Printronix P6000 Series Maintenance Manual page 75

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2-9. Power Supply
-continued
j. Motor Relay Trigger, P6080 Only (Figures 2-25 and 2-26)
The motor relay trigger is used to apply a high starting torque to the shuttle motor at rest and later
disconnect the starting torque once the motor is running at the proper speed. When the printer is
brought online, a solid state relay is actuated to apply ac line voltage to the start winding. The start
winding energy is added to that of the run winding to produce a high starting torque. Once the
shuttle motor approaches normal operating speed, actuation of the relay ends and the start wind
ing is deenergized.
The motor trigger relay circuit is shown in Figure 2-26. While the printer is offline, NSD is high,
and the clock counter and dual flip-flop are held in reset. When the printer goes online, NSD goes
low releasing the counter and flip-flops. The 2 MHz system clock, NCLK, is converted to 1 MHz
(1 microsecond) by the first element of the counter. The 1 microsecond pulse passes through a 17
stage divider and becomes a 59.7 millisecond pulse, which is further divided by stages of the clock
counter to produce a 119.4 millisecond pulse and a 238.8 millisecond pulse.
Then, 238.8 milliseconds after NSD goes low, the 238.8 millisecond pulse sets the upper flip-flop
which actuates the solid state relay and the motor begins turning. The MPU counter begins receiv
ing MPU pulses detected at the flywheel. A count of 96 is decoded at the output of the counter.
Initially, the shuttle motor is not turning fast enough for 96 MPU pulses to be generated before the
119.4 millisecond pulse resets the MPU counter. The MPU counter is reset by the clock counter
59.7 milliseconds after the relay is actuated and at 119.4 milliseconds later. The MPU counter is
released midway between resets. Each time the counter is released, it begins a new count. When
the shuttle motor is turning fast enough, a count of 96 is decoded and the lower flip-flop is set.
Setting the flip-flop halts the relay actuation and the start winding is deenergized. The set flip-
flop also resets and holds the clock counter and the MPU counter. Counting stops until the printer
is cycled offline/online again to keep the relay from being actuated at normal motor speed, which
would have a braking effect on the motor.
P6040/P6080 Principles of Operation 2-55