half step shaping was Re: Newbie question. Second try

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?