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DIGITAL
CONTROL
PC-controlled
layout to NMRA-DCC standards

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Startpage
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"With
DCC you run the train - not the track"
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Some
tips
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When the
decision is taken to go DCC you have several choices.The first
question is whether you want to control your layout from a
computer (PC / Mac) or a digital central unit with traditional
trottles. Next choice is homebuilt or a turnkey system from any
of the model railroad suppliers. The turnkey systems includes
lots of accessories and follows the NMRA DCC standard with
respect to mobile decoders for locos but individual solutions for
stationary decoding for turnouts, signals etc.- i.e. not
compatible. Most new systems based on a central unit have the
option to use a PC. The market offers a large variety of software
for model railroading - mostly in Windows environment.
If you
decide to build a digital system by yourself you will as allways
save some money and also have great fun. With basic knowledge in
electronics and soldering it is not that complicated. You will
find several alternatives in literature on the internet. Rutger
Friberg`s NMRAF- solutions of boosters and stationary decoders is
a very good example. I
started to build my layout based on analog technology with block
sections and four trottels controlled from a panel with LED's and
switches. I took the first step towards digital control in the
beginning of 1996 by looking for PC-software.
My
choice fall on Winlok 2.1 and I started to run the free demo
version downloaded from internet. I recommend to define all
functions on the layout and run the software in simulation mode
to test your ideas before buying or building the digital
hardware. Unfortunatelly Winlok is no longer supported and the
development is closed. A better choice today is Train
Controller
from RR&Co that
I use for my layout.
Today
I have replaced most of my homebuilt decoders to Lenz LS 150 and
Digitrax DS 64 with a lot better functionallity. The mobile
decoders used are Lenz and Tran. Ss centralunit and other
controllers I use the Lenz digital system.
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How
does it work?
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Short
description of digital (DCC) model
railroading
The
central unit with a trottle (alternatively PC) transmits via a
booster a stream of digital pulses to the track. The output
includes both power and data.
All
mobile
loco decoders on the track receives the pulses and decodes the
information. Each loco have an individual "address" and
only one locomotive responds to the actual address followed by
data for loco control. Several locos on the same track can with
this technique be individually controlled from the central unit.
A rectifier in the mobile decoder separates power for the motor
and data for control of various functions in the locomotive.
The NMRA
DCC standard defines a long list of functions included in the
decoder registers. Most mobile decoders will only take care
of the basic functions in the locomotives.
Forward
/ Reverse - Start level -
Speed - Acceleration -
Retardation - Light on / off
The
speed is controlled by 14 to 128 steps depending on type and
manufacturer of the decoder. More advanced functions like
smoke, sound and couples can be operated from some decoders or
more than one decoder installed in the locomotive. A real
challenge for the N-scale model railroader.
The
choice of decoder depends on the available space and current for
the loco usually not more than 0,5 Amps for the N-scale locos. If
you measure the "stall"-current before you install the
decoder you will be safe by knowing the maximum loco current for
any situation. Connect
a DC-amp instrument between the analogue voltage supply and the
track. Hold the loco locked to the track and turn the trottle to
maximum and read the current.Don’t forget to add the loco
lamp current to obtain the total max current.
You can
find suitable N-scale decoders from various vendors. Lenz,
Digitrax, Tran and others have a good assortment in small size.
The new DCC handbook by Rutger Friberg and Stan Ames have a
complete list of decoders with all data. I
have used the Lenz LE 030 and 040 with EMF-technology. This
facility with feedback of motor load to the drive logic’s
in the decoder will keep the loco to a constant speed independent
of load from the wagons or going up or downhill.
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The
block diagram shows an example of a DCC system controlled from a
PC with a feedback from block sensors to obtain a live
presentation of all train movements on the PC-screen. The
software Train Controller is used in this layout. Separate
boosters for track and stationary decoders connected to
individual power supplies minimizes any interaction between the
control of trains and switches.
The PC
transfers the commands to the central unit DR5000 that generates
the DCC-signal powered from an internal booster. The
output from the block sensors indicates if the actual section is
occupied or not - connected to a Lenz feedback unit. The software
Train
Controller
is prepared to indicate the status from the layout.
The
layout can be easily switched from digital to analogue to give
the loco`s not yet modified to digital a chance to show up and
still use the ability to be indicated on the PC-screen from the
feedback from the block sensors.
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Screen
view of Train Controller
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The use
of a computer to run the layout is often missunderstood.
"
I
prefer to run my trains by myself and not let the computer take
over"
A
limited view of computer technology – it is your decision -
manual or automatic.Trottles are available on the PC-screen
controlled from the mouse or the handheld controller attached to
the central unit.. With Train Controller you design a
copy of your track layout on the screen including switches,
blocks and signals as active elements bound to real events on
your railroad model. Before you start your train - a route is
activated that will define the status of involved switches,
blocks and signals. Several routes can be defined simultaneously
sharing common tracks and switches with interaction between the
trains to different priorities.
The
feedback from block sensors indicates the position of the trains
indicated on the PC-screen. All active functions can be operated
by a mouse click on screen by pointing on individual switches,
blocks or routes etc.
Train
Controller also have the ability run your trains fully automatic
in sessions without programming knowledge. Complicated?
– No, all functions are defined in a standard Windows
environment with straight forward instructions and help menus
with the result stored in a database linking all data in a
logical scheme.
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Booster
NMRAF 8
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 A
large layout will take several boosters appointed to different
sections. Some turnouts like PECO takes a lot of current that
will need a separate supply not to interfere with other devices.
The main booster integrated in the central unit is used for the
track (trains) and other functions on the layout is driven from
the booster NMRAF8. This
booster consists of a data logic and a power distribution
circuitry. Multiple boosters can share the same data logic on a
master connected to the central unit expansion port and the slave
boosters only having the power output mated from individual
transformers or separate windings from one transformer. The
NMRAF 8 is be equipped with an overload protection (Polyswitch).
Schematics
and instructions are found
the
in "Electronics for Model Railroading edition 5" by
Rutger Friberg.
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Stationary
decoders - Digitrax DS 64
and
Lenz LS150
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A
stationary decoder used for solenoide turnouts must be able to
supply a short pulse to the turnout not to burn the coil. I have
used Lenz
LS150
capable of 6 turnouts like TRIX / ROCO. The PECO
turnout
coils works with
LS
150
but because of the AC
pulse
supplied it sounds terrible with a high "buzzing" sound
and the turnout will suffer from this in the long run.
A
very good
alternative
for PECO`s turnout solenoides is Digitrax
decoder
DS
64
including a
"CDU"
(Capacitor Discharge Unit) that supplies a short DC-pulse
to
the solenoide
and
the PECO-turnout
is
switched with a silent "click".
For
static functions (no pulse) on a layout like
trainsignals and streetlights Littfinski
decoders is an
exellent alternative.
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Lenz
LS 150 for 6 turnouts
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Digitrax
DS 64 for 4 turnouts
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Littfinski
LS-DEC for 4 signals
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Block
sensor connected to computer
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 Why
block control with DCC? - a DCC layout will operate the loco`s
individually without any block sections! The beauty by having
block sections running DCC is to follow occupied tracks. A nice
feature – with indications on the layout displayed on the
PC-screen alternatively used in the software to keep track
of the trains in "ATC" mode.
The
described hardware above can be operated by any DCC PC-software
capable of supplying a DCC-signal following the NMRA
specifications. The DCC pulses are brought to the track
through the diod bridge D2 giving a signal to the block sensor D3
if there is a load on the track section caused buy a locomotive
or a lighted wagon - moving or parked. The outputs from the
block sensors are connected to a feedback module attached to the
central unit. The diode D4 and capacitor C1 ensures a stable
sensor signal from the transistor T3.
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Simplified block sensor
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A
blocksensor can be stripped to inlude just a rectifierbridge
and a optocoupler. This simplified sensorboard is connected
to the central unit via a feedbackmodule. A blocksensor
without filtering will force either the feedbackmodule or
software to stabilize the blockindication. The program
Train Controller "TC" have functions inbuilt for
such filtering to achive a stable blockindication.
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Loco-
decoder installations
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To
install a decoder in HO-scale loco or larger normally doesn't
give and problems as space is not an issue. N-scale or Z is a
challenge and demands lots of preparations and a good portion of
patience. There are no standard solutions for the mechanical
adaptation - every locomotive has to be taken care of
individually. I
will in following show a couple of examples of decoder
installations with detailed information's for the Fleischmann
"Rc4" and "Du" N-scale loco`s. The decoders
used follows the established NMRA-DCC standards. The NMRA
standard includes a communication protocol and definition of
decoder registers with respect to content and functions. Most
decoder installations will only use the basic functions. I
recommend to study the Rutger
Fribergs book no. 5 and the new DCC book by Rutger
Friberg, Stan Ames and Ed Loizeaux to get a deeper knowledge of
the DCC standards.
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Decoder
installation in swedish Rc4 - loco
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The
RC4 is an example of a N-scale locomotives with extremely good
analogue run characteristics that gets even better with a DCC
modification. The decoder used is the "Lenz mini Gold"
LE 10410 decoder . Alternatively LE 040 or Digitrax smallest fits
also into the RC4. The measured "stall"-current is
300mA, that's ok with good margin for above decoders.
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Start
to prepare the loco both electrically and mechanically and check
for running with no problems from an analogue supply. Very
important if anything fails during the installation. Open the
loco and remove the connections to the pantographs.
The
locomotives normally include a printed circuit board (PCB)
bringing the wheel connections to motor and lamps. Disconnect the
motor from the PCB and remove coils, capacitors and the
rectifiers to the lamps.(hidden at the lamp connections)
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"Mini
Gold" decoder in
RC4 RC4
printed circuit board
Alternate installations of
bulbs
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The
"Lenz mini Gold" decoder is placed from underside in
the space between the boggies after removing the pantograph
switch. Solder the decoder wires to the PCB and cut the PCB
etches (x) as shown in the figure. Check all connections from the
drawing. Use a thin soldering iron and follow general rules for
ESD protection. Make sure the motor poles are only connected
to the orange and grey wires. Other connections like the wheels
may destroy the decoder. Secure the wires with "loctite"
Some
loco`s like the RC4 have the left or right wheel tied to chassis
in connection with the common lamp pole. This doesn't give any
problems except for half rectified supply to the bulbs with less
light that could be compensated by a alternate choice of lamps.
The blue decoder wire is left disconnected in the RC4.
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Decoder
installation in the swedish Du-loco.
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 This
N-scale locomotive have a limited space for a decoder
installation. I am using the LE 040 for the DU-loco. A mid part
of the PCB is removed (cut off) to give some room for the
decoder. The chassis has to be cut down 3 mm, see figure. The LE
040 is fixed by dual glue tape.
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The
DU-loco have as standard dual cable connections to the wheels on
both sides where one pair will loose the connection to the PCB
when it's cut off. Extra wires have to be soldered. Both left
and right wheels are isolated from the chassis so the blue wire
connected to chassis is used as common pole for the lamps. The
wires from the decoder is soldered to the PCB as shown in the
figure. Follow the same procedures as for the RC4 loco.
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Ready
to program the loco`s
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The
moment have come to give the loco decoder the four basic
parameters. Address, start level, acceleration and
retardation. Do always use a separate programming track apart
from the layout - preferable an oval of minimum 1 meter of
diameter for final adjustments of the parameters. If the
programming by mistake takes place on the ordinary layout all
locos will pick up the same parameters and the old erased.
The DCC
central units have a special programming mode and when
running from PC a loco programming software are available. Some
handheld controllers attached to the central unit can be used for
loco programming. The decoder supplier tells the default setting
at delivery and how the parameters can be altered. Test the loco
with the default values before any changes.
Give the
loco a free unique address. Tandem coupled loco`s are given the
same address with individual parameters depending on each
locomotives characteristics. The startlevel can differ a lot
depending on motor and friction. A certain voltage level is
needed to get it moving. The first step shall be tuned to
give a smooth slow start and the rest of the steps distributed up
to top speed. Acceleration and retardation is programmed to give
a realistic movement - run the test track! Keep in mind that
hundreds of tons don`t stop in 10 meters.
The DCC
technique can be treated as "AC" (alternating current)
giving a lot more tolerance against dirt and oxide. A general
problem for the "2R" railroader. Some locomotives
without boogies are difficult to run smoothly even with DCC. I
have tested tandem coupled locos to extend the connetion to the
track. Permanent coupled wagons is another solution to extend the
number of contacts to the track. This method could be the
only alternative to modify a Z-scale loco to DCC by having the
decoder in a wagon with wires to the motor in the loco.
Steam
locomotives with a tender is an excellent example where the
decoder can be installed in a coupled unit. The above solutions
are just example on individual installation used for small scale
locomotives.
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Per-Ake Jansson,
email:

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