Specifications

RailCorp Engineering Manual — Signals — Equipment Manual

Cerberus Level Crossing Monitor Field Equipment Manual TMG E1261

Issued August 2012 UNCONTROLLED WHEN PRINTED Version 2.1

inputs 2-8 is rare but each input can be checked by monitoring the analogue inputs (by

viewing I/O inputs) and connecting 5 volts to each input and confirming that the A/D

reading is close to 255.

The ADC board will also fail if the internal +12V rail fails or goes low voltage. The ADC

board uses this +12 VDC rail to generate a voltage reference. If the +12V rail fails than

the ADC will read zero on all of its inputs. (Note: it is possible for a failed current sensor

or faulty wiring to the sensor supply terminals 1-11 to fail the internal +12V rail and

therefore fail the ADC board.

2.2.4.5 Replacement Procedure

Open lid of the Level Crossing Monitor. Turn off the power. Unplug the cable. Remove

the screw and unplug the ADC module from the SCADA 2000 A I/O board.

Plug in the new module. Re-install the screw and plug in the cable ensuring that the cable

captive clips are engaged.

2.2.5 Backplane

2.2.5.1 Function

The backplane provides the interconnections for the power, digital, and other wiring.

2.2.5.2 Operation

The backplane is a passive device which provides various connectors and

interconnections between them via Printed Circuit Board (PCB) tracks. The backplane

does have a 5.1 VDC transzorb and a diode which is designed to suppress voltage

spikes from the +5 VDC supply and protect against reverse polarity.

2.2.5.3 Configuration and Set-up

The configuration links on the backplane are not used by the level crossing monitor. They

should however be set to the following:

• 375 kbps link set (link between the two bottom pins)

• The node address connections should be left as set by the factory.

2.2.5.4 Troubleshooting

If the backplane is suspected then it is best to test it by continuity testing the relevant

circuits on the backplane. If this is okay test for shorts to test circuits. Close inspection

can only be done by removing the backplane PCB as there are printed circuit board

tracks on both sides of the PCB.

It has been discovered that the 5.1V transzorb designed to protect the 5V supply is

susceptible to failing short circuit after a power surge or lightning strike hits the level

crossing location. If this transzorb has failed short circuit than the level crossing monitor

will draw excessive current blowing the 4A supply fuse. As a temporary measure you can

disconnect the failed transzorb with a pair of side cutters. The level crossing monitor may

then function correctly, although other components on the surge protection and power

supply board may have failed open circuit or PCB tracks may be damaged.