DCC Resources Main Page

Contents

• MERG DCC components
• Alternative decoder software
• Files for downloading
• Other DCC ideas

Updated 14 March 2009. 

Copyright for items on this page is retained by the authors identified. 

The use or misuse for the sale, design, supply, process, installation, delivery, test, repair, servicing, and alteration of the designs, instructions, computer code, photographs, circuits, and any other information that appear on this web site is entirely at the risk of the user or visitor to the web site. The information is made available in good faith without warranty of any kind strictly on the basis that no liability will attach to the Model Electronic Railway Group (MERG), its officers and members.

Many of the items on this page are downloadable acrobat files (.pdf) as recommended by Mike Bolton. The Acrobat viewer is free from this site. if you don't already have it.

MERG DCC Components

The MERG DCC system has been largely developed by Mike Bolton with help from other members including Gordon Hopkins and John Eato. The system follows the NMRA standard and is designed to be easier to use than most commercial systems for those used to more conventional Model Railway controls.  It is also reasonably easy to build, in fact we have successfully assembled decoders on our demonstration stand at exhibitions.  MERG is registered with the NMRA as a manufacturer with the id #165.

More details can be found in the system overview and a .pdf version of this document can be downloaded from the file matrix below. This overview has been revised in February 2003.

Kits
Kits for the programmer, command station, handsets, accessory decoders and encoder are available to MERG members. Members should check the kit pages in the members area for availability of kits.  For various reasons we cannot supply to non-members. However full details to allow construction from purchased components are available for downloading in the file matrix below. 

Programmer
The programmer is a stand alone device able to programme any NMRA compatible decoder and can be used in conjunction with the MERG system or with any commercial DCC system.  The latest batch of  programmer kits use the 16F628A chip and need the version 2x of the software, downloadable below. The latest version, 2K has been revised to cope with the large current inrush of sound decoders and also can handle Digitrax and CT decoders in direct mode. 
(The original version 1x is still available for anyone using the obsolete 16F84).

Auto Reverse and Cutout module (ARC)
This module provides an auto-reverse feature for use on reverse loops etc. and can also be used as a high speed circuit breaker to allow several seperate sections to be fed from one booster.

Simple cutout module (BCO1)
This is a simple cutout without auto reverse and can be used to divide a layout into sections so that a short on one section does not shut down the whole layout. 

Auxiliary lighting unit
FLASH is a small 'add - on' unit for use with DCC decoders to give realistic ditch lights, gyralights and dimming. This is achieved by high frequency pulse width modulation of the LED current and look-up tables for the varying brightness with time. This enables a much slower apparent increase and decrease in brightness or a dimming without flicker. Version 2 software now gives more realistic flash rates, timed from the real thing.

Alternative software for the locomotive decoder
Gil Fuchs provided the alternative available below as 'mbint105.asm', the CVs available are listed in 'INTDEC10version103.pdf'  Click here for Gil's description of his software.  January 2004. Gil Fuchs has informed me that he has discovered a 'bug' in the code for mbint104 - the Decoder 10 /11 code. It only applied when selecting which functions operated when in 'consist' mode so most users will not have noticed it. This bug has been fixed in the mbint105 which also now has the newly allocated MERG manufacturers id included.
Karol Marcinczak has rewritten mbint104 to support the PIC16F628 (cheaper than the original 16F84) and to give slow down/speed up on direction change using the values in CV3 and CV4. Download below as 16f628.asm.

Software for the accessory decoder
The accessory decoder code has been updated to version 4.  This version is included in the kits.
A more detailed description of the software can be found on the supplementary page.

Stefano Curtarolo has provided an alternative, this is available in the download section below.  It supports the "Accessory decoder configuration variable access instruction". This instruction is similar to a OPS program mode for accessory decoders. NCE and SYS1 stations support this useful instruction, and they make life much easier. dbacc5 is the version for PIC16F628. It should work with the PIC16F627 too. The F628 is cheaper, faster, and more powerful than the obsolete F84.

Accessory Decoders for Tortoises etc. (ACC3)
This is a variant of the above decoder with an appropriate output for slow action motors, LEDs etc. It uses the same software. The schematic and board layout can be downloaded below. Note. this decoder needs a supplementary unit to give enough power for Fulgurex type motors.  It can now be replaced by the Acc6 version which has a simpler design and does not need the supplementary unit. Details can be downloaded below.   (Note for members, Acc 6 is not available as a kit).

Handsets (HS2)
The handset is now at Mark 2 This uses a single sided board and is much easier to build than the Mk1.

Bryan Knight offers this idea for Handset users. DCC Controller Rack.

When using the MERG DCC system, it would be useful to have somewhere to park any handsets not requiring immediate attention.  There is a tendency for any not actually in a hand to tumble to the floor, assisted by the weight of the cable.  A rack has been constructed which holds them conveniently.  Basically the device is like a lectern or music stand in which the handsets can sit, the bottom surface having cut-outs to clear the cables.  It is clamped to a convenient surface, such as a table top, using one or two woodworker’s clamps to hold sideways extensions.

The whole thing is made by gluing five pieces of 6mm plywood.  The “reading” surface is 260mm long by 100mm high.  The sill, the same length, is 26mm wide, with the four cable slots 11mm wide and 19mm deep, separated 68mm. A triangular piece at each end supports the “reading” surface so that it is leaning back by about 15 degrees.  The fifth piece is the bottom of the structure and is 340mm long to provide room for the clamps.

This picture shows the front view, with the fixing extensions and the cable clearances.  The surface against which the controllers rest is leaning back in this view.

Here are some photographs of the equipment, click on the thumbnails for the big picture.

8-Channel DCC Track Circuit/Block Occupancy Detector - ‘DTC’

	click image to enlarge
Accessory Decoder Pulse type	Accessory decoder Revised steady state	Auto reverse module	Command station

Booster, above, New Booster, below.

Files for downloading
The files in the matrix below provide the information needed to construct the MERG dcc system. For anyone having trouble downloading the source code .asm files  I have included them in .zip packages.  (The .zip includes all files for the item concerned).

Other DCC ideas

From N C (Fris) Friswell here is a method for driving a bi-polar lighting circuit from standard decoder function leads, could save some tricky rewiring on locos with factory fitted lights.

More on DIY DCC will be found by exploring from our links page.

Test gear.

When you have built your DCC system Schematics, Adobe Portable Document Format (PDF) instructions,
Software, and other goodies needed to test conformance with the NMRA standards from Ken West are now at:
http://www.dccsig.org/ken/readme.html

Cab bus protocols.

The North Coast Engineering Cab Bus Protocol.
This protocol has been made public by North Coast, it is also used by Wangrow (System One).
Details of the protocol are given in this zipped Word document.

The Digitrax "Loconet" Cab bus.
For comparison you can get the details of Loconet from the Digitrax site.

The Lenz "X-bus"
The Lenz bus is also used by ZTC. Roco and by Arnold digital. Lenz now have full details for download in the 'manuals' section of their site, lenz.com .

Back to Top

Contact Information

If you want to follow up any item on this page please contact
Keith Norgrove who looks after these pages.

Copyright to all information on these pages is held by the Authors identified.