SAS2-IR DC Model Railway Shuttle Controller with Infra-Red Detection

About the Product

The BLOCKsignalling SAS2-IR is an automatic DC model railway shuttle controller with infra-red train detection, designed to run a train continuously backwards and forwards along a single length of track. Two infra-red sensors detect the train at each end of the line, allowing automatic end-to-end operation without cutting or isolating the track.

The infra-red sensors are positioned beneath the track at the required stopping points. When the train reaches an end of the line, the SAS2-IR detects it and switches off the track power, bringing the locomotive to a stop. After the selected waiting period, the module reverses the track polarity and restores power, automatically sending the train back in the opposite direction.

The SAS2-IR works with a separate DC speed controller, allowing the normal train speed to be set using your existing throttle. The module then automatically controls stopping, waiting and direction changes.

Waiting times at each end can be independently programmed from 1 to 240 seconds and can operate with either fixed or random timing. When random operation is selected, the waiting period varies between approximately one quarter and the programmed maximum time, creating less repetitive automatic operation.

Key Features

• Automatically operates a DC model train backwards and forwards.
• Infra-red train detection at both ends of the shuttle line.
• No track cutting or isolated stopping sections required when using IR shuttle operation.
• Works with a separate DC speed controller.
• Independently adjustable waiting times at each end.
• Waiting times adjustable from 1 to 240 seconds.
• Fixed or random waiting times.
• Adjustable infra-red sensor sensitivity.
• Detection range of up to approximately 25mm at normal sensitivity.
• Optional control-panel route indication LEDs.
• Optional two-aspect signal control.
• Signals remain red while a train is waiting and change to green before departure.
• Optional push-button departure control available in the alternative operating mode.
• Fully programmable using the on-board push button and LED.
• Requires a 12V DC power supply.
  

Basic DC Shuttle Operation

The main wiring diagram on page 3 is the most important diagram for the product page. It clearly shows the two infra-red sensors, SAS2-IR, separate DC speed controller and track connections.

The DC speed controller provides the traction power and determines the locomotive speed, while the SAS2-IR automatically switches the polarity and controls when the train stops and departs.

Infra-Red Train Detection

Each infra-red sensor is normally mounted beneath the track through an 8mm hole in the baseboard. At the normal sensitivity setting, the sensors can detect rolling stock at distances of up to approximately 25mm. The optical elements are approximately 2.2mm in diameter, allowing them to see between sleepers even on smaller-scale track.

The sensitivity is factory-set to 5 and can be adjusted between 1 and 10, allowing the detection threshold to be adapted for different installations.

Adjustable & Random Waiting Times

Waiting times can be independently programmed for the two ends of the shuttle line from 1 to 240 seconds.

Either end can also be configured for random waiting. In random mode, the actual waiting period varies between approximately 25% and 100% of the programmed maximum, producing more varied automatic train movements.

Optional Two-Aspect Signal Control

The SAS2-IR can also operate optional common-cathode two-aspect LED signals at each end of the shuttle line. A signal remains red while the train is waiting, changes to green five seconds before departure, and returns to red five seconds after the train sets off.

Optional Route Indication

The signal outputs can alternatively be used with LEDs on a control panel or mimic board. These can indicate whether the train is waiting at either end or travelling in either direction. Each LED requires an approximately 1kΩ series resistor.

I wouldn't add the page 10 route-LED diagram as well as the signal diagram—the feature is worth mentioning, but four diagrams would start making the page unnecessarily long.

Electrical Requirements

• Supply voltage: 12V DC.
• Module current consumption: Approximately 0.25A.
• Recommended power supply: 0.5A–1A.
• Traction power: Separate DC speed controller.
• Train detection: Two infra-red reflection sensors.
• Typical detection range: Up to approximately 25mm.
• Sensor mounting hole: 8mm.
• Waiting time: 1–240 seconds at each end.
• Waiting modes: Fixed or random.
• Optional signals: Common-cathode two-aspect LED signals.

The module should be powered from a suitable 12V DC power supply rather than the auxiliary terminals of a train controller, as these accessory outputs may not provide sufficiently smooth or stable power.

Documentation & Support

For full installation instructions, infra-red sensor wiring, programming, signal connections and troubleshooting, please refer to the product instruction manual:

Product Instruction Manual