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Block Occupancy Hardware

Block Occupancy Detection (BOD) logic is built into LCOS. A Client Node can monitor up to 8 local blocks.

What Is it Used For? #

In LCOS, BOD is a foundation of system automation and control. The most obvious use is to allow a control panel to show train locations.

LCOS block objects announce their state changes; any other object configured to listen for block occupancy messages can act on those announcements. This means, for example, that signals can respond to event originating across the layout.

By linking a block to Control Objects, a block becomes a virtual switch, able to operate other layout objects, such as scene objects or animations.

To activate this capability in your installation, you need the BOD Hardware on each Client Node that will use it. BOD Hardware is included in the LCOS Layout Starter Kit and the LC2 Layout Foundation Kit. You can add BOD to any Client node with the LCBDK Block Occupancy Detection Add-On Kit plus up to 2 additional DNCT2B Feeder/Sensor Modules. Or you can buy the parts separately.

Installation is straight forward: subject to the cable length limitations shown below, place the DNCTA Interface near the Client Node, then place DNCT2B Sensor/Feeder boards near track feeders. You’ll plug the feeders into the DNCT2B boards, and connect the boards directly to your track bus.

Boards to Node Connection #

The DNCT2B sensors and the DNCTA interface module connect to each other and to the Client node via conventional Cat 5e Ethernet cables. Cables should be no longer than 7 ft for connecting the DNCT2B Sensors; the cable from the DNCTA to the Client Node should be no more than 1 ft.

Sensor Connections #

The DNCT2B board is a dual feeder/sensor board. Attach the RAIL-IN terminals to your main track bus — we recommend 14 gauge wire for the track bus connection. Then attach block feeders to the block 1 and block 2 terminals. Automatic reversers, reversing relays and/or rail circuit breakers can be placed on either side (input or output) of the board.

DNCT2B Connections. The Rail Terminals are sized for 14 – 26 gauge wire.

Place DNCT2B boards as close as possible to the point where the feeders are attached to the track.

DNCTA Port to Block Mapping #

LCOS supports local blocks with IDs from 0 to 7. DNCT2B sensors are mapped to block ids depending on which DNCTA port they are plugged into. If a DNCT2B is plugged into the first port (“DNCT2B#1”), block 1 on that board maps to local block 0, and block 2 maps to local block 1. If a DNCT2B is plugged into the second port (“DNCT2B#2), block 1 on that board maps to local block 2, and block 2 maps to local block 3. The third port maps to local blocks 4 and 5, and the fourth port maps to local blocks 6 and 7.

DNCTA Ports map to specific local block IDs.

In the Configurator, blocks are referenced by their local block ID (0 through 7). Globally, blocks are referred to by their UID (also 0 through 7).

Sensitivity #

The microprocessor limits detection resolution to approx 1 mA. While that should be sufficient to detect a single 10k wheelset at 15 volts, as a practical matter a single wheelset is insufficient for detection purposes. This is because track and wheel condition conspire to raise that actual resistance to a higher level, especially at smaller scales.

Two 10k resistor wheelsets are required for reliable detection. Bearing mind that locomotives, sound cars and lighted rolling stock on the track are always detected:

  • The last car of a train, usually a caboose, should have two resistor wheelsets on the trailing truck.
  • If you want to trigger block detection on a siding with only one or two cars, there should be two 10 k wheelsets on one or both cars.
  • A few 10k wheelsets should be distributed among other cars on a train, but only enough to ensure detection on your shortest block. In most cases, having a single 10k wheelset on every 4th or 5th car should be sufficient.
  • Any car with lighting or a DCC decoder will be detected and requires no other components.

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