C/MRI for Signaling and Layout Control

A brief overview of C/MRI use on my layout for use in controlling trackside signals and other devices.

Rob BennettNMRA Mid-Central RegionDivision 12

What is & why did I choose C/MRI?• C/MRI = “Computer/Model Railroad Interface”

• The “Bruce Chubb” System• OLD- first introduced in Feb 1985 Model Railroader• Uses computer to read “inputs”, decide what to do based on the inputs,

send “outputs” • Uses “TTL” type logic- Low (0 volts, or ground) and High (+5 Volts, or

Open) • I use an old Windows 98 computer with Visual Basic 6 as programming

language• Computer ideally has a RS232 or RS422/485 Serial Port. If not, can use

USB w/converter (Why older PC’s are better!)• Can use newer computers, other programming languages, JMRI, cpNode

w/Arduino, etc.

What is & why did I choose C/MRI?• Why did I choose it- Not just Signaling, also Layout Control

• Flexibility- can basically do anything you want based on inputs• Approach Lit Signals, Flashing Aspects, Speed or Route Signaling, Color

Light/Position Light/Searchlight signals, etc.• Can buy pre-assembled components or build your own- from kits or buy all parts

yourself (boards are available from JLC Enterprises, Inc.- Chubb’s Company)• Extensive documentation available- three volumes, each ~400 pages, in depth

coverage• Cost- was comparable to/better than existing commercial offerings (~2013)• Totally independent from DCC system- choice of DCC system does not matter*

• I can run layout without C/MRI system “on” (do get funky signal indications!)• NOTE- The DCC power bus does need to run thru the block detectors if using

current sensing• I use “sub-buses” for the various blocks, with the bus running thru the

DCCOD*There are some unique considerations if using Digitrax

C/MRI System- Inputs & Outputs• Inputs:

• Block Detectors- Current sensing (Locos, lighted cars, resistor wheels…Frog Juicers!)• Turnout Position- from Tortoise SPST switches (Open=Normal, Grounded=Reverse)• Lock-Unlock for some turnouts• Motor-Hand (Local) setting for some turnouts• Read Switch Position for other uses- open swing gate, panel & rotary switches, etc.

• Outputs: Think of each output line as a SPST switch, software controllable• Signals• Turnout Control• Grade Crossing trigger• Dream Player (sound card) trigger – TTL Logic Card• Lamps/LEDs• Relays• TTL and CMOS Circuits

Basic Components (“The Hardware”) of C/MRI• C/MRI Specific Hardware That I Used:

• Block Detectors- “DCCOD”- Current Sensing, tells when a block/CP is occupied• I built my own DCCODs from kits

• The “Processor”- takes inputs, communicates w/computer, acts on instructions• SMINI (24 Inputs, 48 Outputs)• SUSIC- Modular/Expandable- Needs (1) SUSIC Control Card and then can use multiple 32 Line Input

and Output Cards• RS232/RS485 Serial Interface Card- From Computer to SMINI/SUSIC Nodes• SMC-12- Switch Motor Control Board. For Tortoise control- only need one output line• ODMB – Optimized Detector Motherboard. For 12 DCCODs, simplifies mounting

• I built “Node Boards” to mount the Block Detectors, SMINI/SUSIC, Terminal Boards, etc. • I have three Nodes- two SMINI and one SUSIC, distributed around the layout• I purchased two (2) SMINI’s and SUSIC cards pre-assembled

Basic Components of C/MRI

DCCOD SMINI

SUSIC-DIN-DOUT

ODMB for DCCOD’s

SMC-12

My C/MRI System Setup- Simplified!

Ancient Computer

RS485 Converter

Node 0- SMINI Node

Node 1- SUSIC Node

To Node 2-SMINI Node

C/MRI- Controlling the HardwareInitialize Program & Interface

Begin Real-Time Loop

Read Inputs from Railroad

Logic Portion of Program to:Calculate outputs based on inputs:

Signal aspects, turnout position, panel displays, etc.

Write Outputs to Railroad

Repeat Real-Time Loop

C/MRI reference books have many examples of Basic code- much is “copy/paste” and modify for your railroad

Data from Your Railroad Needed

There is a bit of work required prior to programming:• Determine the blocks (for detection, not necessarily

operation)• Determine signal locations/types (Absolute,

Intermediate)• Determine “labels” for Blocks, Signals, Turnouts, etc.

• These are the variables for the Basic program

Data from Your Railroad Needed: Labeling

My Layout- Diagram & C/MRI Labels:• Blocks: BK1, 2, 3…CPxx• Signals: SIG-FV-1-E-AB• Direction of Traffic:

DOTBKxx• Turnouts: SMxx

• SMxxFB- Turnout Position

• SMxxMH- Motor/Hand• SMxxL- Lock/Unlock

Data from Your Railroad Needed: Board Setups

Data from Your Railroad Needed: Signal Setups

Need to determine:• Signal type- Common Anode or Common Cathode- Common Anode preferred• Physical signal wiring, resistor values, port wiring, cabling run, etc.• Signal variables for program- to ease setting of signal indications

• Type of signaling to be used- Speed/Route• Aspects to be displayed• Calculate variables based on above two items: REDRED=xx, GRNREDRED=xx, MEDCLR=xx, REST=xx, etc.

Summary:• C/MRI is one of several possible choices for signaling and layout

control/animation• Older system, been around since the mid-1980’s• Three major type of components:

• Hardware• Software• Signals/Grade Crossings/Lights/LEDs/etc.

• Except for DCC power bus, can be totally separate from your DCC system• Expect a lot of work in layout diagramming, block determination, program

setup, device labeling, signal setup, etc.• In the most basic sense- it is the reading of and electronic “throwing” of SPST

switches.

Is it Worth it?

To me…Yes!

References• JLC Enterprises- Chubb’s Site: https://www.jlcenterprises.net/

• “Official” C/MRI documentation, boards, some parts, Downloads• My YouTube Channel- “Controls & C/MRI Electronics” Playlist

• 20 videos covering most aspects of C/MRI (and some other stuff…)• Search YouTube for “The Bennett Railroad” – Channel name is “Stephen Bennett”

• Groups.io: • Dr. Bruce Chubb's Computer/Model Railroad Interface CMRI-Users@groups.io

• Railroad Model Craftsman- “Understanding Railroad Signals”• 14 Part Series, from December 2015-April 2017

Rob BennettNMRA Mid-Central RegionDivision 12Email: nkp746@gmail.com