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Model Electronic Railway Group

The Leading Society for Model Railway Electronics

Over 50 years of Innovation: 1967-2020

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MERG CBUS System

Revised 17 November 2019


The MERG CBUS system was developed over 4 years by Mike Bolton and Gil Fuchs and introduced with specifications and an initial range of kits in 2007. Since then the system has been further developed by many MERG members into a very comprehensive Layout Control Bus. The system is intended to simplfy the wiring of a model railway whilst enhancing the control capabilities. The CBUS system uses a specially developed protocol to communicate between input and output modules. For the most part CBUS uses CANBUS to communicate over a 2 wire (plus power supply) link around the layout although use is also made of Ethernet, USB and WiFi communications when needed. Provision is made in the system for operation of layout accessories, point motors, signals etc. from traditional control panels, lever frames, or from a suitable programme on a computer. The MERG DCC system uses CBUS to link cab handsets, and/or mobile phones/tablets/computers to the Command station. The system is continually developing with recent designs for modules able to incorporate signal and point interlocking or to read RFID tags (Radio Frequency IDentification) fitted to rolling stock. Compatible computer control software is available as follows:

  • JMRI.
  • Rocrail.
  • SSI.
  • Rocrail also offer some compatible control modules. The CBUS system does not require a computer to run and for simple functions can also be set up and configured without use of a computer. However use of the more complex functions of the system does require a computer for setup and configuration. A comprehensive configuration utility is available for this.

    A more detailed description of the CBUS system is available on the CBUS details page. Full details of the current and original CBUS designs can be obtained on the MERG wiki cbus pages.

    Kits

    Kits for a range of modules are available to MERG members. Members should check the Technical Bulletin and Kit pages in the members area for technical descriptions, build instructions and availability of kits. Brief descriptions of most of the current kits are given below. For various reasons we cannot supply to non-members. However full details of many items to allow construction from purchased components are available for downloading on the MERG wiki cbus pages. When the first designs were produced it was common practice for MODEL Railway auxiliaries to be supplied from a nominal 16V AC transformer, hence these designs are primarily intended to operate from such an AC supply. Since then Model Railway power supplies have mostly changed to DC Switch mode power suppliesand all more recent CBUS modules are designed for a 12V DC supply. Most of the original, AC, modules can be operated on the 12V DC or easily modified to do so. Where this is not practical an alternative DC kit is offered.

    CANACE3 Module>

    Control Panel Encoder (CANACE3) Kit 83.

    This module is primarily intended for connection of control panel switches to the CBUS. The design uses matrix techniques to reduce the amount of wiring needed and can read the state of up to 128 toggle switches, push buttons or, for example microswitches attached to a lever frame. Push buttons can be configured in pairs, say for point operation normal and reverse or used singly, say for uncoupling magnets. The CBUS events produced when a switch is operated are taught to output modules as required to operate points, signals, section relays etc. The design includes facilities for configuration without a computer using the SLiM model. The kit is supplied to be powered by 16V AC and can be simply adapted for use on a 12V DC supply if desired.

    CANLED ModuleControl Panel LED driver (CANLED) Kit 82.

    This module is complementary to the CANACE3 and is designed to drive up to 64 LEDs used to indicate the state of points, signals, block sections etc on a control panel. These LED outputs can be taught to respond to feedback from modules on the layout such as the CANACE8C or the CANMIO-SVO or directly from the state of switches connected to a CANACE3. The design includes facilities for configuration without a computer using the SLiM model. The kit is supplied to be powered by 16V AC and can be simply adapted for use on a 12V DC supply if desired.

    CANPAN Module>

    Control Panel encoder/driver (CANPAN) Kit 97.

    This is single module that carries out the functions of both the CANACE3 and CANLED but for smaller control panels with a maximum of 32 switches and 32 LEDs. It provides a more economical solution in such cases. This is a second generation kit supplied for 12V DC power and needs a computer for configuration.

    CANACC8 Module

    General purpose output module (CANACC8) Kit 88

    This module provides 8 general purpose outputs that can be used to operate relays, LEDs or other electronic modules. The outputs can be set for pulse or steady state as required. The design includes facilities for configuration without a computer using the SLiM model. The kit is supplied to be powered by 16V AC and can be simply adapted for use on a 12V DC supply if desired.

    CANACC4 Module

    Solenoid Turnout Driver (CANACC4) Kit 84

    These modules have a built in Capacitor Discharge Unit (CDU) and are optimised for the operation of solenoid point motors requiring a high current pulse. Each decoder has 4 outputs for twin coil solenoids and each output is capable of operating two point motors as required for crossovers. Full design information including a description of the software can be found on the downloads page. The design includes facilities for configuration without a computer using the SLiM model.

    These modules require a 16V AC supply to output enough voltage for operation of most solenoids. Conversion to 12V DC is not practical. The CANSOL module is available for 12V DC systems.

    CANSOL Module>

    Solenoid Turnout Driver (CANSOL) Kit 94

    These decoders have a built in Capacitor Discharge Unit (CDU) and are optimised for the operation of solenoid point motors requiring a high current pulse. Each decoder has 4 outputs for twin coil solenoids and each output is capable of operating two point motors as required for crossovers. Full design information including a description of the software can be found on the downloads page.

    This is a second generation kit supplied for 12V DC power but does include facilities for configuration without a computer using the SLiM model.

    CANACC5 Module

    Motorised Turnout, eg. Tortoise, driver (CANACC5) Kit 85

    This is a variant of the CANACC8 with an appropriate output for slow action motors, LEDs etc. It uses the same software except for the module ID. By setting the appropriate Configuration Variables (CVs) the outputs can be continuous or of timed duration. The outputs can be configured as 4 pairs as required for tortoise motors etc or alternatively as 8 independent outputs for using to light signal lamps etc. The kit is supplied to be powered by 16V AC and can be simply adapted for use on a 12V DC supply if desired. Full design information including a description of the software can be found on the downloads page.

    >
    CANMIO-SVO Module>>

    Servo motor driver (CANMIO-SVO) Kit 98

    This is second generation circuit board designed to be buildable for most combinations of input and output circuits up to 16 in total. In this kit the software and hardware is supplied to build it for operation of 8 servo motors and with the option to add 8 inputs. The servo motors can be adjusted for end positions and operating speed. They are suitable for operation of points and semaphore signals. Note MERG can also supply a variety of mounting bracket suitable for using with the common SG90 type servos. This is a second generation kit supplied for 12V DC power and needs a computer for configuration.

    CANACE8C Module/>

    General purpose input module (CANACE8C) Kit 89

    This module provides 8 input channels that can be use for feedback from the layout to the cntrol system. It is suitable for use with many train on track detectors, such as the DTC TOTI ::::::: for indicating track occupancy and for use with point position detectors etc. The inputs are designed to go active when connected to the 0V of the power supply.

    The design includes facilities for configuration without a computer using the SLiM model. The kit is supplied to be powered by 5V DC. As it has a very low power consumption it can be supplied with 5V power from any other nearby module such as a CANACC4, 5 or 8.

    CANUSB4 Module>

    Computer connection module, USB (CANUSB4) Kit 80A

    This module is designed to simply connect the CBUS system to a computer using the computers USB connector. This allows for system configuration using the FLiM model and/or operation of the layout from computer programmes such as JMRI or Rocrail. The module can be powered from a 12V DC supply or direct from the computer USB connection at 5V. The module does not need configuration.

    CANPiCAP Module>

    Computer connection module for Raspberry Pi (CANPiCAP) Kit 86

    This module connects the CBUS system to a Raspberry Pi computer. In a similar way to other Raspberry Pi enhancements the module mounts directly to an RPi model 3b making a CBUS module with many uses. The RPi can be used to run JMRI providing complex interlocking or layout operation from a touch screen. It can also link by WiFi to other computers or phones allowing train driving from the phone or system setup from a laptop without the need to plug in a USB cable. The module is designed for a 12V DC supply and will provide the power needed by the attached RPi.

    CANACT Module>

    CBUS Activity Monitor (CANACT) Kit 90

    This module is essentially a simple test aid and just monitors the CBUS for activity and flashes an LED for each message seen It operates from the 12V DC supply and no configuration is needed.

    CANGIZMO Module>

    CBUS Test module (CANGIZMO) Kit 492

    This is a more comprehensive test module that can be used to monitor the BUS just like the CANACT but more importantly can test each other module built to show that it's CBUS communication is working properly before attaching it to the bus. It is supplied setup for self contained battery power but can be built for external 12V DC supply if desired.

    Experimenters Kit>

    LCB Experimenters Kit Kit 490

    This kit includes 3 small boards which are especially useful to CBUS novices allowing modules to be tested and configured in a test environment before use on the layout. The TM1 is primarily for use with the CANACE8C and carries 8 switches to provide test inputs. The TM2 is primarily for use with the CANACC8 and carries 8 LEDs that can indicate when each output is active. The TM3 is for use with the CANACC5 and carries 4 bi-colour LEDs that will show the output polarity when the CANACC5 is set up for operation of stall motors such as the Tortoise.

    CANPAN Test Module>>

    Test module for CANPAN (CANTM7) Kit 497

    This kit is similar in concept to the Experimenters Kit but larger and designed to fit directly to a CANPAN. The board includes a set of 32 LEDs so that the state of all outputs can be seen, along with 8 push buttons that can be used with a selector switch to activate any of the 32 inputs.