DCC Controlled Couplings

Nigel Cliffe, July 2009.

This page has the CV values for DCC Controlled Couplings. It is an appendix for various articles I have written for The 2mm Magazine, Model Railway Journal, ScaleFour News and MERG Journal, not all of which have appeared yet. It is also relevant to various web blog articles, such as my personal blog.

In the locos I have built with DCC controlled couplings I have used both Zimo and CT Elektronik decoders. The tables below shows the CV numbers for both, though I recommend using a computer with JMRI/DecoderPro to setup the uncoupling behaviour.   My work on uncouplers has led to several updates of the decoder definitions within DecoderPro, and JMRI versions above 2.6 are recommended.

Zimo Decoders.

A Zimo decoder has fairly simple programming, but only allows one uncoupling option – it is not possible to have two buttons; one with movement and one without movement.  I use a “latching” function button (the normal type on a handset), and remember to turn it off at the end of the uncoupling movements. Alternatively a non-latching button has to be held down throughout the movement.  I have used MX620 and MX63 decoders, though most Zimo decoders use the same CV values.  The very thorough manual, over 40 pages long, in English, can be downloaded from the Zimo website.

Programming stage:

CVs and values for manual entering

JMRI/DecoderPro.

Function mapping; which function keys on throttle control which outputs on chip.

CV33-46. Select CV for relevant function key, then value for required output. Refer to Zimo manual

Function Map Panel, select button required to operate output.

Function Special Effects; enable “uncoupling” on the selected function output

CV125-128. Choose CV for required output (eg. CV126 for yellow wire), select direction(s) and value for uncoupling. Typical value is 48 (uncoupling in both directions)

Lights Panel, select “uncoupling” for required output wire.

Pull In time; how long the electromagnet is operated.

CV115, typical value 90 or 80.  Do not require any “hold” value.

Shunt/Uncouple panel, set value for “uncoupler”

Movement; backing up, time pulling away, speed step to use

CV116, typical value of 189 or 199.  Hundreds digit turns on “reversing” stage. Tens digit sets time (9=5seconds), and units digit sets speed step x 4. So, 189 = reverse, time 4 secs, speed step 36

Shunt/Uncouple panel, set value for “uncouple movement”.

CT Decoders

CT DCX74 and DXC75 decoders have more options, it is possible to have one button to manually operate the uncoupler (without loco movement) and another to trigger the automatic movement and uncoupling sequence.  The automatic sequence is triggered when a function key goes to its “off” state, and works well with a non-latching function key (Fn2 on Digitrax controllers, some other makers have end-user setup of latching/non-latching behaviour).  If your handset only has latching functions, then turn the function on, and then off again to start the automatic movement.   I recommend using the White output wire rather than Yellow, as with some decoder version numbers the Yellow output can be inconsistent with the uncoupler behaviours.

Manuals in English and German are available on the CT (Tran) website, though are frequently inconsistent and lacking in detail.  There is “Commentary” document by Arnold Huebsch which is also available (recommended reading), and a few clues to the coupler behaviour settings on the Krois website.  One or two values are not documented, and I found them by experimentation.   

Programming stage:

CVs and values

JMRI/DecoderPro

Function mapping; which function keys on throttle control which outputs on chip.

This sets a “manual” button to operate the uncoupler. See below for “automatic” button.

CV33-46. Select CV for relevant function key, then value for required output. Refer to manuals

Function Map Panel, select button required to operate output.

Set function output to “uncoupling”

CV58. Bit 0 = white, bit 1 = yellow, etc.  So, CV58=1 for white wire

Yard Mode and Auto Uncoupling panel, first column bottom; select output wire with tick-box.

Set pulse time

CV56. Each value = 1/20th second. Typical value = 40 which is 2 seconds

Yard Mode and Auto Uncoupling panel, first column bottom; enter uncoupler pulse time

Set hold current

CV55. Value=0, do not require coupler to stay on indefinitely

Yard Mode and Auto Uncoupling panel, first column bottom; enter uncoupler holding current as 0

Automatic movement settings:

   

Speed step backing up

CV147, select speed step. Typical value 20

Yard Mode and Auto Uncoupling panel, 2nd column; enter  Speed Step Backup

Speed step driving away

CV148, select speed step, typical value 40

Yard Mode and Auto Uncoupling panel, 2nd column; enter Speed Step Driving Away

Time backing up

CV149, select time in 1/10th seconds, typical value 8

Yard Mode and Auto Uncoupling panel, 2nd column; enter Time Backup Release

Time driving away

CV150, select time in 1/10th seconds, typical value 10

Yard Mode and Auto Uncoupling panel, 2nd column; enter Time Driving Away

Button to activate automatic movement

CV151, select handset function key, values 1-12. Recommend using a “non-latching” key if your handset supports them.

Yard Mode and Auto Uncoupling panel, 2nd column; select function key to start movement

Output to use, rear coupler, loco travelling forwards

CV152, select output wire. Value 1 or 2, but see notes below.

Yard Mode and Auto Uncoupling panel, 2nd column; select outputs with movements

Output to use, front coupler, loco travelling backwards

CV153. If wired in series, same value as CV152 above.

Yard Mode and Auto Uncoupling panel, 2nd column; select outputs with movements

Below is a screen dump showing most of the settings for a CT decoder described in the table above. The coupling settings are made in columns 2 and 3.

 

Note on CV152/153 for CT Elektronik decoders.  There is inconsistency in CV152/153 between different versions of CT decoders.  For decoders between 40 and 59, the values are white=2, yellow=1. For decoders above version 66, the values are white=1, yellow=2.  The version of the decoder can be read from CV7.  JMRI/DecoderPro from 2.5.4 upwards will correctly identify the decoder version, and programs the correct values.