Model Electronic Railway Group

Leading Model Railway Electronics since 1967

Over 50 years of Innovation: 1967-2019

Remote Panel Control System (RPC) Resources Page

Gordon Hopkins

One of the many difficulties in operating large, complex model railway layouts at exhibitions is, as on the prototype, staff shortages. This is particularly true during lunchtimes, where operators have been known to disappear for hours at a time. It was mainly for this reason that the Remote Panel Control (RPC) system was originally devised, although the hardware could be used for a multitude of other purposes not necessarily connected with railway modelling.

The system allows either partial or complete remote control of layout accessories such as points, signals, section switches etc. This makes such things as Interlocking, Timetables and Route Selection relatively easy to implement, as it is all controlled by Software. Similarly, layout modifications are also handled more easily than conventional Hard-Wired Interlocking systems.

Modularity has been one of the main aims of the design, both in Hardware and Software. It should be pointed out that the system is not aimed at absolute beginners. Users must still decide what track switching, signals, block sectioning etc.are required for their application. Thereafter, appropriate modules and accessories can be chosen from the range available to achieve the desired effect. The range of modules will be increased as and when new requirements arise. Most modules and accessories are now available as kits to MERG members.

Modules simply plug into the Remote Panel Interface (RPI) module, using a stacking connector system. This allows any combination of modules to be connected together inside a control panel to form a complete layout input/output system.

Recent developments have produced an alternative design to the RPI, namely the Remote Panel Interface PIC (RPIC). This uses a different type of microcontroller with higher integration and lower cost than the original 8051 based version. The RPIC uses 40 pin Microchip PIC devices from the 16XXXX series, allowing RS232, RS485 and USB 1.1 low speed interfaces to be created, by fitting the appropriate devices onto a common PCB design.

For situations where it is more convenient to locate additional modules away from the main stack, the Remote Stack Extension (RSE) System is available. This consists of a pair of modules, one of which plugs into the main stack, with the other at the "head" of the extended stack.

Accessories are baseboard mounted, adjacent to the item being controlled. Typical items include Point Motor drivers and Colour Light Signal drivers.

Software application programs to generate some of this information are available, including CARLOS by John Down and Graham Plowman's commercial SSI system.

For applications requiring "Manual Only" controls, the Point-to-Point (PTP) System is available. This provides two-way communications between a Control Panel and the Layout, for up to 120 bytes of data, equivalent to 960 layout functions in each direction. Typical functions might include Point (or Turnout) controls (panel to layout) and Train-on-Track indications (layout to panel). The PTP System uses standard RPC Modules, and is directly compatible with the RSE System.

A typical example of an RPC System implementation is shown below, in the form of a panel built for "Carstairs", namely "Fiddle Yard South".

Modules Available

RPI - Remote Panel Interface

PC to Layout Interface Module

The vital link between the PC and the layout. This module receives commands from the PC and distributes the data to and from the other modules in the 'Stack'. Two versions are available: for Single Panel applications using a standard RS232 interface (COM port) and for Multiple Panel applications using an RS485 multi-drop interface.

For RS485 systems, the RSB adaptor is available which simply plugs into a conventional RS232 COM port. and controls the operation of the RS485 side of things automatically, according to the RPC protocol.

Recent development work on the RPI module has resulted in adding DCC Packet generation, either under PC control or manually using Handsets.

This new capability currently extends to:

  • Up to eight 'Virtual' Controllers (Throttles)
  • 14, 28, or 128 Speed Step modes
  • Baseline or Extended Loco Addressing
  • CV Programming using 'Page Mode'
  • Function Group Control
  • Advanced 'Consist' Control

RPIC - Remote Panel Interface PIC

PC to Layout Interface Module

The new design of Interface module using Microchip PIC devices. This module receives commands from the PC and distributes the data to and from the other modules in the 'Stack', just like the original RPI. Four new versions are available: for Single Panel applications using a standard RS232 interface (COM port), Multiple Panel applications using an RS485 multi-drop interface, USB 1.1 low speed for Single Panel applications, and USB 1.1 low speed with RS485 Slave Extension Bus. The first two effectively replace the original RPI types. For RS485 systems, the RSB adaptor is available which simply plugs into a conventional RS232 COM port. and controls the operation of the RS485 side of things automatically, according to the RPC protocol. The PIC based modules do not support DCC as yet. The version shown in the picture is the RPICUSB+, which provides layout operation with an RS485 extension bus, in addition to its own Stack controls. The spare holes in the PCB accommodate the devices used on the alternative versions. As the same PCB is used for all versions, you simply fit the devices required for the chosen type.

DPR - Double Pole Relay

8 x DPDT General purpose switching

Eight BT47 Style DPDT relays individually controlled via the RPI, with the coil drive connections brought out to a separate connector to allow the drive signals to be used externally, particularly intended for point operation, where the associated relay contacts can be used for frog switching on live frog track systems. Additionally, this connector allows external manual switches to operate the relays if desired. Note that the relays themselves are not included in the kit, leaving the choice of coil voltage to the User. +5V, +12V and +24V operating relays are suitable.

QPR - Quad Pole Relay

8 x 4PDT General purpose switching

Eight 4PDT relays individually controlled via the RPI, with the coil drive connections brought out to a separate connector to allow the drive signals to be used externally. Basically the same as the DPR Module, but intended for more complex switching requirements particularly around complicated live frog pointwork. Currently supplied with +24V operating relays.

Floating Track Circuit

8 x Live Rail Continuous Track Circuits

Eight Continuous Train-on-Track Detectors, using current flow in the live (or switched) rail as the detection method. Live rail detection allows standard Common Return layout wiring principles to be used. Each detector circuit is simply wired in series with the existing section feed. Bias supplies are used to allow the detection to function whether the train is in motion (in either direction) or stationary. Detected outputs are fed back to the PC via the RPI under software control. It is also possible to arrange for local indications using LEDs (not supplied). The FTC module is compatible with DCC systems, and because track power is always available in such systems, one less bias supply is needed.

SRO4 - Shift Register Output 4bytes

32 Open Collector Output Drives

Thirty-two Open Collector outputs, arranged as four groups of eight. Each output is individually controlled via the RPI, and can sink up to 500mA each, within the power dissipation limits of the output devices. A ground (0V) connection is provided in each group, as well as an option to use either the in-built Back-EMF protection diodes, or the logic supply rail (+5V). Typical uses for this module include Signal driving (such as with the SD4), Panel LED driving etc.

SRI4 - Shift Register Input 4 bytes

32 Logic Level Inputs

Thirty-two Logic level inputs, arranged as four groups of eight. Each input is individually readable via the RPI, and is TTL/5V CMOS Compatible. Other input levels can easily be accommodated by using external resistor networks if desired. Ground (0V) and Logic supply (+5V) connections are provided in each group. Typical uses for this module include Point Correspondence feedback and Switch inputs.

PTP - Point-to-Point

Point-to-Point System

Used as a "Master-Slave" pair, PTP Modules provide two-way manual control of up to 960 layout functions via a single Screened Twisted Pair cable at distances up to 4000ft (1200m). Layout data is transferred automatically more than twenty times per second, giving the "feel" of continuous operation. Standard RPC Modules plug into the PTP Module at each end of the link, in the same fashion as with an RPI, which the PTP replaces at the "head" of the module stack.

RSE - Remote Stack Extension

Remote Stack Extension Modules

Used as a "Master-Slave" pair, the two RSE Modules (RSM - Master and RSS - Slave) provide the means to split a module stack. This allows modules to be located remotely from the main stack with its interface module (RPI or PTP) controlling both parts. The RSE modules simply buffer the shift register control and data signals present on the stacking connector, and operation is transparent to the user. The RSM (shown left) plugs into the end of the main stack, and the RSS (shown right) forms the "head" of the extended stack. Connection is by standard off-the-shelf 4 pair Cat 5 network cables using RJ45 connectors.

Accessories Available

PMD1 - Point Motor Driver type

Solenoid Point Motor Driver

A self-contained Capacitor Discharge twin-solenoid motor driver, controlled by a single low current wire. This wire is simply connected to Ground (0V) for one direction, and left Open-circuit for the opposite direction. Jumpers links are provided to allow the default 'Normal' and ''Reverse' directions to be selected.

PMR1 - Point Motor driver Relay type 1

Solenoid Point Motor Driver

A variant of the PMD1, which includes a Double Pole Double Throw (DPDT) relay for general purpose switching in the vicinity of the point. under control. Such uses might include frog polarity switching for live frog points. The relay fitted can switch and carry currents up to 2A. Another feature of this design are the unpluggable Terminal Blocks, which are used for all connections, allowing quick and easy maintenance. All other featiures are identical to the PMD1.

SD4 - Signal Driver 4 aspect

Solenoid Point Motor Driver

For use with Multiple Aspect Colour Light Signals using LEDs. This design requires that the LEDs on the Signal itself are arranged as two back-to-back pairs, with a common connection to both pairs. Thus three wires are all that is needed on the Signal to generate all four aspect combinations. The inputs to the SD4 are two bit binary coded derived from, typically, an SRO4 module. Additional facilities are provided for Junction Indicators or 'Feathers'.

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These pages are a resource area for projects members are working on or have completed and wished to make publicly available. Some of these projects have resulted in MERG kits but nothing on these pages should be taken as definitive information about the kits, members should check the kit pages for up to date information on the kits.