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9.1.2 Functional Components
9.1.2.1 Stepper Motors
The forms feed motor and the print head motor
are sealed, dc stepper motors consisting of a per-
manent magnet rotor and two pairs of bifilar
stator windings.
CAUTION
Stepper motors require no maintenance; they
should not be opened or disassembled because the
magnetic flux of the rotor will be reduced, which
reduces the torque.
Each stepper motor is controlled by four direct-
current control lines. The direction the motor
turns is determined by the sequence of the control
pulses; each time the phases are shifted, the motor
shaft rotates 2 degrees.
The timing chart shows the sequence of pulses to
step the motor counterclockwise. The combination
of the not A line and not B line at the end of the
sequence hold the motor detented during settle
time.
Pulse
Sequence for 2°
Counterclockwise
Increments
-----------------~------------------
AS
A
)
(
A
(
)
B
(
)
B
I
AB lAB
I
AS: AS
AB
AB
~
AS
I
I
I
I
I
AS
AB
l
AB: AS:
I
J
I
pa...,
I
..,
I
I
I
:-1
AS
(motor is detented)
J
'\
(
(
' - - - - - Forms Feed Motor
- - - - - - - Print Head Motor
A reverse motor direction or
power off sequence can be
initiated at this time.
9-2
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