Kodak DirectView CR 825 Theory Manual page 76

THEORY GUIDE
10DEC05
Obtaining Smooth Operation of the SLOW SCAN MOTOR
TG4825-1
Page
To obtain smooth operation of the SLOW SCAN MOTOR, it is necessary to have smooth
76 of 120
rotating torque. The COILS make a magnetic field and the MAGNET aligns with the COILS.
When the MAGNET POLES are almost in alignment with the magnetic field, the torque
potential is highest. When the MAGNET rotates out of perfect alignment, more current is
necessary in the COILS to provide the same quantity of torque.
To provide the smoothest torque, the SLOW SCAN CONTROLLER BOARD A6 uses a
sinusoidal current in the COILS. When the polarization of the MAGNET is most out of
alignment with the magnetic field of the COIL, the sinusoidal current is at the maximum.
When the MAGNET and the field are almost perfectly aligned, the current drops to almost 0.
The current in the COIL then changes to negative polarity to repel the MAGNET POLE and
continue the smooth torque. When the next POLE starts to approach, the current reverses
direction and reaches the maximum again.
The SLOW SCAN CONTROLLER BOARD A6 monitors the signals from the ENCODER when
the MOTOR is operating. If the MOTOR is operating too slowly, the SLOW SCAN
CONTROLLER BOARD A6 increases the peak of the COIL current sinuosity to provide more
torque to increase the speed. If the MOTOR is operating at a higher speed than it should, it
decreases the current.
Scan/Erase