Re: [Emc-users] Rewiring the BP

[Dave Cole]

Yes.

And generally (old school US machine wiring) the hot (fused) leg for 120 
VAC control wiring is red and the neutral is white, especially if there 
are higher voltages in the same cabinet (like 480).   Then red is 120 AC 
control, white is Neutral, black is 240 or 480 AC power, Blue is DC etc.

Dave



On 1/1/2016 12:03 PM, John Thornton wrote:
> I just looked at the control transformer and L1 and L2 (240v side are
> fused with type CC fuses and X1 only on the 120v side is fused with a
> slo-blow fuse. So I assume they intended X2 to be the "neutral".
>
> JT
>
> On 1/1/2016 10:15 AM, Gene Heskett wrote:
>> On Friday 01 January 2016 07:00:31 John Thornton wrote:
>>
>>> Hi Gene,
>>>
>>> The frame is most solidly grounded. I'll do the tests in a bit. Keep
>>> in mind that I have a 240v to 120v step down transformer to supply the
>>> 120v not a normal house circuit. Again an effort to kill the noise.
>>> Which by the way I'm running 2.7 now after changing the wires on the
>>> limit/home switches to twisted pair shielded wire. I've attached the
>>> VFD side wiring diagram. I assume the connection is through the
>>> neutral bonding screw at the panel because the step down transformer
>>> is isolated from ground.
>>>
>>> Happy New Year to you too.
>>>
>>> JT
>> So this then was my 2nd guess, is the capacitative interwinding coupling
>> in that transformer capable of supplying a very few microamps of actual
>> current, probably less than 1 or 2. With no loads plugged in, you could
>> connect either of the output phases of that transformer to machine
>> frame "ground" without any fireworks which would bring the other up to
>> 127 to "ground".
>>
>> I believe in that case I would synthesize a std 127 volt circuit out of
>> the control transformers secondary by connecting the lower voltage wire
>> to the machines frame, along with the static ground wire in a short bit
>> of romex & using the std color code where the black wire is the high
>> side of the transformers secondary, feed it to a duplex or 4 plex to
>> power the computer, monitor, and any other 120 volt only loads on the
>> machine as long as the total load is within the ratings of the
>> transformer.
>>
>> That should be 100% safe for everything.  And it should reduce the
>> coupled noise just because its all bouncing in unison.
>>
>> Some of the noise coupling is coming into the 120 volt circuit from
>> the "longitudinal" coupling of the windings un-avoidable capacitance,
>> and grounding one side of it, and the loads static ground to the
>> machines frame & ground should absorb a good share of it.
>>
>> In really obnoxious cases, a small, perhaps a .01 to .1 uF capacitor
>> rated at least at 600 volts from the high side, black wire to the
>> duplex, to the machines frame should gobble up the rest of it. And not
>> just for S, I'd fuse the hot lead of that cap since a failure would
>> take out the control transformer.  Fused at less than the transformer is
>> rated of course since you want to blow the fuse instead of the
>> transformer.
>>
>> That was my theory when I hooked this room up, and I have not lost a
>> piece of gear during an electrical storm in over 10 years since I did
>> it.  With the 50kw can that supplies 4 houses on the pole across the
>> street, that pole has been nailed quite a few times, and I even got a
>> grab the doorknob shock that jumped out of a wired keyboard once.  So I
>> know this whole room full of electronics has bounced at least 25Kv. Not
>> even a computer crash when it happened.
>>
>> Electrical shock is a weirdly defined thing. Below 20 micro-amps directly
>> thru the heart, a currant so low you may not even feel it, is generally
>> harmless, but at 20 micro-amps up to about 20 milli-amps it can disturb
>> the beat, causing fibrillation and eventual death if no one removes the
>> power or you from the source and applies the defibber paddles.
>>
>> Above 20 milli-amps, the survival rate is better because the heart is
>> frozen, and when the currant is removed, and it hasn't been frozen so
>> long you are brain dead from lack of oxygen, then the heart will often
>> start back as if nothing has happened.
>>
>> Your trivia factoid for the day. :)
>>
>> My ex had a cousin that I met once in the 1970's after he had stuck an
>> alu ladder he was carrying into a low hanging 7200 volt line. Lost part
>> of a foot, and the shoulder blade and arm the ladder was laying on.
>> Never was the sharpest tack in the box, but I'd have guessed him at an
>> IQ of 105 to 110 or so after the event.  Some surgery, a specially built
>> boot and a while to heal, which he was still doing when I met him at
>> some sort of a family doin's, but by now he's probably taken over the
>> painting business his father started 50+ years ago and run it, if not
>> retired from it. That was a "few" thousand  days ago. :)  The ex left 31
>> years ago, ending any excuse I had to keep track of someone in Wisconsin
>> I only met once.
>>
>>> On 12/31/2015 

Re: [Emc-users] To Peter C Wallace

[Gene Heskett]

On Friday 01 January 2016 11:23:35 Peter C. Wallace wrote:

> On Thu, 31 Dec 2015, Gene Heskett wrote:
> > Date: Thu, 31 Dec 2015 20:51:08 -0500
> > From: Gene Heskett 
> > Reply-To: "Enhanced Machine Controller (EMC)"
> > 
> > To: "emc-users@lists.sourceforge.net"
> >  Subject: [Emc-users] To Peter C
> > Wallace
> >
> > I tried to hook up my soft start circuit tonight, but when I had it
> > wired in, the spindle didn't run. Checking dmesg, the card did not
> > sign in like it usually does.  Backed out of the mainboard socket at
> > least 1/8", again. By bumping the parport cables molded connector
> > against the wall.
> >
> > So I have an excedrin headache, number unk.  Everytime I turn that
> > computer around, to plug in a usb cable to charge my DS201, or for
> > any reason, the 5i25 comes far enough out of the pci socket to
> > disable something.  Or blow the card.  At 90 bucks a pop, that isn't
> > fun.
> >
> > Do you have a bracket that can somehow hold the card into the
> > socket?
> >
> > Its an LP bracket in an LP box, but it needs something to nail the
> > card down into the slot a lot firmer than the LP bracket is holding
> > it.
> >
> > Ideas, anybody?  Or do I have to make a x-crossed-brace to go across
> > the top of the pci sockets?
> >
> > Thanks all. :)
> >
> > 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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>
> Whats is actually bending when the card works out of the socket?
> We have some standard height brackets with a rib on the edge
> to limit flexing, unfortunately we cannot get stock
> LP brackets with the rib
>
> If the case/bracket are not rigid enough to prevent card motion,
> one possibility is pad on the case top that presses on the connector
> finger area of the top card edge
>
I had previously bent the top of the bracket up a wee bit so the little 
plastic latch Dell uses for a holddown would  put more pressure on it, 
enough that the latch no longer blew around in a mild breeze. The card 
was not in fact out of the socket this time, but I did superglue a 
wooden strip to the lid, and added another 1/16" of some alu angle on 
top of that which should adequately restrict any jacking.

But its temporarily fixed, see the msg I just posted after battling with 
it quite a bit of the afternoon.  Its obvious I have a flaky BoB.

Thanks Peter.
>
> Peter Wallace
> Mesa Electronics
>
>
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Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Rewiring the BP

[John Kasunich]

This is one of those cases where electrical practices on opposite
sides of oceans differ significantly.

On Fri, Jan 1, 2016, at 12:29 PM, Bertho Stultiens wrote:
> On 01/01/2016 05:47 PM, Dave Cole wrote:
> > That's done all of the time.   In fact it is part of the NEC (National 
> > Electric Code) that is followed (for the most part) in the US.
> > Pretty much every house in the US is wired like that.  (I'm not making 
> > this stuff up.  :-) )
> 
> I agree with the connection at power entry in the house. That is quite a
> different story. That is actually the same here in EU (most countries).
> 
> I think that we should separate two things:
> - house installation
> - machine wiring
> 
> House installation is pretty much standardized with a lot of rules and
> reasons. Specifically to ensure referencing and protection.
> 
> Machine wiring is different in that you can have scenarios where
> references are moved, especially in a 2-phase system where you are not
> using the neutral, which is the scenario we have here.

120V transformer secondaries (in the USA) need to be grounded on
one side, even if they are part of a machine control panel.

Such transformers are referred to as "control power transformers"
and traditionally powered electro-mechanical control devices such
as relays and contactors.  Today they still power those things, and
they also power AC-to-DC supplies that run the electronic parts of
the control.The low voltage DC power distribution (typically 24V)
is sometimes un-grounded, sometimes single-point grounded, for 
exactly the noise reasons Berthos mentions.  But the 120V "control
power" isn't used a the "reference" for anything - it is still "dirty"
power, although not as dirty as the main power that might be going
to a VFD or whatever.

The main reason for grounding one side of the 120V control power
circuit is for safety in the event of a primary-to-secondary
transformer insulation breakdown.  Machines in the US are powered
by anything from 240V single phase to 480V three phase.  An insulation
failure in the transformer could put up to 480V on the control circuits if 
the secondary was ungrounded.   With a grounded, secondary, it will
simply blow the transformer primary fuse(s), which are already rated
for the full primary voltage.

Control circuit fuses, wiring, pushbuttons etc, etc, are typically rated
150, 250, or 300V.  Not 480V.  So all kinds of bad things could happen
if 480V wound up on ungrounded control circuits.

Another reason for grounding one side is that you have a distinct
hot and neutral.  Hot is protected by fuses or breakers, neutral is not.
A typical industrial panel might have a half-dozen small single-pole
breakers or fuses feeding multiple low power loads.  If ungrounded,
those would all have to be two-pole devices.

> The reason for /not/ connecting the ground on a secondary winding is to
> prevent a capacitively coupled ground path. Especially if you cannot
> guarantee a 100% balanced primary-to-secondary side wrt. ground (*).
> 
> What happens is that there will be a current in the ground connection
> which causes an imbalanced current on the primary side (remember:
> primary is 2-phase circuit without neutral reference). This is a
> differential current discrepancy on the primary side. If you have an RCD
> (which you should), then it can or will trip due to the current imbalance.

RCD's are extremely uncommon in the USA for industrial stuff.  In fact
the term RCD itself is virtually unknown.  "Ground fault" is the term used
here.

There are two kinds of ground fault protection.  In residences, ground 
fault protected receptacles are required when near water (kitchen and
bathroom sinks, outdoor receptacles, basements, and several other
places).  These GFCI's  (Ground Fault Circuit Interrupter) are intended
to protect people from shock, and have trip points around 6mA IIRC.

In industry, ground fault relays are typically applied at the transformer,
where the neutral is grounded.  They are intended to protect against 
ground faults where the impedance might be high enough (and the 
fault current low enough) that normal overcurrent protection doesn't
trip.  But they don't protect against shock; the trip levels range from
a few amps to a few tens of amps.  They pretty much shrug off stray
capacitive leakage.

> > There are a lot of good reasons to tie one leg the transformer to ground 
> > besides to establish the safety ground and neutral as is common on the US.
> > Intermittent faults to ground, with an ungrounded system, can cause the 
> > secondary of the transformer to fly way above absolute ground causing 
> > connected devices, or the transformer to suffer from insulation 
> > breakdowns.   That's the extreme, but it can happen.
> 
> Actually, the secondary should normally be floating. Most transformer
> setups are to ensure galvanic separation and that means you may never
> connect neutral to the secondary side.

I don't think anyone is saying you would 

Re: [Emc-users] To Peter C Wallace

[Gene Heskett]

On Friday 01 January 2016 10:58:37 linden wrote:

> I just put a gob as far aft as i can get (calling the end where your
> cables come out forward) It is just like sticking things together with
> a wad of gum if you are using an elcheepo glue gut it dose not get hot
> enough to wick in between any thing. Its non conductive the clear
> sticks seem to work better as they do not bond quites as well and you
> can peal it off relatively easily. the yellowy cream colored sticks
> are a more permanent glue.
>
> On 15-12-31 06:53 PM, Gene Heskett wrote:
> > On Thursday 31 December 2015 21:27:52 linden wrote:
> >> Hi Gene,
> >>   I have used hot glue from a hot glue gun in the past (the
> >> Kind for arts and crafts) to hold cards in. It works well for high
> >> vibration and you can peal the glue off to get the card out if you
> >> need too. Not as good as a mechanical hold down but certainly
> >> better than nothing and not as permanent as potting compound. May
> >> be enough added stay puttedness for your application or untill you
> >> can come up with a better solution.
> >
> > Never gave that a thought, but it might be just the ticket. I don't
> > think its electrically conductive. I'm assuming you put a line of it
> > against both the socket and board?
> >
> > I can only access one side, without pulling the mainboard, which
> > might be less than optimum.
> >
> > Did you put anything against the board to keep it from wicking into
> > the socket itself?  Or does it set fast enough thats not a problem?
> >
> > Thanks for the idea Linden, I appreciate a fresh idea.
> >
> >> On 15-12-31 05:51 PM, Gene Heskett wrote:
> >>> I tried to hook up my soft start circuit tonight, but when I had
> >>> it wired in, the spindle didn't run. Checking dmesg, the card did
> >>> not sign in like it usually does.  Backed out of the mainboard
> >>> socket at least 1/8", again. By bumping the parport cables molded
> >>> connector against the wall.
> >>>
> >>> So I have an excedrin headache, number unk.  Everytime I turn that
> >>> computer around, to plug in a usb cable to charge my DS201, or for
> >>> any reason, the 5i25 comes far enough out of the pci socket to
> >>> disable something.  Or blow the card.  At 90 bucks a pop, that
> >>> isn't fun.
> >>>
> >>> Do you have a bracket that can somehow hold the card into the
> >>> socket?
> >>>
> >>> Its an LP bracket in an LP box, but it needs something to nail the
> >>> card down into the slot a lot firmer than the LP bracket is
> >>> holding it.
> >>>
> >>> Ideas, anybody?  Or do I have to make a x-crossed-brace to go
> >>> across the top of the pci sockets?
> >>>
> >>> Thanks all. :)
> >
> > Cheers, Gene Heskett

As it turned out when I had pulled it down to where I could look at it, 
the card was fully seated, my last bending of the bracket seems to have 
nailed it into the socket firmly enough.  I did add a wood and alu pad 
to the lid so that it can't come up more than 20 thou anyway.

That leaves the hal file I worked on to convert what was the axis a 
stepgen into usable gpio on the BoB's pin 8-9 and "wired" it up to the 
charge pumps outputs.  That part, FWIW, is working well since the logic 
highs coming out of the BoB are at 5.08 volts.  However, sitting off 
overnight emphasized that I need a bleeder on that supply, very badly.  
Before powering things up today, I measured the voltage on that bank of 
caps. Live, its 127, off overnight it was still showing 113 volts.  Very 
low leakage caps I think. :)

So I've printed a fresh copy of the hal file to see if I can find where I 
screwed up the pwmgen inputs, the enable is coming out, and reverse is 
coming out, both on the proper queue & pins on the BoB.  But theres no 
output on the BoB's pin 14, which is the pwmgen output, its sitting 
high, which is driving the - input on Jon's pwm-servo amp.  No leds on 
it, and the reset switch has no effect.  Humm, thinking out loud, I 
haven't checked the volts on the pwm inputs + pin of Jon's driver, brb.  
Yup, +5.08 as expected. And no pulses on the BoB's pin 14 with that wire 
disconnected.

On a hal-meter, pid-s looks normal and is outputing about 5x the input 
because there is no feedback from a stationary spindle. 
hm2_5i25.0.pwmgen.00.value matches.

That leaves my hal file, the BoB, or the 5i25. Or a broken conductor in 
the interconnecting db-25 cable.  It is screwed to the panel connectors 
at both ends.  But from the diameter of that cable, even 25 pieces of 30 
gauge would be bigger. That one is all of 42" long, and I don't have 
another more than 30".

Now its fixed, but I've NDI why/how.

I powered everything but the computer down, stopping linuxcnc.
Pulled the db25 off the breakout boards input, found pin 14 & hooked the 
ds201 to it.

Started linuxcnc up again, enabled the machine, hit the CW button and + 
several times.  On the ds201 it looks like it might be 10 Hz! But very 
slow attack and decay times, like it was pushing the ds201's bandwidth.

Scratching 

Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/01/2016 07:25 PM, Kirk Wallace wrote:
>> Machine wiring is different in that you can have scenarios where
>> references are moved, especially in a 2-phase system where you are not
>> using the neutral, which is the scenario we have here.
> My understanding is, and I could be wrong, that "two-phase" in reference 
> to modern mains circuits does not exist. Circuits with two hot legs, L1 
> and L2, are single phase and referenced to each other. Two phase used to 
> be two legs that were 90 degrees apart, but is long gone.

That was (almost) my faulty thought too at first, but it turns out that
the 2-phase system referred to comes from a single transformer with two
secondary windings. This gives you two 120V lines wrt. neutral (L1 and
L2) which are 180 degrees shifted. Therefore, the difference between L1
and L2 is 240V.


-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Measuring Noise - Oscilloscope

[John Thornton]

Mark,

The short answer is replacing the limit/home switch wiring with shielded 
cable and grounding it to one place was the difference in making the 
sserial errors go away. Unless you need 2.7 back up to 2.6 till you get 
rid of the sserial errors.

JT

On 1/1/2016 4:28 PM, Mark Johnsen wrote:
> I have a very similar setup to John Thornton and same noise issue w/ 2.7.3:
> Mesa 5i25/7i77
> Transformer 120vac:80Vac, rectified w/ large cap to run 3-axes West Amp
> servo's (Not sure John has this)
> GS2 Automation direct 3hp drive, powered by separate 240Vac single phase
> input.  Also, I use his serial modbus setup from the PC.
> 120Vac powering the PC (not enclosed in computer case)
>
> Anyway, I've been reading all the posts here and on the IRC as I've been
> away for X-mas Holiday and I think I would like to be able to measure the
> noise to be able to determine if my changes make an effect.  I've
> unsuccessfully dealt w/ noise issues before and find it a daunting task to
> trouble shoot.
>
> I'm assuming using a scope is the right way to do it?
>
> But I need a scope and would use it for this and some smaller circuit board
> type projects (total hack type stuff).  I've seen a lot on the rigol, but
> I've also come across a siglet that seems to be slightly better.  I read
> that readings should be 10:1 over the signal and an arduino is around 8Mhz,
> so 70Mhz is probably good enough for me.
>
> Siglent SDS1072CML 7'' TFT-LCD Display Bench-Top Oscilloscope, 70MHz
> http://www.amazon.com/Siglent-SDS1072CML-TFT-LCD-Bench-Top-Oscilloscope/dp/B00GQNNHJG
>
> Wondering if anyone has an opinion on that one?  Seems like it would fit
> the bill for a low end O-scope?
>
> Here's the standard Rigol DS-1052E
> http://www.amazon.com/Rigol-DS1052E-Digital-Channels-sampling/dp/B003MYND5A
>
> Thanks,
> Mark
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Re: [Emc-users] Rewiring the BP

[John Dammeyer]

Isn't it commonly called Split Phase in North America?

Draw 15A on each side of the 120-0-120 VAC circuit and measure that with a
clamp on ammeter and you get 15A on each leg.  Put the clamp on meter on the
white wire (the neutral return)  and you get 0A. In effect the two phases
are 180 degrees out of phase.  If it weren't so you'd have to make the white
neutral wire handle twice the current of the black (and/or  red) hot wires.

John Dammeyer


> In the USA, Kirk is 100% correct.  Two phase means 90 degree phase
> shift, and is pretty much non-existent.  120V-0V-120V with 240V from
> end to end is "single phase".  Call it two-phase and people in the States
> will look at you funny.
> 
> John Kasunich
> 
> 
> 
>

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Re: [Emc-users] Rewiring the BP

[John Dammeyer]

Thank you.
Well said.
John Dammeyer


> -Original Message-
> From: John Kasunich [mailto:jmkasun...@fastmail.fm]
> Sent: January-01-16 4:41 PM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Rewiring the BP
...
> 
> Three phase or single phase doesn't matter.  When a transformer delivers
> power at 120VAC one side is grounded.  There are a few very limited
> exceptions in the code, such as:
> 
>  A control circuit derived from a transformer with a primary not
>  over 1000 volts need not be grounded if:
>  (1) only qualified persons will service the installation,
>  (2) continuity of control power is required, and
>  (3) ground detectors are installed on the control circuit. [250-21]
> 
> Some more detail at:
> http://www.ecmag.com/section/codes-standards/motor-control-circuits-
> ground-or-not-ground
> 
> 
> --
>   John Kasunich
>   jmkasun...@fastmail.fm


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Re: [Emc-users] Rewiring the BP

[John Kasunich]

On Fri, Jan 1, 2016, at 08:18 PM, Bertho Stultiens wrote:
> On 01/02/2016 01:41 AM, John Kasunich wrote:
> > This is one of those cases where electrical practices on opposite
> > sides of oceans differ significantly.
> 
> Yes, there are some significant differences. That has become obvious.
> 
> 
> [snip]
> > Three phase or single phase doesn't matter.  When a transformer delivers
> > power at 120VAC one side is grounded.  There are a few very limited 
> > exceptions in the code, such as:
> [snip]
> > Some more detail at:
> > http://www.ecmag.com/section/codes-standards/motor-control-circuits-ground-or-not-ground
> 
> That is a nice link because the first paragraph apparently gives the
> answer afaics:
>   If a motor control circuit is tapped from the motor circuit and
>   does not leave the controller enclosure (the push buttons are
>   in the cover), then it need not be grounded. [90-7 ¶ 2,
>   300-1(b), 450-1 Exc.No.2]
> 
> The control circuit is inside and the PC with all other control logic
> and electronics too. Nothing ever leaves the enclosure. So, that would
> mean that my argument still holds. Or am I reading this completely wrong?
> 

"Tapped from" means directly, without a transformer.

So if you have a three-phase 480V motor, and a contactor with a 480V coil,
you could tap 480V directly from L1 and L2 to run the contactor coil, if the
control circuit doesn't leave the enclosure.  (Likewise with a 240V motor and
a 240V contactor coil).

Most of the National Electrical Code was written back when "control"
meant "motor starter", and that consisted of a contactor with start
and stop buttons.  The exception that you cited allowed for cheap
(because no transformer) motor starters, if you could live with the
buttons being on the cover of the box.

If the buttons were external, the normal arrangement for many years
was a small 480 (or whatever) to 120V control transformer, one side
grounded, start and stop buttons in the ungrounded side so an
accidental short to ground would blow a fuse instead of starting 
the motor.  Contactor coil was 120V.

We have only recently started following the rest of the world in using
24V for the buttons and coils.  Much safer, and the NEC doesn't have
nearly as much to say about how you ground (or don't ground) a 24V
circult.  Except that you still need to make sure a transformer failure
doesn't put primary voltage on the low voltage wiring.  Grounding one
side is probably the easiest way to do that.
 
John Kasunich

-- 
  John Kasunich
  jmkasun...@fastmail.fm

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Re: [Emc-users] To Peter C Wallace

[Gregg Eshelman]

On 1/1/2016 4:29 PM, Jack Coats wrote:
> Back when I received computers via fedex with multiple 'boards' in
> them, the ones that did the best were ones where after each board was
> inserted, a bead of pure silicon caulk (the clear kind) was put along
> the top of the connector so it would contact both the connector and
> the board.  It stayed soft over time and was easy to pull off when the
> board is pulled for any reason.  Typically it was put on one side of
> the connector/daughter board (often the back) to ease installation.
>
> The idea of using hot-glue is similar, but hot-glue can set up
> 'harder' than the caulk over time. --- Still, it is the same thought.

I assume/hope aquarium silicone was used. The common stuff with acetic 
acid in it can be disastrous for electronics. If it smells like vinegar, 
you want it nowhere near anything electronic.


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Re: [Emc-users] Measuring Noise - Oscilloscope

[Bertho Stultiens]

On 01/02/2016 12:27 AM, andy pugh wrote:
>>> I'm assuming using a scope is the right way to do it?
>> Yes and no. It depends on what you are tracking and how it is induced.
> Also, there is no way to detect an occasional microsecond spike
> without recording and analysing unfeasible quantities of data.
> 
> I tried looking for noise on my system with a scope, but soon gave up.

Indeed, transients are nearly impossible to track. A scope is fine for
recurring signals, but terrible at finding that one-off spike that
throws your system into neverneverland.


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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/02/2016 01:41 AM, John Kasunich wrote:
> This is one of those cases where electrical practices on opposite
> sides of oceans differ significantly.

Yes, there are some significant differences. That has become obvious.


[snip]
> Three phase or single phase doesn't matter.  When a transformer delivers
> power at 120VAC one side is grounded.  There are a few very limited 
> exceptions in the code, such as:
[snip]
> Some more detail at:
> http://www.ecmag.com/section/codes-standards/motor-control-circuits-ground-or-not-ground

That is a nice link because the first paragraph apparently gives the
answer afaics:
If a motor control circuit is tapped from the motor circuit and
does not leave the controller enclosure (the push buttons are
in the cover), then it need not be grounded. [90-7 ¶ 2,
300-1(b), 450-1 Exc.No.2]

The control circuit is inside and the PC with all other control logic
and electronics too. Nothing ever leaves the enclosure. So, that would
mean that my argument still holds. Or am I reading this completely wrong?


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Re: [Emc-users] Rewiring the BP - where to connect ground

[Bertho Stultiens]

On 01/01/2016 10:28 PM, Bertho Stultiens wrote:
> Short explanation:
> You must ensure that a grounding connection does not carry current and
> is located at such a point where a symmetric coupling can be achieved.
> 
> A bit longer explanation:
[snip]

Just one comment on the explanation...
It is still quite a simplification of the actual electrical AC analysis
of the circuit as a whole. However, such analysis would be far beyond
the scope of this mailing list IMO. The intricacies can be subtle and
complex and sometimes slightly counter-intuitive.

Not to cut of any detailed discussion, but to prevent to go completely
off topic. Otherwise we should start a new thread for that purpose.

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Re: [Emc-users] Measuring Noise - Oscilloscope

[Mark Johnsen]

John,

Thanks for the direction, I'll look at that for the limits.  My machine is
the _one_ switch type for limits on both ends without a home.  I didn't
setup a home, but after using the mill for the last year, probably a good
idea.

I have been running 2.6.11 on a different harddrive, so good when I need to
go.

I do think I'll buy that O-scope, only because I've always wanted one and
it seems like that one is a decent enough hobby scope for someone like me...

Regards,
Mark

Mark,

The short answer is replacing the limit/home switch wiring with shielded
cable and grounding it to one place was the difference in making the
sserial errors go away. Unless you need 2.7 back up to 2.6 till you get
rid of the sserial errors.

JT
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Re: [Emc-users] Rewiring the BP

[Gene Heskett]

On Friday 01 January 2016 12:03:23 John Thornton wrote:

> I just looked at the control transformer and L1 and L2 (240v side are
> fused with type CC fuses and X1 only on the 120v side is fused with a
> slo-blow fuse. So I assume they intended X2 to be the "neutral".
>
> JT
>
An excellent assumption, John. Do carry on. :)

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] To Peter C Wallace

[Jack Coats]

Back when I received computers via fedex with multiple 'boards' in
them, the ones that did the best were ones where after each board was
inserted, a bead of pure silicon caulk (the clear kind) was put along
the top of the connector so it would contact both the connector and
the board.  It stayed soft over time and was easy to pull off when the
board is pulled for any reason.  Typically it was put on one side of
the connector/daughter board (often the back) to ease installation.

The idea of using hot-glue is similar, but hot-glue can set up
'harder' than the caulk over time. --- Still, it is the same thought.

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Re: [Emc-users] Rewiring the BP - where to connect ground

[Gene Heskett]

On Friday 01 January 2016 18:04:34 Ben Potter wrote:

> > From: Bertho Stultiens [mailto:ber...@vagrearg.org]
> > A bit longer explanation:
> > See attached image. Outputs of the step-down transformer A and B are
>
> capacitively coupled to L1 and L2 through four parasitic capacitors.
>
> > Connecting A to ground when C1A not equal C2A or connecting B to
> > ground
>
> when C1B not equal C2B will create a current in the ground connection.
> 
>
> Thank you for this image - I think I've finally got my head around the
> utter basics of the American electricity supply system. Some of that
> may have been is it single/two phase?
> Having 3 phases and a neutral coming into your premises (aka UK
> 3-phase supply) somehow seems less... subject to complexity
>
> Going really OT here (and I should probably start a new thread for
> this) - what beyond a 1:1 ratio makes a transformer an 'isolation'
> transformer.
>
No ohmic connection between primary and secondary.  If there is, and its 
not just a carbon track from a lightning strike, its an autoformer, and 
potentially a killer because it doesn't isolate.  Two pieces of wire are 
exactly equal to a 1/1 autoformer IOW..

> I have used the below transformer or similar as the primary power
> transformer for machines (in the case of the 2kva one, a ram edm). And
> have considered it to provide sufficient isolation
> http://www.jmsonline.co.uk/product_info.php?cPath=22_id=54
>
> If I'm wrong, please let me know (and ideally how to fix it)
>
> Thanks
> Ben
>
>
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Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Rewiring the BP

[andy pugh]

On 27 December 2015 at 00:32, John Kasunich  wrote:
> Each house has a ground rod.  The neutral from the transformer, the
> house ground rod, a connection from the house cold water plumbing (if
> copper), the neutrals from all the receptacles, and the ground wires from
> all the receptacles are all tied together at a large bus bar in the main 
> panel.


Something of a digression, but this document describes the earthing
systems legal for use in the UK
http://electrical.theiet.org/wiring-matters/16/earthing-questions.cfm

None of those seem to have an earthing spike _and_ a neutral to GND link.

-- 
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Re: [Emc-users] Smart-Serial cabling

[Jack Coats]

My only suggestion is to ensure the wire you have is stranded, not
solid.  Stranded will be 'softer' and deal better with the bending
needed for use in drag-chain use.  Solid core is better for
infrastructure use (putting in walls), stranded is found in 'patch
cables' and used in wiring closets to connect the infrastructure or
from a wall to equipment in an office.

Great use.  BTW, Cat6 or 7 will have a bit more noise rejection, but
Cat 5 is cheaper and will do well.  You will find some of the higher
cat numbers have shielding, much cat 5 does not have shielding but
depends on the twisted wire pairs for noise rejection (each pair is
twisted at a different twist rate, so they don't cross contaminate
each others signal).

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Re: [Emc-users] Measuring Noise - Oscilloscope

[Gene Heskett]

On Friday 01 January 2016 18:33:32 Bertho Stultiens wrote:

> On 01/02/2016 12:27 AM, andy pugh wrote:
> >>> I'm assuming using a scope is the right way to do it?
> >>
> >> Yes and no. It depends on what you are tracking and how it is
> >> induced.
> >
> > Also, there is no way to detect an occasional microsecond spike
> > without recording and analysing unfeasible quantities of data.
> >
> > I tried looking for noise on my system with a scope, but soon gave
> > up.
>
> Indeed, transients are nearly impossible to track. A scope is fine for
> recurring signals, but terrible at finding that one-off spike that
> throws your system into neverneverland.

I could argue that when the scope is both digital and very wide band.

You can set the triggering voltage 10% above the logic 1, or 10% below 
ground, then set it for a sweep everytime its triggered.  Capture one, 
or a few thousand of those bits of noise, and analyze/measure them at 
your leasure.

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] Rewiring the BP

[richshoop]

Excellent references on what actually works, and stays shipped is available 
from any of the cnc machine tool manufacturers maintenance manuals. My 
reference that I used to solve my 8 year long search for intermittent noise 
problem is from Morbidelli, their U-15 machine (A woodworking oriented panel 
processor). The Italian and Spanish manufacturers are a great source since all 
of their machines have to be designed to work with electrical systems all over 
the world. 

- Original Message -

From: emc-users-requ...@lists.sourceforge.net 
To: emc-users@lists.sourceforge.net 
Sent: Friday, January 1, 2016 11:14:43 AM 
Subject: Emc-users Digest, Vol 117, Issue 7 

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Today's Topics: 

1. Re: Smart-Serial cabling (Peter C. Wallace) 
2. Re: Rewiring the BP (Bertho Stultiens) 
3. Re: Rewiring the BP (Jon Elson) 
4. Re: Rewiring the BP (andy pugh) 
5. Re: Rewiring the BP (Kirk Wallace) 
6. Re: Rewiring the BP (John Dammeyer) 
7. Re: Rewiring the BP (John Dammeyer) 


-- 

Message: 1 
Date: Fri, 1 Jan 2016 09:24:26 -0800 (PST) 
From: "Peter C. Wallace"  
Subject: Re: [Emc-users] Smart-Serial cabling 
To: "Enhanced Machine Controller (EMC)" 
 
Message-ID:  
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed 

On Fri, 1 Jan 2016, andy pugh wrote: 

> Date: Fri, 1 Jan 2016 16:59:12 + 
> From: andy pugh  
> Reply-To: "Enhanced Machine Controller (EMC)" 
>  
> To: "Enhanced Machine Controller (EMC)"  
> Subject: Re: [Emc-users] Smart-Serial cabling 
> 
> On 1 January 2016 at 16:16, Peter C. Wallace  wrote: 
>> SSerial is differential RS-422 at 2.5 MBits/sec and requires ~100 Ohm 
>> differential cable cable impedance. This usually means twisted pairs 
>> are required for TX and RX (the 5V/GND power connections are not critical) 
> 
> The pairs are twisted inside the individual foil screen with drain 
> wire then there are 4 other small (0.14mm2) wires and two bigger 
> (0.5mm2) wires all inside an overall braided screen. 
> 
> I suppose the thing to do is to try it and see. I have determined that 
> the pairs fit nicely in an RJ45 connector, but I can't decide what to 
> do about the 2x 5V and 2x 0V positions in the connector. Are the 0V 
> and 5V contacts commoned at the PCB ends, such that leaving two 
> positions unpopulated in the RJ45 is OK? I only need enough 5V power 
> to run the 7i73 logic. 

Yes, they are commoned at the sserial remote and FPGA side RS-422 interface 



> 
> -- 
> atp 
> If you can't fix it, you don't own it. 
> http://www.ifixit.com/Manifesto 
> 
> --
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> 

Peter Wallace 
Mesa Electronics 

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




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Message: 2 
Date: Fri, 1 Jan 2016 18:29:16 +0100 
From: Bertho Stultiens  
Subject: Re: [Emc-users] Rewiring the BP 
To: "Enhanced Machine Controller (EMC)" 
 
Message-ID: <5686b76c.4030...@vagrearg.org> 
Content-Type: text/plain; charset=windows-1252 

On 01/01/2016 05:47 PM, Dave Cole wrote: 
> That's done all of the time. In fact it is part of the NEC (National 
> Electric Code) that is followed (for the most part) in the US. 
> Pretty much every house in the US is wired like that. (I'm not making 
> this stuff up. :-) ) 

I agree with the connection at power entry in the house. That is quite a 
different story. That is actually the same here in EU (most countries). 

I think that we should separate two things: 
- house installation 
- machine wiring 

House installation is pretty much standardized with a lot of rules and 
reasons. Specifically to ensure referencing and protection. 

Machine wiring is different in that you can have scenarios where 
references are moved, especially in a 2-phase system where you are not 
using the neutral, which is the scenario we have here. 


> Now, if you don't want to do that inside the panel for some reason 
> (which I might have missed), 

Re: [Emc-users] Rewiring the BP - where to connect ground

[Bertho Stultiens]

On 01/01/2016 08:24 PM, Rafael wrote:
>> There are a lot of good reasons to tie one leg the transformer to ground
>> besides to establish the safety ground and neutral as is common on the US.
>> Intermittent faults to ground, with an ungrounded system, can cause the
>> secondary of the transformer to fly way above absolute ground causing
>> connected devices, or the transformer to suffer from insulation
>> breakdowns.   That's the extreme, but it can happen.
> 
> Strongly agree! Do not float transformer secondary and have a PC 
> connected to it! This is not about an isolation transformer, it's about 
> stepdown transformer which is way different. Primary side of this step 
> down transformer needs to float in this case. In ideal situation, CT on 
> the primary side would be neutral and connected to local ground but it 
> is better to not use it; transformer is not ideal.

For good measure; I did not say that you should not ground the PC.
Actually, I noted that it already is, but it is grounded at a
_different_ point in the chain of connections.

There is a reason why the PC /should/ be grounded and that has been
underlined in the replies here. The question that seems to be popping up
is _where_ to have the ground connected.

Short explanation:
You must ensure that a grounding connection does not carry current and
is located at such a point where a symmetric coupling can be achieved.


A bit longer explanation:
See attached image. Outputs of the step-down transformer A and B are
capacitively coupled to L1 and L2 through four parasitic capacitors.
Connecting A to ground when C1A not equal C2A or connecting B to ground
when C1B not equal C2B will create a current in the ground connection.

CxA and CxB form capacitive voltage dividers, which will create a
virtual zero point equal to neutral only if both capacitors are equal.
Otherwise, you will have a potential differential and therefore a
current through the ground connection from the secondary(*).

An RCD measures the currents IL1 and IL2 where it must be ensured that
IL1 + IL2 < threshold, where threshold depends on the particular RCD.
When you cannot guarantee that the ground-current is zero, because the
capacitive couplings are not equal, then you risk tripping the RCD. If
you have no RCD, then you are creating an unbalanced circuit that will
come to haunt you at another time (any imbalance in L1 and L2 will
propagate through the system wreaking havoc).

If you look at the DC side of the system, then you have a symmetric
coupling from 0V (DC) to both A and B through Cf. The coupling stems
from the rectifier system, which couples both A and B through the same
circuit (which is why Cf is drawn twice).

Therefore, connecting the output of the PSU's 0V (DC) line to ground
will carry nearly(**) no current. This will protect the whole circuit
from inadvertent potentials and calm the noise in the system.


The /problem/ with having 0V (DC) at ground are again the rise of the
dreaded ground-loops. If you have multiple PSUs all connected to ground
and connecting the 0V (DC) lines through the signal return connections,
then you have two distinct paths (a loop). That is where you need the
galvanic isolator(s) to break the ground-loop.


(*) JT has done a measurement that show a different voltage from
A-to-ground and B-to-ground. Thereby establishing that the parasitic
capacitances are not equal.

(**) the parasitic capacitances are in series and the differentials are
guaranteed less than 90 degrees shifted. The effective leakage is
normally in the order of micro-amps and a few orders of magnitude away
from tripping an RCD.


>> One of way too many references on the web.
>> http://ecmweb.com/bonding-amp-grounding/basics-bonding-and-grounding-transformers
> I hope that nobody gets zapped before this highly charged and perhaps 
> the long(est) thread is over.

Always have a bleeder resistor over your caps. Running a bleeder
resistor over an email-thread helps too ;-)

And then, coffee will help too.

-- 
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Re: [Emc-users] Smart-Serial cabling

[Ben Potter]

From: andy pugh [mailto:bodge...@gmail.com] 
> On 1 January 2016 at 16:16, Peter C. Wallace  wrote:
> > SSerial is differential RS-422 at 2.5 MBits/sec and requires ~100 Ohm 
> > differential cable cable impedance. This usually means twisted pairs 
> > are required for TX and RX (the 5V/GND power connections are not 
> > critical)

> The pairs are twisted inside the individual foil screen with drain wire
then there are 4 other small (0.14mm2) wires and two bigger
> (0.5mm2) wires all inside an overall braided screen.

> I suppose the thing to do is to try it and see. I have determined that the
pairs fit nicely in an RJ45 connector, but I can't decide what to do about
the 2x 5V and 2x 0V positions in the connector. Are the 0V and 5V contacts 
> commoned at the PCB ends, such that leaving two positions unpopulated in
the RJ45 is OK? I only need enough 5V power to run the 7i73 logic.

If it doesn't work, have a look at igus chainflex CFBUS.045 - cat5, should
be good for e-chains and oil from the specs. I think the link should be:
http://www.igus.co.uk/iPro/iPro_01_0013_0056_GBen.htm?ArtNr=CFBUS.045=GB
=en

I should be ordering some in a month or two for a pendant (I've been saying
that for a year or so though)

If it does work, let us all know - good test data is always good

> atp
> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto

Ben


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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/02/2016 12:24 AM, Gene Heskett wrote:
> this is a single phase system delivering 240+ volts AC 
> to the two ends of a single core transformers primary winding.

Well, yes and no. It depends on what you are looking at.

The point in normal AC systems is that your ground potential is at or
near neutral potential. In the system we have here, we have no neutral
and ground is at half the potential of the input.


> While I personally am not 100% happy with a no neutral hook up, it is 
> legal as long as it never leaves the confines of the load machine.  The 
> machine itself is grounded well.  The fact that the core/frame of the 
> control transformer isn't grounded probably enhances the capacitative 
> coupling, which might amount to something in the 100 pF neighborhood.  
> If the frame/core were also grounded, I would expect some of that 
> un-balance to go away and the total, added up, would be less than the 
> delivered voltage primarily because the measureing meter is going to 
> absorb some of it when hooked up to measure it, causing its own 
> imbalance.

Some points here; I agree with the no-neutral is a problem assessment.
However, that is something we have to live with.

Capacitive coupling does not depend on being grounded or not. It is an
inherent property of wires running close to each other, such as in a
transformer.

The capacitance is often a bit higher, but that does not matter too much
for the argument. The unbalance as JT showed is measuring with the same
multimeter at two points. The fact that two different values com out of
that is enough to conclude that the imbalance is in the
system-under-measurement and not caused by the multimeter. Otherwise you
would see the same discrepancy for both measurements. I have not seen a
multimeter that is so bad that it will throw a measurement off more that
few percent.


[snip]
> The reason I wrote 240+ is that 127+127=254, which if Johns meter is a 
> decent one, he should be reading within say 2 volts of that from L1 to 
> L2.  With no neutral, only the secondary of that control transformer is 
> to be considered the src of a 127 volt AC feed, and either end of it can 
> and should be tied to the well grounded machine frame, but not both of 
> course.  Having it grounded gives a direct path to ground for the noises 
> the VFD might induce from close proximity.

This is where we disagree. Whether it is 2x120V=240V or 2x127V=254V does
not matter. The principle of re-referencing an un-referenced system in
the way you suggest is wrong for the purpose because the installation
does not leave the machine. If this was part of a house-installation,
then I'd agree to re-referencing, but it is not.

Also, the VFD's path to ground is quite a different one from the one
after the transformer.

A good grounding plan for the entire machine and a careful plan of /all/
other wiring is how you reduce the noise. There are many more gotchas
than just one ground connection or a VFD. It is the connection plan as a
whole that defines immunity and stability.

-- 
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Re: [Emc-users] Rewiring the BP - where to connect ground

[Ben Potter]

> From: Bertho Stultiens [mailto:ber...@vagrearg.org] 
> A bit longer explanation:
> See attached image. Outputs of the step-down transformer A and B are
capacitively coupled to L1 and L2 through four parasitic capacitors.
> Connecting A to ground when C1A not equal C2A or connecting B to ground
when C1B not equal C2B will create a current in the ground connection.


Thank you for this image - I think I've finally got my head around the utter
basics of the American electricity supply system. Some of that may have been
is it single/two phase?
Having 3 phases and a neutral coming into your premises (aka UK 3-phase
supply) somehow seems less... subject to complexity

Going really OT here (and I should probably start a new thread for this) -
what beyond a 1:1 ratio makes a transformer an 'isolation' transformer.

I have used the below transformer or similar as the primary power
transformer for machines (in the case of the 2kva one, a ram edm). And have
considered it to provide sufficient isolation
http://www.jmsonline.co.uk/product_info.php?cPath=22_id=54

If I'm wrong, please let me know (and ideally how to fix it)

Thanks
Ben


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Re: [Emc-users] Measuring Noise - Oscilloscope

[John Thornton]

If you have limit switches set them up to home also, saves time when 
firing up as last offsets are still good. Also the soft limits work when 
you home. Got a photo of the el cabinet?

JT

On 1/1/2016 5:01 PM, Mark Johnsen wrote:
> John,
>
> Thanks for the direction, I'll look at that for the limits.  My machine is
> the _one_ switch type for limits on both ends without a home.  I didn't
> setup a home, but after using the mill for the last year, probably a good
> idea.
>
> I have been running 2.6.11 on a different harddrive, so good when I need to
> go.
>
> I do think I'll buy that O-scope, only because I've always wanted one and
> it seems like that one is a decent enough hobby scope for someone like me...
>
> Regards,
> Mark
>
> Mark,
>
> The short answer is replacing the limit/home switch wiring with shielded
> cable and grounding it to one place was the difference in making the
> sserial errors go away. Unless you need 2.7 back up to 2.6 till you get
> rid of the sserial errors.
>
> JT
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Re: [Emc-users] Measuring Noise - Oscilloscope

[andy pugh]

On 1 January 2016 at 23:21, Bertho Stultiens  wrote:

>> I'm assuming using a scope is the right way to do it?
>
> Yes and no. It depends on what you are tracking and how it is induced.

Also, there is no way to detect an occasional microsecond spike
without recording and analysing unfeasible quantities of data.

I tried looking for noise on my system with a scope, but soon gave up.

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[Emc-users] Measuring Noise - Oscilloscope

[Mark Johnsen]

Bertho,

Thanks for the note.  I replied inline below.

--
>
> Message: 4
> Date: Sat, 2 Jan 2016 00:21:12 +0100
> From: Bertho Stultiens 
> Subject: Re: [Emc-users] Measuring Noise - Oscilloscope
> To: "Enhanced Machine Controller (EMC)"
> 
> Message-ID: <568709e8.2030...@vagrearg.org>
> Content-Type: text/plain; charset=windows-1252
>
> On 01/01/2016 11:28 PM, Mark Johnsen wrote:
> > Anyway, I've been reading all the posts here and on the IRC as I've been
> > away for X-mas Holiday and I think I would like to be able to measure the
> > noise to be able to determine if my changes make an effect.  I've
> > unsuccessfully dealt w/ noise issues before and find it a daunting task
> to
> > trouble shoot.
>
> Noise problems are the most difficult to trace because the source(s) can
> be very obscure.
>
> >From the current thread(s) of discussion it seems clear that there is a
> lot of confusion. I may add, as a relatively experienced EE/CS guy, I
> have a hard time once in a while wrapping my head around noise problems.
> Having high power systems combined with low power control systems makes
> it only harder.
>
> It seems appropriate to make how-and-why-to-connect list and a checklist
> of do's and don'ts added with a structured guide how to track problems.
> I have to think a bit about that, but it seems a reasonable thing to do.
> However, it may not be finished overnight and input is welcome.
>
> Would be useful in this situation as I think I'm not the only one w/ this
setup and it would help others.


>
> > I'm assuming using a scope is the right way to do it?
>
> Yes and no. It depends on what you are tracking and how it is induced. A
> scope may actually worsen or remove the problem under certain
> circumstances because the scope influences the system. That is what
> makes it so hard to track.
>
> I agree - it's hard to track...


>
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>
> (disclaimers are disclaimed)
>
>
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Re: [Emc-users] Measuring Noise - Oscilloscope

[Ben Potter]

From: andy pugh [mailto:bodge...@gmail.com] 
> On 1 January 2016 at 23:21, Bertho Stultiens  wrote:
>>> I'm assuming using a scope is the right way to do it?
>> Yes and no. It depends on what you are tracking and how it is induced.
>Also, there is no way to detect an occasional microsecond spike without
recording and analysing unfeasible quantities of data.
>I tried looking for noise on my system with a scope, but soon gave up.

On the other hand, some types of failure are super obvious with a scope. 

On the level of 'Aiee! My resolvers look like that! Aie!' obvious.
Which, to continue a theme, turned out to be due to wiring. (in particular,
no problems when moving over =/- 1mm, spiky noise when moving over +/- 10mm)

It's a useful tool - which often can't help diagnose subtle and intermittent
errors. Well, not without a crazy amount of logging as per atp's post.

As daft as it sounds - nearly every significant problem I've had to date on
both my hobby level systems (gecko or clone) or my industrial systems (up to
a 30 kw servo) has been traced to a poorly specified cable. Shielding is
awesome...

>atp

Ben


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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/02/2016 01:47 AM, John Kasunich wrote:
> This is ENTIRELY a function of where you are and what language you 
> speak.  (English and American are not the same language :-)  

Yes, and neither is my native language... I'm trying, so confusion is
probably pre-programmed for some "features" and hope I can be forgiven ;-)


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Re: [Emc-users] Rewiring the BP

[Gene Heskett]

On Friday 01 January 2016 12:29:16 Bertho Stultiens wrote:

> On 01/01/2016 05:47 PM, Dave Cole wrote:
> > That's done all of the time.   In fact it is part of the NEC
> > (National Electric Code) that is followed (for the most part) in the
> > US. Pretty much every house in the US is wired like that.  (I'm not
> > making this stuff up.  :-) )
>
> I agree with the connection at power entry in the house. That is quite
> a different story. That is actually the same here in EU (most
> countries).
>
> I think that we should separate two things:
> - house installation
> - machine wiring
>
> House installation is pretty much standardized with a lot of rules and
> reasons. Specifically to ensure referencing and protection.
>
> Machine wiring is different in that you can have scenarios where
> references are moved, especially in a 2-phase system where you are not
> using the neutral, which is the scenario we have here.
>
> > Now, if you don't want to do that inside the panel for some reason
> > (which I might have missed), that may be a different story.
> > I'm just saying that is standard practice in the US and on the
> > European machines I have worked on as well.
>
> The reason for /not/ connecting the ground on a secondary winding is
> to prevent a capacitively coupled ground path. Especially if you
> cannot guarantee a 100% balanced primary-to-secondary side wrt. ground
> (*).
>
> What happens is that there will be a current in the ground connection
> which causes an imbalanced current on the primary side (remember:
> primary is 2-phase circuit without neutral reference). This is a
> differential current discrepancy on the primary side. If you have an
> RCD (which you should), then it can or will trip due to the current
> imbalance.
>
>
> (*) and from the example measurements presented by JT, we can be
> assured that there is an imbalance, as seen from the phase shift
> causing a difference in voltage measured wrt. ground on the secondary.
>
> > There are a lot of good reasons to tie one leg the transformer to
> > ground besides to establish the safety ground and neutral as is
> > common on the US. Intermittent faults to ground, with an ungrounded
> > system, can cause the secondary of the transformer to fly way above
> > absolute ground causing connected devices, or the transformer to
> > suffer from insulation breakdowns.   That's the extreme, but it can
> > happen.
>
> Actually, the secondary should normally be floating. Most transformer
> setups are to ensure galvanic separation and that means you may never
> connect neutral to the secondary side.
>
> Connecting ground on a secondary is a different scenario, where you
> most often see the 0V (DC) potential connected to protective ground.
> This is often done in the PC's power supply. The 0V (DC) to protective
> ground connection prevents the scenario to which you refer to.
>
> The 0V (DC) to protective ground connection is repeated in many
> devices, which have both power and signal connections. This gives rise
> to ground-loops, which are to be prevented at all times and it is the
> cause of the whole thread.
>
> > One of way too many references on the web.
> > http://ecmweb.com/bonding-amp-grounding/basics-bonding-and-grounding
> >-transformers
>
> It looks like the link is about a 3-phase system, where you would
> connect the center point in a star-configured secondary to ground.
> That is a different scenario.

So is this Bertho, this is a single phase system delivering 240+ volts AC 
to the two ends of a single core transformers primary winding.

While I personally am not 100% happy with a no neutral hook up, it is 
legal as long as it never leaves the confines of the load machine.  The 
machine itself is grounded well.  The fact that the core/frame of the 
control transformer isn't grounded probably enhances the capacitative 
coupling, which might amount to something in the 100 pF neighborhood.  
If the frame/core were also grounded, I would expect some of that 
un-balance to go away and the total, added up, would be less than the 
delivered voltage primarily because the measureing meter is going to 
absorb some of it when hooked up to measure it, causing its own 
imbalance.

In short, this is not a 2 phase system where the phase angles are +- 90 
degrees, so for practical purposes the 2 phase math is irrelevant.

The reason I wrote 240+ is that 127+127=254, which if Johns meter is a 
decent one, he should be reading within say 2 volts of that from L1 to 
L2.  With no neutral, only the secondary of that control transformer is 
to be considered the src of a 127 volt AC feed, and either end of it can 
and should be tied to the well grounded machine frame, but not both of 
course.  Having it grounded gives a direct path to ground for the noises 
the VFD might induce from close proximity.

Cheers, Gene Heskett
-- 
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Re: [Emc-users] Measuring Noise - Oscilloscope

[Ben Potter]

> From: Mark Johnsen [mailto:m...@ijohnsen.com] 
> John,
> Thanks for the direction, I'll look at that for the limits.  My machine is
the _one_ switch type for limits on both ends without a home.  I didn't
setup a home, but after using the mill for the last year, probably a good
idea.
> I have been running 2.6.11 on a different harddrive, so good when I need
to go.
> I do think I'll buy that O-scope, only because I've always wanted one and
it seems like that one is a decent enough hobby scope for someone like me...

I haven't heard a bad review of the Rigol scopes, for the price. I've been
tempted many a time to replace my salvaged Tektronix scope with a Rigol -
mainly for the DSO capabilities (and the overclocked firmware options).

Note, I've seen a lot of good reviews - but I tend to pay more attention to
the bad ones.

> Regards,
> Mark
> > Mark,
> > The short answer is replacing the limit/home switch wiring with shielded
cable and grounding it to one place was the difference in making the sserial
errors go away. Unless you need 2.7 back up to 2.6 till you get rid of the
> > sserial errors.
> > JT

Good to know John - I missed that from the previous thread - it's odd how
often cable standard/layout causes odd issues


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Re: [Emc-users] Rewiring the BP

[Gene Heskett]

On Friday 01 January 2016 12:34:37 Jon Elson wrote:

> On 01/01/2016 06:02 AM, John Thornton wrote:
> > Hi Jon,
> >
> > So tie say the 48v side to ground to create the neutral? I
> > attached the drawing of what I have so far on the VFD side.
>
> With power off, use an Ohmmeter to verify the secondary is
> isolated from the frame.  If so, tie either end to ground.
> If NOT, then further investigation is required.
>
> > Happy New year to you and I hope you stayed dry during the
> > recent monsoon we got.
>
> It was fine here, but lots of highways closed.  My mother in
> law's house had some basement leakage.  During the strongest
> rain, we had a drip where the furnace flue goes through the
> roof.
>
> Jon
>
Good to hear Jon, thanks.

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Cheers, Gene Heskett
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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/01/2016 08:13 PM, John Dammeyer wrote:
> (Reposted with link to pdf fixed)
> Here's what I did for my SouthBend Lathe.  Not run with CNC but with my
> Electronic Lead Screw.
> http://www.autoartisans.com/Lathe/SouthBendPower.pdf

The connection from the secondary to ground (chassis) effectively kills
the common-mode filter which is located inside your computer's power
supply. You have shorted one side of the common-mode filter, rendering
it completely ineffective and injecting the computer's PSU noise into
the chassis.

See my other mail for a detailed explanation.

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[Emc-users] Measuring Noise - Oscilloscope

[Mark Johnsen]

I have a very similar setup to John Thornton and same noise issue w/ 2.7.3:
Mesa 5i25/7i77
Transformer 120vac:80Vac, rectified w/ large cap to run 3-axes West Amp
servo's (Not sure John has this)
GS2 Automation direct 3hp drive, powered by separate 240Vac single phase
input.  Also, I use his serial modbus setup from the PC.
120Vac powering the PC (not enclosed in computer case)

Anyway, I've been reading all the posts here and on the IRC as I've been
away for X-mas Holiday and I think I would like to be able to measure the
noise to be able to determine if my changes make an effect.  I've
unsuccessfully dealt w/ noise issues before and find it a daunting task to
trouble shoot.

I'm assuming using a scope is the right way to do it?

But I need a scope and would use it for this and some smaller circuit board
type projects (total hack type stuff).  I've seen a lot on the rigol, but
I've also come across a siglet that seems to be slightly better.  I read
that readings should be 10:1 over the signal and an arduino is around 8Mhz,
so 70Mhz is probably good enough for me.

Siglent SDS1072CML 7'' TFT-LCD Display Bench-Top Oscilloscope, 70MHz
http://www.amazon.com/Siglent-SDS1072CML-TFT-LCD-Bench-Top-Oscilloscope/dp/B00GQNNHJG

Wondering if anyone has an opinion on that one?  Seems like it would fit
the bill for a low end O-scope?

Here's the standard Rigol DS-1052E
http://www.amazon.com/Rigol-DS1052E-Digital-Channels-sampling/dp/B003MYND5A

Thanks,
Mark
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Re: [Emc-users] Measuring Noise - Oscilloscope

[Bertho Stultiens]

On 01/01/2016 11:28 PM, Mark Johnsen wrote:
> Anyway, I've been reading all the posts here and on the IRC as I've been
> away for X-mas Holiday and I think I would like to be able to measure the
> noise to be able to determine if my changes make an effect.  I've
> unsuccessfully dealt w/ noise issues before and find it a daunting task to
> trouble shoot.

Noise problems are the most difficult to trace because the source(s) can
be very obscure.

>From the current thread(s) of discussion it seems clear that there is a
lot of confusion. I may add, as a relatively experienced EE/CS guy, I
have a hard time once in a while wrapping my head around noise problems.
Having high power systems combined with low power control systems makes
it only harder.

It seems appropriate to make how-and-why-to-connect list and a checklist
of do's and don'ts added with a structured guide how to track problems.
I have to think a bit about that, but it seems a reasonable thing to do.
However, it may not be finished overnight and input is welcome.


> I'm assuming using a scope is the right way to do it?

Yes and no. It depends on what you are tracking and how it is induced. A
scope may actually worsen or remove the problem under certain
circumstances because the scope influences the system. That is what
makes it so hard to track.


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Re: [Emc-users] Rewiring the BP

[John Kasunich]

On Fri, Jan 1, 2016, at 04:44 PM, Bertho Stultiens wrote:
> On 01/01/2016 07:25 PM, Kirk Wallace wrote:
> >> Machine wiring is different in that you can have scenarios where
> >> references are moved, especially in a 2-phase system where you are not
> >> using the neutral, which is the scenario we have here.
> > My understanding is, and I could be wrong, that "two-phase" in reference 
> > to modern mains circuits does not exist. Circuits with two hot legs, L1 
> > and L2, are single phase and referenced to each other. Two phase used to 
> > be two legs that were 90 degrees apart, but is long gone.
> 
> That was (almost) my faulty thought too at first, but it turns out that
> the 2-phase system referred to comes from a single transformer with two
> secondary windings. This gives you two 120V lines wrt. neutral (L1 and
> L2) which are 180 degrees shifted. Therefore, the difference between L1
> and L2 is 240V.
 
This is ENTIRELY a function of where you are and what language you 
speak.  (English and American are not the same language :-)  

In the USA, Kirk is 100% correct.  Two phase means 90 degree phase 
shift, and is pretty much non-existent.  120V-0V-120V with 240V from
end to end is "single phase".  Call it two-phase and people in the States
will look at you funny.

John Kasunich



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[Emc-users] Smart-Serial cabling

[andy pugh]

My lathe build is going to have a smart-serial device mounted in the
lathe apron. This means that I need a CAT5 cable in the drag-chain,
and also a 24V supply for the proximity sensors.
Finding oil/coolant resistant CAT5 rated for drag-chain use is likely
to be a challenge.
I have lots of this cable:
https://picasaweb.google.com/108164504656404380542/Holbrook#6217838146609796818
(Lapp Ölflex drag-chain encoder cable).
Is there any reason to think that the 2x3 screened pairs in that cable
will be unsuitable for transporting smart-serial data (if I can
persuade an RJ45 connector on to them)?

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Re: [Emc-users] To Peter C Wallace

[Peter Blodow]

Andy, this idea is good and saves space, but has limitations as to the 
bus speed. Siemens built their desk top PCs (in fact, there were no 
others) like this in the 1990ies and dropped it as processing speed rose 
rapidly in these days. The L-shaped connector board had too much 
impedance for the megacycles.
Peter


Am 01.01.2016 12:08, schrieb andy pugh:
> My latest build has a different approach: 
> https://picasaweb.google.com/108164504656404380542/Holbrook#6234774182242152002
>  



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Re: [Emc-users] To Peter C Wallace

[andy pugh]

On 1 January 2016 at 01:51, Gene Heskett  wrote:
> Ideas, anybody?  Or do I have to make a x-crossed-brace to go across the
> top of the pci sockets?

Are there any standoffs / tapped holes on the motherboard that you can
get a bracket to?

It seems to me to be a problem with the PCI port design, and has
caught me a few times.
My latest build has a different approach:
https://picasaweb.google.com/108164504656404380542/Holbrook#6234774182242152002

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Re: [Emc-users] To Peter C Wallace

[andy pugh]

On 1 January 2016 at 11:29, Peter Blodow  wrote:
> Andy, this idea is good and saves space, but has limitations as to the
> bus speed. Siemens built their desk top PCs (in fact, there were no
> others) like this in the 1990ies and dropped it as processing speed rose
> rapidly in these days. The L-shaped connector board had too much
> impedance for the megacycles.

This one is actually an "official" accessory for the motherboard.
It came with a suitable backplate, which I didn't use.

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Re: [Emc-users] Rewiring the BP

[John Thornton]

Hi Gene,

The frame is most solidly grounded. I'll do the tests in a bit. Keep in 
mind that I have a 240v to 120v step down transformer to supply the 120v 
not a normal house circuit. Again an effort to kill the noise. Which by 
the way I'm running 2.7 now after changing the wires on the limit/home 
switches to twisted pair shielded wire. I've attached the VFD side 
wiring diagram. I assume the connection is through the neutral bonding 
screw at the panel because the step down transformer is isolated from 
ground.


Happy New Year to you too.

JT

On 12/31/2015 5:50 PM, Gene Heskett wrote:

On Thursday 31 December 2015 16:20:40 John Thornton wrote:


On the 120v side if I measure from the hot to the ground I get 79
volts, if I measure from hot to neutral I get the expected 128v...
what is that telling me?

JT

My first guess is that the Bridgeport itself, is not grounded.  It really
should be, just to keep it from becoming lethally hot when somethings
insulation fails.  Generally speaking, if I can measure more than a volt
between neutral and the static ground, it concerns me UNLESS its a wild
phase , which I don't believe you have since its not a 3 phase circuit.

TBE if something is running that uses that neutral you might see more
volts, but I'd re-measure after turning whatever it was off.

As to the 79 volts, I would put a small light bulb (7.5 watt night lite)
from the Bp frame to neutral to see if there is any real current, or its
just capacitative coupling. If capacitative coupling, a 7.5 watt night
light bulb will remain dark, and that voltage should drop to less than 1
or 2 volts. If it lights up at all, and the voltage doesn't drop
drastically, there really is a fault someplace.  I'd start disconnecting
motors for starters.

Happy New Year John.

Cheers, Gene Heskett


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Re: [Emc-users] Smart-Serial cabling

[Rene Hopf]

> On 01 Jan 2016, at 12:23, andy pugh  wrote:
> 
> My lathe build is going to have a smart-serial device mounted in the
> lathe apron. This means that I need a CAT5 cable in the drag-chain,
> and also a 24V supply for the proximity sensors.
> Finding oil/coolant resistant CAT5 rated for drag-chain use is likely
> to be a challenge.
> I have lots of this cable:
> https://picasaweb.google.com/108164504656404380542/Holbrook#6217838146609796818
> (Lapp Ölflex drag-chain encoder cable).
> Is there any reason to think that the 2x3 screened pairs in that cable
> will be unsuitable for transporting smart-serial data (if I can
> persuade an RJ45 connector on to them)?

the cable looks ok. there are loads of drag chain compatible cat cables 
available, just google for industrial ethernet cable.

> 
> -- 
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> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto
> 
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Re: [Emc-users] Smart-Serial cabling

[Bertho Stultiens]

On 01/01/2016 12:23 PM, andy pugh wrote:
> Is there any reason to think that the 2x3 screened pairs in that cable
> will be unsuitable for transporting smart-serial data

The bandwidth of rs232 style serial connections is so low that you will
not see any problems with twisted pairs. I assume that you are not
connecting half a kilometer of cable with a speed higher than 115k2 baud
(or you may run into capacitive loading problens).

Pairing TX and RX with a GND may actually improve noise immunity. But
the cable is already well shielded.


> (if I can persuade an RJ45 connector on to them)?

That is actually a hard thing to do on these cables. The isolation is
very hard and does not bend easily. Standard crimp-connectors will be
almost impossible to attach while ensuring a mechanically stable
connection. There is also a minimum bend-radius which can be rather large.

These cables are normally used as distribution cables and go into female
plug assemblies with seperate holding facilities for the cable.


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Re: [Emc-users] To Peter C Wallace

[Gene Heskett]

On Friday 01 January 2016 06:08:31 andy pugh wrote:

> On 1 January 2016 at 01:51, Gene Heskett  wrote:
> > Ideas, anybody?  Or do I have to make a x-crossed-brace to go across
> > the top of the pci sockets?
>
> Are there any standoffs / tapped holes on the motherboard that you can
> get a bracket to?

TBD when I take it down here in a couple hours.  Twould need to be near 
the rear of the card to make it a simple one piece.

> It seems to me to be a problem with the PCI port design, and has
> caught me a few times.

Yes, and apparently caught the video card folks too so the AGP cards all 
have a latch at the rear of the socket.  Exactly what the PCI should 
have had from the gitgo IMNSHO.

> My latest build has a different approach:
> https://picasaweb.google.com/108164504656404380542/Holbrook#6234774182
>242152002

Looks good, but would need a full length pci riser I haven't seen at TD 
or NewEgg, and in an LP case, might not clear the connection tower 
sticking up off the mobo.  That and this Dell 745 doesn't have any pci-e 
slots that I've noticed enough to recall.

Cheers, Gene Heskett
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Genes Web page 

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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 12/31/2015 10:24 PM, John Thornton wrote:
> I went and checked the control transformer and one side is 48v to ground 
> and the other side is 79v to ground. I guess I was confused by that.

I did a quick calculation and if your protective ground has a voltage
with a phase shift of about 62 degrees wrt. the transformer's output and
the open voltage of the transformer is 132V, then one lead will show 48V
(RMS)(*) and the other will show 80V (RMS) with respect to ground.

>From this we can conclude that you are measuring a capacitive coupling.


Calculated from:
Ground potential : V * sin(a + p)
Transformer out A: V * sin(a)
Transformer out B: V * sin(-a)

with:   a = running angle
p = phase shift
V = Voltage

Transformer output A wrt. ground:
V * RMS(sin(a) - sin(a + p))
Transformer output B wrt. ground:
V * RMS(sin(-a) - sin(a + p))


(*) I assume that your multimeter is measuring root-mean-square (RMS)
voltage in AC mode. That should be a pretty safe assumption.

-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] To Peter C Wallace

[John Thornton]

I'll get a photo of what I did on my CHNC which has the motherboard just 
mounted to a panel...

JT

On 12/31/2015 7:51 PM, Gene Heskett wrote:
> I tried to hook up my soft start circuit tonight, but when I had it wired
> in, the spindle didn't run. Checking dmesg, the card did not sign in
> like it usually does.  Backed out of the mainboard socket at least 1/8",
> again. By bumping the parport cables molded connector against the wall.
>
> So I have an excedrin headache, number unk.  Everytime I turn that
> computer around, to plug in a usb cable to charge my DS201, or for any
> reason, the 5i25 comes far enough out of the pci socket to disable
> something.  Or blow the card.  At 90 bucks a pop, that isn't fun.
>
> Do you have a bracket that can somehow hold the card into the socket?
>
> Its an LP bracket in an LP box, but it needs something to nail the card
> down into the slot a lot firmer than the LP bracket is holding it.
>
> Ideas, anybody?  Or do I have to make a x-crossed-brace to go across the
> top of the pci sockets?
>
> Thanks all. :)
>
> Cheers, Gene Heskett


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Re: [Emc-users] Smart-Serial cabling

[Gene Heskett]

On Friday 01 January 2016 06:23:06 andy pugh wrote:

> My lathe build is going to have a smart-serial device mounted in the
> lathe apron. This means that I need a CAT5 cable in the drag-chain,
> and also a 24V supply for the proximity sensors.
> Finding oil/coolant resistant CAT5 rated for drag-chain use is likely
> to be a challenge.
> I have lots of this cable:
> https://picasaweb.google.com/108164504656404380542/Holbrook#6217838146
>609796818 (Lapp Ölflex drag-chain encoder cable).
> Is there any reason to think that the 2x3 screened pairs in that cable
> will be unsuitable for transporting smart-serial data (if I can
> persuade an RJ45 connector on to them)?

Other than cat-5 is 4 twisted pairs with no shielding, no.  If its a real  
ethernet, the shielding would mess up the termination impedance. Even 
going thru a pair of crimp on rj45's plugged into a splicer block is 
enough of an impedance and echo causing bump that a 100megabit circuit 
can downgrade itself to a 10megabit circuit.  We've been bitten by that 
when rearranging gear in the racks at the tv station & had to add 
another 4 feet of cable.  To get the speed back Jim had to pull new 
cable.

For serial, where signalling is single ended, I'd make sure that txdata 
and rxdata were in separate shielded pairs.  I'd assume the protocol is 
similar to the common 7 wire that is usually terminated in db9 
connectors?  That works well for the baud rates used 20 years ago, but 
no first-hand experience above 56kbaud, and I expect this is 10x that. 
460k or better.  At those speeds termination is very important to 
control edge reflections and ringing.

Any idea what the baud rate is, Andy? These are tires I've never 
kicked. :(

Cheers, Gene Heskett
-- 
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Re: [Emc-users] To Peter C Wallace

[John Thornton]

the photo

http://gnipsel.com/images/chnc/CHCN-5i20.jpg

On 1/1/2016 6:05 AM, John Thornton wrote:
> I'll get a photo of what I did on my CHNC which has the motherboard just
> mounted to a panel...
>
> JT
>
> On 12/31/2015 7:51 PM, Gene Heskett wrote:
>> I tried to hook up my soft start circuit tonight, but when I had it wired
>> in, the spindle didn't run. Checking dmesg, the card did not sign in
>> like it usually does.  Backed out of the mainboard socket at least 1/8",
>> again. By bumping the parport cables molded connector against the wall.
>>
>> So I have an excedrin headache, number unk.  Everytime I turn that
>> computer around, to plug in a usb cable to charge my DS201, or for any
>> reason, the 5i25 comes far enough out of the pci socket to disable
>> something.  Or blow the card.  At 90 bucks a pop, that isn't fun.
>>
>> Do you have a bracket that can somehow hold the card into the socket?
>>
>> Its an LP bracket in an LP box, but it needs something to nail the card
>> down into the slot a lot firmer than the LP bracket is holding it.
>>
>> Ideas, anybody?  Or do I have to make a x-crossed-brace to go across the
>> top of the pci sockets?
>>
>> Thanks all. :)
>>
>> Cheers, Gene Heskett
>
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Re: [Emc-users] Rewiring the BP

[John Thornton]

Ground to chassis is 0.01 ohm.

JT

On 1/1/2016 7:42 AM, Bertho Stultiens wrote:
> There is one remaining measurement that you should do: Measure the DC 
> resistance between the chassis and the protective ground of the 
> wall-outlet. That should be close to zero. Then, assuming that the 
> wall-outlet's ground is properly connected, you have assured that you 
> actually have a protective ground connected to your equipment. 


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Re: [Emc-users] To Peter C Wallace

[linden]

I just put a gob as far aft as i can get (calling the end where your 
cables come out forward) It is just like sticking things together with a 
wad of gum if you are using an elcheepo glue gut it dose not get hot 
enough to wick in between any thing. Its non conductive the clear sticks 
seem to work better as they do not bond quites as well and you can peal 
it off relatively easily. the yellowy cream colored sticks are a more 
permanent glue.

On 15-12-31 06:53 PM, Gene Heskett wrote:
> On Thursday 31 December 2015 21:27:52 linden wrote:
>
>> Hi Gene,
>>   I have used hot glue from a hot glue gun in the past (the Kind
>> for arts and crafts) to hold cards in. It works well for high
>> vibration and you can peal the glue off to get the card out if you
>> need too. Not as good as a mechanical hold down but certainly better
>> than nothing and not as permanent as potting compound. May be enough
>> added stay puttedness for your application or untill you can come up
>> with a better solution.
>>
> Never gave that a thought, but it might be just the ticket. I don't think
> its electrically conductive. I'm assuming you put a line of it against
> both the socket and board?
>
> I can only access one side, without pulling the mainboard, which might be
> less than optimum.
>
> Did you put anything against the board to keep it from wicking into the
> socket itself?  Or does it set fast enough thats not a problem?
>
> Thanks for the idea Linden, I appreciate a fresh idea.
>
>> On 15-12-31 05:51 PM, Gene Heskett wrote:
>>> I tried to hook up my soft start circuit tonight, but when I had it
>>> wired in, the spindle didn't run. Checking dmesg, the card did not
>>> sign in like it usually does.  Backed out of the mainboard socket at
>>> least 1/8", again. By bumping the parport cables molded connector
>>> against the wall.
>>>
>>> So I have an excedrin headache, number unk.  Everytime I turn that
>>> computer around, to plug in a usb cable to charge my DS201, or for
>>> any reason, the 5i25 comes far enough out of the pci socket to
>>> disable something.  Or blow the card.  At 90 bucks a pop, that isn't
>>> fun.
>>>
>>> Do you have a bracket that can somehow hold the card into the
>>> socket?
>>>
>>> Its an LP bracket in an LP box, but it needs something to nail the
>>> card down into the slot a lot firmer than the LP bracket is holding
>>> it.
>>>
>>> Ideas, anybody?  Or do I have to make a x-crossed-brace to go across
>>> the top of the pci sockets?
>>>
>>> Thanks all. :)
> Cheers, Gene Heskett


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Re: [Emc-users] Rewiring the BP

[John Thornton]

Hi Jon,

So tie say the 48v side to ground to create the neutral? I attached the 
drawing of what I have so far on the VFD side.


Happy New year to you and I hope you stayed dry during the recent 
monsoon we got.


JT

On 12/31/2015 7:16 PM, Jon Elson wrote:

On 12/31/2015 03:24 PM, John Thornton wrote:

I went and checked the control transformer and one side is 48v to ground
and the other side is 79v to ground. I guess I was confused by that.


Do you have a ground connected to that winding?  If not,
then the capacitance of that winding to other windings and
the core will set what AC potential you get at each end.
I'm guessing you have a totally floating secondary, and this
adds up to 127 VAC, which sounds right for a nominal 120 V
output.  You can tie one end of the winding to frame ground,
establishing a new neutral in the cabinet for the computer,
etc. loads.

Jon

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Re: [Emc-users] To Peter C Wallace

[andy pugh]

On 1 January 2016 at 12:05, John Thornton  wrote:
> I'll get a photo of what I did on my CHNC which has the motherboard just
> mounted to a panel...

That's what I have. The question is how to stop the PCI card from
falling out of the motherboard.


-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/01/2016 01:02 PM, John Thornton wrote:
> So tie say the 48v side to ground to create the neutral? I attached the
> drawing of what I have so far on the VFD side.

No, then you just short a capacitive path to ground.

If you have no neutral, then you do not have it. All voltages you
measure wrt. ground are relative values and are influenced by the
induced phase angle of whatever you have on the lines wrt. ground.

The ground line will be floating due to capacitive couplings and it may
not be entirely symmetric from the phases L1 and L2. Therefore, if you
mesaure wrt. ground, you see differences in the RMS voltage. The
multimeter is no real load and will not influence the phase angle of any
capacitive coupling. However, note that such measurements do not
represent the the voltages you have at your displosal for the loads.

There are in principle only two voltages you can measure:
- input lines between L1 and L2 -> ~240V
- after the transformer at the output of the transformer -> ~120V

These are the only voltages that make sense to measure.

There is one remaining measurement that you should do: Measure the DC
resistance between the chassis and the protective ground of the
wall-outlet. That should be close to zero.
Then, assuming that the wall-outlet's ground is properly connected, you
have assured that you actually have a protective ground connected to
your equipment.

-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Rewiring the BP

[Dave Cole]

Yes,

Anytime you have a 120 volt source for computer, misc power etc, you 
need to declare one side of the 120 vac winding the neutral (white wire) 
and tie that terminal to the machine frame.
It similar to what is required at the service entrance of your house.  
The neutral is always tied to the ground at the entrance box.   
Oftentimes they drive  a screw through the neutral buss bar in the 
service entrance box into the box sheetmetal and then tie a green or 
bare copper ground wire to the same neutral buss bar and run that to a 
metal water pipe or ground rod.   Oftentimes they just put a green 
copper jumper wire between the "declared" neutral terminal on the 
transformer and the transformer attachment screw in the panel and they 
use the steel panel backplane for "ground". If you are using a single 
point ground just run a green ground wire from the neutral terminal on 
the transformer and the single point ground in the panel.

Dave

On 1/1/2016 7:02 AM, John Thornton wrote:
> Hi Jon,
>
> So tie say the 48v side to ground to create the neutral? I attached 
> the drawing of what I have so far on the VFD side.
>
> Happy New year to you and I hope you stayed dry during the recent 
> monsoon we got.
>
> JT
>
> On 12/31/2015 7:16 PM, Jon Elson wrote:
>> On 12/31/2015 03:24 PM, John Thornton wrote:
>>> I went and checked the control transformer and one side is 48v to 
>>> ground
>>> and the other side is 79v to ground. I guess I was confused by that.
>>>
>> Do you have a ground connected to that winding?  If not,
>> then the capacitance of that winding to other windings and
>> the core will set what AC potential you get at each end.
>> I'm guessing you have a totally floating secondary, and this
>> adds up to 127 VAC, which sounds right for a nominal 120 V
>> output.  You can tie one end of the winding to frame ground,
>> establishing a new neutral in the cabinet for the computer,
>> etc. loads.
>>
>> Jon
>>
>> --
>>  
>>
>> ___
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>
>
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Re: [Emc-users] Rewiring the BP

[John Dammeyer]

Here's what I did for my SouthBend Lathe.  Not run with CNC but with my
Electronic Lead Screw.

http://www.autoartisans.com/lathe/SouthBendPower.pdf
http://www.autoartisans.com/Lathe/ControlBox.jpg
http://www.autoartisans.com/Lathe/ControlBoxInside.jpg

The System Relay is wired as a latching relay that stays ON until ESTOP is
hit.  Both the coolant pump switch and Spindle Start relay must be off
before the Relay is energized.  An ESTOP disconnects power to the dangerous
voltages but leaves the ELS powered.  Since I fed this box with 220VAC there
is no neutral and I used a transformer to power a split duplex outlet.  One
side of the 120VAC is bonded to Earth.

I haven't had any electrical noise problems.  But I have also not yet wired
the RS232 port of the ELS to the VFD for speed control.

John Dammeyer



> -Original Message-
> From: Dave Cole [mailto:linuxcncro...@gmail.com]
> Sent: January-01-16 8:14 AM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Rewiring the BP
> 
> 
> Yes,
> 
> Anytime you have a 120 volt source for computer, misc power etc, you
> need to declare one side of the 120 vac winding the neutral (white wire)
> and tie that terminal to the machine frame.
> It similar to what is required at the service entrance of your house.
> The neutral is always tied to the ground at the entrance box.
> Oftentimes they drive  a screw through the neutral buss bar in the
> service entrance box into the box sheetmetal and then tie a green or
> bare copper ground wire to the same neutral buss bar and run that to a
> metal water pipe or ground rod.   Oftentimes they just put a green
> copper jumper wire between the "declared" neutral terminal on the
> transformer and the transformer attachment screw in the panel and they
> use the steel panel backplane for "ground". If you are using a single
> point ground just run a green ground wire from the neutral terminal on
> the transformer and the single point ground in the panel.
> 
> Dave
> 
> On 1/1/2016 7:02 AM, John Thornton wrote:
> > Hi Jon,
> >
> > So tie say the 48v side to ground to create the neutral? I attached
> > the drawing of what I have so far on the VFD side.
> >
> > Happy New year to you and I hope you stayed dry during the recent
> > monsoon we got.
> >
> > JT
> >
> > On 12/31/2015 7:16 PM, Jon Elson wrote:
> >> On 12/31/2015 03:24 PM, John Thornton wrote:
> >>> I went and checked the control transformer and one side is 48v to
> >>> ground
> >>> and the other side is 79v to ground. I guess I was confused by that.
> >>>
> >> Do you have a ground connected to that winding?  If not,
> >> then the capacitance of that winding to other windings and
> >> the core will set what AC potential you get at each end.
> >> I'm guessing you have a totally floating secondary, and this
> >> adds up to 127 VAC, which sounds right for a nominal 120 V
> >> output.  You can tie one end of the winding to frame ground,
> >> establishing a new neutral in the cabinet for the computer,
> >> etc. loads.
> >>
> >> Jon
> >>
> >>

--
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> >> https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> >
> >
> >

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Re: [Emc-users] Rewiring the BP

[John Dammeyer]

(Reposted with link to pdf fixed)

Here's what I did for my SouthBend Lathe.  Not run with CNC but with my
Electronic Lead Screw.

http://www.autoartisans.com/Lathe/SouthBendPower.pdf
http://www.autoartisans.com/Lathe/ControlBox.jpg
http://www.autoartisans.com/Lathe/ControlBoxInside.jpg

The System Relay is wired as a latching relay that stays ON until ESTOP is
hit.  Both the coolant pump switch and Spindle Start relay must be off
before the Relay is energized.  An ESTOP disconnects power to the dangerous
voltages but leaves the ELS powered.  Since I fed this box with 220VAC there
is no neutral and I used a transformer to power a split duplex outlet.  One
side of the 120VAC is bonded to Earth.

I haven't had any electrical noise problems.  But I have also not yet wired
the RS232 port of the ELS to the VFD for speed control.

John Dammeyer



> -Original Message-
> From: Dave Cole [mailto:linuxcncro...@gmail.com]
> Sent: January-01-16 8:14 AM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Rewiring the BP
> 
> 
> Yes,
> 
> Anytime you have a 120 volt source for computer, misc power etc, you
> need to declare one side of the 120 vac winding the neutral (white wire)
> and tie that terminal to the machine frame.
> It similar to what is required at the service entrance of your house.
> The neutral is always tied to the ground at the entrance box.
> Oftentimes they drive  a screw through the neutral buss bar in the
> service entrance box into the box sheetmetal and then tie a green or
> bare copper ground wire to the same neutral buss bar and run that to a
> metal water pipe or ground rod.   Oftentimes they just put a green
> copper jumper wire between the "declared" neutral terminal on the
> transformer and the transformer attachment screw in the panel and they
> use the steel panel backplane for "ground". If you are using a single
> point ground just run a green ground wire from the neutral terminal on
> the transformer and the single point ground in the panel.
> 
> Dave
> 
> On 1/1/2016 7:02 AM, John Thornton wrote:
> > Hi Jon,
> >
> > So tie say the 48v side to ground to create the neutral? I attached
> > the drawing of what I have so far on the VFD side.
> >
> > Happy New year to you and I hope you stayed dry during the recent
> > monsoon we got.
> >
> > JT
> >
> > On 12/31/2015 7:16 PM, Jon Elson wrote:
> >> On 12/31/2015 03:24 PM, John Thornton wrote:
> >>> I went and checked the control transformer and one side is 48v to
> >>> ground
> >>> and the other side is 79v to ground. I guess I was confused by that.
> >>>
> >> Do you have a ground connected to that winding?  If not,
> >> then the capacitance of that winding to other windings and
> >> the core will set what AC potential you get at each end.
> >> I'm guessing you have a totally floating secondary, and this
> >> adds up to 127 VAC, which sounds right for a nominal 120 V
> >> output.  You can tie one end of the winding to frame ground,
> >> establishing a new neutral in the cabinet for the computer,
> >> etc. loads.
> >>
> >> Jon
> >>
> >>

--
> >>
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> >> https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> >
> >
> >

--
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Re: [Emc-users] Rewiring the BP

[Jon Elson]

On 01/01/2016 11:37 AM, andy pugh wrote:
> On 1 January 2016 at 17:29, Bertho Stultiens  wrote:
>> The reason for /not/ connecting the ground on a secondary winding is to
>> prevent a capacitively coupled ground path.
> Another reason is that if you connect either secondary winding end  to
> ground using body parts then nothing bad happens. This is the point of
> an isolation transformer.
> If there is an isolation transformer fitted in the machine then
> grounding one of its terminals makes it pointless.
>
Well, it still isolates the 120 V circuit from disturbances 
on the 240 V input.  So, if your building ground to neutral 
has a bunch of noise or offsets between them, the internal 
120 V circuit will be "clean" with respect to the frame ground.

The problem with a totally floating 120 V circuit is that 
various devices plugged in to that system may have somewhat 
large capacitors between hot or neutral and safety ground.  
Very typical in switching power supplies.  Depending on the 
configuration of all the devices on that supply, it could 
cause the neutral to be higher than the hot (with respect to 
ground).  This could cause some equipment to malfunction, if 
they assume the neutral will stay near ground potential.  
Also, a fault in one of the units could persist for some 
time until somebody touches something, and gets a nasty shock.

Open safety grounds are a common problem in the US.  I've 
gotten zapped quite good a few times when touching two 
pieces of equipment at the same time.  Leaving the secondary 
totally floating is kind of the same thing.  In the UK, they 
ground the center tap of those job site transformers for 
exactly this reason.

Now, when testing inside power equipment using an isolation 
transformer so you can use a scope on a switching power 
supply, for instance, then you DO want the transformer 
secondary floating.

Jon

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Re: [Emc-users] Rewiring the BP

[Rafael]

On 01/01/2016 08:47 AM, Dave Cole wrote:
> On 1/1/2016 11:26 AM, Bertho Stultiens wrote:
>> On 01/01/2016 05:13 PM, Dave Cole wrote:
>>> Anytime you have a 120 volt source for computer, misc power etc, you
>>> need to declare one side of the 120 vac winding the neutral (white wire)
>>> and tie that terminal to the machine frame.
>>> It similar to what is required at the service entrance of your house.
>>> The neutral is always tied to the ground at the entrance box.
>>> Oftentimes they drive  a screw through the neutral buss bar in the
>>> service entrance box into the box sheetmetal and then tie a green or
>>> bare copper ground wire to the same neutral buss bar and run that to a
>>> metal water pipe or ground rod.
>> You should never tie a secondary winding of a transformer to ground. The
>> transformer makes the secondary float wrt. the primary and that is just
>> fine.
>>
>> In this scenario, you would create a (capacitive) feed-through from the
>> transformer to ground because the primary is not referenced at ground.
>> The primary has two phases attached, which creates a virtual circuit at
>> the primary side.
>>
>> The difficulty here is that you must take account for the floating
>> references, which make most of the things you measure local phenomena.
>> Once you go through the transformer, your reference to the primary line
>> input is lost and you must not try to reestablish it. It would only make
>> things bad and worse.
>>
> Hi Bertho,
>
> That's done all of the time.   In fact it is part of the NEC (National
> Electric Code) that is followed (for the most part) in the US.

(for the most part) unfortunately. Books on this subject matter say the 
same thing. When cities have their own codes I wonder about it 
sometimes. It's about physics, not about politically correct or union 
prescribed codes that matters. I've seen silly codes in EU as well as in 
the US. Code is not going to kill, but large amount of moving electrons 
will.

> Pretty much every house in the US is wired like that.  (I'm not making
> this stuff up.  :-) )
>
> Now, if you don't want to do that inside the panel for some reason
> (which I might have missed), that may be a different story.
> I'm just saying that is standard practice in the US and on the European
> machines I have worked on as well.
>
> There are a lot of good reasons to tie one leg the transformer to ground
> besides to establish the safety ground and neutral as is common on the US.
> Intermittent faults to ground, with an ungrounded system, can cause the
> secondary of the transformer to fly way above absolute ground causing
> connected devices, or the transformer to suffer from insulation
> breakdowns.   That's the extreme, but it can happen.

Strongly agree! Do not float transformer secondary and have a PC 
connected to it! This is not about an isolation transformer, it's about 
stepdown transformer which is way different. Primary side of this step 
down transformer needs to float in this case. In ideal situation, CT on 
the primary side would be neutral and connected to local ground but it 
is better to not use it; transformer is not ideal.

A PC or anything else for that matter, that is not grounded is against 
all safety rules based on physics, never mind the code. You don't want 
your mouse or the monitor electrically float in relation to the metal 
machine!

For comparison, I used _isolation_ transformer (that is 1:1) to repair 
switching power supplies in early 90's when it was still profitable. 
Oscilloscope ground was connected to a point on the "primary side" of 
switching power supply and 1MOhm probe was good for hundreds of volts. 
Of course, I was well isolated from the "house ground" and made sure I 
didn't touch grounds on scope or outlet ground to be safe. Touching 
outlet and scope ground could of course be fatal!

One of magazines [1] in the 70's suggested to use a neutral wire if you 
don't have an antenna for the radio. Experiment for my first AM and SW 
radio detector worked fine until one day I accidentally reversed the 
plug, yes you can do that in one of STUPID EU power outlet designs, DIN 
code in my case I believe. I mention this to support my thesis that 
"electric codes" don't necessarily cover all aspects of safety.

Based on that experience I lost my interest in electricity and 
experiments for a week which surprised my mom knowing that building a 
radio detector with 3 or 5 transistors, handmade coils, all on PCB with 
traces cut with a knife was fun.

Since then I always used only one hand to work on live mainframe power 
supplies and such. That experience also confirmed my interests in "low 
voltage" side of electric phenomena: radios, TV, computers ;-)  There 
were exceptions to my work, like TVs and radios with vacuum tubes ...

[1] I don't think they write such articles anymore. I hope not.

> One of way too many references on the web.
> http://ecmweb.com/bonding-amp-grounding/basics-bonding-and-grounding-transformers
>
> 

Re: [Emc-users] To Peter C Wallace

[Peter C. Wallace]

On Thu, 31 Dec 2015, Gene Heskett wrote:

> Date: Thu, 31 Dec 2015 20:51:08 -0500
> From: Gene Heskett 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "emc-users@lists.sourceforge.net" 
> Subject: [Emc-users] To Peter C Wallace
> 
> I tried to hook up my soft start circuit tonight, but when I had it wired
> in, the spindle didn't run. Checking dmesg, the card did not sign in
> like it usually does.  Backed out of the mainboard socket at least 1/8",
> again. By bumping the parport cables molded connector against the wall.
>
> So I have an excedrin headache, number unk.  Everytime I turn that
> computer around, to plug in a usb cable to charge my DS201, or for any
> reason, the 5i25 comes far enough out of the pci socket to disable
> something.  Or blow the card.  At 90 bucks a pop, that isn't fun.
>
> Do you have a bracket that can somehow hold the card into the socket?
>
> Its an LP bracket in an LP box, but it needs something to nail the card
> down into the slot a lot firmer than the LP bracket is holding it.
>
> Ideas, anybody?  Or do I have to make a x-crossed-brace to go across the
> top of the pci sockets?
>
> Thanks all. :)
>
> 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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>


Whats is actually bending when the card works out of the socket?
We have some standard height brackets with a rib on the edge
to limit flexing, unfortunately we cannot get stock
LP brackets with the rib

If the case/bracket are not rigid enough to prevent card motion,
one possibility is pad on the case top that presses on the connector
finger area of the top card edge


Peter Wallace
Mesa Electronics


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Re: [Emc-users] Smart-Serial cabling

[Bertho Stultiens]

On 01/01/2016 05:16 PM, Peter C. Wallace wrote:
>> The bandwidth of rs232 style serial connections is so low that you will
>> not see any problems with twisted pairs. I assume that you are not
>> connecting half a kilometer of cable with a speed higher than 115k2 baud
>> (or you may run into capacitive loading problens).
>>
>> Pairing TX and RX with a GND may actually improve noise immunity. But
>> the cable is already well shielded.
> 
> SSerial is differential RS-422 at 2.5 MBits/sec and requires ~100 Ohm
> differential cable cable impedance. This usually means twisted pairs
> are required for TX and RX (the 5V/GND power connections are not critical)

Then the cable should be just fine. Each differential pair takes a
twisted pair. Most Ethernet cabling has a characteristic impedance of
about 115 Ohm.

The crux is then to have appropriate drivers and correct impedance
matching (termination) at the end of the cable pairs.

-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Rewiring the BP

[Dave Cole]

On 1/1/2016 11:26 AM, Bertho Stultiens wrote:
> On 01/01/2016 05:13 PM, Dave Cole wrote:
>> Anytime you have a 120 volt source for computer, misc power etc, you
>> need to declare one side of the 120 vac winding the neutral (white wire)
>> and tie that terminal to the machine frame.
>> It similar to what is required at the service entrance of your house.
>> The neutral is always tied to the ground at the entrance box.
>> Oftentimes they drive  a screw through the neutral buss bar in the
>> service entrance box into the box sheetmetal and then tie a green or
>> bare copper ground wire to the same neutral buss bar and run that to a
>> metal water pipe or ground rod.
> You should never tie a secondary winding of a transformer to ground. The
> transformer makes the secondary float wrt. the primary and that is just
> fine.
>
> In this scenario, you would create a (capacitive) feed-through from the
> transformer to ground because the primary is not referenced at ground.
> The primary has two phases attached, which creates a virtual circuit at
> the primary side.
>
> The difficulty here is that you must take account for the floating
> references, which make most of the things you measure local phenomena.
> Once you go through the transformer, your reference to the primary line
> input is lost and you must not try to reestablish it. It would only make
> things bad and worse.
>
Hi Bertho,

That's done all of the time.   In fact it is part of the NEC (National 
Electric Code) that is followed (for the most part) in the US.
Pretty much every house in the US is wired like that.  (I'm not making 
this stuff up.  :-) )

Now, if you don't want to do that inside the panel for some reason 
(which I might have missed), that may be a different story.
I'm just saying that is standard practice in the US and on the European 
machines I have worked on as well.

There are a lot of good reasons to tie one leg the transformer to ground 
besides to establish the safety ground and neutral as is common on the US.
Intermittent faults to ground, with an ungrounded system, can cause the 
secondary of the transformer to fly way above absolute ground causing 
connected devices, or the transformer to suffer from insulation 
breakdowns.   That's the extreme, but it can happen.

One of way too many references on the web.
http://ecmweb.com/bonding-amp-grounding/basics-bonding-and-grounding-transformers

Dave

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Re: [Emc-users] Smart-Serial cabling

[andy pugh]

On 1 January 2016 at 16:16, Peter C. Wallace  wrote:
> SSerial is differential RS-422 at 2.5 MBits/sec and requires ~100 Ohm
> differential cable cable impedance. This usually means twisted pairs
> are required for TX and RX (the 5V/GND power connections are not critical)

The pairs are twisted inside the individual foil screen with drain
wire  then there are 4 other small (0.14mm2) wires and two bigger
(0.5mm2) wires all inside an overall braided screen.

I suppose the thing to do is to try it and see. I have determined that
the pairs fit nicely in an RJ45 connector, but I can't decide what to
do about the 2x 5V and 2x 0V positions in the connector. Are the 0V
and 5V contacts commoned at the PCB ends, such that leaving two
positions unpopulated in the RJ45 is OK? I only need enough 5V power
to run the 7i73 logic.

-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Rewiring the BP

[John Thornton]

I just looked at the control transformer and L1 and L2 (240v side are 
fused with type CC fuses and X1 only on the 120v side is fused with a 
slo-blow fuse. So I assume they intended X2 to be the "neutral".

JT

On 1/1/2016 10:15 AM, Gene Heskett wrote:
> On Friday 01 January 2016 07:00:31 John Thornton wrote:
>
>> Hi Gene,
>>
>> The frame is most solidly grounded. I'll do the tests in a bit. Keep
>> in mind that I have a 240v to 120v step down transformer to supply the
>> 120v not a normal house circuit. Again an effort to kill the noise.
>> Which by the way I'm running 2.7 now after changing the wires on the
>> limit/home switches to twisted pair shielded wire. I've attached the
>> VFD side wiring diagram. I assume the connection is through the
>> neutral bonding screw at the panel because the step down transformer
>> is isolated from ground.
>>
>> Happy New Year to you too.
>>
>> JT
> So this then was my 2nd guess, is the capacitative interwinding coupling
> in that transformer capable of supplying a very few microamps of actual
> current, probably less than 1 or 2. With no loads plugged in, you could
> connect either of the output phases of that transformer to machine
> frame "ground" without any fireworks which would bring the other up to
> 127 to "ground".
>
> I believe in that case I would synthesize a std 127 volt circuit out of
> the control transformers secondary by connecting the lower voltage wire
> to the machines frame, along with the static ground wire in a short bit
> of romex & using the std color code where the black wire is the high
> side of the transformers secondary, feed it to a duplex or 4 plex to
> power the computer, monitor, and any other 120 volt only loads on the
> machine as long as the total load is within the ratings of the
> transformer.
>
> That should be 100% safe for everything.  And it should reduce the
> coupled noise just because its all bouncing in unison.
>
> Some of the noise coupling is coming into the 120 volt circuit from
> the "longitudinal" coupling of the windings un-avoidable capacitance,
> and grounding one side of it, and the loads static ground to the
> machines frame & ground should absorb a good share of it.
>
> In really obnoxious cases, a small, perhaps a .01 to .1 uF capacitor
> rated at least at 600 volts from the high side, black wire to the
> duplex, to the machines frame should gobble up the rest of it. And not
> just for S, I'd fuse the hot lead of that cap since a failure would
> take out the control transformer.  Fused at less than the transformer is
> rated of course since you want to blow the fuse instead of the
> transformer.
>
> That was my theory when I hooked this room up, and I have not lost a
> piece of gear during an electrical storm in over 10 years since I did
> it.  With the 50kw can that supplies 4 houses on the pole across the
> street, that pole has been nailed quite a few times, and I even got a
> grab the doorknob shock that jumped out of a wired keyboard once.  So I
> know this whole room full of electronics has bounced at least 25Kv. Not
> even a computer crash when it happened.
>
> Electrical shock is a weirdly defined thing. Below 20 micro-amps directly
> thru the heart, a currant so low you may not even feel it, is generally
> harmless, but at 20 micro-amps up to about 20 milli-amps it can disturb
> the beat, causing fibrillation and eventual death if no one removes the
> power or you from the source and applies the defibber paddles.
>
> Above 20 milli-amps, the survival rate is better because the heart is
> frozen, and when the currant is removed, and it hasn't been frozen so
> long you are brain dead from lack of oxygen, then the heart will often
> start back as if nothing has happened.
>
> Your trivia factoid for the day. :)
>
> My ex had a cousin that I met once in the 1970's after he had stuck an
> alu ladder he was carrying into a low hanging 7200 volt line. Lost part
> of a foot, and the shoulder blade and arm the ladder was laying on.
> Never was the sharpest tack in the box, but I'd have guessed him at an
> IQ of 105 to 110 or so after the event.  Some surgery, a specially built
> boot and a while to heal, which he was still doing when I met him at
> some sort of a family doin's, but by now he's probably taken over the
> painting business his father started 50+ years ago and run it, if not
> retired from it. That was a "few" thousand  days ago. :)  The ex left 31
> years ago, ending any excuse I had to keep track of someone in Wisconsin
> I only met once.
>
>> On 12/31/2015 5:50 PM, Gene Heskett wrote:
>>> On Thursday 31 December 2015 16:20:40 John Thornton wrote:
 On the 120v side if I measure from the hot to the ground I get 79
 volts, if I measure from hot to neutral I get the expected 128v...
 what is that telling me?

 JT
>>> My first guess is that the Bridgeport itself, is not grounded.  It
>>> really should be, just to keep it from becoming lethally hot when
>>> somethings insulation 

Re: [Emc-users] Smart-Serial cabling

[Peter C. Wallace]

On Fri, 1 Jan 2016, andy pugh wrote:

> Date: Fri, 1 Jan 2016 16:59:12 +
> From: andy pugh 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "Enhanced Machine Controller (EMC)" 
> Subject: Re: [Emc-users] Smart-Serial cabling
> 
> On 1 January 2016 at 16:16, Peter C. Wallace  wrote:
>> SSerial is differential RS-422 at 2.5 MBits/sec and requires ~100 Ohm
>> differential cable cable impedance. This usually means twisted pairs
>> are required for TX and RX (the 5V/GND power connections are not critical)
>
> The pairs are twisted inside the individual foil screen with drain
> wire  then there are 4 other small (0.14mm2) wires and two bigger
> (0.5mm2) wires all inside an overall braided screen.
>
> I suppose the thing to do is to try it and see. I have determined that
> the pairs fit nicely in an RJ45 connector, but I can't decide what to
> do about the 2x 5V and 2x 0V positions in the connector. Are the 0V
> and 5V contacts commoned at the PCB ends, such that leaving two
> positions unpopulated in the RJ45 is OK? I only need enough 5V power
> to run the 7i73 logic.

Yes, they are commoned at the sserial remote and FPGA side RS-422 interface



>
> -- 
> atp
> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto
>
> --
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
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>

Peter Wallace
Mesa Electronics

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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/01/2016 05:47 PM, Dave Cole wrote:
> That's done all of the time.   In fact it is part of the NEC (National 
> Electric Code) that is followed (for the most part) in the US.
> Pretty much every house in the US is wired like that.  (I'm not making 
> this stuff up.  :-) )

I agree with the connection at power entry in the house. That is quite a
different story. That is actually the same here in EU (most countries).

I think that we should separate two things:
- house installation
- machine wiring

House installation is pretty much standardized with a lot of rules and
reasons. Specifically to ensure referencing and protection.

Machine wiring is different in that you can have scenarios where
references are moved, especially in a 2-phase system where you are not
using the neutral, which is the scenario we have here.


> Now, if you don't want to do that inside the panel for some reason 
> (which I might have missed), that may be a different story.
> I'm just saying that is standard practice in the US and on the European 
> machines I have worked on as well.

The reason for /not/ connecting the ground on a secondary winding is to
prevent a capacitively coupled ground path. Especially if you cannot
guarantee a 100% balanced primary-to-secondary side wrt. ground (*).

What happens is that there will be a current in the ground connection
which causes an imbalanced current on the primary side (remember:
primary is 2-phase circuit without neutral reference). This is a
differential current discrepancy on the primary side. If you have an RCD
(which you should), then it can or will trip due to the current imbalance.


(*) and from the example measurements presented by JT, we can be assured
that there is an imbalance, as seen from the phase shift causing a
difference in voltage measured wrt. ground on the secondary.


> There are a lot of good reasons to tie one leg the transformer to ground 
> besides to establish the safety ground and neutral as is common on the US.
> Intermittent faults to ground, with an ungrounded system, can cause the 
> secondary of the transformer to fly way above absolute ground causing 
> connected devices, or the transformer to suffer from insulation 
> breakdowns.   That's the extreme, but it can happen.

Actually, the secondary should normally be floating. Most transformer
setups are to ensure galvanic separation and that means you may never
connect neutral to the secondary side.

Connecting ground on a secondary is a different scenario, where you most
often see the 0V (DC) potential connected to protective ground. This is
often done in the PC's power supply. The 0V (DC) to protective ground
connection prevents the scenario to which you refer to.

The 0V (DC) to protective ground connection is repeated in many devices,
which have both power and signal connections. This gives rise to
ground-loops, which are to be prevented at all times and it is the cause
of the whole thread.


> One of way too many references on the web.
> http://ecmweb.com/bonding-amp-grounding/basics-bonding-and-grounding-transformers

It looks like the link is about a 3-phase system, where you would
connect the center point in a star-configured secondary to ground. That
is a different scenario.



-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Rewiring the BP

[andy pugh]

On 1 January 2016 at 17:29, Bertho Stultiens  wrote:
> The reason for /not/ connecting the ground on a secondary winding is to
> prevent a capacitively coupled ground path.

Another reason is that if you connect either secondary winding end  to
ground using body parts then nothing bad happens. This is the point of
an isolation transformer.
If there is an isolation transformer fitted in the machine then
grounding one of its terminals makes it pointless.

-- 
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If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Rewiring the BP

[Gene Heskett]

On Friday 01 January 2016 07:00:31 John Thornton wrote:

> Hi Gene,
>
> The frame is most solidly grounded. I'll do the tests in a bit. Keep
> in mind that I have a 240v to 120v step down transformer to supply the
> 120v not a normal house circuit. Again an effort to kill the noise.
> Which by the way I'm running 2.7 now after changing the wires on the
> limit/home switches to twisted pair shielded wire. I've attached the
> VFD side wiring diagram. I assume the connection is through the
> neutral bonding screw at the panel because the step down transformer
> is isolated from ground.
>
> Happy New Year to you too.
>
> JT

So this then was my 2nd guess, is the capacitative interwinding coupling 
in that transformer capable of supplying a very few microamps of actual 
current, probably less than 1 or 2. With no loads plugged in, you could 
connect either of the output phases of that transformer to machine 
frame "ground" without any fireworks which would bring the other up to 
127 to "ground".

I believe in that case I would synthesize a std 127 volt circuit out of 
the control transformers secondary by connecting the lower voltage wire 
to the machines frame, along with the static ground wire in a short bit 
of romex & using the std color code where the black wire is the high 
side of the transformers secondary, feed it to a duplex or 4 plex to 
power the computer, monitor, and any other 120 volt only loads on the 
machine as long as the total load is within the ratings of the 
transformer.

That should be 100% safe for everything.  And it should reduce the 
coupled noise just because its all bouncing in unison.

Some of the noise coupling is coming into the 120 volt circuit from 
the "longitudinal" coupling of the windings un-avoidable capacitance, 
and grounding one side of it, and the loads static ground to the 
machines frame & ground should absorb a good share of it.

In really obnoxious cases, a small, perhaps a .01 to .1 uF capacitor 
rated at least at 600 volts from the high side, black wire to the 
duplex, to the machines frame should gobble up the rest of it. And not 
just for S, I'd fuse the hot lead of that cap since a failure would 
take out the control transformer.  Fused at less than the transformer is 
rated of course since you want to blow the fuse instead of the 
transformer.

That was my theory when I hooked this room up, and I have not lost a 
piece of gear during an electrical storm in over 10 years since I did 
it.  With the 50kw can that supplies 4 houses on the pole across the 
street, that pole has been nailed quite a few times, and I even got a 
grab the doorknob shock that jumped out of a wired keyboard once.  So I 
know this whole room full of electronics has bounced at least 25Kv. Not 
even a computer crash when it happened.

Electrical shock is a weirdly defined thing. Below 20 micro-amps directly 
thru the heart, a currant so low you may not even feel it, is generally 
harmless, but at 20 micro-amps up to about 20 milli-amps it can disturb 
the beat, causing fibrillation and eventual death if no one removes the 
power or you from the source and applies the defibber paddles.

Above 20 milli-amps, the survival rate is better because the heart is 
frozen, and when the currant is removed, and it hasn't been frozen so 
long you are brain dead from lack of oxygen, then the heart will often 
start back as if nothing has happened.

Your trivia factoid for the day. :)

My ex had a cousin that I met once in the 1970's after he had stuck an 
alu ladder he was carrying into a low hanging 7200 volt line. Lost part 
of a foot, and the shoulder blade and arm the ladder was laying on.  
Never was the sharpest tack in the box, but I'd have guessed him at an 
IQ of 105 to 110 or so after the event.  Some surgery, a specially built 
boot and a while to heal, which he was still doing when I met him at 
some sort of a family doin's, but by now he's probably taken over the 
painting business his father started 50+ years ago and run it, if not 
retired from it. That was a "few" thousand  days ago. :)  The ex left 31 
years ago, ending any excuse I had to keep track of someone in Wisconsin 
I only met once.

> On 12/31/2015 5:50 PM, Gene Heskett wrote:
> > On Thursday 31 December 2015 16:20:40 John Thornton wrote:
> >> On the 120v side if I measure from the hot to the ground I get 79
> >> volts, if I measure from hot to neutral I get the expected 128v...
> >> what is that telling me?
> >>
> >> JT
> >
> > My first guess is that the Bridgeport itself, is not grounded.  It
> > really should be, just to keep it from becoming lethally hot when
> > somethings insulation fails.  Generally speaking, if I can measure
> > more than a volt between neutral and the static ground, it concerns
> > me UNLESS its a wild phase , which I don't believe you have since
> > its not a 3 phase circuit.
> >
> > TBE if something is running that uses that neutral you might see
> > more volts, but I'd re-measure after turning 

Re: [Emc-users] Smart-Serial cabling

[Peter C. Wallace]

On Fri, 1 Jan 2016, Bertho Stultiens wrote:

> Date: Fri, 1 Jan 2016 14:55:47 +0100
> From: Bertho Stultiens 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "Enhanced Machine Controller (EMC)" 
> Subject: Re: [Emc-users] Smart-Serial cabling
> 
> On 01/01/2016 12:23 PM, andy pugh wrote:
>> Is there any reason to think that the 2x3 screened pairs in that cable
>> will be unsuitable for transporting smart-serial data
>
> The bandwidth of rs232 style serial connections is so low that you will
> not see any problems with twisted pairs. I assume that you are not
> connecting half a kilometer of cable with a speed higher than 115k2 baud
> (or you may run into capacitive loading problens).
>
> Pairing TX and RX with a GND may actually improve noise immunity. But
> the cable is already well shielded.

SSerial is differential RS-422 at 2.5 MBits/sec and requires ~100 Ohm
differential cable cable impedance. This usually means twisted pairs
are required for TX and RX (the 5V/GND power connections are not critical)

>
>
>> (if I can persuade an RJ45 connector on to them)?
>
> That is actually a hard thing to do on these cables. The isolation is
> very hard and does not bend easily. Standard crimp-connectors will be
> almost impossible to attach while ensuring a mechanically stable
> connection. There is also a minimum bend-radius which can be rather large.
>
> These cables are normally used as distribution cables and go into female
> plug assemblies with seperate holding facilities for the cable.
>
>
> -- 
> Greetings Bertho
>
> (disclaimers are disclaimed)
>
> --
> ___
> Emc-users mailing list
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>

Peter Wallace
Mesa Electronics

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Re: [Emc-users] Rewiring the BP

[Bertho Stultiens]

On 01/01/2016 05:13 PM, Dave Cole wrote:
> Anytime you have a 120 volt source for computer, misc power etc, you 
> need to declare one side of the 120 vac winding the neutral (white wire) 
> and tie that terminal to the machine frame.
> It similar to what is required at the service entrance of your house.  
> The neutral is always tied to the ground at the entrance box.   
> Oftentimes they drive  a screw through the neutral buss bar in the 
> service entrance box into the box sheetmetal and then tie a green or 
> bare copper ground wire to the same neutral buss bar and run that to a 
> metal water pipe or ground rod.

You should never tie a secondary winding of a transformer to ground. The
transformer makes the secondary float wrt. the primary and that is just
fine.

In this scenario, you would create a (capacitive) feed-through from the
transformer to ground because the primary is not referenced at ground.
The primary has two phases attached, which creates a virtual circuit at
the primary side.

The difficulty here is that you must take account for the floating
references, which make most of the things you measure local phenomena.
Once you go through the transformer, your reference to the primary line
input is lost and you must not try to reestablish it. It would only make
things bad and worse.


-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Rewiring the BP

[Jon Elson]

On 01/01/2016 06:02 AM, John Thornton wrote:
> Hi Jon,
>
> So tie say the 48v side to ground to create the neutral? I 
> attached the drawing of what I have so far on the VFD side.
>
With power off, use an Ohmmeter to verify the secondary is 
isolated from the frame.  If so, tie either end to ground.  
If NOT, then further investigation is required.
> Happy New year to you and I hope you stayed dry during the 
> recent monsoon we got.
>
It was fine here, but lots of highways closed.  My mother in 
law's house had some basement leakage.  During the strongest 
rain, we had a drip where the furnace flue goes through the 
roof.

Jon

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Re: [Emc-users] Rewiring the BP

[Kirk Wallace]

On 01/01/2016 09:29 AM, Bertho Stultiens wrote:
... snip

> Machine wiring is different in that you can have scenarios where
> references are moved, especially in a 2-phase system where you are not
> using the neutral, which is the scenario we have here.

... snip

My understanding is, and I could be wrong, that "two-phase" in reference 
to modern mains circuits does not exist. Circuits with two hot legs, L1 
and L2, are single phase and referenced to each other. Two phase used to 
be two legs that were 90 degrees apart, but is long gone.

https://en.wikipedia.org/wiki/Two-phase_electric_power

I had fits trying to understand how rotary three-phase converters worked 
until I purged the notion of the input being two-phase.

Two phase does exist for stepper motors.
https://en.wikipedia.org/wiki/Stepper_motor#Two-phase_stepper_motors

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

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