half step shaping was Re: Newbie question. Second try

Hi Antonio,

Let me quote from an earlier post from Mariss:


" Here are the rules:

4-wire motor. No problem. Use the rated current and you will be fine.
No options here.

6-wire motor (unipolar). This is the same as the 4-wire except the
windings are center-tapped and the center taps are brought out.

You have two choices here; half-winding or full winding. You use half-
winding if yours is a high speed application or full winding if it is
a low speed one. Use the unipolar current rating for half-winding and
1/2 that for full winding.

8-wire motor. The same as a 4 wire motor except the windings are
center-tapped and brought out as seperate wires for the center tap
instead of being internally connected.

The performance in parallel is only 2% better in parallel compared to
half-winding connection on a 6-wire motor. The series connection is
exactly identical to full winding performance on a 6-wire motor.

Of all the motor types I prefer the 6-wire, or unipolar motors. You
can't screw up the winding phasing like you can with 8-wire motors
(buck vs. boost) and the performance penalty of 2% is essentialy
meaningless. You simply pick 4 out of the 6 wires available and it
will work. "

Looks like "... use the unipolar rating for the half winding...".

Deans's got quite a bit of information on his drivers on his website.
Looks good!

Lotta good stuff in the archieves!

HTH

Alan KM6VV


antonio-ximenez@... wrote:

>
> Thanks Ballendo for the explanation. Now I am making an a idea, half
> step shaping is.
> I had read something in L297 withe papers, but your explanation is
> cristal.
>
> Thanks Alan Marconnet by the early reply too.
>
> But with this, I have not clear, what is max current that I can set
> in the driver without fry the motors.
>
> Motors are 1.4 A half winding wiring and I want to get the max torque
>
> Please ????
>
> PD. Allan the url for this drivers is
> http://plaza.powersurfr.com/deanc/
>
> --- In CAD_CAM_EDM_DRO@y..., ballendo@y... wrote:
> > Hello,
> >
> > "Half step shaping" probably refers to the process of increasing
> > the amperage in "single coil on" positions of the half step
> sequence.
> > Most of the time it is referred to as "modified" half stepping.
> >
> > Some background:
> > Half stepping is the combination of "single coil on" and "two coil
> on"
> > full stepping. If we imagine a very simple stepper motor with four
> > coils set at the 12,3,6,9 0'clock positions, we can see that by
> > turning on one coil the motor rotor will "point" to the 12,3,6,9
> > directly. This type of "full step" is often called "wave" drive. If
> we
> > now power two coils in the standard sequence, 1&2,2&3,3&4,4&1, we
> will
> > get the rotor pointing midway BETWEEN the 12,3,6,9 o'clock
> positions.
> >
> > Combining these two gives us eight positions, but four of them are
> > only using ONE coil; and therefore have less torque than the "two
> coil
> > positions. So what "shaping" does is INCREASE the current supplied
> > during these "single coil on" positions, to "even out" the torque
> of
> > the motor through all positions.
> >
> > This is often accomplished by a resistor divider in the voltage
> > reference section of the drive. The increase is 1.414 times
> the "two
> > coil on" setting. Some driver chips have inputs that approximate
> this
> > with a 66% or 70% position; these instead REDUCE current to .707 in
> > the "two coil on" positions.
> >
> > Either way, the result is a much smoother 1/2 stepping drive. The
> down
> > side is that without ALSO incorporating "auto-idle", there may be a
> > risk of over-driving the motor if it is left in the 1.4 times
> position
> > for any length of time.
> >
> > Hope this helps.
> >
> > Ballendo
> >
> >
> > --- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...>
> wrote:
> > > Hi Antonio,
> > >
> > > Sorry you didn't get an immediate reply. I don't recall seeing
> this
> > > exact post, but I'll try to give you a few answers, below:
> >
> > > > The first thing different an other combos is the next phrase in
> > the
> > > > operation manual "The new SD1V1.2 incorporates half step
> shaping
> > for
> > > > 95% torque of full step mode"
> > >
> > > Haven't heard of "half step shaping" Do you have a URL for the
> > SD1V1.2?
>
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