3.2.1 Introduction

The signals in the altitude and azimuth subsystems are almost the same except the prefix "AL" or "AZ" respectively. Therefore, they are both described in this section. The signals are named as azimuth signals. They 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):

The above abbreviations are used as the second prefix after the standard prefix AL and AZ for altitude and azimuth respectively.

3.2.2 Power Amplifier Signals

AZPACUR1 AI*12 PA current to motor 1
AZPACUR2 AI*12 PA current to motor 2
AZPACUR3 AI*12 PA current to motor 3
AZPACUR4 AI*12 PA current to motor 4

3.2.3 Motor Signals

In each motor unit, there are three temperature switches of 70 degrees Celsius and three of 90 degrees. All the motor temperature signals in this table are the 70 degrees Celsius switches.

The 90 degree switches are in the interlock chain. They generate the signal ILMOTOR; see Subsection 3.2.7 for more information.

AZMTWIND1 DI*1 Motor 1, winding over-temperature
AZMTBEAR1 DI*1 Motor 1, bearing over-temperature
AZMTBRAK1 DI*1 Motor 1, brake winding over-temperature
AZMTWIND2 DI*1 Motor 2, winding over-temperature
AZMTBEAR2 DI*1 Motor 2, bearing over-temperature
AZMTBRAK2 DI*1 Motor 2, brake winding over-temperature
AZMTWIND3 DI*1 Motor 3, winding over-temperature
AZMTBEAR3 DI*1 Motor 3, bearing over-temperature
AZMTBRAK3 DI*1 Motor 3, brake winding over-temperature
AZMTWIND4 DI*1 Motor 4, winding over-temperature
AZMTBEAR4 DI*1 Motor 4, bearing over-temperature
AZMTBRAK4 DI*1 Motor 4, brake winding over-temperature

3.2.4 PI Controller Signals

AZPIVREF AO*12 Velocity reference to PI controller
AZPITORQUE AO*12 Torque reference to PI controller
AZPIVERR AI*12 Velocity error
AZPIACTV AI*12 Actual velocity (sum of four tacho signals)
AZPICREF AI*12 Net current ref. (without pre-tension for motors)
AZPIVRS8* DO*1 Velocity reference, 8 times greater sensitivity
AZPIATR* DO*1 Apply torque reference
AZPICVL* DO*1 Close velocity loop
AZPIAPT* DO*1 Apply pre-tension
AZPIRESET DO*1 Reset PI controller after interlock

3.2.5 Absolute Encoder connections via Digital I/O ACRO-0 BOARD TO SAE interface

AEDATI DO 1 Pin 1 (bit 20)
AEDATI DO 1 Pin 2 (bit 21)
AEDATI DO 1 Pin 3 (bit 22)
AEDATI DO 1 Pin 4 (bit 23)
AEDATI DO 1 Pin 5 (bit 24)
AEDATI DO 1 Pin 6 (bit 25)
AEDATI DO 1 Pin 7 (bit 26)
AEPARI DO 1 Pin 8 (bit 27) - Parity bit

3.2.6 Proximity limit switch signals

The following signals indicate that the telescope is close to the interlock limits. The computer should stop the telescope in an orderly fashion. The signals do not imply any interlock at all. Interlock in hardware first takes place when the interlock limit switches are passed.

These signals are generated in AL only. The corresponding bits in the AZ are indicated as "Reserved" in the schematic diagrams and are connected to the negated logic level. In this way, the software can be the same.

VSPOSLIMI* DI*1 Altitude 90 deg proximity limit switch (Upper limit=1)
VSNEGLIM* DI*1 Altitude 10 deg proximity limit switch (Lower Limit=1)

3.2.7 Computer Interlock Signals

The signals described in this subsection enables the computer to gather information about the interlock situation, or to issue commands to the interlock subsystem.

Some interlock signals are generated only in the AL system or only in the AZ system; the corresponding bits in the AZ or AL respectively is indicated on the hardware drawings as "Reserved" and are connected to the negated logic level. This has the advantage that the basic software for both AL and AZ can be the same.

If the emergency stop signal ILEMCOM is asserted, it indicates that any emergency stop button is pressed. Note that ILEMSTO shows that the emergency stop button on the AL or AZ power rack respectively has been pressed.

Interlock Signals for AL and AZ

AZILENABLE* DO*1 Disengage brakes and enable amplifiers
AZILORIDE* DO*1 Override interl. (parallel with manual override)
AZIL380PF DI*1 380V AC phase failure, amplifier disabled
AZILEMSTO DI*1 AZ emergency stop pushbutton; amplifier disabled
AZILEMCOM DI*1 Any! em. stop button pressed; amplifier disabled
AZILPI DI*1 Max. velocity exceeded; amplifier disabled
(generated by PI controller; reset via AZPIRESET)
AZILMOTOR DI*1 Overtemp (90 deg) of any of the four motors; amplifier disabled
AZILPADIS DI*1 Power amplifiers disabled; ie. any interlock active

Interlock Signals for AL Only

ALILLOCK DI*1 Locking device engaged; amplifier disabled
ALILPOSLIM* DI*1 Positive interlock limit signal; amplifier disabled
ALILNEGLIM* DI*1 Negative interlock limit signal; amplifier disabled
ALILBRMAN DI*1 Brakes manually disengaged; amplifier disabled

Interlock Signals for AZ Only

AZIL3D DI*1 3 degree limit passed; amplifier disabled
AZILHB DI*1 Hydrostatic pressure low; amplifier disabled

3.2.8 Miscellaneous Signals

WATCH DOG DO 1 Trigger output for alitude amplifiers watch-dog
AZSPAREx DI*1 Spare, x=1 through 3