CAD CAM EDM DRO - Yahoo Group Archive

Re: Stepper questions

on 2006-05-03 11:22:52 UTC
"Shorting the coil out" does all that but it also severely limits
motor performance. Current decays at a V/L rate, a diode is 0.7V so
current decays at a very leisurely rate.

The idea is to both rapidly inject and remove current in the winding.
If a 70V supply were used, current would decay at 1/100th the rate it
built up at (0.7V / 70V). This slow decay would bind the motor to a
tiny percentage of its potential.

The motor-winding energy is still wasted as heat, albeit slowly. It
didn't get recycled and it is substantial a high speeds (motor back-
EMF is also "shorted out").

Mariss



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Phil Mattison"
<mattison20@...> wrote:
>
> <snip>
> The most common technique is to place diodes to return the current
to the
> power supply, but this basically leaves the coil short-circuited.
> <snip>
>
> From all I have read and all the schematics I have looked at, the
porpose of
> the diodes is to protect the power supply from harmful reverse
current cased
> by inductive kick-back as the field collapses. Shorting out the
coil is
> precisely the objective. Otherwise the switching transistors can
become
> reverse-biased and burn out.
> --Phil M.
> http://www.ohmikron.com/
>
>
> ----- Original Message -----
> From: Jon Elson <elson@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Wednesday, May 03, 2006 10:05 AM
> Subject: Re: [CAD_CAM_EDM_DRO] RE: Stepper questions
>
>
> > Alan Marconett wrote:
> >
> > >HI Dave,
> > >
> > >That's an interesting point! I don't recall reading anything
like that,
> I
> > >could be wrong. Basically the windings do not interact as far
as I know.
> > >
> > >
> > The two halves of a stepper phase coil (on 6- and 8-wire motors)
DO
> > interact.
> > They are usually wound on the same coil bobbin, and act as two
windings of
> > a transformer. If you have twice the turns, then the inductance
is
> squared.
> > Because you only need half the current in full winding mode, it
only
> > takes twice
> > the voltage to turn the current around in the same time. But, at
the
> > same voltage,
> > it takes 4 times longer to turn the current around. That's why
the
> > half-winding
> > scheme is often used on a 6-wire motor with a bipolar drive.
> >
> > >Actually, one would think that "turning around" a winding, as in
a
> bipolar
> > >drive would take longer. The field would have to collapse
before it
> could
> > >build up in the opposite direction. Therefore wouldn't a
unipolar drive,
> > >with its four windings have the advantage?
> > >
> > No, because the current in the winding that is shut off has to
decay,
> > and that takes
> > time, or infinite voltage standoff of the transistors. Second,
the
> > decaying of the
> > "old" winding interferes with the filling up of the "new"
winding, so it
> > is the SAME
> > problem as the bipolar faces, really.
> >
> > > And I'd think that the unipolar
> > >stepper would have the further advantage of having two windings
available
> > >for microstepping. Half-stepping of a unipolar stepper is
relatively
> easy!
> > >Just alternate one winding on and two windings on! Ever see a 5
phase
> > >stepper? I still haven't figured out the stepping sequence for
that, but
> > >they do 400 steps!
> > >
> > >
> > >
> > You can do this with a bipolar drive, too. Just turn one winding
> > completely off inbetween
> > + and - polarities. Of course, you lose 33% of your torque that
way.
> >
> > >I'd like to see the "dual" specs for such a stepper. I'm
guessing that
> they
> > >rely on a difference in current, and possibly some dissipation
> differences
> > >between the two modes. Same current * turns = same torque!
> > >
> > >
> > >
> > For holding torque, this is absolutely correct. For running
torque,
> > EVERYTHING is
> > up in the air. It depends entirely on how the drive manages the
> > collapse of the
> > field in the winding that is being turned off. Providing an
effective
> > scheme to
> > dump the inductive energy quickly can greatly improve the running
> > performance.
> > But, that adds a lot of parts. The most common technique is to
place
> > diodes to
> > return the current to the power supply, but this basically leaves
the
> > coil short-
> > circuited. Putting some resistance in series with those diodes
will
> > increase the
> > voltage on the transistors, but will make the field collapse
faster.
> > But, then the
> > resistors will get hot. Especially in a chopper-type drive, they
will
> > be carrying the
> > circulating current nearly all the time while the motor is holding
> > position, and get
> > REAL hot. So, you need more transistors to shunt the resistors
except
> > when moving
> > above some speed. Eventually, it becomes obvious why a bipolar
drive is
> the
> > easiest way to get a simple, high performance drive. And, as for
> > microstepping,
> > if it doesn't do microstepping, it isn't worth having! (My
opinion, of
> > course! But,
> > if you've worked with a Gecko G201 drive, not much else even comes
> > close! And,
> > a full-step, or even half-step unipolar, L/R drive is so FAR from
a
> > Gecko that it is just
> > a really bad joke.)
> >
> > Jon
> >
> >
> >
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
> > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> > Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
> >
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> timg@...
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> >
> > OFF Topic POSTS: General Machining
> > If you wish to post on unlimited OT subjects goto:
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reach it if
> you have trouble.
> > http://www.metalworking.com/news_servers.html
> >
> > http://groups.yahoo.com/group/jobshophomeshop I consider this
to be a
> sister site to the CCED group, as many of the same members are
there, for OT
> subjects, that are not allowed on the CCED list.
> >
> > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
POSTING THEM.
> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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> > List Mom
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>

Discussion Thread

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(Was: COMPLETE 3 axis CNC...) Tony Jeffree 2006-05-02 22:46:33 UTC Re: [CAD_CAM_EDM_DRO] Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) Andrew Werby 2006-05-02 23:07:24 UTC Re: Re: Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) ballendo 2006-05-02 23:33:02 UTC Re: How much torque is enough? (Was: COMPLETE 3 axis CNC...) turbulatordude 2006-05-03 06:13:26 UTC Re: Steppers, bi- vs uni ?? who cares ? turbulatordude 2006-05-03 06:21:50 UTC Re: How much torque is enough? (Was: COMPLETE 3 axis CNC...) Alan Marconett 2006-05-03 08:20:56 UTC RE: Stepper questions Andy Wander 2006-05-03 08:24:55 UTC RE: [CAD_CAM_EDM_DRO] RE: Stepper questions Alan Marconett 2006-05-03 09:01:06 UTC RE: [CAD_CAM_EDM_DRO] RE: Stepper questions Alan Marconett 2006-05-03 09:15:07 UTC RE: [CAD_CAM_EDM_DRO] Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) Tony Jeffree 2006-05-03 09:39:28 UTC Re: [CAD_CAM_EDM_DRO] Re: How much torque is enough? (Was: COMPLETE 3 axis CNC...) Roy J. Tellason 2006-05-03 09:42:21 UTC Re: [CAD_CAM_EDM_DRO] RE: Stepper questions Jon Elson 2006-05-03 10:05:16 UTC Re: [CAD_CAM_EDM_DRO] RE: Stepper questions Mariss Freimanis 2006-05-03 10:15:12 UTC Re: Stepper questions Mariss Freimanis 2006-05-03 10:38:26 UTC Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) John Dammeyer 2006-05-03 10:43:10 UTC RE: [CAD_CAM_EDM_DRO] RE: Stepper questions Mariss Freimanis 2006-05-03 10:54:30 UTC Re: Stepper questions Phil Mattison 2006-05-03 10:58:44 UTC Re: [CAD_CAM_EDM_DRO] RE: Stepper questions Mariss Freimanis 2006-05-03 11:22:52 UTC Re: Stepper questions Roy J. Tellason 2006-05-03 11:48:38 UTC Re: [CAD_CAM_EDM_DRO] RE: Stepper questions Alan Marconett 2006-05-03 13:24:28 UTC RE: [CAD_CAM_EDM_DRO] RE: Stepper questions Alan Marconett 2006-05-03 13:31:29 UTC RE: [CAD_CAM_EDM_DRO] Re: Stepper questions Alan Marconett 2006-05-03 13:46:49 UTC RE: [CAD_CAM_EDM_DRO] Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) Alan Marconett 2006-05-03 14:05:41 UTC RE: [CAD_CAM_EDM_DRO] RE: Stepper questions Alan Marconett 2006-05-03 14:08:49 UTC RE: [CAD_CAM_EDM_DRO] RE: Stepper questions John Dammeyer 2006-05-03 14:47:15 UTC RE: [CAD_CAM_EDM_DRO] RE: Stepper questions ballendo 2006-05-03 15:00:40 UTC Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? R Rogers 2006-05-03 15:15:20 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? juan gelt 2006-05-03 15:15:51 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? ballendo 2006-05-03 16:29:58 UTC The best stepper driver??? was Re: Stepper questions ballendo 2006-05-03 16:46:32 UTC Re: Stepper questions ballendo 2006-05-03 16:48:36 UTC Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? ballendo 2006-05-03 16:52:30 UTC Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? Wayne Weedon 2006-05-03 16:52:50 UTC Re: [CAD_CAM_EDM_DRO] The best stepper driver??? was Re: Stepper questions R Rogers 2006-05-03 17:19:46 UTC Re: [CAD_CAM_EDM_DRO] The best stepper driver??? was Re: Stepper questions ballendo 2006-05-03 17:41:09 UTC The best stepper driver??? was Re: Stepper questions Mariss Freimanis 2006-05-03 18:04:12 UTC The best stepper driver??? was Re: Stepper questions turbulatordude 2006-05-03 18:16:44 UTC Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) Mariss Freimanis 2006-05-03 18:29:22 UTC The best stepper driver??? was Re: Stepper questions turbulatordude 2006-05-03 18:30:10 UTC Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? turbulatordude 2006-05-03 18:39:26 UTC The best stepper driver??? was Re: Stepper questions Alan Marconett 2006-05-03 18:54:16 UTC Re: stepper questions Jon Elson 2006-05-03 19:20:11 UTC Re: [CAD_CAM_EDM_DRO] RE: Stepper questions Jon Elson 2006-05-03 19:28:13 UTC Re: [CAD_CAM_EDM_DRO] RE: Stepper questions Jon Elson 2006-05-03 19:40:29 UTC Re: [CAD_CAM_EDM_DRO] RE: Stepper questions jeffalanp 2006-05-03 19:56:40 UTC The best stepper driver??? was Re: Stepper questions juan gelt 2006-05-03 21:48:03 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? Mariss Freimanis 2006-05-03 22:00:36 UTC The best stepper driver??? was Re: Stepper questions Mariss Freimanis 2006-05-03 22:46:47 UTC The best stepper driver??? was Re: Stepper questions JanRwl@A... 2006-05-03 22:51:27 UTC Re: [CAD_CAM_EDM_DRO] The best stepper driver??? was Re: Stepper questions Mariss Freimanis 2006-05-03 22:58:10 UTC Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? juan gelt 2006-05-04 00:01:41 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? Tony Jeffree 2006-05-04 00:08:20 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? ballendo 2006-05-04 02:36:42 UTC The best stepper driver??? was Re: Stepper questions ballendo 2006-05-04 02:41:39 UTC The best stepper driver??? was Re: Stepper questions ballendo 2006-05-04 03:20:04 UTC Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? Graham Stabler 2006-05-04 03:56:27 UTC Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? juan gelt 2006-05-04 04:44:26 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? going O.T. juan gelt 2006-05-04 04:54:17 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? going O.T. art 2006-05-04 06:40:05 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? going O.T. JCullins 2006-05-04 07:07:52 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? going O.T. Wayne Weedon 2006-05-04 07:14:27 UTC Re: [CAD_CAM_EDM_DRO] The best stepper driver??? was Re: Stepper questions caudlet 2006-05-04 07:43:32 UTC Re: Almost plug-n-play??? going O.T. {moderator WARNING!} R Rogers 2006-05-04 07:54:58 UTC Re: [CAD_CAM_EDM_DRO] Almost plug-n-play??? was Re: Steppers, bi- vs uni ?? who cares ? jeffalanp 2006-05-04 08:28:48 UTC The best stepper driver??? was Re: Stepper questions jeffalanp 2006-05-04 09:32:27 UTC The best stepper driver??? was Re: Stepper questions Mariss Freimanis 2006-05-04 09:57:55 UTC The best stepper driver??? was Re: Stepper questions Aaron 2006-05-05 08:46:42 UTC Re: [CAD_CAM_EDM_DRO] Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) Mariss Freimanis 2006-05-05 09:48:24 UTC Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go) wthomas@g... 2006-05-05 10:02:41 UTC W.E.T. CAD_CAM_EDM_DRO] : Stepper speed question