Chapter 7 - Hydrostatic Bearing

7.1 HYDROSTATIC BEARING VME SYSTEM

The Hydrostatic Bearing VME system provides interfacing to the following subsystems:

• Hydrostatic Bearing.
• Weather data.
• ergency stop buttons in the building basement.

7.1.1 Reference Information

The following sections refer to specific information:

• Section 7.2 gives a description of the abbreviations of all the signals connected to the VME system of the Hydrostatic Bearing.
  
• Section 7.3 Gives a connection list of all the computer I/O signals.
  
• Section 7.4 provides a list of the available drawings and data sheets plus maintenance information.

7.1.2 Hydrostatic Bearing Control

The Hydrostatic Bearing control comprises a local PLC controller, provided by the company INNSE. A VME system, provided by ESO, controls this PLC. This chapter describes only the interface signals between the ESO computer and the PLC. For detailed information on the PLC, refer to the INNSE documentation listed in Subsection 7.4.3.

Interlock for Azimuth Motion

The azimuth motion is interlocked if the oil pressure behind the valve is too low.

7.1.3 Emergency Stops

Emergency stop buttons in the building are routed to the Hydrostatic Bearing VME rack. Here, each button generates a computer signal.

7.1.4 Signal Conventions

The signals to and from the Hydrostatic Bearing controller are connected to the VME computer via opto-couplers. This is done to interface from 24V logic to 5V logic and to provide galvanic separation.

The signals from the Hydrostatic Bearing side are 24V true in most cases. The opto-couplers invert the signals; therefore the VME I/O signals are 0V true in most cases. The signals are described in the true state (as normal). The false state is indicated, in the cases where it is not ovbious, with an "f".

In all cases, the description in the documents is defined such that:

• Description true = VME I/O signal 5V; no "*" in abbreviation.
  
• Description true = VME I/O signal 0V, "*" in abbreviation.

7.2 SIGNAL DESCRIPTIONS

The signals in the Hydrostatic Bearing subsystem are divided into the following groups that indicate where the signals originate (inputs to the computer), or where they have to be routed (outputs from the computer).

• Parallel signals transmitted by the ESO computer.
  
• Parallel signals transmitted by the PLC.
  
• Multiplexed bus signals.

Refer to the INNSE documents for a detailed description of the multiplexed bus; in this chapter, only the hardware signal names are described. The signal abbreviation is the same as used by INNSE, this means that it is not similar to, for example, the Altitude system. In order to integrate the INNSE abbreviation system in the NTT signal system, all Hydrostatic Bearing signals have the prefix HB.

7.2.1 Emergency Stop Buttons

The emergency stop buttons in the building basement are series connected in the HB VME cabinet, and routed from there via two slipring contacts to the building VME cabinet. Each button also generates a computer signal.

7.2.2 Parallel Signals Transmitted by the ESO Computer

Note: Impulsive signals must be at least 500 msec in length.

7.2.3 Parallel Signals Transmitted by PLC

7.2.4 Multiplexed Bus Signals

Note 1: Software assignment for the address bus is HBADDRESS*,this accesses the whole port (8 bits, of which 6 are used).

Note 2: Software assignment for the data bus is HBDATAHBYTE* and HBDATALBYTE* for the high and low bytes respectively. This accesses one port (8 bits) each.

7.2.5 Emergency Stop Signals

7.3 CONNECTION SCHEDULE

This signal schedule describes the location of the VME computer signals of the Hydrostatic Bearing. The signals are explained in Section 7.2.

This section provides the information to track each signal from the software driver to the input or output of the VME board. The VME system for the Hydrostatic Bearing contains two digital I/O interface boards.

The signals are connected via flat cable to the Weidmueller multi-termination strips (MTS1 through MTS4). From here, two special cables run to the INNSE opto-coupler box connectors J2 and J4,

The assignment of the signals is such that MTS1 is connected with J4 only; MTS2 and MTS3 are connected with J2 only; MTS4 is spare. From J4, some signals are connected to TS1 (power, emergency). The weather data enters via the RS232 port.

7.3.1 Multiplexed Bus and Parallel Output.- (DIG I/O 1, SLOT 9, ROW A)

7.3.2 Multiplexed Bus Input.- (DIG I/O 1, SLOT 9, ROW C)

7.3.3 Parallel Input.- (DIG I/O 2, SLOT 8, ROW A)

7.3.4 Emergency Stop and Spare.- (DIG I/O 2, SLOT 9, ROW C)

7.3.5 Emergency Signals

7.3.6 Miscellaneous Signals

Some interconnections on the INNSE opto-coupler box connectors are required to provide the INNSE signal; CKSICC (connector safety).

These connections are not related to any VME signal.

The VME 5V supply is used for the INNSE opto-couplers.

The VME+ and -12V power is used for interfacing the weather data.

Connector Safety

• J2-HH to J2-FF (black) and J4-HH to J4-FF (black).

Power

• VME 5V to J4-AA (red); note that this line goes via a 1 Amp fuse.
  
• VME 0V to J4-BB (blue).
  
• VME +12V to TS2-1.
  
• VME 0V to TS2-2.
  
• VME -12V to TS2-3.

7.4 MAINTENANCE INFORMATION

This section refers to the maintenance information for the NTT Hydrostatic Bearing VME System; references to drawings, data sheets and other information are included.

Interfacing of weather data (RS232 link) and the VME supply (+12V and -12V)is via TS2.

7.4.1 Drawing List

7.4.2 Data Sheets

DESCRIPTIONNO. OF SHEETSBurr-Brown Opto-transceiver LDM803INNSE Bearing System Controller.

7.4.3 PLC Documentation

Separate documentation from:

'INNSE-SPA', Milan, Italy.

"PLC- SIMATIC", 'STEP-5' source files