Application Outline:

A railroad intermodal yard is a place where large, truck trailer size, containers are loaded onto and off of rail cars and truck tractors. The name 'intermodal' arises because a change of the 'mode' of transportation occurs; highway traveling trucks and railroad cars.

This application note describes one more or less typical installation that is now in operation in California and used by a major railroad.

These yards consist of several parallel track sections that can be several miles long. The railroad cars are parked temporarily on very specific sections of these tracks and overhead cranes move the containers between the rail cars and the trucks.

The status of each track section is very rigidly controlled for both safety and efficiency of operation.

The status of each track section is indicated to the workers by a 'lamp post' located adjacent to the ends of each track section. These lamp posts have red and green lights (in most cases) that are visible to workers, truck drivers, crane dispatchers and locomotives.

Red meaning the track section is closed to train entry and movement of the cars within the track section because containers are in the process of being loaded or unloaded. Green means the cars within that track section is vacant or open for movement of any cars within that segment.

The lamps on each lamp post is controlled by a yard dispatcher using a PC type computer and following rigid safety guidelines of operation.

The use of this type of system is relatively new and it has been proven in many cases that radio control of the lamp posts is both economical and rapidly deployable. The alternative of electrical wiring would often involve placing wires and conduit under a foot or more of reinforced concrete pavement for many miles; a very costly and time consuming job.

HARDWARE DESCRIPTION

The system consists of a 'dispatcher' (master) site, a radio repeater and 25 remote 'lamp posts'

Dispatch Site:

This is the location that controls and monitors the light control system.

This site includes a spread spectrum radio, antenna system, a computer with a specialized graphic operating program and a printer.

The radio is programmed to operate as a multipoint master station.

The radio and antenna are located in a communications room adjacent to a radio tower. A directional antenna is used and pointed to the repeater radio location near the center of the yard.

The operating position where the computer and printer are located is in another room and connected to the radio via a RS232 cable. This computer is a PC type and not used for any other purpose.

Repeater Site:

Due to the length of the yard and the low elevation of the lamp post radio antennas (approximately 6 feet above ground), a repeater site was placed at a location that is visible to all but one of the lamp posts even when tall steel containers are located on the train cars.

This uses a spread spectrum radio programmed as a multipoint repeater and a 3 dB gain omni-directional antenna approximately 60 feet high.

The radio is mounted onto the side of a telephone pole inside a NEMA 4 weather proof cabinet.

The repeater is powered from local 110 VAC power without any backup battery since there is no need for control if the lamp posts do not have power (from the same source). In most applications a 2 to 8 hour battery back-up would be recommended.

Lamp Post Sites:

The lamp post sites are located at the end of, and adjacent to, each controlled track section.

A NEMA 4 weather proof cabinet and a dual obstruction light fixture (one red lens and one green lens) are mounted atop a 36 inch diameter concrete post that is approximately 5 feet tall.

The spread spectrum radios are programmed as multi-point slaves.

A 'smart' controller is attached to the radio to control and monitor the two 110 VAC, 100 watt lamps.

In this case, the controller is a 'micro-rtu' model ICL-4120 made by Industrial Control Links. These controllers provide two relay contact outputs, 6 digital (contact closure) inputs and 2 analog inputs.

The ICL-4120 controller was programmed to provide the lamp post selection address and to communicate to/from the spread spectrum radio via a RS232 connection.

The spread spectrum radio that was used and the ICL-4120 mini-rtu are compatible without any modification or special software.

The status of the lamps is determined by the actual AC current being used by each lamp, thus if current is within a given range, the lamp has been selected and operating properly. If the current is out of this range, the lamp is burned out or the wiring shorted which causes an alarm to be sent when polled by the master radio.

TYPICAL LAMP POST WIRING DIAGRAM

Due to the high vibration from heavy equipment moving near the lamp posts, lamp failure is common and the dispatcher needs to know of failures within a few minutes to maintain maximum safety.

The Lamp post radio, mini-rtu and current sensors are mounted inside a NEMA 4 weather proof box and, as stated before, operate from local 110 VAC power with no power back-up required.

The radio antennas are 3 dB gain omnidirectional mobile types mounted on the top of the NEMA 4 cabinets.

Note that one lamp post site radio path is obscured due to a bend in the tracks and nearby truck trailer parking so its antenna is a 3 dB directional pointed towards the repeater site and located atop a 25 foot pipe support.

OPERATIONAL DESCRIPTION

The light control system is used to control and monitor the operation of signal lights arranged as red and green lamp pairs at locations alongside the tracks used for loading and unloading intermodal freight onto or off train cars.

The lights are placed atop large concrete pedestals ( called 'lamp posts') for greater visibility and to reduce damage.

A box is located on top of each lamp posts to hold the radio, the controller and sensors and power supply. This called a Remote Telemetry Unit or "RTU".

The light control dispatcher is located at the dispatchers office at the west end of the yard. A computer, monitor, keyboard and printer is located near the dispatcher and a radio base station is located in the communications equipment room in the same building. The dispatchers computer is connected to the radio via a RS232 cable.

The radio portion of the system also uses a "repeater" station which is located on a tall telephone pole near the center of the yard. All radio communications for this system passes through the repeater station.

In this installation, there are 12 separate track sections within the lamp control system. These are called track sections 11 to 16 and 21 to 26. There are TWO lamp posts per track , one at the East end and one at the West end of each section.

(NOTE: Due to a long curve on the East end of track 16, there are three lamp posts, the East end, the West end and in the middle. All other tracks have two lamp posts each.)

In normal operation, one of the lamps will always be lit. This means the lamp site must either be RED or GREEN in color and never both ON or both OFF. Any other lamp condition is considered a 'failure' by the system.

The selection of the lamp color is made by an dispatcher located in the dispatchers office via spread spectrum radios which are located at every lamp post.

Each lamp post has a RTU box and each controller in these boxes is programmed specifically for that lamp post.

The dispatchers computer screen reflects the light situation of the yard and is updated continuously by scanning the whole system at approximately 5 minute intervals.

The system selects and reports each lamp post condition based on the RTU Controller address! IF a controller is moved to any other location, the computer will still think it is at the original location and switch the wrong lights! It is important to use the proper RTU address at the lamp post!

Password protection is used with any dispatchers command that could cause a lamp to change color and a System Dispatcher pass word is provided to edit the dispatchers password file. These files are encrypted and not legible when read by a file editor.

The System Dispatchers password also allows that person to shut down the program in the rare event that a software change or other computer maintenance is required. Note that when the computer is turned 'on' after a shut-down of any kind it automatically starts the light control program without any user action required.

The following is an abbreviated version of the dispatcher instructions which explains the functional operation of this system.

LIGHT CONTROL SYSTEM OPERATING INSTRUCTIONS

General Information

The light control system allows the dispatcher to switch the color of lights located at each end of a loading/unloading track section within the intermodal yard.

The track sections are shown as their full track number. That is; track 13 is shown as "13" .

Note that the compass directions on the computer screen are INVERTED from a normal map, with South being at the top of the screen. This is done intentionally to make the computer screen more closely appear as the yard does to the dispatcher who will be facing either south or east in the dispatch building.

The lights may be either red or green, and both colors ON or both OFF is not an dispatchers choice.

The individual light posts at each end of a track section are referred to as either the 'East' end or the 'West' end of that track section. For example, Track 25 has lights located at "25 East" and "25 West". This notation helps identify exactly where to go if a lamp is burned out or some other failure has occurred.

A special case exists for track 16 which has three lamp posts; East, Middle and West. The middle post was added to because the two track ends are not visible around the long curve at the east end of this track section.

All lights on the same track section are normally the same color and the dispatcher does not have the ability to command different colors at different lamp posts on the same track section.

When the dispatcher initiates an action in the system, that is called a "command" message. When the lamp post sends information back to the dispatcher, that is called a "reply" message which tells the dispatchers computer the "status" of the lights at that specific lamp post.

IF you send overlapping commands (that is; a new command was entered before the last command cycle was completed) the new command may override the earlier command and it result in a 'failure' status due to a message collision beyond the radios ability to prevent. If this occurs, simply re-enter the command you wanted.

Power Interruptions at the lamp post will cause BOTH lights to be OFF when the power is restored. This is most likely to occur during construction work in the area around the lamp post or , more rarely, an interruption of commercial power due to a storm, etc. This is caused by the type of relays used in the lamp post lamp controllers.

This is an intentional feature because IF the lights came back on in any preset color after a period of no power, the color could be wrong! This feature always leaves the color of the ON lights under the dispatchers control.

Since the computer cannot distinguish between a burned out "ON" light and the 'both lights OFF' condition, the dispatcher is advised to RETRY by sending the proper command to reinstate the proper light color if it was a power interruption.

Duplicated (not overlapping!) commands will NOT harm the system and may clear a problem or correct a failure of an earlier command.

Automatic Test Lamp Testing (Auto-Testing) Software Feature

In this system, the computer is continually checking each lamp post to see if a lamp has failed for any reason. The progress of the Auto-Testing is shown on the screen.

These checks occur during the idle periods when the dispatcher is not actively using the computer. A small notation above the 'Current date' shows these test as they are progressing.

The dispatcher has no control over these tests nor can they be altered.

It takes approximately 5 minutes for the automatic lamp testing to check all the lamp posts. Note that the automatic testing is suspended when the dispatcher is using the computer, so the time to check all lamps varies according to how much the dispatcher is using the system.

How the Lamp is Tested

It may help to understand the various abnormal (YELLOW) conditions by knowing the system the computer actually checks to see which lamps at each lamp post are using power.

The system works with bulbs from 50 to 150 watts in size, ONLY! Too small a bulb may appear OFF when it is ON and too large a bulb will blow out fuses at the lamp post.

When a lamp is using power, within the proper range, it is obviously ON and the lamp is OK.

When the lamp is NOT using power, it may be (in descending order of occurrence)

• turned OFF on purpose (therefore the other lamp should be ON)
• the bulb is burned out or loose in the light socket.
• turned OFF by an earlier power interruption.
• a failure in the circuits inside the controller atop the lamp post.

Note: There is a 2 amp fuse inside each lamp post controller.

The Computer Screen Layout:

The Upper Screen:

The upper half of the screen is a graphic representation of the intermodal yard.

The colors indicate the condition of the lights for each track. Note that the tracks and track number themselves are the appropriate color also.

The RED and GREEN colored tracks are obviously set to those colors as requested by the dispatcher.

ALL the lights for each track must be the same color before the tracks and track number are RED or GREEN colored!

The YELLOW colored tracks indicate an abnormal condition exists that the dispatcher should be aware of, such as burned out lamps, power failures, radio interference or communications failures.

The computer screen illustration above shows three different YELLOW track situations;

1. On track 23, the last command was to switch to RED.

The lamp post at 22 East End switched the RED lamp ON and the lamp is OK.

The last time 22 West was checked, it reported that NO lamp was lit, which means the lamp is probably burned out OR power was interrupted since the last time the 23 West was checked. This occurred either when the command was sent OR during automatic lamp testing, which can be verified in the lower message screen.

2. On track 24, the situation is the same as above, except the valid color is GREEN and it is the East lamp post that is reporting a problem.

3. On Track 26 a very rare condition exists; there are different colors at each end of the track, so the tracks and track number are YELLOW. The possibility of this condition is extremely rare and generally requires more than one failure to occur in a particular sequence.

This is an unacceptable condition so the dispatcher should immediately attempt several RETRYs to clear the error. It may be possible to change the GREEN end to RED until repairs can be made, so try that possibility also.

The Lower Screen

The lower 1/2 of the screen is the 'message' screen. It confirms actions taken by the dispatcher and provides more details about replies from the lamp posts.

Every message that appears with a date on it will also be printed out IF the printer is "ON" AND a copy is stored in the permanent History Log inside the computer.

The computer generates all these messages and the dispatcher cannot change them or type in messages.

Below the message box are three function key selection choices. The function keys are those at the top of the key board numbered F1 to F12.

TIMED RESPONSES

Many of the selections suspend the program operation when in use, so they are 'timed' to clear automatically IF you do not enter the required information within 10 to 15 seconds. There is usually a message saying the time has expired.

If this happens, simply make the selection again and start over.

The HELP menu ( [F1] key pressed)

Once you are familiar with the operation of this system, this will be the only screen you will need to remind you of the many optional selections you chose.

The HELP menu will 'pop' on in the upper left hand corner of the screen and will disappear if you press any key while it is on. Using the help screen does not effect the normal program, so use it as much as needed.

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