Digitrax DCC System Hints and Tips
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These notes are an evolving tip sheet on operation of Digitrax
DCC systems. The source of these tips comes from customer questions,
personal experience, the internet and the Digitrax manuals and technical
Digitrax has been producing a their popular DCC system since the
1990's. There are now three starter systems available from Digitrax.
On the low end is the all-in-one Zephyr, in the middle is the Super
Empire Builder and on the top is the Super Chief. This family of
products will all interconnect thru the LocoNet LAN connection.
The LocoNet links the command station to boosters and the handheld
throttles. Even the low cost Zephyr has the LocoNet connection and
can be used with the handheld throttles. If you start with a Zephyr
and later expand your system the Zephyr can be used as a power booster.
Digitrax also m akes a long list of decoders for different scales.
The NMRA standard applies to the signals that are on the rails.
In practice this means that it is up to the m anufacturer to build
a system to generate the signals. This is why you need to buy handheld
controller, power stations (booster) and other components by the
same manufacturer. Since the DCC signal on the rails is standard
any manufacturers decoders must respond to this standard.
This is why some parts of a system may not be interchangeable, but
you can use a mix decoders from any manufacturer.
Choosing a System
With the choice of three different starter sets, the one that is
right for you depends of how the system will be used. Things to
consider include number of operators, scale and number of locom
otives running. All three systems will program basic, universal
and advance consists. All three use LocoNet connections to allow
use of handheld throttles. The throttles can be linked by tether,
radio or IR. For the amount of power
needed look at Layout Power Requirements later in this document.
Additional power booster also connect to the LocoNet.
For a small home layout the Zephyr will work and can run up to 10
locomotives. The Zephyr is a stationary unit, but with the LocoNet
you can add handheld throttles around the layout. The amount of
power from the Zephyr is only 2.5 amps. This may limit the number
of locomotives that can be run in your scale. On the positive side
the Zephyr is full function and can read back CVs with a program
track. Has function output for F0 to F8. The Zephyr can be programmed
to be a 2.5 amp booster if you upgrade systems. The Zephyr is the
only system that has 2 novel JUMP Ports which allow a dc power pack
to run DCC decoders.
One of the local clubs has obtained a Zephyr to determine if their
existing dc layout wiring will work with DCC. A bigger system will
be needed once converted. After conversion the Zephyr can then be
used at the work bench to program decoders without interrupting
layout operation or as an additional booster.
SUPER EMPIRE BUILDER- (DB150)
A step up from the Zephyr with the ability to run up to 22 locom
otives and throttles. Available with a 5 am p power booster. This
system has function outputs for F0 to F8. The Super Empire Builder
does have one limiting item as it does not have a separate output
for a program track.
SUPER CHIEF- (DSC100/DSC200)
This is the top of the line system with the ability to support up
to 120 locomotives and throttles. A good choice for large home or
club layout. This system has function outputs for F0 to F12. The
Super Chief supports an output for a program track. Also available
with a 5 amp (DSC100 )or 8 amp (DSC200) power booster.
Digitrax Upgrade of Older Chiefs
Older DCS100s that cannot access Functions 6 and higher can send
their DCS100 to Digitrax for an upgrade. Cost for the upgrade is
$35, which includes return shipping. Contact Digitrax for more information.
Layout Wiring and System Setup
The 22 AWG wire may be OK for the program track, but is too small
for the mainline. Wire has resistance and the longer the wire the
higher the resistance. Smaller wire has more resistance per foot.
Resistance causes a loss of voltage. More current equals higher
voltage loss resulting in loss in train speed and dimming lights.
It is best to keep the voltage loss to under one volt. To add to
the loss in wiring, nickel-silver rail is not a good electrical
conductor. Wire should be installed in parallel to the rails and
a drop from the rails to the wiring at least every 6 to10 feet.
Here is a chart listing wire size, currents and lengths. A good
source of wire is the speaker wire from
Radio Shack. Be sure to get the stranded wire.
Chart for 1/2 volt drop. This
would equal a one volt drop
for a wire to the layout and back to the base unit.
To determine the voltage drop of an existing layout wiring you
can use an RRampMeter. Put one end of the m eter on the rails and
put a load on the other end to get a reading under load. You can
make a simple load from an automotive lamp. Measure the voltage
with the load and then without the load to determine the amount
of loss. The 1156 lamp will give little over a 2 amp load, a 1141
is about 1.5 amps
and the 912 lamp near 1 amp. The RRam pMeter is a versatile handy
tool to have for testing and monitoring the electrical system of
Checking voltage drop with an
RRampMeter. Automotive lamp used as a load.
Blocking the Layout
With only two wires connected to the main track connection a single
short circuit will shut down the layout. To prevent a single short
from shutting down the entire layout, the layout should be divided
into sections known as districts and subdistricts. A district is
a section of the layout that is powered by a single power booster.
A subdistrict is a section of track or block that has a separate
circuit breaker. Another type of block or subdistrict is a reversing
loop or reversing section like a turning wye.
Common or House Wiring
There are two ways to wire to rails of a layout. One is the House
Wiring where two wires are used to feed each block. Called
house wiring because it is like the wiring in your home. The other
is Common Wiring or sometim es called Common Rail
wiring. This is where a heavy wire is round around the layout and
a single wire used for each block and then the other rail wired
to the heavy wire. This is like a car is wired where one wire is
connected to the frame. Most modeler use house wiring, but the common
wiring will work with DCC. There is one rule-of-thumb that applies
to either style of wiring. Only one item can be wired in common.
For common wiring the return wire is the common item . With house
wiring you can use a common transformer. But even with house wiring
it is still best to use separate transformers for each the command
station/booster and each booster.
Layout Pow er Requirements
Digitrax supplies a either a 5 am p or 8 amp booster with the command
station. The 5 amp is am ple power for most sm all to medium size
layouts in N thru S scales This will even work well with newer O
scale locom otives. (Ive run 2 newer O scale locomotives on
a 2.5 amp Zephyr system.) Power boosters are connected thru the
LocoNet bus. For older O scale and G scale the 8 amp unit should
The 5 amp power booster should handle the requirements of most
layouts. To determine if you will need additional power here are
some figures you can use for planning. If you have a consist, add
the number of powered locomotives in the consist.
To find out whether the maximum current of the system used is sufficient
for the supply of your model railway system, simply add up the power
consumption of all locomotives running at the same time as well
as that of all other items that consume power. The following approximate
values can be used to determine layout power requirem ents.
Running locomotives - depending on gauge and attached load,
the power consumption ranges from 200m A to 2000mA. Calculate per
locomotive 300mA for N gauge, 600mA for HO gauge and 2000mA for
larger gauges. This ensures that you
still have som e reserve left.
Standing locomotives - not illuminated 5mA, illuminated
approx. 50mA for each bulb. 15mA for each LED, illuminated passenger
cars - each bulb approx. 50m A.
If the calculated sum exceeds the maximum current available from
the Power Booster you need to split your layout into multiple power
districts and install additional power boosters to provide power
for each of these power districts. The Digitrax fam ily includes
three power booster models depending on the current needs and scale
of your railroad. Remember to plan for the future.
There are two power boosters available from Digitrax plus the Zephyr.
The Zephyr is rated at 2.5 amps and boosters are available at 5
or 8 amps. Output voltage of the Zephyr is fixed at about 13 to
14 volts. The 5 amp power booster is the most common and the 8 am
p power booster should be reserved for G and O scale. Some of the
booster have a three position SCALE switch to set the output voltage.
The positions are N for 12 volts, HO for 15 volts and O/G for 20
volts. Regardless of your scale you should use the lowest setting
that works. There is also an internal voltage adjustment on som
e of the booster. Check your manual for m ore information on voltage
The command station and power boosters require a transformer for
power. If a transformer is used that has an amp rating less than
the output of the power booster there may not be enough power to
trip the over-current protection. For most applications a 16 to
18 volts ac transformer works best. Digitrax specs call for an ac
voltage input of 12 to 20 volts or a dc input of 12 to 28 volts
.Exceeding these voltages can cause damage. Current ratings should
be the same or slightly higher than the booster output.
|COMMAND STATION (Power Booster)
|| SUGGESTED TRANSFORMER
||Supplied with the Zephyr
|Super Empire Builder DB150 (5 amp)
|Super Empire Builder DB200+ (8 amp)
||XFR10 18VAC 10 Am p for O and G scale
|Super Chief DSC100 (5 amp)
|Super Chief DSC200 (8 amp)
||XFR10 18VAC 10 Am p for O and G scale
Circuit Breakers and Accessory Decoder Wiring
One of the most common causes of short circuits is running into
a turnout that is set the wrong way. If you power an Accessory Decoder
from the rails the short will cut the power to the decoder and you
can not throw the switch the clear the short. This situation can
be avoided by wiring the power directly from the power booster to
the Accessory Decoder. A short circuit will trip the circuit breaker
while the accessory decoder continues to receive power via the base
unit and allows you can throw the switch to clear the short.
Even without Accessory Decoder(s) using circuit breakers will allow
sections of the layout to continue to operate with a short circuit
in one of the other subdistricts. On-Guard (OG-CB) circuit breakers
are available. There is also an On-Guard (OG-AR) for reverse loops
which also has a integrated circuit breaker and can automatically
operate the switch at the throat of the loop with a Switch-It.
A reversing loop is a section of track that allow the train to turn
around and reverse directions. Reverse loop wiring and operation
is much simpler with DCC than dc. On dc the reverse loop was wired
so the you could flip the polarity of the mainline while the train
was in the loop. On DCC it is done the opposite way. With DCC the
polarity of the train can be reversed under the train while it is
in the loop. Polarity can be automated with a reverse loop adapter.
The On-Guard Reverse Loop Adapter (OG-AR) is a solid state electronic
device. Two wires are connected to the mainline or power booster
and the other two wires to the isolated loop. When the metal wheels
cause a short either entering or leaving the loop the adapter automatically
switches the loop polarity.
Output Track Status Light.
Track Status Light on the command station/booster is normally an
amber color. If it is either shifted to red or green it can m ean
one of two things. Either a fault in the output of the booster or
you have run an engine using the 00 address feature.
If you put a non-decoder equipped engine on the layout and set
it to full speed in one direction or the other it can leave the
output biased. To fix this you need to select address 00 and turn
the throttle to zero speed setting for that address. Then dispatch
address 00! If you had a large layout with lots of engines you will
find that this feature can slow response and be sluggish.
You can use a bicolor LED to monitor the status of the track power.
Here is a simple circuit that will give you the information. Normally
it is a yellow/amber, a distinct red or green indicates a DC output
bias and may be indication of a malfunction.
System Cab Cables
If you need to make or buy cab cables to run from the base unit
to remote locations on the layout they should be correctly wired.
Correct wiring has the same wire connected to the same pin on both
ends of the cable. The connector are 6 pin phone type connectors
and the supplied cables have all 6 wires connected. If you buy cables
be sure they are the 6 Pin type! If you make your own be sure to
use a good quality crimper that will handle 6 pin connectors. Some
cheap crimpers dont apply enough pressure to adequately connect
the wires to the pins. (The cost of a good tool is soon forgotten,
the problems with a cheap tool linger on!)
Parts to make your own cables are also available along with a crimper.
The UTP (Universal Throttle Panel) cab bus panel is also available
that provides additional throttle connections around the layout.
The UTP has two RJ12 connectors in the front for connecting two
throttles and two in the back to allow you to daisy chain
to the next UT P.
Correctly connected ends for use
with Digitrax systems.
You should not connect the command station or power station to
any device even if other devices use the same connectors. The fact
that the connectors are similar does not autom atically m ean that
the device is designed to work with the Digitrax. This is true even
if you are dealing with other model railroad DCC control system
Digitrax Mobile Decoders Defined
Digitrax supplies decoders for most scales. The decoder part number
is used to define the model tells a lot about the decoders
use and features. Starting with the 4th generation decoders here
is some information on the code used. Start with the decoder ID
DN163K2". They always start with a D for Digitrax. The
next character is the scale. In this case the N is for N scale.
The third is the motor current rating.
The number is one digit and in this case is 1.5 amps, but rounded
down to a single digit. The next digit, a 6, is the number of functions
available on the decoder. The fifth character is a series designator
and may run from 0 to 9. The next two characters are optional. In
this example the K is for Kato and the 2 is the second style for
Kato or interface used. For a more complete definition see the Digitrax
Mobile Decoder Manual. This manual is kept up to date and available
from Digitrax or a free
download over the internet from the Digitrax website. (www.digitrax.com)
This website has the manuals of present production and most of the
out of production equipm ent.
A center off toggle switch allows
you to have a section of dead track
to put equipment on the tracks without shorting out the sys tem.
Just because a decoder is intended for a one scale does not mean
that is the only scale that it will work with. Ive seen an
N scale decoder used in an On3 Shay. Why, because it fit! It is
the motor rating that is important not the scale.
Programing with Digitrax
The Zephyr and the Super Chief have outputs for a program track.
This track can be a siding off the mainline. This section of track
MUST BE ISOLATED with gaps on both rails. If you use a center off
toggle switch the program track can be setup to select the track
for programming or use for normal operations. With the center off
the track can be used to put equipment on the rails without affecting
operation or shorting out the rails.
The new BLI locomotives with the QSI sound decoders require more
startup power to charge the capacitors. This can cause a problem
programing on the program track. If you have a problem the PowerPax
can fix it. The PowerPax is an adapter that is wired in between
the command station and the program track. The PowerPax is guaranteed
to fix this problem.
Decimal, Binary or Hex
. The Zephyr system uses decimal notation and some of the other
systems have information in hex. (Hex is short for hexadecimal.)
A knowledge of the hex, binary and decimal numbering system is a
big help when you start setting up some of the special lighting
or sound settings CVs. The values stored in a CV runs from 0 to
255 (0 to FF in Hex). There are conversion charts available to convert
from one numbering system to any of the other number systems. There
is a decimal to hex chart in the back of the Digitrax decoder manual.
DCC or dc Settings
Bit 2 of CV-29 permits som e decoders operate when d.c. in on the
rails. This bit should be left off unless you have a real need to
operate between DCC and dc. Leaving this bit off can reduce the
possibility of runaways. Some decoder do not support dc operation.
Check with the decoder manual.
Function (When on)
|Normal Direction of Travel (NDOT)
||To correct direction problems so forward
is forward. Reverses the norm al direction of travel.
||14 or 28/128 speed steps
||Sets use of 14 or 28/128 Speed Steps. Should
be on unless you have an old decoder(14 speed step is obsolete
and rarely used)
|| Power Source Conversion
||Allows the decoder to operate on dc or DCC.
Not supported by all decoders. Best left off.
||Advance Decoder Acknowledgment
||This is a feature in some newer decoders
Leave this bit off unless you have the function.
||Use Speed Alternate Table
||Used for speed matching. Leave off unless
you set up the speed table at CV67 to CV94.
||4 Digit Address (Off for 2 digit)
||Sets 4 digit addressing. (2 Digit in CV-3
and 4 digit in CV-17 & 18.)
||Reserved for Future use
||Not used at the present time.
||Defines Accessory Decoders
||On if an accessory decoder/Off for mobile
Addressing VS. Other Systems.
The Digitrax system used addresses 1 to 127 as a two digit address
and 128 to 9983 as four digit addressing. Address 00 is used to
operate a single locomotive without a decoder. There are some address
ranges that can be setup in other DCC systems that m ay not work
on a Digitrax system. Addresses from 9984 to 9999 are not addressable
with Digitrax systems. Some systems can setup address 0001 to 0128
as four digit addresses. This range of four digit address are also
not addressable with the Digitrax systems. Problem s with these
address ranges only occur when locom otive decoders have been setup
with non Digitrax system s.
Another area of addressing conflict is the two digit addresses
and the addresses used for consists in CV19. A decoder can not tell
the difference between a two digit address and a consist address
of the same num ber.
Four Digit Addressing
Most system automatically setup 4 digit (long) addresses. These
systems put the correct values in CV-17 and CV-18 based on the locomotive
address. CV-29 bit 5 (weight 32) also needs to be set for 4 digit
addresses. If your system does not automatically setup 4 digit addressing
here is a way to do it manually. The basic idea for this cam e from
a QSI manual. The following way uses a calculator.
A. Start with the locomotive address and divide it by 256. Sample
4449 ÷ 256 = 17.3789
B. Take the whole number (17) and add it to 192. Sample 17 + 192
C. Program the value (207) in step B is into CV-17.
D. Multiply the whole number from step A by 256. Sample 17 X 256
E. Subtract the locomotive address from the computed value in step
D. Sample 4449 - 4352 = 97.
F. Program the value (97) in step E is into CV-18.
G. To activate 4 digit addressing a value of 32 (bit 5) needs to
be added to CV-29.
Consisting or MUing (multiple unit)is the ability to run more than
one locomotive together as a single unit. Three methods are available,
Basic Universal and Advance. Basic is addressing more than one decoder
with the same address. W ith Universal the command station keeps
track of the locomotives in a consist. The advance consisting is
a newer way and uses CVs in the decoders to control the consist.
The Digitrax system s can setup any of these type of consists.
With the Universal type of consist the base unit can only run one
consist with up to four locom otives. Any functions are controlled
by entering the locomotives number and using the function keys.
The lead locomotive number is used for the consist number. With
the old type of consisting the base unit sends out a separate commands
to each locomotive for each change in speed or direction. When you
enter a locomotive number and the locomotive is headed in the reverse
direction from the other units push the direction key after entering
the address. This tells the system to send this locomotive commands
that are in reverse of the other units.
The Advance method uses CV-19 of each locomotive of the consist
to hold the consist number. Any value in CV-19 other than zero tell
the decoder it is in a consist. Advance consists use the 1 to 127
address range. This is the same as the two digit addressing range.
A conflict can be setup if you use a 2 digit locom otive address
the sam e as a consist address. When in a consist the decoder will
not respond to any speed or direction at its normal address. A value
of 128 is added to CV-19 when a locomotive is reversed in the consist.
In a consist with the an address of 10 in CV-19 a locomotive in
reverse would have a value of 138 in CV-19. There is a group of
CVs that allow even more control of features while in an Advance
consist. CV-21 to 24 are used for these controls.
Programming on the Main Track
Programming on the Main Track is sometimes referred to as OPS
Mode Programming. This allows you to change the value in a
CV while out on the mainline. Functions like lighting, sound levels,
acceleration/deceleration rates can be changed on-the-fly while
operating a locomotive. The change will only apply to the address
shown in the display. With a little practice you will appreciate
what this feature can do for you in train operation. The value in
a CV can not be read back in OPS mode.
Operation with the Digitrax DCC systems
The Zephyr and Super Empire Builder have a function key range of
F0 to F8. The Super Chief range is F0 to F12. F9-F12 are accessible
on the DT400 and the UT-4 throttle when used in conjunction with
the Super Chief comm and station. The new SoundTraxx Tsunami and
QSI sound decoder use the function keys higher than F8. Below is
a sample of the function keys and actions. Functions can be re-mapped
if you need a function that is not in the range your system.
||Water Stop Sound
||Short Air Let Off/Pop Off
||Speed Read out
||Short Air Let Off/Boiler Blow Down
||Short Air Let off
* Note-- The above chart is subject to change
depending on the type of locomotive or decoder.
DCC system and decoders all come with manuals or information sheets.
When you buy DCC products you get a receipt from the supplier. All
of these documents should be retained. You may need a receipt to
prove when you bought a device when getting som ething repaired
under warrantee. Manuals are needed for reference, like when a decoder
gets amnesia and needs to be reprogrammed. It is a good idea to
write down the programing of a decoders CVs and keep the information
with the decoder manuals. Even though many of the manuals are now
available over the internet in time they get obsoleted and can get
removed. Digitrax does a good job of keeping manuals of obsolete
equipment on their website, many others do not.
Sources of Help
There are ways to get help or have questions answered. One of the
best is to join the Digitrax Yahoo group on the internet. The Digitrax
Yahoo Group Chat list has near 5000 mem bers that can answer almost
any questions you have. If you monitor the group you will find a
lot of answers and many suggestions. Another source is Digitrax.
If you still have questions after reading the operating manual,
you can contact Digitrax at Sales@Digitrax.com or call Digitrax
at 1-770-441-7992. Their address is Digitrax, 450 Cemetery Street,
Norcross, GA USA 30071.