Vinten Radamec SP-2000 Pedestal - Manual (Page 96)

SP-2000/X-Y Maintenance And Repair
4-30 User Manual
Theory Of Operation
System
Refer to the Dolly Wiring diagram in the drawings file for a block diagram of
the overall AutoCam system. The primary circuit boards in the pedestal are the
motor drivers, the 4-channel servo boards which control up to four motors each,
the dolly board which handles targeting and several other functions and the bat-
tery-pack board which manages battery charging. Other components such as
relays, switches and so on are also shown on the block diagram.
Power Bus
The boards in the pedestal are all connected to a common power bus. The
power is nominally 36 volts DC.
Each board locally regulates its own operating voltages from the single 36V
supply. Usually these on-board supplies include a 24V supply for relays, lamps,
and solenoids, +15V and -15V for analog circuitry, and +5V for digital circuitry.
The +5V and -15V supplies are switching supplies.
The pedestal should always be switched off before disconnecting cables. The
dolly is designed to operate at voltages as high as 40V, but at voltages higher
than approximately 45V, the circuit boards will clamp the voltage from going
higher to minimize damage and will possibly blow on-board fuses in the pro-
cess.
Data Bus
The data bus is a 4-wire bi-directional 9600-baud RS-422 signal originating at
the controller, looping through the power supply to the pedestal. From the ped-
estal the data is looped up to the head. Feedback data from the pedestal loops
through the power supply and back to the controller. With RS-422, both sides of
the data leads are electrical mirror images of each other. Each should look like a
TTL signal. A fault condition is indicated by identical signal phase on both
lines, or one line stuck. Some types of problems with the data areas of the
boards can block data from reaching other boards downstream. A symptom of
missing data can be a useful troubleshooting aid. The on-board “happy light”
LEDs are a valuable aid when troubleshooting data path problems.
The data frames are sent to and received from the dolly at 25ms intervals.
Within each frame are command bytes for each servo axis, which each servo
board picks off as appropriate. Each servo board has an address, as determined
by an on-board jumper (J1) and the wiring harness. This allows 4-channel
boards complete with ROMs to be interchangeable.
Under local control, the pan bar mounted joystick is used to drive and steer the
pedestal with the dolly board generating the serial data instead of the controller.