PPI4-DC Model Railway Points Position Indicator + Red & Green Dual-Colour LEDs

About the Product

The BLOCKsignalling PPI4-DC is a model railway points position indicator supplied with red/green dual-colour LEDs, monitoring up to 8 sets of points and displaying their last operated position on a control panel or mimic board.

When a set of points is operated, the PPI4-DC detects the brief positive switching voltage applied to the point motor and automatically updates the corresponding LED indication. Only the colour representing the most recently selected position remains illuminated, providing a clear visual indication of the last point operation.

This version is supplied with common-anode three-leg red/green dual-colour LEDs, allowing each set of points to be represented by a single LED that changes between red and green. This provides a particularly neat solution for model railway control panels and route mimics.

The PPI4-DC provides 16 opto-isolated input channels for monitoring up to eight pairs of point positions. Input states are automatically stored in memory, so when power is switched off and restored, the panel LEDs return to their previously recorded states.

Designed for model railway control panels and mimic boards, the PPI4-DC also includes adjustable LED brightness and built-in diagnostic LEDs to assist with installation and troubleshooting.

Key Features

• Monitors up to 8 sets of points.
• 16 points-monitoring input channels.
• Supplied with red/green dual-colour LEDs.
• One dual-colour LED can indicate both positions of each set of points.
• Displays the last operated point position on a control panel or mimic board.
• Automatically remembers point positions when power is switched off.
• Adjustable LED brightness.
• Opto-isolated points inputs.
• Accepts points-monitoring voltages from +5V to +25V.
• Built-in input and output diagnostic LEDs.
• Suitable for control panels and model railway mimic boards.
• Supports red and green route indication.
• Can be used to automatically control compatible 2-aspect signal LEDs from point operation.
• Supports 3-way points with suitable additional wiring.
• Optional programming – no programming required for normal operation.
• Built-in LED lamp test function.
  

Dual-Colour Red & Green LEDs Included

This version is supplied with common-anode three-leg red/green dual-colour LEDs for mounting directly into a control panel or route mimic.

Each dual-colour LED can display either red or green, allowing a single panel LED to indicate both positions of a set of points. This reduces the number of individual LEDs required on the control panel and provides a neat, compact route indication.

The PPI4-DC manual includes a dedicated wiring arrangement for common-anode dual-colour LEDs.

Points Position Indication

The PPI4-DC monitors the brief switching voltage applied when a point motor is operated.

Each set of points uses a pair of inputs. When one input receives a positive switching pulse, its associated indication is selected and the other indication for that pair is switched off.

This means the control panel continues to show the last operated position of each set of points, even though the electrical pulse used to operate the point motor lasts only briefly.

The diagram shows a typical PPI4-DC installation, with the module monitoring the point motor switching circuit and displaying the last operated position on the control panel.

Monitoring Up to 8 Sets of Points

The PPI4-DC provides 16 input channels (I1–I16), allowing it to monitor up to 8 sets of points.

Each pair of inputs controls the corresponding point-position indication, making the PPI4-DC particularly useful for larger control panels where the operator needs to see the last selected route at a glance.

Automatic Position Memory

Each time the PPI4-DC detects a change in point position, the new state is automatically stored in memory.

If power to the layout or PPI4-DC is switched off, the stored positions are retained. When power is restored, the LED outputs automatically return to their last recorded condition.

Dual-Colour LED Indication

The supplied dual-colour LEDs combine red and green indication within a single three-leg LED, making them particularly suitable for compact control panels and mimic boards.

The PPI4-DC is designed to work with the common-anode three-leg type. The common anode connects to the appropriate A output, with the red and green connections connected to the corresponding C1- and C2- outputs.

The diagram shows how a common-anode red/green dual-colour LED is connected to the PPI4-DC, allowing a single panel LED to indicate both point positions.

2-Aspect Signal Control

The PPI4-DC can also be incorporated into suitable 2-aspect model railway signal arrangements.

By wiring red and green LEDs appropriately, signals can automatically indicate which route through the points is clear. For this arrangement, the signal LED connections must be individually accessible rather than using a common-anode or common-cathode signal head.

This arrangement allows a pair of red and green signal LEDs to automatically indicate which route through the points is clear.

Full wiring information is provided in the instruction manual.

Points Motor Compatibility

The PPI4-DC is designed for point-control systems where the point motor coil common is connected to ground (negative/common GND).

The opto-isolated inputs accept positive switching voltages from approximately +5V to +25V.

When using solenoid point motors, a Capacitor Discharge Unit (CDU) must be used to prevent damage to the PPI4-DC. Points directly powered from an AC supply must not be connected directly to the PPI4-DC.

For KATO points, BLOCKsignalling also produces a dedicated PPI4-K version. The standard PPI4-DC can be used with KATO and Cobalt points using the additional wiring arrangements shown in the instruction manual.

Diagnostic LEDs

Built-in LEDs provide useful information during installation and troubleshooting.

The red uP LED indicates that the microprocessor is operating, while the yellow IP LED flashes when a point operation is detected. Changes to the stored point position are also indicated by the module during operation.

Electrical Requirements

• Power Supply: Regulated 12V DC.
• Typical Current Consumption: Approximately 50mA with all panel LEDs illuminated.
• Recommended Power Supply Rating: 0.25A to 1A.
• Points Input Voltage: +5V to +25V.
• Number of Inputs: 16.
• Points Capacity: Up to 8 sets of points.
• Points Input Type: Opto-isolated.
• Point Motor Common: Ground / negative common.

The PPI4-DC should be powered from a regulated 12V DC supply. A supply rated between 0.25A and 1A is recommended.

A compatible regulated power supply is available separately: PSU2 12V DC 1A Model Railway Power Supply.

Documentation & Support

For complete installation instructions, dual-colour LED wiring, points connections, programming, additional applications and troubleshooting guidance, please download the latest PPI4 instruction manual.

Product Instruction Manual