9600 Service Manual - gmecorp-usa.com

12 Image System
LEAF IN/OUT MOTOR
The collimator has a set of semi-transparent copper leaves (or shutter blades) that are
driven in and out of the beam by using the leaf sizing controls on the control panel (see
Figure 6). U17 on the Image Function PCB receives the commands from the Technique
Processor. Microcontroller U16 on the Image Function PCB receives the instructions
and communicates the data to U11, the Motor Driver PLD (programmable logic device).
U11 then enables and drives the leaf in/out motor in the desired direction via U4, the
motor driver IC for the leaf in/out and leaf rotation motors. See Table 3 and Figure 8 for
details of the drive logic.
Motor speed is varied by pulse width modulation (PWM), 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 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. The software and microcontroller
can therefore vary the speed of the collimator motors via the PWM signal.