and adequate noise filtering upstream of 
the VFD?


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Re: [Emc-users] Grounding Issues

[Jon Elson]

On 12/20/2015 05:06 PM, John Thornton wrote:
> Well it works fine till I plug in the VFD so I guess I'll have to rewire
> the machine and my shop again :(
>
>
Well, that is now very important information!  Just plugging 
in the VFD, without having it start the spindle motor causes 
the problem? Then you are probably right.  If you only had 
problems when the spindle was running, then the line 
reactors might help.

I put a commercial line filter box on the VFD on my mill, I 
was having interference in a couple units, but only when the 
VFD was running the spindle.  The filter fixed it.

Jon

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Re: [Emc-users] Grounding Issues

[John Thornton]

Hi John,

You are correct I have a 220vac and a 120vac line coming into the 
machine. I didn't pull a 4 wire 220 line to those outlets in the shop so 
no neutral is there. If making a star ground doesn't fix the issue then 
I'll pull the 3 wire out and replace it with a 4 wire run. Not much fun 
but doable as I ran conduit up the wall to the attic.

Thanks for the great explanation, I'll save that and other things I've 
learned for future use.

JT

On 12/20/2015 2:25 PM, John Dammeyer wrote:
> Hi John,
>
> It sounds as if you have two AC lines coming into the machine.  One for the
> controller and one for the VFD.  The comments about a single star ground
> point are standard industry practice.  One breaker at the panel which
> protects the wire to the machine.  Another breaker inside the machine that
> protects the equipment.
>
> The Earth (green) comes in and is connected to a welded stud with a ring
> terminal, not a spade and double nutted so it can't possibly come loose.
> >From that point your controller and VFD are run.Never ever rely on the
> frame to carry the AC Ground (Earth) from one section to another.
>
> DC grounds are isolated from Earth Ground.  You can, connect the DC power
> supply minus to the Earth ground and it may even be a code requirement where
> you are.  Be aware, some PCs do this inside their power supply as do other
> types of COTS hardware.
>
> And here is the problem you have to watch out for.  Just because your DC
> volt meter reads continuity  (Zero Ohms)  between all the ground points
> doesn't mean that there is actually a path of lowest resistance following
> what you think it should.
>
> The moment you get into the switching power world which includes the VFD,
> Stepper Motors and Servos along with switching power supplies you get
> something called impedance.  That's based on the DC resistance (usually low)
> and a combination of the wire inductance and capacitance and frequency.
>
> Depending on how things are wired and routed the impedance of the return
> signal of the VFD may be lower through the RS232 (RS485) shield than it is
> through the green wire or even the shield around the power cable.  So just
> imagine the very noisy VFD signal returns through the communication shield
> because that has an impedance of 200 Ohms while the green wire has 1K.
> That's problem #1.
>
> There's two types of electrical noise.  Electrical coupling and magnetic
> coupling.  Electrical you shield against.  Usually with the shield tied to a
> common earth somewhere.
> Magnetic coupling is the same thing that makes a transformer or a motor
> function.  A rapidly changing magnetic field caused by rapidly changing
> current in a wire is coupled onto another wire that is in close proximity.
> Shielding doesn't protect against that. Twisted pairs do to a certain
> extent.
>
> The best protection is distance.  That's why you don't run the VFD power or
> Servo power tightly tie wrapped to the encoder signal.
>
> Therefore put the AC power side for the VFD on one side of the cabinet and
> run the control signals as far away as possible.
>
> There are lots of books written on this subject and probably as many
> opinions on what to do.  Ground shield at both ends.  Ground at one end.
> Don't ground.   Twist the wires.  Don't twist the wires.
>
> Start with the Star Grounding.  Make sure there aren't any DC paths that are
> unexpected as explained earlier.   Then start looking at how the noisy
> signals might find their way back through alternate paths.  Filters,
> Ferrites are all useful to block the signals.  Always best to block at the
> source.
>
> John
>
>
>
>
>
>
>> -Original Message-
>> From: John Thornton [mailto:j...@gnipsel.com]
>> Sent: December-20-15 10:27 AM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Grounding Issues
>>
>>
>> I have a line reactor for the VFD but I've never hooked it up.
>>
>> http://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive
>> _%28VFD%29_Spare_Parts_-a-_Accessories/AC_Line_Reactors/LR-23P0-1PH
>>
>> Speaking of VFD's mine is grounded to the breaker panel and not in the
>> machine anywhere. When I check from the ground terminal to the panel I
>> get 0 ohms so I assume that the back of the VFD is grounded to the
>> ground lug on the VFD.
>>
>> JT
>
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Re: [Emc-users] Grounding Issues

[Stephen Dubovsky]

Peter, this is the root cause in the change of behavior between <=2.6 and
2.7 w/ the 5i25+7i77 that a couple of us have been having (was discussed
here about a week ago)?  I have noticed an occasional warning in the prior
version I was running (just at startup iirc.)  I need to put some more
noise filters in, but my error is from the motor contactors pulling in when
I hit enable.  The original dc servo drives have big contactors that
disconnect the motor from the drive and put a braking resistor across it
when you disable them (or hit a limit switch, etc.)  Hitting the enable
(F2) causes those 3 big guys to pull in and reconnect the drives to the
motors.  That causes the sserial glitch and trips the contactors right back
off. I can't get past that step.  I haven't had time this week to play w/
the inc/dec parameters like Andy Pugh suggested.

Best,
Stephen

On Sun, Dec 20, 2015 at 1:34 PM, Peter C. Wallace  wrote:

>
> I looked into the 2.7 source and see that there is a problem with sserial
> error reporting that makes some single errors fatal (because the error
> reporting does not distinguish between per cycle error bits and sticky
> error
> status bits)
>
> That is errors that caused just a random popup on 2.6 will cause 2.7
> to shut down the sserial port (you still need a pretty bad noise spike to
> cause these errors but they should not be fatal)
>
>
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Re: [Emc-users] Grounding Issues

[John Dammeyer]

I used to have problems with one particular LED board I designed that would
reset or stop talking on IIC bus when I turned on my workbench circular
fluorescent light.  The type with the magnifying glass.  Turned out to be a
PC board layout problem and pull up resistors in the wrong place and the
wrong value.

Not an easy problem to solve when on a deadline.

Way back in the early nineties a stepper motor that adjusted the tool height
of a punch press by turning a ball screw would put noise onto the control
network.  It was worse during each punch cycle since the force on the press
would try and rotate the ball screw a tiny bit and the drive circuits became
noisier.   

The solution as simple but not applicable to CNC unfortunately.  The
engineers designed in a mechanical brake.  Once the tool was inserted and
the press closed to the calibrated position, the brake was enabled and the
stepper driver was disabled.  Noise gone.  Network better.

Moral of the story, always better to try and remove the noise from the
source rather than protect every device from it.

John Dammeyer



> -Original Message-
> From: Stephen Dubovsky [mailto:smdubov...@gmail.com]
> Sent: December-20-15 6:59 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding Issues
> 
> 
> Peter, this is the root cause in the change of behavior between <=2.6 and
> 2.7 w/ the 5i25+7i77 that a couple of us have been having (was discussed
> here about a week ago)?  I have noticed an occasional warning in the prior
> version I was running (just at startup iirc.)  I need to put some more
> noise filters in, but my error is from the motor contactors pulling in
when
> I hit enable.  The original dc servo drives have big contactors that
> disconnect the motor from the drive and put a braking resistor across it
> when you disable them (or hit a limit switch, etc.)  Hitting the enable
> (F2) causes those 3 big guys to pull in and reconnect the drives to the
> motors.  That causes the sserial glitch and trips the contactors right
back
> off. I can't get past that step.  I haven't had time this week to play w/
> the inc/dec parameters like Andy Pugh suggested.
> 
> Best,
> Stephen
> 
> On Sun, Dec 20, 2015 at 1:34 PM, Peter C. Wallace <p...@mesanet.com>
> wrote:
> 
> >
> > I looked into the 2.7 source and see that there is a problem with
sserial
> > error reporting that makes some single errors fatal (because the error
> > reporting does not distinguish between per cycle error bits and sticky
> > error
> > status bits)
> >
> > That is errors that caused just a random popup on 2.6 will cause 2.7
> > to shut down the sserial port (you still need a pretty bad noise spike
to
> > cause these errors but they should not be fatal)
> >
> >
>

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Re: [Emc-users] Grounding Issues

[John Thornton]

I hope the procedure goes well.

Yes I have a scope.

JT

On 12/20/2015 1:23 PM, Gene Heskett wrote:
> But I am shortly going to be out of pocket till Monday afternoon. 
> Cataract fixings in the XYL's right eye are scheduled for first thing 
> in the morning, so we've reserved a room about a mile from the O.R. 
> Figures. :( Do you have an oscilloscope? Cheers, Gene Heskett 


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Re: [Emc-users] Grounding Issues

[John Thornton]

An update, I made a star grounding configuration so EVERY ground comes 
from the same place. I tested with the VFD unplugged and all is fine, 
plug the VFD in and same problem sserial errors. The VFD is 220v so to 
use one power source I'd have to run new wire from the panel to the 220v 
outlet and get a 4 wire plug. Not impossible but a PIA to work up in the 
attic

JT

On 12/20/2015 7:20 AM, John Thornton wrote:
> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> all the Anilam controls a while back. I've retained the drives and power
> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>   From the get go I've had problems with the electronics on this machine.
> The VFD is controlled by modbus via the gs2 component. The VFD gets
> reset to default parameters all the time from noise on the modbus. the
> 5i25 get sserial errors. The sserial errors are so bad now it won't even
> move an axis. The spindle works ok. The power supply is a simple bridge
> rectifier with a huge blue cap and a large power resistor across the cap.
>
> Peter keeps telling me it's a grounding issue so where do I start
> looking and what do I need to do?
>
> Thanks
> JT
>
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Re: [Emc-users] Grounding Issues

[John Dammeyer]

John
You're welcome.
My  _Go_To_  book is "Electromagnetic Compatibility Engineering" By Henry
W.Ott.  Published by WILEY.
http://ca.wiley.com/WileyCDA/WileyTitle/productCd-0470189304.html
I've retained perhaps 5% and for a while the book went everywhere with me as
I tried to absorb the details.  
It's not black magic although it appears that way sometimes.
John Dammeyer


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Re: [Emc-users] Grounding Issues

[John Thornton]

Well it works fine till I plug in the VFD so I guess I'll have to rewire 
the machine and my shop again :(

JT

On 12/20/2015 2:25 PM, John Dammeyer wrote:
> Hi John,
>
> It sounds as if you have two AC lines coming into the machine.  One for the
> controller and one for the VFD.  The comments about a single star ground
> point are standard industry practice.  One breaker at the panel which
> protects the wire to the machine.  Another breaker inside the machine that
> protects the equipment.
>
>


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Re: [Emc-users] Grounding Issues

[TJoseph Powderly]

if you can get a scope (2 trace)
and _SEE_ the noise
from your machine ground to a good ground,
then you can see when you make a difference.

a good ground can be tested with a megger ( hard to find)
a good ground can be a copper rod driven 10 ft into good earth
so find the best you can and look to see if theres a difference.

a scope is a very visual thing, forget the scales for now, the picture 
is more important.

my 2c ( hmm 2b here )
tomp tjtr33

On 12/20/2015 07:20 AM, John Thornton wrote:
> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> all the Anilam controls a while back. I've retained the drives and power
> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>   From the get go I've had problems with the electronics on this machine.
> The VFD is controlled by modbus via the gs2 component. The VFD gets
> reset to default parameters all the time from noise on the modbus. the
> 5i25 get sserial errors. The sserial errors are so bad now it won't even
> move an axis. The spindle works ok. The power supply is a simple bridge
> rectifier with a huge blue cap and a large power resistor across the cap.
>
> Peter keeps telling me it's a grounding issue so where do I start
> looking and what do I need to do?
>
> Thanks
> JT
>
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Re: [Emc-users] Grounding Issues

[John Dammeyer]

Don't get too carried away with Earth as the most important part of
grounding.  After all those big metal tubes that fly through the sky aren't
connected to ground and they have all sorts of power systems from DC to AC
(if you can afford business class).

The point is to make sure that the current that leaves from one location
ends up back there since current only flows when there's a complete circuit.


John


> -Original Message-
> From: TJoseph Powderly [mailto:tjt...@gmail.com]
> Sent: December-20-15 4:17 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding Issues
> 
> 
> if you can get a scope (2 trace)
> and _SEE_ the noise
> from your machine ground to a good ground,
> then you can see when you make a difference.
> 
> a good ground can be tested with a megger ( hard to find)
> a good ground can be a copper rod driven 10 ft into good earth
> so find the best you can and look to see if theres a difference.
> 
> a scope is a very visual thing, forget the scales for now, the picture
> is more important.
> 
> my 2c ( hmm 2b here )
> tomp tjtr33
> 
> On 12/20/2015 07:20 AM, John Thornton wrote:
> > I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> > all the Anilam controls a while back. I've retained the drives and power
> > supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
> >   From the get go I've had problems with the electronics on this
machine.
> > The VFD is controlled by modbus via the gs2 component. The VFD gets
> > reset to default parameters all the time from noise on the modbus. the
> > 5i25 get sserial errors. The sserial errors are so bad now it won't even
> > move an axis. The spindle works ok. The power supply is a simple bridge
> > rectifier with a huge blue cap and a large power resistor across the
cap.
> >
> > Peter keeps telling me it's a grounding issue so where do I start
> > looking and what do I need to do?
> >
> > Thanks
> > JT
> >
> >

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> 
>

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Re: [Emc-users] Grounding Issues

[John Dammeyer]

John,
I'd still take a close look at your existing system to see if it is robust.

Perhaps an example from a different project my give you an idea.  Bear with
me.  The story is kind of long.

I designed an LED lighting system that ran of a 48V bank of batteries
charged by generator.  

Charging could  raise the voltage as high as 56 volts.  The voltage
regulators on each LED lamp was good to 70V so I had plenty of leeway, or so
I thought.  The power distribution system was in the centre of a long barge.
The genset and batteries at one end.  The first time we powered up the
system and flashed the lights on and off a few times something odd happened.
The lights went a funny colour and then many of them went off.

Since I'd already built one system that ran on 24V and had been operational
for 8 months we were perplexed.  True, this one had different boards with
48V instead of 24V.  On the way back out we were discussing what could have
damaged so many lights.The Chief Engineer asked if the coil of wire
would have any impact.  I asked what coil.

Well it turns out the wire running the DC from the battery pack and the
control panel was very expensive.  So to avoid cutting out a section that
would end up useless they coiled it under the cabinet.A change from 70A
to about 10A was much like an ignition coil when the points open.  The
inductive kick was probably well over 100V especially since the generator
was running at the time.

We cut the cable to the exact length needed.  It still ran in a metal trough
under steel plates on the barge deck but looking at the power with a scope
showed the problem had gone away.  One wouldn't think a coil of about 5
turns would make a difference but it did.

The second issue that was prevalent on both systems was that each string of
lamps was up to 35m long with a restriction of 8A current on the power
conductors.  The lamps were all in the last 10m so there was 25m worth of
feed cable.   That means at full lights on the first lamp after the 20m had
the highest voltage and the last lamp 10m further down had the least voltage
due to the multiple voltage drops as each lamp used power.

I'll introduce another term here.  It's called common mode voltage.  The
power through the 24V or 48V connection to the lamps has a voltage drop
based on current consumption.  There's an identical drop across the ground
power wire.  The one on the 24V line isn't that important as long as it can
still run the load. 

But the voltage drop across the ground lead means the local lamps see a
different potential between ground and the communications bus than at the
other end of the 35m cable.  Most communications chips have a specification
called maximum common mode voltage.That essentially means you can't have
more of a difference between the grounds when the signal is also part of the
connection.  

So for example if the common mode is a 6V drop across the ground conductor
then the voltage at one end between tx and gnd might be 2.5V.  At the lamp
at the other end the signal is also 2.5V since the lamps sees the local
ground.   But that 6V shows up as soon as there's enough current on the
ground to cause the 6V drop.  Now one end sees 8.5V relative to ground.
This is static and measurable with a simple meter.

OK back to CNC.

This is the biggest reason you run 4 servo or stepper motor drives with the
power and as a single point on the power supply rather than ground to ground
to ground to ground.  If each Servo draws 8A and the last one sees the
ground shift up because of voltage drops along the ground bus and the
signals to the motors (or encoder feedback) may be compromised.

Now let's look at the AC side of things.  You run all your power to  a
single point doing it right. 

Each wire to each driver has inductance.  And there's capacitance between
the wire and the cabinet.  At the right frequencies the noise ground return
path is now through the capacitance to the cabinet rather than along the
wire.  

Since each driver and each wire is further away from the power supply we're
back to the daisy chained power distribution system with more common mode
voltage at the far end higher than at the end close to the power.  And again
that can affect the encoder or control signals.  But now it's sporadic.
Hard to track.  Stepper winding current collapsing creating noise spikes at
the same instant as a message to a VFD.

So shielding power cabling to your devices with the shield terminated at the
distribution end and open at the other can suppress those kinds of problems.
Now the high frequency signals and noise are brought back to where you want.

Does that all make sense?

John Dammeyer







> -Original Message-
> From: John Thornton [mailto:j...@gnipsel.com]
> Sent: December-20-15 3:06 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding Issues
> 
> 
> Well it works fine till I plug in the VFD so I guess I'll have to rewire
> th

Re: [Emc-users] Grounding Issues

[Bertho Stultiens]

On 12/21/2015 12:59 AM, John Thornton wrote:
> An update, I made a star grounding configuration so EVERY ground comes 
> from the same place. I tested with the VFD unplugged and all is fine, 
> plug the VFD in and same problem sserial errors. The VFD is 220v so to 
> use one power source I'd have to run new wire from the panel to the 220v 
> outlet and get a 4 wire plug. Not impossible but a PIA to work up in the 
> attic

If you have a dual supply and a transformer for AC 110V -> 220V (or the
other way around), then you may need to reverse the polarity of phase
and neutral of the transformer.

You may see common-mode injection because the phase-polarity of the two
supplies are 180 degrees out of sync. The chassis will then be
conducting the capacitively coupled common-mode, which may interfere a lot.


-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Grounding Issues

[R.L. Wurdack]

Some of them tubes are Carbon fiber composite these days. Makes grounding 
more fun.


- Original Message - 
From: "John Dammeyer" <jo...@autoartisans.com>
To: "'Enhanced Machine Controller (EMC)'" <emc-users@lists.sourceforge.net>
Sent: Sunday, December 20, 2015 4:59 PM
Subject: Re: [Emc-users] Grounding Issues


> Don't get too carried away with Earth as the most important part of
> grounding.  After all those big metal tubes that fly through the sky 
> aren't
> connected to ground and they have all sorts of power systems from DC to AC
> (if you can afford business class).
>
> The point is to make sure that the current that leaves from one location
> ends up back there since current only flows when there's a complete 
> circuit.
>
>
> John
>
>
>> -Original Message-
>> From: TJoseph Powderly [mailto:tjt...@gmail.com]
>> Sent: December-20-15 4:17 PM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Grounding Issues
>>
>>
>> if you can get a scope (2 trace)
>> and _SEE_ the noise
>> from your machine ground to a good ground,
>> then you can see when you make a difference.
>>
>> a good ground can be tested with a megger ( hard to find)
>> a good ground can be a copper rod driven 10 ft into good earth
>> so find the best you can and look to see if theres a difference.
>>
>> a scope is a very visual thing, forget the scales for now, the picture
>> is more important.
>>
>> my 2c ( hmm 2b here )
>> tomp tjtr33
>>
>> On 12/20/2015 07:20 AM, John Thornton wrote:
>> > I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>> > all the Anilam controls a while back. I've retained the drives and 
>> > power
>> > supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>> >   From the get go I've had problems with the electronics on this
> machine.
>> > The VFD is controlled by modbus via the gs2 component. The VFD gets
>> > reset to default parameters all the time from noise on the modbus. the
>> > 5i25 get sserial errors. The sserial errors are so bad now it won't 
>> > even
>> > move an axis. The spindle works ok. The power supply is a simple bridge
>> > rectifier with a huge blue cap and a large power resistor across the
> cap.
>> >
>> > Peter keeps telling me it's a grounding issue so where do I start
>> > looking and what do I need to do?
>> >
>> > Thanks
>> > JT
>> >
>> >
> 
> --
>> > ___
>> > Emc-users mailing list
>> > Emc-users@lists.sourceforge.net
>> > https://lists.sourceforge.net/lists/listinfo/emc-users
>>
>>
>>
> 
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Re: [Emc-users] Grounding Issues

[Peter C. Wallace]

On Sun, 20 Dec 2015, Stephen Dubovsky wrote:

> Date: Sun, 20 Dec 2015 21:59:26 -0500
> From: Stephen Dubovsky <smdubov...@gmail.com>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <emc-users@lists.sourceforge.net>
> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Subject: Re: [Emc-users] Grounding Issues
> 
> Peter, this is the root cause in the change of behavior between <=2.6 and
> 2.7 w/ the 5i25+7i77 that a couple of us have been having (was discussed
> here about a week ago)?  I have noticed an occasional warning in the prior
> version I was running (just at startup iirc.)  I need to put some more
> noise filters in, but my error is from the motor contactors pulling in when
> I hit enable.  The original dc servo drives have big contactors that
> disconnect the motor from the drive and put a braking resistor across it
> when you disable them (or hit a limit switch, etc.)  Hitting the enable
> (F2) causes those 3 big guys to pull in and reconnect the drives to the
> motors.  That causes the sserial glitch and trips the contactors right back
> off. I can't get past that step.  I haven't had time this week to play w/
> the inc/dec parameters like Andy Pugh suggested.
>
> Best,
> Stephen


Yes I'm pretty sure this is the issue. Error reporting was improved in 2.7
but the error reporting of sticky error bits needs to be conditional on per 
cycle general (new) error flags and its not.

I will try and get this fixed ASAP

Also there is a small chance that updating the 5I25 sserial firmware from 
pre-35 versions to the current version 43 makes the RX UART a bit more
sensitive to input noise as the internal processor and UART clock are
changed from 33 MHz to 100 MHz.

I do have a fix for this ( a 1/2 bit time digital filter on the RX 
UART input ) and will add this to all bitfiles containing sserial firmware
but currently I have new bitfiles for the 5I25/6I25 and 7I76 and 7I77 here:

http://freeby.mesanet.com/filtered.zip


>
> On Sun, Dec 20, 2015 at 1:34 PM, Peter C. Wallace <p...@mesanet.com> wrote:
>
>>
>> I looked into the 2.7 source and see that there is a problem with sserial
>> error reporting that makes some single errors fatal (because the error
>> reporting does not distinguish between per cycle error bits and sticky
>> error
>> status bits)
>>
>> That is errors that caused just a random popup on 2.6 will cause 2.7
>> to shut down the sserial port (you still need a pretty bad noise spike to
>> cause these errors but they should not be fatal)
>>
>>
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Mesa Electronics

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Re: [Emc-users] Grounding Issues

[tom-emc]

There was a thread back in May (11-15) of 2015 Subject was "If there's one 
thing I hate, all the noise, noise, noise, noise” where I was having strange 
noise issues.  There are a lot of helpful suggestions there for tracking down 
noise.  In my case the problem was an overly sensitive keyboard, but before I 
narrowed that down I spent quite a bit of time tracing down grounds and also 
adding both an input power filter (ebay search "Rasmi Filter" for inexpensive 
options) for the VFD and also adding 4 Ferrites to the output VFD power leads 
to the motor.  These are the ferrites I used: 
https://www.digikey.com/product-detail/en/74277290/732-3092-ND/2626031

Good luck.
-Tom

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Re: [Emc-users] Grounding Issues

[John Thornton]

I have a line reactor for the VFD but I've never hooked it up.

http://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive_%28VFD%29_Spare_Parts_-a-_Accessories/AC_Line_Reactors/LR-23P0-1PH

Speaking of VFD's mine is grounded to the breaker panel and not in the 
machine anywhere. When I check from the ground terminal to the panel I 
get 0 ohms so I assume that the back of the VFD is grounded to the 
ground lug on the VFD.

JT

On 12/20/2015 11:44 AM, Kirk Wallace wrote:
> On 12/20/2015 05:20 AM, John Thornton wrote:
>> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>> all the Anilam controls a while back. I've retained the drives and power
>> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>>From the get go I've had problems with the electronics on this machine.
> I have had good results (noise on encoder lines) by adding mains filters
> to my VFD power inputs.
>
> The shiny box here:
> http://www.wallacecompany.com/cnc_lathe/HNC/00024-1a.jpg
>
> I suspect any switching power circuit might benefit from installing an
> input filter.
>


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Re: [Emc-users] Grounding Issues

[John Thornton]

The bpel04 has a star washer and the stud is welded to the back plane. 
The cases are bolted tight to the main column. The DIN rail is fastened 
down with star washers and the locking screws are tight.

JT

On 12/20/2015 11:42 AM, Dave Caroline wrote:
> The din rail in the 05 pic is that real tight to the back panel (add
> star washers to cut through paint), make sure the green/yellow blocks
> have the middle screw tight.
>
> One mighty thin grounding wire in bpel04.jpg, also could add star
> washer to cut through paint
>
> You could measure the ground resistance too if you can.
>
> Others are likely to mention you have two grounds rather than a star
> ground. Make sure cases are tight to frame to guarantee continuity
>
> Dave Caroline
>
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Re: [Emc-users] Grounding Issues

[Peter C. Wallace]

On Sun, 20 Dec 2015, John Thornton wrote:

> Date: Sun, 20 Dec 2015 12:26:51 -0600
> From: John Thornton <j...@gnipsel.com>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <emc-users@lists.sourceforge.net>
> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Subject: Re: [Emc-users] Grounding Issues
> 
> I have a line reactor for the VFD but I've never hooked it up.
>
> http://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive_%28VFD%29_Spare_Parts_-a-_Accessories/AC_Line_Reactors/LR-23P0-1PH
>
> Speaking of VFD's mine is grounded to the breaker panel and not in the
> machine anywhere. When I check from the ground terminal to the panel I
> get 0 ohms so I assume that the back of the VFD is grounded to the
> ground lug on the VFD.
>
> JT

I looked into the 2.7 source and see that there is a problem with sserial 
error reporting that makes some single errors fatal (because the error 
reporting does not distinguish between per cycle error bits and sticky error 
status bits)

That is errors that caused just a random popup on 2.6 will cause 2.7
to shut down the sserial port (you still need a pretty bad noise spike to 
cause these errors but they should not be fatal)


Peter Wallace

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Re: [Emc-users] Grounding Issues

[John Thornton]

On 12/20/2015 11:47 AM, Gene Heskett wrote:
> On Sunday 20 December 2015 12:15:21 John Thornton wrote:
>
>> Back from shopping...
>>
>> Pencil sketch of the power side
>> http://gnipsel.com/images/bp-knee-mill/bpel03.in
> the left box probably needs the paint cleaned off under it, and maybe a
> star washer under the spade lug for extra connection bite. And there
> ought to be a similar ground to the box in the right box. But as sub
> boxes generally have isolated busses for the static (bare wires in the
> romex */3 wires) in order to bot short circuit the connection at the
> main entrance a foot or so from the meterhead.
>
>> Incoming terminal block on left panel where extra ground is
>> http://gnipsel.com/images/bp-knee-mill/bpel04.jpg
> Here I cannot see the above green wire, the static, while connected to
> the  to the box, but it does not leave to connect the rest of the stuff,
> just the white (neutral) and black (127 hot) wires leaving are all I see
> leaving. Tieing to the box, is to ground the box to the static
> grounding.
>
>> next terminal block on right panel
>> http://gnipsel.com/images/bp-knee-mill/bpel05.jpg
>>
> And here, unless its in the block mounting for the two green wires I can
> see, and I am not at all familiar with that style of terminal block,
> they are floating.  Are the two pieces of SJ I see coming in at the top,
> source or load?

The green/yellow terminal blocks are standard ground blocks, the center 
screw tightens a gripper that forces a tight metal to metal contact with 
the DIN rail and the terminals. It's very much grounded to the DIN rail 
and the DIN rail is fastened to the back plane with welded on studs and 
star washers and nuts.

http://www.automationdirect.com/adc/Shopping/Catalog/Terminal_Blocks/DINnector_DIN-Rail_Terminal_Blocks/Ground_Terminal_Blocks/DN-G10

They are very expensive...
> Offhand, it does tend to look like a noise factory from here. :(  Those
> green wires should come from the real ground at the service entrance and
> go all the way to that single point bolt in the driver cabinet wall,
> then from there to everything else as a star ground.
>
>> JT
>>
>> On 12/20/2015 8:37 AM, Gene Heskett wrote:
>>> On Sunday 20 December 2015 08:20:38 John Thornton wrote:
 I have a BP knee mill with an Anilam 1100M CNC kit on it. I've
 removed all the Anilam controls a while back. I've retained the
 drives and power supply and added a GS2 VFD for the spindle. I have
 a 5i25 7i77 setup. From the get go I've had problems with the
 electronics on this machine. The VFD is controlled by modbus via
 the gs2 component. The VFD gets reset to default parameters all the
 time from noise on the modbus. the 5i25 get sserial errors. The
 sserial errors are so bad now it won't even move an axis. The
 spindle works ok. The power supply is a simple bridge rectifier
 with a huge blue cap and a large power resistor across the cap.

 Peter keeps telling me it's a grounding issue so where do I start
 looking and what do I need to do?

 Thanks
 JT
>>> Start with a roll of flat braid equ to a 8 or 10 gauge wire.
>>> Establish a bolt to the case of the controller as a master ground,
>>> and make sure everything that references ground in the controller
>>> box is grounded at this bolt.
>>>
>>> Tie this bolt to the buildings static ground using that pin of the
>>> controllers power cable, BUT not to the building supply neutral as
>>> thats usually noisy as can be.  Or to a real ground rod but that may
>>> have a considerable damaging joltage on it when there is lightning
>>> nearby so is both against the NEC and would be poor practice.
>>>
>>> Then extend that ground, using this braid, to the bridgeports main
>>> casting, and perhaps also to the table and knee as the lube oil in
>>> the ways might preclude a really good ground on the table without
>>> it.
>>>
>>> Extend that ground from that bolt to the computers case if it is
>>> separated from the controller box.
>>>
>>> This is called a star ground system, where everything is common at
>>> this bolt.  If you can disconnect each wire from that bolt, and
>>> still measure continuity of 200 ohms or less from the bolt to the
>>> disconnected wire, then that wire has an unwanted ground somewhere,
>>> run it down and remove it, you want that to be "grounded" only at
>>> that bolt.
>>>
>>> The idea is that even if it does bounce a bit from a nearby
>>> lightning strike, it all bounces in unison with no big voltage drops
>>> between anything that can damage it, or induce noise that would be
>>> miss-detected as a signal.
>>>
>>> Years ago when I was screwing with vz & their bad copper, I figured
>>> on losing a modem everytime I heard thunder. Getting PO'd, I first
>>> opened up the wall a bit, pulled out the duplex that was going to
>>> power what I had in mind, and soldered all the connections in that
>>> box. Then I bought the biggest surge arrestor I could find, one that

Re: [Emc-users] Grounding Issues

[Gene Heskett]

On Sunday 20 December 2015 08:20:38 John Thornton wrote:

> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> all the Anilam controls a while back. I've retained the drives and
> power supply and added a GS2 VFD for the spindle. I have a 5i25 7i77
> setup. From the get go I've had problems with the electronics on this
> machine. The VFD is controlled by modbus via the gs2 component. The
> VFD gets reset to default parameters all the time from noise on the
> modbus. the 5i25 get sserial errors. The sserial errors are so bad now
> it won't even move an axis. The spindle works ok. The power supply is
> a simple bridge rectifier with a huge blue cap and a large power
> resistor across the cap.
>
> Peter keeps telling me it's a grounding issue so where do I start
> looking and what do I need to do?
>
> Thanks
> JT
>
Start with a roll of flat braid equ to a 8 or 10 gauge wire. Establish a 
bolt to the case of the controller as a master ground, and make sure 
everything that references ground in the controller box is grounded at 
this bolt. 

Tie this bolt to the buildings static ground using that pin of the 
controllers power cable, BUT not to the building supply neutral as thats 
usually noisy as can be.  Or to a real ground rod but that may have a 
considerable damaging joltage on it when there is lightning nearby so is 
both against the NEC and would be poor practice.

Then extend that ground, using this braid, to the bridgeports main 
casting, and perhaps also to the table and knee as the lube oil in the 
ways might preclude a really good ground on the table without it.  

Extend that ground from that bolt to the computers case if it is 
separated from the controller box.

This is called a star ground system, where everything is common at this 
bolt.  If you can disconnect each wire from that bolt, and still measure 
continuity of 200 ohms or less from the bolt to the disconnected wire, 
then that wire has an unwanted ground somewhere, run it down and remove 
it, you want that to be "grounded" only at that bolt.

The idea is that even if it does bounce a bit from a nearby lightning 
strike, it all bounces in unison with no big voltage drops between 
anything that can damage it, or induce noise that would be miss-detected 
as a signal.

Years ago when I was screwing with vz & their bad copper, I figured on 
losing a modem everytime I heard thunder. Getting PO'd, I first opened 
up the wall a bit, pulled out the duplex that was going to power what I 
had in mind, and soldered all the connections in that box. Then I bought 
the biggest surge arrestor I could find, one that had phone line & cable 
tv arrestors in it.  And I bought the biggest home UPS I could find. 
Everything in this room but the lights is plugged in either to that UPS 
or that surge arrestor, and both are plugged into this all soldered 
duplex. Now lightning can hit the pole my transformer is on, possibly 
bouncing everything in this room by 100 kilovolts, but it all bounces in 
unison and I haven't lost a modem or anything else that I could 
associate the loss with local lightning strikes. But since I did get, 
from a wired keyboard I was typing on at the time, a really good jolt 
thru my fingers like shuffling ones feet on the rug and then grabbing 
the doorknob, but it didn't hurt the computer or the keyboard, but I now 
use wireless keyboard and mice.

If the frame of the bridgeport is grounded thru other means, such as a 
3rd pin on a power cable, this should be defeated in order to remove the 
potential ground loop which can be a source of quite a bit of induced 
noise.

Motor drive, and feedback cables from the motors should be shielded, with 
the shields cut off at the motor ends of the cable but tied to this bolt 
at the controller end, thereby interrupting that potential ground loop.

The general idea is to have one common "ground" point, even if its is not 
an earthen ground. That s/b, by the NEC, at the service entrance, a 
minimum of two full rods driven 6 feet apart, with an 8 gauge wire 
bonding them to the buildings static ground for the 3rd pin of all the 
duplexes and neutral from the pole drop, the only place it is legal to 
interconnect them.  Hanging an amprobe on any of the bare static wires 
in the service box should get you a zero reading regardless of what is 
powered up.  If you do see a reading, something out on that circuit is 
miss-wired. Fix it. Its just good practice.

It and I, may sound arbitrary John, but it works.  And its NEC legal.
If you have a decent scope, just waving a probe around with the gain 
turned up near suspected noise sources can be very educational.

I've had to follow too many electricians around, fixing their mix-n-match 
attitude about static and neutral being the same thing, way too many 
times.

Let us know what you did find when you've cleaned up the problem, please.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, 

Re: [Emc-users] Grounding Issues

[John Thornton]

Ok, I'll work on that this morning.

Thanks
JT

On 12/20/2015 7:57 AM, Dave Caroline wrote:
> It might help to draw a diagram showing the electronics (drives
> modules etc) and where they are grounded showing outlines of the
> cases.
>
> This is to get an idea where any common mode interference signals can come 
> from.
>
> Also pictures of the wiring with annotation of wire bundles to get an
> idea of any capacitive or inductive coupling.
>
> Dave Caroline
>
> On 20/12/2015, John Thornton  wrote:
>> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>> all the Anilam controls a while back. I've retained the drives and power
>> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>>   From the get go I've had problems with the electronics on this machine.
>> The VFD is controlled by modbus via the gs2 component. The VFD gets
>> reset to default parameters all the time from noise on the modbus. the
>> 5i25 get sserial errors. The sserial errors are so bad now it won't even
>> move an axis. The spindle works ok. The power supply is a simple bridge
>> rectifier with a huge blue cap and a large power resistor across the cap.
>>
>> Peter keeps telling me it's a grounding issue so where do I start
>> looking and what do I need to do?
>>
>> Thanks
>> JT
>>
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Re: [Emc-users] Grounding Issues

[John Thornton]

I'll start with a couple of photos of the el cabinets before breakfast 
and get more details after.

http://gnipsel.com/images/bp-knee-mill/bpel01.jpg
http://gnipsel.com/images/bp-knee-mill/bpel02.jpg

JT


On 12/20/2015 7:57 AM, Dave Caroline wrote:
> It might help to draw a diagram showing the electronics (drives
> modules etc) and where they are grounded showing outlines of the
> cases.
>
> This is to get an idea where any common mode interference signals can come 
> from.
>
> Also pictures of the wiring with annotation of wire bundles to get an
> idea of any capacitive or inductive coupling.
>
> Dave Caroline
>
> On 20/12/2015, John Thornton  wrote:
>> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>> all the Anilam controls a while back. I've retained the drives and power
>> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>>   From the get go I've had problems with the electronics on this machine.
>> The VFD is controlled by modbus via the gs2 component. The VFD gets
>> reset to default parameters all the time from noise on the modbus. the
>> 5i25 get sserial errors. The sserial errors are so bad now it won't even
>> move an axis. The spindle works ok. The power supply is a simple bridge
>> rectifier with a huge blue cap and a large power resistor across the cap.
>>
>> Peter keeps telling me it's a grounding issue so where do I start
>> looking and what do I need to do?
>>
>> Thanks
>> JT
>>
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Re: [Emc-users] Grounding Issues

[Marius Liebenberg]

John
Some things to look for.
1: Make sure that you field supply is not grounded to the same ground as 
the VFD. I.E the 24v Filed supply must be floating.
2: All cables must be screened where possible.
3: Screen must only be connected at the source and and to one single 
place to the physical earth of the box as well as the mains earth.
4: Earth must only be connected at one single point (star connection)

I had a similar problem with my lathe and found in the end that my 
spindle motor cage was not physical earth and caused huge noise.




>I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>all the Anilam controls a while back. I've retained the drives and 
>power
>supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>  From the get go I've had problems with the electronics on this 
>machine.
>The VFD is controlled by modbus via the gs2 component. The VFD gets
>reset to default parameters all the time from noise on the modbus. the
>5i25 get sserial errors. The sserial errors are so bad now it won't 
>even
>move an axis. The spindle works ok. The power supply is a simple bridge
>rectifier with a huge blue cap and a large power resistor across the 
>cap.
>
>Peter keeps telling me it's a grounding issue so where do I start
>looking and what do I need to do?
>
>Thanks
>JT
>
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Re: [Emc-users] Grounding Issues

[John Thornton]

On 12/20/2015 8:37 AM, Gene Heskett wrote:
> Start with a roll of flat braid equ to a 8 or 10 gauge wire. Establish a
> bolt to the case of the controller as a master ground, and make sure
> everything that references ground in the controller box is grounded at
> this bolt.
>
> Tie this bolt to the buildings static ground using that pin of the
> controllers power cable, BUT not to the building supply neutral as thats
> usually noisy as can be.  Or to a real ground rod but that may have a
> considerable damaging joltage on it when there is lightning nearby so is
> both against the NEC and would be poor practice.
I'll start here, I see 4 places where things are grounded, the encoders 
all have a ground connection to the electrical cabinet and one on the 
other cabinet where the VFD lives. I know without looking that every 
panel has the neutral bonded to ground and I have two ground rods one 
for the house and one for the garage/shop (one panel for each one back 
to back). I do think this is local to the machine as I have other 
machines in the shop that do not have this problem. Let me study the 
grounds a bit...
> Then extend that ground, using this braid, to the bridgeports main
> casting, and perhaps also to the table and knee as the lube oil in the
> ways might preclude a really good ground on the table without it.
>
> Extend that ground from that bolt to the computers case if it is
> separated from the controller box.
>
> This is called a star ground system, where everything is common at this
> bolt.  If you can disconnect each wire from that bolt, and still measure
> continuity of 200 ohms or less from the bolt to the disconnected wire,
> then that wire has an unwanted ground somewhere, run it down and remove
> it, you want that to be "grounded" only at that bolt.
>
> The idea is that even if it does bounce a bit from a nearby lightning
> strike, it all bounces in unison with no big voltage drops between
> anything that can damage it, or induce noise that would be miss-detected
> as a signal.
>
> Years ago when I was screwing with vz & their bad copper, I figured on
> losing a modem everytime I heard thunder. Getting PO'd, I first opened
> up the wall a bit, pulled out the duplex that was going to power what I
> had in mind, and soldered all the connections in that box. Then I bought
> the biggest surge arrestor I could find, one that had phone line & cable
> tv arrestors in it.  And I bought the biggest home UPS I could find.
> Everything in this room but the lights is plugged in either to that UPS
> or that surge arrestor, and both are plugged into this all soldered
> duplex. Now lightning can hit the pole my transformer is on, possibly
> bouncing everything in this room by 100 kilovolts, but it all bounces in
> unison and I haven't lost a modem or anything else that I could
> associate the loss with local lightning strikes. But since I did get,
> from a wired keyboard I was typing on at the time, a really good jolt
> thru my fingers like shuffling ones feet on the rug and then grabbing
> the doorknob, but it didn't hurt the computer or the keyboard, but I now
> use wireless keyboard and mice.
>
> If the frame of the bridgeport is grounded thru other means, such as a
> 3rd pin on a power cable, this should be defeated in order to remove the
> potential ground loop which can be a source of quite a bit of induced
> noise.
>
> Motor drive, and feedback cables from the motors should be shielded, with
> the shields cut off at the motor ends of the cable but tied to this bolt
> at the controller end, thereby interrupting that potential ground loop.
>
> The general idea is to have one common "ground" point, even if its is not
> an earthen ground. That s/b, by the NEC, at the service entrance, a
> minimum of two full rods driven 6 feet apart, with an 8 gauge wire
> bonding them to the buildings static ground for the 3rd pin of all the
> duplexes and neutral from the pole drop, the only place it is legal to
> interconnect them.  Hanging an amprobe on any of the bare static wires
> in the service box should get you a zero reading regardless of what is
> powered up.  If you do see a reading, something out on that circuit is
> miss-wired. Fix it. Its just good practice.
>
> It and I, may sound arbitrary John, but it works.  And its NEC legal.
> If you have a decent scope, just waving a probe around with the gain
> turned up near suspected noise sources can be very educational.
>
> I've had to follow too many electricians around, fixing their mix-n-match
> attitude about static and neutral being the same thing, way too many
> times.
>
> Let us know what you did find when you've cleaned up the problem, please.
>
> Cheers, Gene Heskett


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Re: [Emc-users] Grounding Issues

[Dave Caroline]

It might help to draw a diagram showing the electronics (drives
modules etc) and where they are grounded showing outlines of the
cases.

This is to get an idea where any common mode interference signals can come from.

Also pictures of the wiring with annotation of wire bundles to get an
idea of any capacitive or inductive coupling.

Dave Caroline

On 20/12/2015, John Thornton  wrote:
> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> all the Anilam controls a while back. I've retained the drives and power
> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>  From the get go I've had problems with the electronics on this machine.
> The VFD is controlled by modbus via the gs2 component. The VFD gets
> reset to default parameters all the time from noise on the modbus. the
> 5i25 get sserial errors. The sserial errors are so bad now it won't even
> move an axis. The spindle works ok. The power supply is a simple bridge
> rectifier with a huge blue cap and a large power resistor across the cap.
>
> Peter keeps telling me it's a grounding issue so where do I start
> looking and what do I need to do?
>
> Thanks
> JT
>
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Re: [Emc-users] Grounding Issues

[John Thornton]

Back from shopping...

Pencil sketch of the power side
http://gnipsel.com/images/bp-knee-mill/bpel03.jpg

Incoming terminal block on left panel where extra ground is
http://gnipsel.com/images/bp-knee-mill/bpel04.jpg

next terminal block on right panel
http://gnipsel.com/images/bp-knee-mill/bpel05.jpg

JT

On 12/20/2015 8:37 AM, Gene Heskett wrote:
> On Sunday 20 December 2015 08:20:38 John Thornton wrote:
>
>> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
>> all the Anilam controls a while back. I've retained the drives and
>> power supply and added a GS2 VFD for the spindle. I have a 5i25 7i77
>> setup. From the get go I've had problems with the electronics on this
>> machine. The VFD is controlled by modbus via the gs2 component. The
>> VFD gets reset to default parameters all the time from noise on the
>> modbus. the 5i25 get sserial errors. The sserial errors are so bad now
>> it won't even move an axis. The spindle works ok. The power supply is
>> a simple bridge rectifier with a huge blue cap and a large power
>> resistor across the cap.
>>
>> Peter keeps telling me it's a grounding issue so where do I start
>> looking and what do I need to do?
>>
>> Thanks
>> JT
>>
> Start with a roll of flat braid equ to a 8 or 10 gauge wire. Establish a
> bolt to the case of the controller as a master ground, and make sure
> everything that references ground in the controller box is grounded at
> this bolt.
>
> Tie this bolt to the buildings static ground using that pin of the
> controllers power cable, BUT not to the building supply neutral as thats
> usually noisy as can be.  Or to a real ground rod but that may have a
> considerable damaging joltage on it when there is lightning nearby so is
> both against the NEC and would be poor practice.
>
> Then extend that ground, using this braid, to the bridgeports main
> casting, and perhaps also to the table and knee as the lube oil in the
> ways might preclude a really good ground on the table without it.
>
> Extend that ground from that bolt to the computers case if it is
> separated from the controller box.
>
> This is called a star ground system, where everything is common at this
> bolt.  If you can disconnect each wire from that bolt, and still measure
> continuity of 200 ohms or less from the bolt to the disconnected wire,
> then that wire has an unwanted ground somewhere, run it down and remove
> it, you want that to be "grounded" only at that bolt.
>
> The idea is that even if it does bounce a bit from a nearby lightning
> strike, it all bounces in unison with no big voltage drops between
> anything that can damage it, or induce noise that would be miss-detected
> as a signal.
>
> Years ago when I was screwing with vz & their bad copper, I figured on
> losing a modem everytime I heard thunder. Getting PO'd, I first opened
> up the wall a bit, pulled out the duplex that was going to power what I
> had in mind, and soldered all the connections in that box. Then I bought
> the biggest surge arrestor I could find, one that had phone line & cable
> tv arrestors in it.  And I bought the biggest home UPS I could find.
> Everything in this room but the lights is plugged in either to that UPS
> or that surge arrestor, and both are plugged into this all soldered
> duplex. Now lightning can hit the pole my transformer is on, possibly
> bouncing everything in this room by 100 kilovolts, but it all bounces in
> unison and I haven't lost a modem or anything else that I could
> associate the loss with local lightning strikes. But since I did get,
> from a wired keyboard I was typing on at the time, a really good jolt
> thru my fingers like shuffling ones feet on the rug and then grabbing
> the doorknob, but it didn't hurt the computer or the keyboard, but I now
> use wireless keyboard and mice.
>
> If the frame of the bridgeport is grounded thru other means, such as a
> 3rd pin on a power cable, this should be defeated in order to remove the
> potential ground loop which can be a source of quite a bit of induced
> noise.
>
> Motor drive, and feedback cables from the motors should be shielded, with
> the shields cut off at the motor ends of the cable but tied to this bolt
> at the controller end, thereby interrupting that potential ground loop.
>
> The general idea is to have one common "ground" point, even if its is not
> an earthen ground. That s/b, by the NEC, at the service entrance, a
> minimum of two full rods driven 6 feet apart, with an 8 gauge wire
> bonding them to the buildings static ground for the 3rd pin of all the
> duplexes and neutral from the pole drop, the only place it is legal to
> interconnect them.  Hanging an amprobe on any of the bare static wires
> in the service box should get you a zero reading regardless of what is
> powered up.  If you do see a reading, something out on that circuit is
> miss-wired. Fix it. Its just good practice.
>
> It and I, may sound arbitrary John, but it works.  And its NEC legal.
> If you have a 

Re: [Emc-users] Grounding Issues

[Kirk Wallace]

On 12/20/2015 05:20 AM, John Thornton wrote:
> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've removed
> all the Anilam controls a while back. I've retained the drives and power
> supply and added a GS2 VFD for the spindle. I have a 5i25 7i77 setup.
>   From the get go I've had problems with the electronics on this machine.

I have had good results (noise on encoder lines) by adding mains filters 
to my VFD power inputs.

The shiny box here:
http://www.wallacecompany.com/cnc_lathe/HNC/00024-1a.jpg

I suspect any switching power circuit might benefit from installing an 
input filter.

-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/

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Re: [Emc-users] Grounding Issues

[Dave Caroline]

The din rail in the 05 pic is that real tight to the back panel (add
star washers to cut through paint), make sure the green/yellow blocks
have the middle screw tight.

One mighty thin grounding wire in bpel04.jpg, also could add star
washer to cut through paint

You could measure the ground resistance too if you can.

Others are likely to mention you have two grounds rather than a star
ground. Make sure cases are tight to frame to guarantee continuity

Dave Caroline

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Re: [Emc-users] Grounding Issues

[Gene Heskett]

On Sunday 20 December 2015 12:15:21 John Thornton wrote:

> Back from shopping...
>
> Pencil sketch of the power side
> http://gnipsel.com/images/bp-knee-mill/bpel03.in
the left box probably needs the paint cleaned off under it, and maybe a 
star washer under the spade lug for extra connection bite. And there 
ought to be a similar ground to the box in the right box. But as sub 
boxes generally have isolated busses for the static (bare wires in the 
romex */3 wires) in order to bot short circuit the connection at the 
main entrance a foot or so from the meterhead.

> Incoming terminal block on left panel where extra ground is
> http://gnipsel.com/images/bp-knee-mill/bpel04.jpg

Here I cannot see the above green wire, the static, while connected to 
the  to the box, but it does not leave to connect the rest of the stuff, 
just the white (neutral) and black (127 hot) wires leaving are all I see 
leaving. Tieing to the box, is to ground the box to the static 
grounding.

> next terminal block on right panel
> http://gnipsel.com/images/bp-knee-mill/bpel05.jpg
>
And here, unless its in the block mounting for the two green wires I can 
see, and I am not at all familiar with that style of terminal block, 
they are floating.  Are the two pieces of SJ I see coming in at the top, 
source or load?

Offhand, it does tend to look like a noise factory from here. :(  Those 
green wires should come from the real ground at the service entrance and 
go all the way to that single point bolt in the driver cabinet wall, 
then from there to everything else as a star ground.

> JT
>
> On 12/20/2015 8:37 AM, Gene Heskett wrote:
> > On Sunday 20 December 2015 08:20:38 John Thornton wrote:
> >> I have a BP knee mill with an Anilam 1100M CNC kit on it. I've
> >> removed all the Anilam controls a while back. I've retained the
> >> drives and power supply and added a GS2 VFD for the spindle. I have
> >> a 5i25 7i77 setup. From the get go I've had problems with the
> >> electronics on this machine. The VFD is controlled by modbus via
> >> the gs2 component. The VFD gets reset to default parameters all the
> >> time from noise on the modbus. the 5i25 get sserial errors. The
> >> sserial errors are so bad now it won't even move an axis. The
> >> spindle works ok. The power supply is a simple bridge rectifier
> >> with a huge blue cap and a large power resistor across the cap.
> >>
> >> Peter keeps telling me it's a grounding issue so where do I start
> >> looking and what do I need to do?
> >>
> >> Thanks
> >> JT
> >
> > Start with a roll of flat braid equ to a 8 or 10 gauge wire.
> > Establish a bolt to the case of the controller as a master ground,
> > and make sure everything that references ground in the controller
> > box is grounded at this bolt.
> >
> > Tie this bolt to the buildings static ground using that pin of the
> > controllers power cable, BUT not to the building supply neutral as
> > thats usually noisy as can be.  Or to a real ground rod but that may
> > have a considerable damaging joltage on it when there is lightning
> > nearby so is both against the NEC and would be poor practice.
> >
> > Then extend that ground, using this braid, to the bridgeports main
> > casting, and perhaps also to the table and knee as the lube oil in
> > the ways might preclude a really good ground on the table without
> > it.
> >
> > Extend that ground from that bolt to the computers case if it is
> > separated from the controller box.
> >
> > This is called a star ground system, where everything is common at
> > this bolt.  If you can disconnect each wire from that bolt, and
> > still measure continuity of 200 ohms or less from the bolt to the
> > disconnected wire, then that wire has an unwanted ground somewhere,
> > run it down and remove it, you want that to be "grounded" only at
> > that bolt.
> >
> > The idea is that even if it does bounce a bit from a nearby
> > lightning strike, it all bounces in unison with no big voltage drops
> > between anything that can damage it, or induce noise that would be
> > miss-detected as a signal.
> >
> > Years ago when I was screwing with vz & their bad copper, I figured
> > on losing a modem everytime I heard thunder. Getting PO'd, I first
> > opened up the wall a bit, pulled out the duplex that was going to
> > power what I had in mind, and soldered all the connections in that
> > box. Then I bought the biggest surge arrestor I could find, one that
> > had phone line & cable tv arrestors in it.  And I bought the biggest
> > home UPS I could find. Everything in this room but the lights is
> > plugged in either to that UPS or that surge arrestor, and both are
> > plugged into this all soldered duplex. Now lightning can hit the
> > pole my transformer is on, possibly bouncing everything in this room
> > by 100 kilovolts, but it all bounces in unison and I haven't lost a
> > modem or anything else that I could associate the loss with local
> > lightning strikes. But since I did get, from a wired 

Re: [Emc-users] Grounding Issues

[Gene Heskett]

On Sunday 20 December 2015 13:37:38 John Thornton wrote:

> On 12/20/2015 11:47 AM, Gene Heskett wrote:
> > On Sunday 20 December 2015 12:15:21 John Thornton wrote:
> >> Back from shopping...
> >>
> >> Pencil sketch of the power side
> >> http://gnipsel.com/images/bp-knee-mill/bpel03.in
> >
> > the left box probably needs the paint cleaned off under it, and
> > maybe a star washer under the spade lug for extra connection bite.
> > And there ought to be a similar ground to the box in the right box.
> > But as sub boxes generally have isolated busses for the static (bare
> > wires in the romex */3 wires) in order to bot short circuit the
> > connection at the main entrance a foot or so from the meterhead.
> >
> >> Incoming terminal block on left panel where extra ground is
> >> http://gnipsel.com/images/bp-knee-mill/bpel04.jpg
> >
> > Here I cannot see the above green wire, the static, while connected
> > to the  to the box, but it does not leave to connect the rest of the
> > stuff, just the white (neutral) and black (127 hot) wires leaving
> > are all I see leaving. Tieing to the box, is to ground the box to
> > the static grounding.
> >
> >> next terminal block on right panel
> >> http://gnipsel.com/images/bp-knee-mill/bpel05.jpg
> >
> > And here, unless its in the block mounting for the two green wires I
> > can see, and I am not at all familiar with that style of terminal
> > block, they are floating.  Are the two pieces of SJ I see coming in
> > at the top, source or load?
>
> The green/yellow terminal blocks are standard ground blocks, the
> center screw tightens a gripper that forces a tight metal to metal
> contact with the DIN rail and the terminals. It's very much grounded
> to the DIN rail and the DIN rail is fastened to the back plane with
> welded on studs and star washers and nuts.
>
That makes me feel a lot better John.

But I am shortly going to be out of pocket till Monday afternoon. 
Cataract fixings in the XYL's right eye are scheduled for first thing in 
the morning, so we've reserved a room about a mile from the O.R.

> http://www.automationdirect.com/adc/Shopping/Catalog/Terminal_Blocks/D
>INnector_DIN-Rail_Terminal_Blocks/Ground_Terminal_Blocks/DN-G10
>
> They are very expensive...

Figures. :(

Do you have an oscilloscope?

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Some mill pix are at:
Genes Web page 

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Re: [Emc-users] Grounding Issues

[John Dammeyer]

Hi John,

It sounds as if you have two AC lines coming into the machine.  One for the
controller and one for the VFD.  The comments about a single star ground
point are standard industry practice.  One breaker at the panel which
protects the wire to the machine.  Another breaker inside the machine that
protects the equipment.

The Earth (green) comes in and is connected to a welded stud with a ring
terminal, not a spade and double nutted so it can't possibly come loose.
>From that point your controller and VFD are run.Never ever rely on the
frame to carry the AC Ground (Earth) from one section to another.  

DC grounds are isolated from Earth Ground.  You can, connect the DC power
supply minus to the Earth ground and it may even be a code requirement where
you are.  Be aware, some PCs do this inside their power supply as do other
types of COTS hardware.

And here is the problem you have to watch out for.  Just because your DC
volt meter reads continuity  (Zero Ohms)  between all the ground points
doesn't mean that there is actually a path of lowest resistance following
what you think it should.

The moment you get into the switching power world which includes the VFD,
Stepper Motors and Servos along with switching power supplies you get
something called impedance.  That's based on the DC resistance (usually low)
and a combination of the wire inductance and capacitance and frequency.  

Depending on how things are wired and routed the impedance of the return
signal of the VFD may be lower through the RS232 (RS485) shield than it is
through the green wire or even the shield around the power cable.  So just
imagine the very noisy VFD signal returns through the communication shield
because that has an impedance of 200 Ohms while the green wire has 1K.
That's problem #1.

There's two types of electrical noise.  Electrical coupling and magnetic
coupling.  Electrical you shield against.  Usually with the shield tied to a
common earth somewhere.   
Magnetic coupling is the same thing that makes a transformer or a motor
function.  A rapidly changing magnetic field caused by rapidly changing
current in a wire is coupled onto another wire that is in close proximity.
Shielding doesn't protect against that. Twisted pairs do to a certain
extent.  

The best protection is distance.  That's why you don't run the VFD power or
Servo power tightly tie wrapped to the encoder signal.  

Therefore put the AC power side for the VFD on one side of the cabinet and
run the control signals as far away as possible.

There are lots of books written on this subject and probably as many
opinions on what to do.  Ground shield at both ends.  Ground at one end.
Don't ground.   Twist the wires.  Don't twist the wires.  

Start with the Star Grounding.  Make sure there aren't any DC paths that are
unexpected as explained earlier.   Then start looking at how the noisy
signals might find their way back through alternate paths.  Filters,
Ferrites are all useful to block the signals.  Always best to block at the
source.

John






> -Original Message-
> From: John Thornton [mailto:j...@gnipsel.com]
> Sent: December-20-15 10:27 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Grounding Issues
> 
> 
> I have a line reactor for the VFD but I've never hooked it up.
> 
> http://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive
> _%28VFD%29_Spare_Parts_-a-_Accessories/AC_Line_Reactors/LR-23P0-1PH
> 
> Speaking of VFD's mine is grounded to the breaker panel and not in the
> machine anywhere. When I check from the ground terminal to the panel I
> get 0 ohms so I assume that the back of the VFD is grounded to the
> ground lug on the VFD.
> 
> JT


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Re: [Emc-users] Grounding Issues

[tom-emc]

I bought some Weidmuller WPE6 off ebay for less than $1/ea.  In fact, I bought 
various DIN terminal blocks off ebay for a fraction of the price new.  I’d 
watch ebay, you may find a deal…
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.XWEIDMULLER+WPE6.TRS0&_nkw=WEIDMULLER+WPE6&_sacat=0

-Tom


> On Dec 20, 2015, at 1:37 PM, John Thornton  wrote:
> The green/yellow terminal blocks are standard ground blocks, the center 
> screw tightens a gripper that forces a tight metal to metal contact with 
> the DIN rail and the terminals. It's very much grounded to the DIN rail 
> and the DIN rail is fastened to the back plane with welded on studs and 
> star washers and nuts.
> 
> http://www.automationdirect.com/adc/Shopping/Catalog/Terminal_Blocks/DINnector_DIN-Rail_Terminal_Blocks/Ground_Terminal_Blocks/DN-G10
>  
> 
> 
> They are very expensive...

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Re: [Emc-users] Grounding Issues

[Rafael]

John,

On 12/20/2015 06:31 AM, John Thornton wrote:
> I'll start with a couple of photos of the el cabinets before breakfast
> and get more details after.
>
> http://gnipsel.com/images/bp-knee-mill/bpel01.jpg
> http://gnipsel.com/images/bp-knee-mill/bpel02.jpg
>
> JT
>

We used to have cabinet grounding problems on PDP-11 series until we 
connected ground wires from each cabinet, doors, and computer chassis to 
one point in the power entry cabinet. Wires were thick, over 2mm or so 
if I remember correctly.

As Gene and others have pointed out, star configuration is the only way 
to go. As far as I can see from your pictures (bpel01.jpg right top 
corner for example), you seem to have more than one ground connection in 
the box. That seem OK logically but it's not good for a number of 
reasons, resistance, ground loops, RF. Box is not a GND star center. 
Metal brackets don't seem to be grounded to one point either but they 
have circuit boards with spacers on them.

You can get a copper grounding bar with holes and screws in hardware 
store to create a large ground post for everything in the box. Outside 
ground from power cable needs to be attached to it first then other 
things including box, the door, and shielded wires between the 
electronic devices. Don't forget the fans.

Since this is a retrofit (?) I would remove all ground wires, check for 
corrosion or electrolytic effects, and connect them to one ground. Note 
that a mix of steel washers and copper wires has it's own issues. In 
addition, I would turn all screws on boards back and forth to make 
better connections also.

Next thing is PSU. Old electrolytic caps may not be good enough anymore, 
there might be RF noise problem between the circuits, wires too thin to 
carry the current, etc.

-- 
Rafael

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