half step shaping was Re: Newbie question. Second try

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?