9600 Service Manual - gmecorp-usa.com

14 Image System
LEAF ROTATION MOTOR
The collimator has a set of semi-transparent copper leaves (or shutter blades) that are
rotated by using the leaf rotation controls on the control panel (see Figure 6). U17 on the
Image Function PCB receives the commands from the Technique Processor.
Microcontroller U16 receives the instructions and communicates the data to U11, the
Motor Driver PLD (programmable logic device).
U11 then enables and drives the leaf rotation motor in the desired direction via U4, the
motor driver IC for the leaf in/out and leaf rotation motors. See Table 4 and Figure 9 for
details of the drive logic.
Motor speed is varied by pulse width modulation, output from microcontroller U16, pin 39
(PWM0) to the Motor Driver PLD, U11 pin 11. Pulse width modulation control was
selected because the speed required to operate the leaf in/out motor when operated
alone is different than the speed required to operate it when the leaves are rotating. This
is a result of the mechanical linking of these two motors.
Relay K3 provides a direct short through its normally closed contacts across the leaf
rotate motor to provide a high degree of dynamic braking to the motor when it is not
being driven. This is done because the mechanical linkage between the motors will tend
to back drive the leaf rotation motor when the leaf in/out motor is driven. When the leaf
rotation motor is driven, the shorting path through relay K3 is opened by the output of
motor driver U18, pin 14.