The X-Drive and Y-Drive
DSX™ System Service Manual 6-9
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6.2.4 Hardware Considerations
6.2.4.1. Motors and Drive Mechanism
The XY module drives and controls two stepping motors which can be operated singly or
both can be driven at the same time. The position of the two axes is verified using encoders
and a slotted-opto switch is provided for reference. The XY module communicates via a
standard Trilogy module interface which is routed from the back Plane via the X transition
and drive board.
The motor drive supply is 48V so that the motors can develop the torque and speed
required to drive the arms. The Bit Pattern generator is a MACH211 device that with
Direction and Step produces the bit patterns required to drive the motors in quarter step
mode.
Additional current control is supplied by the boost signal which when held low reduces
Vref and thus reduces the current at which the current chopper cuts in. This is to allow the
motor current to be reduced when the motor is stationary and thereby reduces the heat
dissipation of the motor and driver chips.
The brake signal momentarily short circuits the motor drives causing the motor current to
be reduced rapidly to bring the motor to a halt.
6.2.4.2. Voltage Generation and Regulation
Motor Supplies - The motor supply (48v) is supplied from the Interlock switches
directly to the X transition board. It arrives on the board as two separate 24 V supplies.
One supply is tied to ground, via the 0 V line, at the Back Plane. On the Transition
board the second 0v line is tied to the first 24v volts. This produces 24 V and 48 V
supplies for the stepper motors. The 24 V motor supply is not used for the X-Drive or
Y-Drive, but is routed through for the Z-Drive.
Logic and Control supplies - The +12 V from the module interface is used directly
for the flash programming voltage (FVPP), it is also the input to a dc\dc converter
which provides the 5 V logic supply. The logic GND is star connected to chassis on
the Back Plane.
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