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Switchback Automation Module

Introducing SAM, a circuit module designed for automating switchbacks. If you're looking for a full-featured off-the-shelf switchback automation solution, SAM's your man.

If you're seeking simpler switchback automation methods that you can quickly build for yourself using automation tools, see Switchback Automation.

Description

A self-contained circuit module with three train detection inputs, an output for turnout control, three on/off status outputs, and a reset button and input. All inputs expect pulse signals.

The module recognises the direction from which a train is approaching and, after the train has entered the reversing stub track, switches the turnout so that the train departs on the opposite track to its arrival. Under normal operating conditions it will also set the turnout correctly for the approaching train, although this action is of cosmetic value only.

The module can process any sequence of arrivals from either direction.

To control the turnout you will need a Remote trigger activator with on/off state (Room.8). The two train detectors on the arrival/departure tracks must be set to Start only. The train detector on the reversing track must be set to End only.

S represents the straight position of the turnout and its associated track and detector switch.
T represents the turn position of the turnout and its associated track and detector switch.
X represents the stub track where the train reverses direction and its detector switch.

In order to reset itself after each pass the module requires all three detectors to be in place and connected even if traffic only passes in one direction.

I do not require attribution if you incorporate this logic into a published layout, but if you do so please post a link in the comments so I can see it in action.

Example layouts

At left is a demonstration of basic set-up, plus tapping the status outputs to operate signals and lighting. More advanced signal control (specifically switching to red when the train enters the switchback) can easily be achieved with some additional automation.

At right is an example of the use of tags to selectively direct a train through a switchback, and of wireless detector switch connection. The turnout activator must be connected by wire. Note that the module does not perform the cosmetic action of setting the mainline turnout for trains that do not bear the tag, because it is not informed of the presence of these trains. For methods to perform this action for all traffic see Automated Turnout Exit Switching.

How to copy the module to your layout

Use the Bulk move tool (Room.6). Before selecting objects you will need to make the Details (circuitry), Terrain (baseboard) and Room (labels) layers editable. You should see a "Props selected" count of at least 128.

Click Copy and then Done in the tool dialog. Close this layout and open the destination layout. Grab and position another Bulk move tool, open its dialog and click Paste. Then save, close and reload the destination layout (the wiring will not work until this has been done).

Pasting the module into another layout does not create a dependency on this mod. Neither you nor any other user of your layout will need to be subscribed to this mod thereafter.