Servo driven turnouts/points

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While there is already a reasonable amount of information available for servo driven turnouts/points within our documentation, it is distributed among other pages, so this page will primarily be a central location pointing to the existing documentation, along with any other considerations that need to be taken into account that may not be covered elsewhere.

Important considerations for servo operation

Test, test, test your servo parameters prior to connecting to an actual turnout/point. If you have defined angles that exceed the physical limits of your turnout, you will likely damage it and/or the servo mechanism.

Treat each servo and turnout as an individual as not all servos (or turnouts/points for that matter) are created equal. An angle that works with one servo and associated turnout will not necessarily provide the exact same result with another. Differences in servo brands, mounting methods, and even normal manufacturing tolerances will need to be factored in to the servo angles in use.

Use flexible wire to connect your servo arm to the turnout/point. Using a flexible connection between the turnout and the servo mechanism means if anything does go wrong such as the turnout getting jammed or an incorrect servo angle being sent, it reduces the chance of damaging the turnout or servo.

Defining servo based turnout objects

To define servo based turnouts directly in your EX‑CommandStation via the serial console, use the appropriate one of these commands:

  • <T id SERVO vpin thrown_position closed_position profile> - use this command when using a servo module connected to your EX‑CommandStation

  • <T id DCC linear_address> - use this command when using DCC accessory decoders to control the servos

Refer to Defining (Setting up) a Turnout/Point for details on these commands.

To define servo based turnouts using EX‑RAIL (whether or not they are to be automated) via the “myAutomation.h” file, use the appropriate one of these commands:

  • SERVO_TURNOUT(id, vpin, active_angle, inactive_angle, profile [, "description"]) - use this command when using a servo module connected to your EX‑CommandStation

  • TURNOUT(id, addr, sub_addr [, "description"]) - use this command when using DCC accessory decoders to control the servos

Note when providing the name of the profile to the SERVO_TURNOUT(...) command that the profile names are case sensitive, and must be written exactly as they appear in the reference (e.g. Slow, not slow or SLOW).

Refer to Turnout/Point Objects - Definition and Control for details on these commands, along with Defining Servo Turnouts, Stage 3 - Turnouts/Points, Accessories, Sensors & Blocks, and Adding Turnouts/Points for some further information and examples.

Connecting the hardware

For turnouts/points controlled by DCC accessory decoders, you will need to refer to the manufacturer documentation on how to connect these to your layout.

For servos controlled by a servo module connected to your EX‑CommandStation, sufficient information should be available on the Connecting a Servo Module page.