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DCC Turntables/traversers

This feature is not available in the current 'Production' version

Defining DCC turntables/traversers

DCC turntables have pre-configured positions around the turntable that are selected by activating the associated linear DCC address.

To define a DCC turntable, you must create the turntable object with the <I id DCC home> command, or the DCC_TURNTABLE(id, home [,"description"]) EX‑RAIL command.

Once the turntable object is defined, you must add each defined position using the <I id ADD position dcc_address angle> command, or the TT_ADDPOSITION(turntable_id, position_id, dcc_address, angle [, "description"]) EX‑RAIL command.

In these commands, the home and angle parameters are there to enable throttle developers to “draw” turntables in software throttles, and have no impact on the operation of the turntable. These can simply be set to 0 (zero) when not in use.

DCC-EX native command example

To define a DCC accessory turntable with an ID of 201, starting at linear DCC address 201, and with a total of 10 positions, these DCC-EX native commands must be run (note we are not caring about the home or angle parameters):

<I 201 DCC 0>           // This creates the turntable object
<I 201 ADD 1 201 0>     // This adds position 1 with the DCC address 201
<I 201 ADD 2 202 0>
<I 201 ADD 3 203 0>
<I 201 ADD 4 204 0>
<I 201 ADD 5 205 0>
<I 201 ADD 6 206 0>
<I 201 ADD 7 207 0>
<I 201 ADD 8 208 0>
<I 201 ADD 9 209 0>
<I 201 ADD 10 210 0>    // This adds position 10 with the DCC address 210

Once these are defined, it can be operated using the <I id position> command:

<I 201 1>   - Rotate to the first position at linear address 201
<I 201 10>  - Rotate to the last position at linear address 210

EXRAIL command example

To repeat the above example using EX‑RAIL instead, these commands need to be added to “myAutomation.h”, noting the addition of the description parameter not available using the native commands:

DCC_TURNTABLE(201,0,"My DCC turntable")           // This creates the turntable object
TT_ADDPOSITION(201,1,201,0,"Roundhouse stall 1")  // This adds position 1 with the DCC address 201
TT_ADDPOSITION(201,2,202,0,"Roundhouse stall 2")
TT_ADDPOSITION(201,3,203,0,"Roundhouse stall 3")
TT_ADDPOSITION(201,4,204,0,"Roundhouse stall 4")
TT_ADDPOSITION(201,5,205,0,"Roundhouse stall 5")
TT_ADDPOSITION(201,6,206,0,"Roundhouse stall 6")
TT_ADDPOSITION(201,7,207,0,"Turntable entry")
TT_ADDPOSITION(201,8,208,0,"Maintenance bay 1")
TT_ADDPOSITION(201,9,209,0,"Maintenance bay 2")
TT_ADDPOSITION(201,10,210,0,"Maintenance bay 3")  // This adds position 10 with the DCC address 210

Throttle control

The result of both examples above is that the turntable objects are advertised to throttles that understand turntable objects, meaning they can be controlled in a similar manner to turnouts/points.

Note, however, that as this is brand new functionality, there are likely to be no throttles that understand these commands yet (subtle hint for throttle developers here!).

Automation options

Other EX‑RAIL commands have been added to enable automation related to turntable/traverser activities, including the ONROTATE(id) event handler and IF_TTPOSITION(id,position) test command to respond to turntable movements, and the ROTATE_DCC(id,position) command to control the turntable from sequences.

The limitation of DCC accessory turntables is the lack of feedback as to when a rotation or movement has completed, so a suitable delay would need to be calculated for automation sequences to allow sufficient time for rotations to complete prior to performing other activities.

For example, if you wish a warning light to be lit for the duration of a rotation, you could achieve this with the ONROTATE(ID) event handler:

ONROTATE(201)     // This event triggers when turntable ID 201 is rotated
  SET(26)         // Turn the warning light on connected to pin 26
  DELAY(10000)    // Wait 10 seconds for the rotation to complete
  RESET(26)       // Turn the warning light off