[Emc-users] oshpark registration rules?

[Gene Heskett]

Greetings folks;

Is anyone familiar enough with oshpark's registration rules to advise 
me?. I apparently tried to use too long a password, but my attempts to 
fix that are uniformly rejected with "email is taken" dotmarks.  I've 
sent a mild nastygram asking for directions, and for my email address to 
be scrubbed so I can try again.

Cheers, Gene Heskett
-- 
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-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Eagle mill retro fit

[Przemek Klosowski]

On Thu, Jan 26, 2017 at 9:45 PM, Dan Bloomquist  wrote:
> Another question I have. Would it be a big deal to go PC-104? That would
> really keep the size of the new hardware down. I've never worked with a
> PC-104 before. The pc-104 version of the LX25 board is like $140 more
> than the PCI version. I don't get that.

I think PC-104 is only being kept around because of legacy issues
(industrial and military). I wouldn't put it in a new
project---everything about it is expensive, Even though PC-104 does
support PCI, it uses a non-standard connector so it's just a headache.
On the other hand, it does still have the ISA bus so it is much easier
to add your own hardware.
The small NUC boxes are basically the same size as PC-104---around 4"
on the side.
https://www.newegg.com/Product/Product.aspx?item=N82E16856102141

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Re: [Emc-users] Eagle mill retro fit

[Dan Bloomquist]

Hi John, all.
Sorry, when I re'd it was just to John instead of the group. So...

I'm back at it. I posted here about a year ago, in this thread. I 
finally got a scope on the wires for my mill. The glass output is 5v 
digital quad output. Looks very close to 5um per step, so I'm going with 
that. The drive on the servos looks like the standard +-10 volts 
differential. But the Anilam is driving one pin at ~25% of the other. 
I'm not worried because with 6 volts the thing moves at 120ipm. So what 
I think I need is the Mesa 7i48. 6 channel servo output with quad 
encoder inputs. but what I'm not sure about is which of the anything i/o 
board I should use. I'm guessing that I don't need that much horse  
power and the likes of the 5I24-25-SP should do? After going through the 
wiring on this mill I now feel comfortable enough to replace the old 
Anilam hardware with new stuff. It will be nice to disappear that huge box.

Another question I have. Would it be a big deal to go PC-104? That would 
really keep the size of the new hardware down. I've never worked with a 
PC-104 before. The pc-104 version of the LX25 board is like $140 more 
than the PCI version. I don't get that. I will keep the servo amp rack 
separate as I'm sure someday I'll replace it with modern/smaller stuff.

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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Nicklas Karlsson]

On Wed, 25 Jan 2017 23:22:29 -0500
Stephen Dubovsky  wrote:

> On Wed, Jan 25, 2017 at 10:25 PM, Jon Elson  wrote:
> 
> > Field weakening is not possible on permanent magnet
> > brushless motors.
> >
> >
> It actually is.  Apply current in the D axis will oppose and reduce the net
> flux in the gap.  Move a coil in between two N poles permanent magnets
> facing each other and you will get no voltage as the field is zero at the
> center.  You risk demagnetizing the magnets at high temp.  You also risk a
> fault in the drive shutting off all the fets/igbts while running near top
> speed, loosing the field weakening, back emf goes to full strength, and
> rectified voltage back through the bridge becomes MUCH higher than the DC
> bus can handle.

Did not try that but have blown up many inverters for other reasons.

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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Nicklas Karlsson]

> On 01/25/2017 11:22 AM, Nicklas Karlsson wrote:
> > For permanent magnet motors there is a rather linear correlation between 
> > RPM and voltage although field weakening might be possible to lower voltage 
> > then loaded below rated torque.
> >
> >
> Field weakening is not possible on permanent magnet 
> brushless motors.

Never thought to much about it. I think some configurations of the magnets are 
rather hard to demagnetize but are not sure.

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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Gene Heskett]

On Thursday 26 January 2017 10:11:05 Stephen Dubovsky wrote:

> Eric, Did you lock the rotor?  If you don't and just apply a field the
> motor will align to a stable N-S.  Even at VERY high temps & fields
> you will not damage the magnets (you are actually trying to magnetize
> them even more - its how magnets are made afterall.)  You need to lock
> the rotor (or use active field/orientation control) if using opposing
> forces just sitting still N-N & S-S as this is a highly unstable
> condition.  Any tiny offset will generate Q axis forces and the rotor
> will *RAPIDLY* move to the stable N-S state.  We never ruined a motor
> but were instructed by the motor designers that it can happen.  No
> idea what the coercivity of a modern neodymium magnet is at typical
> motor operating temp.
>
In useing Jon's pwm-servo amp to run 1 hp spindle motors, that concern 
has allways entered into my thinking when setting the current limit of 
that amplifier. Those motors have an FLA of about 9.5 amps, so the amps 
were setup to hold to 15 max. I ran an ER32 nut down onto a clamp and 
stalled it for 3 or 4 seconds 2 days ago, but when it had moved off the 
clamp, everything fired right back up. I can hear the motor iron singing 
at about 14 kilohertz as it limits. But I don't believe I have damaged 
the magnets.  Bearings in the mills headstock, now those we won't 
discuss.  They were crap from the gitgo and I have got to replace them 
with quality bearings by spring if not sooner.

> On Thu, Jan 26, 2017 at 7:09 AM, Eric Keller  wrote:
> > On Wed, Jan 25, 2017 at 11:22 PM, Stephen Dubovsky
> > 
> >
> > wrote:
> > > On Wed, Jan 25, 2017 at 10:25 PM, Jon Elson
> > > 
> >
> > wrote:
> > >> Field weakening is not possible on permanent magnet
> > >> brushless motors.
> > >
> > > It actually is.  Apply current in the D axis will oppose and
> > > reduce the
> >
> > net
> >
> > > flux in the gap.  Move a coil in between two N poles permanent
> > > magnets facing each other and you will get no voltage as the field
> > > is zero at the center.  You risk demagnetizing the magnets at high
> > > temp.
> >
> > We tried to do this for some fault detection research.  We set the
> > winding currents so that the motor didn't move, but just heated
> > itself.  No failures.  There is enough change in the magnets with
> > heat that we could detect the changes, but they went right back to
> > normal when the temperature went back down. We were hoping to get
> > some degradation in the magnets over time, but it never happened. It
> > was disappointing and reassuring at the same time. I suppose we
> > should have gone higher with the current, because we never had any
> > winding failures either. The drive was made for a lot more current
> > than the motors could take.
> >
> > 
> > --
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Stephen Dubovsky]

Eric, Did you lock the rotor?  If you don't and just apply a field the
motor will align to a stable N-S.  Even at VERY high temps & fields you
will not damage the magnets (you are actually trying to magnetize them even
more - its how magnets are made afterall.)  You need to lock the rotor (or
use active field/orientation control) if using opposing forces just sitting
still N-N & S-S as this is a highly unstable condition.  Any tiny offset
will generate Q axis forces and the rotor will *RAPIDLY* move to the stable
N-S state.  We never ruined a motor but were instructed by the motor
designers that it can happen.  No idea what the coercivity of a modern
neodymium magnet is at typical motor operating temp.

On Thu, Jan 26, 2017 at 7:09 AM, Eric Keller  wrote:

> On Wed, Jan 25, 2017 at 11:22 PM, Stephen Dubovsky 
> wrote:
> > On Wed, Jan 25, 2017 at 10:25 PM, Jon Elson 
> wrote:
> >
> >> Field weakening is not possible on permanent magnet
> >> brushless motors.
> >>
> >>
> > It actually is.  Apply current in the D axis will oppose and reduce the
> net
> > flux in the gap.  Move a coil in between two N poles permanent magnets
> > facing each other and you will get no voltage as the field is zero at the
> > center.  You risk demagnetizing the magnets at high temp.
>
> We tried to do this for some fault detection research.  We set the
> winding currents so that the motor didn't move, but just heated
> itself.  No failures.  There is enough change in the magnets with heat
> that we could detect the changes, but they went right back to normal
> when the temperature went back down. We were hoping to get some
> degradation in the magnets over time, but it never happened. It was
> disappointing and reassuring at the same time. I suppose we should
> have gone higher with the current, because we never had any winding
> failures either. The drive was made for a lot more current than the
> motors could take.
>
> 
> --
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> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Eric Keller]

On Wed, Jan 25, 2017 at 11:22 PM, Stephen Dubovsky  wrote:
> On Wed, Jan 25, 2017 at 10:25 PM, Jon Elson  wrote:
>
>> Field weakening is not possible on permanent magnet
>> brushless motors.
>>
>>
> It actually is.  Apply current in the D axis will oppose and reduce the net
> flux in the gap.  Move a coil in between two N poles permanent magnets
> facing each other and you will get no voltage as the field is zero at the
> center.  You risk demagnetizing the magnets at high temp.

We tried to do this for some fault detection research.  We set the
winding currents so that the motor didn't move, but just heated
itself.  No failures.  There is enough change in the magnets with heat
that we could detect the changes, but they went right back to normal
when the temperature went back down. We were hoping to get some
degradation in the magnets over time, but it never happened. It was
disappointing and reassuring at the same time. I suppose we should
have gone higher with the current, because we never had any winding
failures either. The drive was made for a lot more current than the
motors could take.

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Re: [Emc-users] Connecting thin gears to shafts

[andy pugh]

On 26 January 2017 at 08:19, Roland Jollivet  wrote:
> You already have very little meat to work with, so why split the thickness
> between the two parts.
> If it was a through-hole like a typical taperbush, you'd have more
> engagement on the threads and the parts would be easier to machine?

I am not sure what sort of alternative you are describing.
I don't think I had enough thickness to make a "classic" taperlock
work, and the grub-screws would have been absolutely tiny.
(And tapping a half-and-half hole at M1.6 sounds like asking for trouble)

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

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[Emc-users] Connecting thin gears to shafts

[Roland Jollivet]

Nice, but I'm curious;

You already have very little meat to work with, so why split the thickness
between the two parts.
If it was a through-hole like a typical taperbush, you'd have more
engagement on the threads and the parts would be easier to machine?

Regards
Roland



On 26 January 2017 at 00:48, andy pugh  wrote:

> (As discussed on IRC a few days back).
> I had a bit of a puzzle about how to mount some thin gears to coaxial
> shafts. I came up with something that seems to work, and wrote it up
> on Blogger so that future folk might get more Goolg-luck than I got.
> http://bodgesoc.blogspot.co.uk/2017/01/gears.html
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1916
>
> 
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