Re: [Emc-users] About the 7i76E and possible DB25 expansion cards

[Gene Heskett]

On Monday 21 June 2021 22:01:25 Leonardo Marsaglia wrote:

> Thanks a lot Peter and Andy,
>
> I re read through the manual and found the SSERIAL port connection and
> the recommendation of using a CAT5 cable cut in half. I missed that
> part so I was a little confused about how to expand the I/Os. So, I'll
> be more than ok with this board :)
>
Another possibility if you need lots of i/o, is the 7i90HD, which has a 
total of 72 lines. Firmware options for uo to 8 axises of steppers and 
encoders. Or I believe pwm-gens and encoders. The disadvantages are its 
3, 50 pin i/o's that are all tied to the fpga, and easily damaged by 
noise. The fix for that is a trio of 7i42TA's which are effectly used as 
breakout boards, tradeing some bandwidth for the usual surge protection 
and giving you nice screw terminals to wire it up with. It can be driven 
from an epp parport, or from an spi port from a pi. With all the 
gingerbread I've put on the sheldon, I probably have 35 i/o lines unused 
yet. And I can fire up firefox and browse the net at the same time its 
running the sheldon. I felt keeping the ethernet port out of the lcnc 
arena, so the net port was available for updating and such was more 
important, and still do. 2 of my 4 machines are building and installig 
their own versions of linuxcnc from github master-gtk3 as I type this, 
including that rpi4.

> El lun, 21 jun 2021 a las 4:45, andy pugh () 
escribió:
> > On Mon, 21 Jun 2021 at 03:27, Leonardo Marsaglia
> > 
> >
> > wrote:
> > > Is the 7i75
> > > breakout board the way to add more I/Os to the 7i76E? And in that
> > > case I suppose the direction of the I/O pins in determined in HAL
> > > at the startup right?
> >
> > That depends on what you want. If it is just GPIO then look at
> > smart-serial boards on the built-in port.
> > If that still isn't enough, you could add one or two 7i74 boards to
> > the 7i76E for a theoretical extra 3584 extra IO lines
> >
> > (smart serial has been recently expanded from 96 to 224 bits, but I
> > am not sure if any available boards actually add more than 48 io
> > pins each)
> >
> > --
> > atp
> > "A motorcycle is a bicycle with a pandemonium attachment and is
> > designed for the especial use of mechanical geniuses, daredevils and
> > lunatics."
> > — George Fitch, Atlanta Constitution Newspaper, 1912
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
> ___
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] About the 7i76E and possible DB25 expansion cards

[andrew beck]

I second the recommendation to use a 7i84. I use one on all my machines.
For extra io.  They are awesome

On Tue, Jun 22, 2021, 2:04 PM Leonardo Marsaglia 
wrote:

> Thanks a lot Peter and Andy,
>
> I re read through the manual and found the SSERIAL port connection and the
> recommendation of using a CAT5 cable cut in half. I missed that part so I
> was a little confused about how to expand the I/Os. So, I'll be more than
> ok with this board :)
>
> El lun, 21 jun 2021 a las 4:45, andy pugh () escribió:
>
> > On Mon, 21 Jun 2021 at 03:27, Leonardo Marsaglia 
> > wrote:
> >
> > > Is the 7i75
> > > breakout board the way to add more I/Os to the 7i76E? And in that case
> I
> > > suppose the direction of the I/O pins in determined in HAL at the
> startup
> > > right?
> >
> > That depends on what you want. If it is just GPIO then look at
> > smart-serial boards on the built-in port.
> > If that still isn't enough, you could add one or two 7i74 boards to
> > the 7i76E for a theoretical extra 3584 extra IO lines
> >
> > (smart serial has been recently expanded from 96 to 224 bits, but I am
> > not sure if any available boards actually add more than 48 io pins
> > each)
> >
> > --
> > atp
> > "A motorcycle is a bicycle with a pandemonium attachment and is
> > designed for the especial use of mechanical geniuses, daredevils and
> > lunatics."
> > — George Fitch, Atlanta Constitution Newspaper, 1912
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
>
> ___
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>

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[Emc-users] Machining question

[Roland Jollivet]

I've worked with Fanuc robots,and was amazed to find that none of the
cables were shielded. The robot, with motors and encoders, is linked to the
control box with a 6m cable. All unshielded. Ok, the power and signal
cables are separate, but once installed, all extra cable is looped together
next to the control box.

A while back I stripped some Motoman robots. Internal on the arm, all the
motor wires, and encoder wires, are tightly bundled together. No shielding
on either.





On Mon, 21 Jun 2021 at 22:15, Thaddeus Waldner  wrote:

>
> Okuma machine builders really don’t like quantization noise so they use 40
> million CPR encoders on the axis motors.
>
> > On Jun 21, 2021, at 11:34 AM, Chris Albertson 
> wrote:
> >
> > Quantization noise is fundamental and present in all digital systems.
> > There is absolutely no way to avoid it.  All you can do is minimize it.
> >
> > To know how fast a shaft is spinning or how far it moves, you have to
> count
> > edges and if you get 100 counts you just can not know if you are closer
> to
> > 100 or to 101 counts.  Basically the counter always rounds down even if
> at
> > 100.9 it tells you "100".So the cound is "wrong" 50% of the time.
> > This applies not only to encoders, but A/D converts and every other kind
> of
> > measurement.
> >
> > This is the nature of digital data, of representing the world  with a
> fixed
> > number of bits.
> >
> >> On Sat, Jun 19, 2021 at 4:00 PM John Dammeyer 
> >> wrote:
> >>
> >> But doesn't the 7i92 FPGA deal with quadrature encoders and therefore
> >> doesn't really need to deal with a sampling process but instead looks at
> >> edges?  And because of the way quadrature works, with the A/B phasing
> you
> >> don't get the same types of errors compared to polling a bit level X
> times
> >> per second and trying to decide when it's high/low.
> >>
> >> John
> >>
> >>
> >>> -Original Message-
> >>> From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> >>> Sent: June-19-21 3:21 PM
> >>> To: Enhanced Machine Controller (EMC)
> >>> Subject: Re: [Emc-users] Machining question
> >>>
> >>> There are two kinds of noise,
> >>> 1) electrical noise superimposed on the signal.
> >>> 2) quantization noise from the sampling process.  What happens here is
> >> that
> >>> the computer counts the number of line crossings during a given time.
> it
> >>> is just random luck when the time starts so on average there is a plus
> or
> >>> minus one count error.
> >>>
> >>> So a one count error sounds small but lets say we have a 600 count
> >>> encoder and we are running at 500 RPM and sampling 100 times per
> second.
> >>> This works out to 50 counts per period.  a one count error is a 2%
> >> error.
> >>>   You will see a larger percent error at slower speeds or with a lower
> >>> resolution encoder.
> >>>
> >>> So even with perfect wires and perfect grounding and zero electrical
> >> noise
> >>> the RPM speed is going to jump around randomly over a 4 RPM range
> because
> >>> of unavoidable quantization error.
> >>>
> >>> The solutions either the use a larger sample time apply a low-pass
> >> DIGITAL
> >>> filter to the signal.  No amount of analog filters on the wires will
> >> work.
> >>>
> >>> On Sat, Jun 19, 2021 at 2:55 PM Gene Heskett 
> >> wrote:
> >>>
>  On Saturday 19 June 2021 12:59:19 John Dammeyer wrote:
> 
> > I need to do a couple of things.  For one the AC Servo makes a lot of
> > electrical noise.  The frame of the motor is connected to earth
> > through power line ground.  But my bench setup has the control side
> >> 5V
> > not isolated from the 'PC' side (optos are kind of useless here) and
> > although the Pi4 doesn't appear to have any trouble the scope shows a
> > pretty noisy encoder signal.
> 
>  You are about to learn the star ground system I think.
> 
>  Thats where all grounds go to a single bolt, and no other grounds are
>  allowed anyplace.
> 
>  Shielding in motor cables ends without touching the motor, only
> >> connected
>  to this same single bolt which is grounded. The common line of any
> >> power
>  supply is connected only to this bolt, and the common grounds to every
>  piece of pcb in the system comes from that bolt. The used to be green
>  static ground wire in any power cord is rerouted to this bolt. And
>  static grounds on a power supply are fed from this single bolt.
> Because
>  the psu case is usually bolted down wherever its at, you may have to
>  uncover the supply and remove any connection from the earth labeled
>  terminal, and the psu's case. It may be a screw in the corner of a
> pcb,
>  but it needs to be removed.
> 
>  Anything connected to ground at some other point in addition to that
> >> bolt
>  becomes an antenna, is called a ground loop, picking up both magnetic
>  and electrostatic noises. I had to learn that the hard way while
>  building the Sheldon, 

Re: [Emc-users] About the 7i76E and possible DB25 expansion cards

[Leonardo Marsaglia]

Thanks a lot Peter and Andy,

I re read through the manual and found the SSERIAL port connection and the
recommendation of using a CAT5 cable cut in half. I missed that part so I
was a little confused about how to expand the I/Os. So, I'll be more than
ok with this board :)

El lun, 21 jun 2021 a las 4:45, andy pugh () escribió:

> On Mon, 21 Jun 2021 at 03:27, Leonardo Marsaglia 
> wrote:
>
> > Is the 7i75
> > breakout board the way to add more I/Os to the 7i76E? And in that case I
> > suppose the direction of the I/O pins in determined in HAL at the startup
> > right?
>
> That depends on what you want. If it is just GPIO then look at
> smart-serial boards on the built-in port.
> If that still isn't enough, you could add one or two 7i74 boards to
> the 7i76E for a theoretical extra 3584 extra IO lines
>
> (smart serial has been recently expanded from 96 to 224 bits, but I am
> not sure if any available boards actually add more than 48 io pins
> each)
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
>
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>

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[Emc-users] high speed parallel bus on Raspberry Pi

[Ralph Stirling]

I read a very interesting article on Hackaday this
morning about the "Secondary Memory Interface"
on the Pi.  This is a little-known (poorly documented)
alternative pin set on the GPIO header that enables
a bus-type i/o with up to 18 data bits, 6 address lines,
read and write, and DMA request, all with programmable
sample and hold times with nsec resolution.  This site
has lots of info and examples on using it:
https://iosoft.blog/2020/07/16/raspberry-pi-smi/

This looks to me like it could be readily used to make
a parallel interface to Mesa cards like the 7i90 and
7i43 for very low latency.

-- Ralph

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Re: [Emc-users] Machining question

[Thaddeus Waldner]

Okuma machine builders really don’t like quantization noise so they use 40 
million CPR encoders on the axis motors.

> On Jun 21, 2021, at 11:34 AM, Chris Albertson  
> wrote:
> 
> Quantization noise is fundamental and present in all digital systems.
> There is absolutely no way to avoid it.  All you can do is minimize it.
> 
> To know how fast a shaft is spinning or how far it moves, you have to count
> edges and if you get 100 counts you just can not know if you are closer to
> 100 or to 101 counts.  Basically the counter always rounds down even if at
> 100.9 it tells you "100".So the cound is "wrong" 50% of the time.
> This applies not only to encoders, but A/D converts and every other kind of
> measurement.
> 
> This is the nature of digital data, of representing the world  with a fixed
> number of bits.
> 
>> On Sat, Jun 19, 2021 at 4:00 PM John Dammeyer 
>> wrote:
>> 
>> But doesn't the 7i92 FPGA deal with quadrature encoders and therefore
>> doesn't really need to deal with a sampling process but instead looks at
>> edges?  And because of the way quadrature works, with the A/B phasing you
>> don't get the same types of errors compared to polling a bit level X times
>> per second and trying to decide when it's high/low.
>> 
>> John
>> 
>> 
>>> -Original Message-
>>> From: Chris Albertson [mailto:albertson.ch...@gmail.com]
>>> Sent: June-19-21 3:21 PM
>>> To: Enhanced Machine Controller (EMC)
>>> Subject: Re: [Emc-users] Machining question
>>> 
>>> There are two kinds of noise,
>>> 1) electrical noise superimposed on the signal.
>>> 2) quantization noise from the sampling process.  What happens here is
>> that
>>> the computer counts the number of line crossings during a given time.  it
>>> is just random luck when the time starts so on average there is a plus or
>>> minus one count error.
>>> 
>>> So a one count error sounds small but lets say we have a 600 count
>>> encoder and we are running at 500 RPM and sampling 100 times per second.
>>> This works out to 50 counts per period.  a one count error is a 2%
>> error.
>>>   You will see a larger percent error at slower speeds or with a lower
>>> resolution encoder.
>>> 
>>> So even with perfect wires and perfect grounding and zero electrical
>> noise
>>> the RPM speed is going to jump around randomly over a 4 RPM range because
>>> of unavoidable quantization error.
>>> 
>>> The solutions either the use a larger sample time apply a low-pass
>> DIGITAL
>>> filter to the signal.  No amount of analog filters on the wires will
>> work.
>>> 
>>> On Sat, Jun 19, 2021 at 2:55 PM Gene Heskett 
>> wrote:
>>> 
 On Saturday 19 June 2021 12:59:19 John Dammeyer wrote:
 
> I need to do a couple of things.  For one the AC Servo makes a lot of
> electrical noise.  The frame of the motor is connected to earth
> through power line ground.  But my bench setup has the control side
>> 5V
> not isolated from the 'PC' side (optos are kind of useless here) and
> although the Pi4 doesn't appear to have any trouble the scope shows a
> pretty noisy encoder signal.
 
 You are about to learn the star ground system I think.
 
 Thats where all grounds go to a single bolt, and no other grounds are
 allowed anyplace.
 
 Shielding in motor cables ends without touching the motor, only
>> connected
 to this same single bolt which is grounded. The common line of any
>> power
 supply is connected only to this bolt, and the common grounds to every
 piece of pcb in the system comes from that bolt. The used to be green
 static ground wire in any power cord is rerouted to this bolt. And
 static grounds on a power supply are fed from this single bolt. Because
 the psu case is usually bolted down wherever its at, you may have to
 uncover the supply and remove any connection from the earth labeled
 terminal, and the psu's case. It may be a screw in the corner of a pcb,
 but it needs to be removed.
 
 Anything connected to ground at some other point in addition to that
>> bolt
 becomes an antenna, is called a ground loop, picking up both magnetic
 and electrostatic noises. I had to learn that the hard way while
 building the Sheldon, blowing two 7i90HD boards out by picking up 80
 volts p-p of switching noise that reached up to the bandwidth limits of
 both of my 100mhz scopes. Hell on an fpga with a 3 volt limit.  I
>> killed
 the power and redid it to the single bolt model, and that 80 volts of
 noise was reduced to under 100 millivolts. Took me about a week to find
 all the connections that should not have been made. Even a small bypass
 capacitor to a local ground instead of back to that bolt can become a
 lethal weapon to the elecronics.  Its a noise injector in that case.
 
 The whole idea is to make the ground, if it bounces from a lightning
 strike on the can on the pole that powers your place, which may make
>> the

Re: [Emc-users] Machining question

[Chris Albertson]

Quantization noise is fundamental and present in all digital systems.
There is absolutely no way to avoid it.  All you can do is minimize it.

To know how fast a shaft is spinning or how far it moves, you have to count
edges and if you get 100 counts you just can not know if you are closer to
100 or to 101 counts.  Basically the counter always rounds down even if at
100.9 it tells you "100".So the cound is "wrong" 50% of the time.
This applies not only to encoders, but A/D converts and every other kind of
measurement.

This is the nature of digital data, of representing the world  with a fixed
number of bits.

On Sat, Jun 19, 2021 at 4:00 PM John Dammeyer 
wrote:

> But doesn't the 7i92 FPGA deal with quadrature encoders and therefore
> doesn't really need to deal with a sampling process but instead looks at
> edges?  And because of the way quadrature works, with the A/B phasing you
> don't get the same types of errors compared to polling a bit level X times
> per second and trying to decide when it's high/low.
>
> John
>
>
> > -Original Message-
> > From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> > Sent: June-19-21 3:21 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] Machining question
> >
> > There are two kinds of noise,
> > 1) electrical noise superimposed on the signal.
> > 2) quantization noise from the sampling process.  What happens here is
> that
> > the computer counts the number of line crossings during a given time.  it
> > is just random luck when the time starts so on average there is a plus or
> > minus one count error.
> >
> > So a one count error sounds small but lets say we have a 600 count
> > encoder and we are running at 500 RPM and sampling 100 times per second.
> >  This works out to 50 counts per period.  a one count error is a 2%
> error.
> >You will see a larger percent error at slower speeds or with a lower
> > resolution encoder.
> >
> > So even with perfect wires and perfect grounding and zero electrical
> noise
> > the RPM speed is going to jump around randomly over a 4 RPM range because
> > of unavoidable quantization error.
> >
> > The solutions either the use a larger sample time apply a low-pass
> DIGITAL
> > filter to the signal.  No amount of analog filters on the wires will
> work.
> >
> > On Sat, Jun 19, 2021 at 2:55 PM Gene Heskett 
> wrote:
> >
> > > On Saturday 19 June 2021 12:59:19 John Dammeyer wrote:
> > >
> > > > I need to do a couple of things.  For one the AC Servo makes a lot of
> > > > electrical noise.  The frame of the motor is connected to earth
> > > > through power line ground.  But my bench setup has the control side
> 5V
> > > > not isolated from the 'PC' side (optos are kind of useless here) and
> > > > although the Pi4 doesn't appear to have any trouble the scope shows a
> > > > pretty noisy encoder signal.
> > >
> > > You are about to learn the star ground system I think.
> > >
> > > Thats where all grounds go to a single bolt, and no other grounds are
> > > allowed anyplace.
> > >
> > > Shielding in motor cables ends without touching the motor, only
> connected
> > > to this same single bolt which is grounded. The common line of any
> power
> > > supply is connected only to this bolt, and the common grounds to every
> > > piece of pcb in the system comes from that bolt. The used to be green
> > > static ground wire in any power cord is rerouted to this bolt. And
> > > static grounds on a power supply are fed from this single bolt. Because
> > > the psu case is usually bolted down wherever its at, you may have to
> > > uncover the supply and remove any connection from the earth labeled
> > > terminal, and the psu's case. It may be a screw in the corner of a pcb,
> > > but it needs to be removed.
> > >
> > > Anything connected to ground at some other point in addition to that
> bolt
> > > becomes an antenna, is called a ground loop, picking up both magnetic
> > > and electrostatic noises. I had to learn that the hard way while
> > > building the Sheldon, blowing two 7i90HD boards out by picking up 80
> > > volts p-p of switching noise that reached up to the bandwidth limits of
> > > both of my 100mhz scopes. Hell on an fpga with a 3 volt limit.  I
> killed
> > > the power and redid it to the single bolt model, and that 80 volts of
> > > noise was reduced to under 100 millivolts. Took me about a week to find
> > > all the connections that should not have been made. Even a small bypass
> > > capacitor to a local ground instead of back to that bolt can become a
> > > lethal weapon to the elecronics.  Its a noise injector in that case.
> > >
> > > The whole idea is to make the ground, if it bounces from a lightning
> > > strike on the can on the pole that powers your place, which may make
> the
> > > whole system bounce 100+ kilovolts, and if you are in that circuit at
> > > that instant it WILL get your attention. BUT, everything tied to that
> > > bolt should bounce in unison, meaning an 

Re: [Emc-users] LinuxCNC in use on 5axis

[Valerio Bellizzomi]

On Sun, 2021-06-20 at 19:33 +, Tomaz T. wrote:
> Recent project done on my DIY 5-axis, controlled by LinuxCNC, just to
> encourage if anyone taking similar path:
> 
> https://www.youtube.com/watch?v=TobQG2T7YV4
> 
> Regards!


It is a very nice machine.

Regards.




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Re: [Emc-users] About the 7i76E and possible DB25 expansion cards

[andy pugh]

On Mon, 21 Jun 2021 at 03:27, Leonardo Marsaglia  wrote:

> Is the 7i75
> breakout board the way to add more I/Os to the 7i76E? And in that case I
> suppose the direction of the I/O pins in determined in HAL at the startup
> right?

That depends on what you want. If it is just GPIO then look at
smart-serial boards on the built-in port.
If that still isn't enough, you could add one or two 7i74 boards to
the 7i76E for a theoretical extra 3584 extra IO lines

(smart serial has been recently expanded from 96 to 224 bits, but I am
not sure if any available boards actually add more than 48 io pins
each)

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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