Re: Stepper Motor Power supply Sizing.

Dave,

That's not the way microstepping works. If you are familiar with a
full-step sequence then you know it repeats after 4 full steps and
goes: (+A,+B), (+A,-B), (-A,-B) and (-A,+B).

Now if you look at the signs (direction of current) of winding A and
B currents, they are the same as the signs for sine and cosine from
zero degrees to 360 degrees. They too repeat after that.

Looked at that way, you could say with a straight face that a full
step sequence is a single-bit approximation of the sine and cosine
function.

Going to a half-step sequence: (0A,+B), (+A,+B), (+A,0B), (+A,-B),
(0A,-B), (-A,-B), (-A,0B) and (-A,+B). Graph it out, now it actally
starts to look a little like a sine and cosine if you squint just a
little. Call this either a 2-bit sine-cosine approximation or you can
call it 2 microsteps per step. You would be right both ways.

You can see where this is leading; the finer the degree you
approximate the sine-cosine function, the finer the microstep
resolution will be.

The practical limit occurs at 10 microsteps per step. At this level,
(sine-cosine quantified for every 9 degrees) the motor resolution is
now equal to its accuracy. Any microstep fineness beyond 10
microsteps is beyond the accuracy of the motor and is empty
resolution.

Mariss




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<davemucha@j...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Peter Homann"
> <peter.homann@a...> wrote:
> > Hi,
> >
> > I have been looking at Marriss's White paper on Power Supply's
> where it
> > states that the current requirements for a stepper motor is 2/3

of

> the
> > motors rated current in Parallel and 1/3 when in series.
> >
> > So, If I have a 4ohm, 4A/phase 8 wire stepper and I wire it in
> parallel, is
> > the current requirements for the motor 4*2/3 = 2.66A or is it
> 2*2.66 =
> > 5.333A as the motor has 2 phases.
>
>
> amp sizing is done on the nameplate of the motor. so if the
> nameplate is 4A, that's what you need to use.
>
> if you think about the coils, only one coil can/will be energized

to

> FLA at a time. microstepping will ballance the proportion between
> phases. half stepping is half amps to each coil, quarter stepping
> is 1/4 ot one coil, 3/4 to the other and so on.
>
> If you plan on using the motor as a brake with full amps to both
> coils, I'm not sure if you would actually lose torque.
>
> Dave
>
>
>
>
> >
> > Thanks,
> >
> >
> > Peter Homann
> > mailto:Peter.Homann@a...
> > Adacel Technologies Limited,
> > 250 Bay St, BRIGHTON, 3186, AUSTRALIA
> > http://www.adacel.com <http://www.adacel.com>
> > Telephone +61 (3) 8530 7777, Facsimile +61 (3) 9596 2960
> > Mobile 0421-601 665