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If, instead of physically rotating the stator,
we electrically rotate its magnetic field (by
switching current in the stator winding), the
stator remains stationary and the rotor turns
until the closest opposite-polarity (shaded) mag-
net poles attract each other into alignment.
Note that polarity of the stator poles has ro-
tated one position clockwise from that shown
in the first illustration.
The stepper motor is advanced by pulses pro-
vided by two triggers in the adapter.
The two triggers (A and B) provide four pulses
to step the motor:
(A8,
AS, AB, AB).
Direction of rotation depends on the sequence
of stator magnet switching. This, in turn, de-
pends on the triggers.
Clockwise
AS
AS
AB
AB
AB
Counterclockwise
AB
AB
AB
AB
AB
Note:
Current flows only in one-half of the
winding at a time. Polarity of the stator pole
is determined by which half of the winding
has current.
Home Position
AS
(Reset)
The rotor is in its static detented condition
when triggers
A
and
B
are active. This results in
the stator polarity shown. The stepper motor
is stopped.
Adapter
TR A
OFF
TR B
OFF
B
8-2
Stepper Motor
~----~DR~------------------~
First Advance Pulse A B (Generated by Adapter)
When the triggers advance to the AB condition,
the polarity of the stator magnets is rotated
clockwise.
TR
A
ON
TR B
OFF
ON
Because the rotor segment (shaded) is near the
next stator pole to its right, the rotor moves
nine degrees until the rotor and stator poles
align with each other; then stops.
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