Introduction to Digital Command Control

Digital Command Control

Demystified

By Lee Ryan

Why go DCC?As a DC owner/operator, would you like any of these features when operating your trains on your personal or club layout?

-Easy individual loco control

-Operation more typical of the prototype

-No block controls and no more “Who's got my train”

-Easier wiring

-Better motor performance by tuning your locos

-Walk around capability

-Sound in your existing locos.

-Light effects that can be selected off/dim/on at a constant intensity! Can also be on when the loco is stationary.

Do you want to operate trains and not your layout?

Advantage to Digital Operation

•Component Standards – NMRA Conformance

•Large product selection

•Secure investment – upgradable

•Large base of support

•One technology for multiple scales

•High functionality: Speed Control – Lighting – Sound – Accessories

•Full voltage – Uses existing layout wiring – Can operate one analog locomotive (not recommended).

•Multiple locomotive operation with multiple users on the same track

Components of DCC Systems

•Cab / Throttle

•Command Station

•Power Supply

•Power Station (Booster)

•Mobile decoder

•Accessory decoder

Cab / Throttle•Controls locomotive speed, direction, lighting, and sound functions

•Tethered, wireless, and built-in to the command station

•Multiple throttles per 1 system for multi-operator ease

Wired / Wireless: $90 – $250

Command Station•Brains of the DCC system – generates the information decoders use to operate your locomotive

•Each system needs just one command station no matter the size of the layout

Power SupplyNCE P515

5 Amp power supply

Input: 120VAC

Output: 15VAC, 5 Amps

MSRP: $59.95

NCE Brutis

10 Amp power supply

Input: 120VAC

Output: 18VAC, 10 Amps

MSRP:

$169.95

Digitrax PS 2012

20 Amp power supply

Input : 120VAC

Output: Selectable: 13.8, 18, or 23 VAC

Can power four 5 amp boosters

MSRP: $179.99

Power Station (Booster)•Amplifies the digital signal to the rails

•Built-in to the command station most often

•Some provide short circuit protection, voltage regulation, and

auto-reversing capabilities

SB5 for use with NCE PowerCab only!

MSRP: $219.95NCE PB5 (updated PB105) same box

Incl. P514 5 amp power supply. MSRP: $199.95

Digitrax DB 200+ 8 amp booster

Power supply not included

MSRP: $199.99

Mobile Decoders•The brains for the locomotives

•Connects between the locomotive motor and the rails

•Receives the digital signal from the command station and translates (decodes) the signal into visual or audible effects from the locomotive

•Uses a unique address to identify it amongst multiple locomotives – user assigned – usually the cab number

Non-Sound: $10 - $40

Sound: $100 - $140

Speakers: $10 - $15

Accessory Decoders•Similar to mobile decoders except that these are stationary around the layout

•Used for controlling line side items such as track switches, signals, turntables, lighting, or anything you wish to animate

Prices range from $20 - $75

for standard switch control

Signal components are

$50 - $125

How the Pieces Work Together1) The user adjusts the Cab / Throttle settings, which are sent to the command station. 2) The command station then transforms the data into a digital packet which is amplified by the booster and sent to the rails. 3) The decoder receives the information packet and decides if the packet is addressed to it or if it is meant for a different decoder.

4) If the information packet is intended for the decoder, it processes the data and changes a visual or audible effect on the locomotive. This includes motion, lights, sound effects, etc. 5) If the information packet is not intended for the decoder, it ignores the data and continues doing what it was doing for the locomotive it is installed in.

DCC Track Signal•Bi-Polar DC Signal

•Full voltage 100% of the time

•Each cycle encodes a data bit

•Pulse width encodes a “1” or a “0” (Stretched “0” for DC loco on DCC)

•8000 bits per second

•Multiple bits make up a data packet

DCC Decoder Information PacketInformation (Data) packets consist of 4 basic parts

*Preamble

*Address Byte

*Instruction Byte

*Error Detection Byte

*200 data packets are sent each second

Measuring DCC Current and VoltageCannot use standard multimeter

Root Mean Square (RMS) Multimeter

FLUKE 87V $399.95

RRAmpMeter I $64.95

RRAmpMeter II $94.95

RRAmpMeter III $104.95Same as II with battery backup for measurements below 7 volts--------------------------------------------------------------------

RRAmpMeter IV HP $124.95Same as III - for large scale high voltageand current applicationsDCC: 38.6 volts and 18-20 ampsAC: 27.6 volts and 18-20 ampsDC: 38.6 volts and 18-20 amps

Root Mean Square(RMS) Oscilloscope

Tenma 72-8474 $949.99 FLUKE 179 $299.95 Tenma 72-8470 $699.99

Terminology•Lots of jargon and acronyms

•DCC Ready vs. DCC Equipped

DCC Ready means the locomotive is “ready” for a decoder. Its motor is isolated from the track through a circuit board. The circuit board may have a plug (8-pin or 9-pin) for easy decoder installation. Others require replacing the factory circuit board with a similarly shaped and sized DCC decoder.

DCC Equipped means the locomotive is “equipped” from the factory with a DCC decoder. Place on a DCC layout and have fun. Some factory installed decoders are pre-programmed to the last 2 digits of the cab number. Others are default to address 3. Decoder equipped locomotives can be operated on analog DC.

Sound Equipped locomotives are automatically DCC Equipped!

Configuration Variables•Configuration Variables (CVs) are used to make changes to parameters within decoders

•NMRA Standard CVs

•Manufacturer specific CVs

•Numerous CVs available for use – not all are used

•Some CVs have multiple ‘levels’ and control many different parameters – Indexing

Changing CVsThere are two methods for changing CV settings:

•Service Mode Programming –Program track

•Operations (Ops) Mode Programming -Main Operating Track

Service Mode Programming•Uses a separate track called the ‘program track’

•Requires an isolated section of track – can be a dead end siding with a Run / Program toggle switch

•Can read CVs back with most systems

•Do not need to know the locomotive address

•Cannot test settings changes in Service Mode

•Program track booster required for some sound decoders

•Some systems may have difficulty reading or programming other brands of decoders

Operations (Ops) Mode Programming

•Also known as “Programming on the Main (POM)”

•Reliable

•No need for a separate track or to shut down the layout

•No need for programing boosters for sound decoders

•Can test settings changes immediately

•Cannot read CVs

•Must know the locomotive address

•Each locomotive on the main needs to have a different address OR locos programmed individually

•Multiple locomotives can get programmed accidentally

What is a Configuration Variable?(Warning - Technical Jargon)

• To humans a numbered information slot

• Really a computer byte which means it is 8 bits

• A bit is a simple 0 (off or ‘low’) OR 1 (on or ‘high’)

• Bits in the bytes are numbered from right to left

• First bit is called bit number 0 on the right

• Last bit is called bit number 7 on the left

• Each higher bit has double the value of the previous one

• 7 6 5 4 3 2 1 0• 0 0 0 0 0 0 0 0 = 0

0 0 0 0 0 0 0 1 = 10 0 0 0 0 0 1 1 = 1 + 2 = 30 0 0 0 0 1 1 1 = 1 + 2 + 4 = 70 0 0 0 1 1 1 1 = 1 + 2 + 4 + 8 = 150 0 0 1 1 1 1 1 = 1 + 2 + 4 + 8 + 16 = 310 0 1 1 1 1 1 1 = 1 + 2 + 4 + 8 + 16 + 32 = 630 1 1 1 1 1 1 1 = 1 + 2 + 4 + 8 + 16 + 32 + 64 = 1271 1 1 1 1 1 1 1 = 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255

• A CV value cannot be higher than 255

• Can take any value between 0 and 255 (256 possibilities)

• CVs can be used to:Store a unique configuration item (CV 1)Store part of a configuration item, larger than 255 (CV 17 & 18)Store many configuration items (CV 29)

7 6 5 4 3 2 1 0

128 64 32 16 8 4 2 1

Important CVs

CV 1 – Short Address

*Decoder’s Primary Address (ID)

*Range is 1 to 127 - (bit 7 not used by DCC norm)

*Usually set to the last two digits of locomotive cabnumber

*CV 1 is almost always set to 03 from the factory

*Some Atlas locomotives CV 1 is pre-programmed tolast 2-digits of cab number

Important CVs continued

CV 17 & 18, Long Address

*Range 1 – 9999

*Two CVs needed

*Often set to locomotive cab number

*Can be set manually - (back door programming)

DCC Extended (4-Digit) Locomotive Addresses Using CV17 and CV18

From to CV17 From to CV17 From to CV17

0 255 192 3584 3839 206 7168 7423 220

256 511 193 3840 4095 207 7424 7679 221

512 767 194 4096 4351 208 7680 7935 222

768 1023 195 4352 4607 209 7936 8191 223

1024 1279 196 4608 4863 210 8192 8447 224

1280 1535 197 4864 5119 211 8448 8703 225

1536 1791 198 5120 5375 212 8704 8959 226

1792 2047 199 5376 5631 213 8960 9215 227

2048 2303 200 5632 5887 214 9216 9471 228

2304 2559 201 5888 6143 215 9472 9727 229

2560 2815 202 6144 6399 216 9728 9983 230

2816 3071 203 6400 6655 217 9984 10239 231

3072 3327 204 6656 6911 218

3328 3583 205 6912 7167 219

Range of Addresses Range of Addresses Range of Addresses

CV29 MUST be set to 34 OR 38 to enable the Extended (4-digit) Address!

Desired Address: 6492 Desired Address: 9267

Range: 6400 to 6655 Range: 9216 to 9271

CV17: 217 CV17: 228

CV18: 6492 - 6400 = 92 CV18: 9267 – 9216 = 51

More Important CVs

CV 29 Decoder Configuration

*Sets the type of address used – 2 or 4 digit

*Sets the Speed Step mode (14/27 or 28/128)

*Sets the use of speed tables

*Sets operation of decoder equipped loco on DC

*Sets locomotive directionality in case of miswire

Yet More Important CVsCV 19 – Advanced Consist (MU) Address

*Range of consist addresses 1 – 127(NCE PowerCab 112-127 only)

*Used to combine two or more locomotives into lash-ups

*Can be programmed manually or through DCC system“Consist” menu(s)

*Takes priority over regular locomotive address unless setto 0

*Add 128 to consist address for locos running in reverse

Last of the Important CVs

Decoder Reset CV

*Most decoders CV 8 to 8 resets the decoder

*Some decoders use other methods

*SoundTraxx uses CV 30 to 2 (CV 8 to 8 also)(Must interrupt track power – 16 headlight flashes confirms reset)

*Lenz uses register 8 to 33

Decoder Function Outputs•Functions are outputs for controlling bulbs, LEDs, relays, etc.

•Color coding for easy wiring – NMRA standardPin 1 – orange motor + Pin 8 – red right rail track pickup

Pin 2 – yellow reverse light (F0r) Pin 7 – blue + common for lights

Pin 3 – green wire (typically not used) Pin 6 – white forward light (F0f)

Pin 4 – black left rail track pickup Pin 5 – grey motor –

•White, Yellow, Green (Purple) are function output wires (-)

•Some decoders have 4, 5, or 6 function outputs for more lights

•Blue wire is ALL lights common (+) and about 12 volts

•1k ohm ¼ watt resistors required in most cases for LEDs(Some decoders have resistors built-in)

-LED Cathode (-) goes to function output wire-Each LED should use its own resistor

Function Outputs Continued

•Lighting effects available on some decoders – Gyralite,MARS light, beacons, strobe lights, firebox flicker, FRED,dimming, ditchlights, etc.

•Sound decoders use functions to control sound effects –some sound effects can be tied to lighting effects(alternate flashing ditchlights when horn is sounded)

•Represented on cabs / throttles by F0 to F12 – mostsystems and some decoders follow the newer NMRAstandard 28 function control

Motor Control

PWM – Pulse Width Modulation

•All decoders use PWM to control motor speed and direction

•The motor is switched on and off between zero and full power

•Speed is controlled by varying the ratio of OFF and ON time

•Example half speed is full power 50% of the time

Speed Steps•Decoder splits minimum and maximum throttle range intospeed steps

•Speed steps are set via the throttle per locomotive

•More speed steps means finer control of the locomotive

•14 and 28 speed steps are NMRA standard

•128 speed steps is also supported

•For a maximum voltage of 14 volts DC, each speed step ona straight line speed curve will equal:

-14 Speed Steps - 1 volt per Speed Step increment-28 Speed Steps 0.5 volt per Speed Step increment-128 Speed Steps 0.11 volts per Speed Step increment

Back EMF Motor Control

•Motors generate electricity when they turn and it can bemeasured

•Also called cruise control

•Uses motor back-EMF to sense motor speed

•Helps maintain constant speed up and down grades

•Improves low speed performance and control

High Frequency Drive

•Known as silent drive, Supersonic, HyperDrive

•Increases the frequency of the PWM signal to prevent motor buzzing

Stall Current

•The amount of current drawn by a motor at full voltage witharmature locked up

•Must be matched to decoder specifications

•Most HO decoders are rated for 1.1A continuous with up to 2A peak

•A locomotive that draws more current than the decoderis rated for can turn a decoder into a smoke unit!

High End DCC SystemsAll Prices M.S.R.P. as of March 2014

ESU ECoS 2 - $899.90

NCE Power Pro

Wireless - $699.95

Wired - $529.95

Lenz Set-100 - $497.50 Digitrax Super Chief Xtra

Wireless - $665.00

Wired - $455.00

MRC Prodigy Elite - $549.98

Mid Range DCC SystemsAll Prices M.S.R.P. as of March 2014

Digitrax Super Empire Builder Xtra

Wireless – $575.00

Wired – $355.00

Lenz Set-90 - $442.50CVP Easy DCC


Wired – $429.00

MRC Prodigy Advance2


Wired – $439.98

Bachmann Dynamis

Basic – $175.00

+ Dynamis Pro Box ($500) = $675.00

Entry Level Systems

NCE PowerCab: $199.95 Digitrax Zephyr Xtra: $225.00

NCE DCC Twin: $159.95

MRC Prodigy Express2: $224.98 Bachmann E-Z Command: $168.00

All Prices M.S.R.P. as of March 2014

Lenz Set 01: $199.87

Due Dec. 2013

CVP Easy DCC Basic: $279.98

Common Myth #1“DCC allows you to control your whole layout with only two wires connected to the track”

Yeah, Right!

•Reverse loops & wyes must be wired with a reversing switch or DCC compatible reversing module.

•Blocks are still needed for signaling

•Power districts are recommended for medium and larger layouts

•Cables are needed for cab buses, electric turnout control, and any other animation you desire

Common Myth #2

“Stall current is the same as operating current”

Stall current can be three or four times larger than the operating current and should always be verified to prevent pre-mature decoder failure.

Common Myth #3“The NMRA DCC standard is comprehensive and all equipment works together”

The NMRA standard only defines the signal on the rails. Most other aspects of a system are left to the manufacturer such as cab wiring, CV assignments, and so forth. Some interoperability occurs between manufacturers sharing or copying certain proprietary specifications.

Basic compatibility between decoders and systems is actually very good (not perfect) and represents the bulk of a users time and money investment.

Common Myth #4

“DCC layouts require special track switches”

So called DCC friendly track switches simply have an insulated frog. You must gap the frog rails just as you would for an analog DC layout. Track switches with non-insulated frogs can be used just as readily.

Common Myth #5

“The track doesn’t need to be kept clean because it is always at full voltage”

DCC requires extremely clean track as does an analog DC layout. Clean track is essential for reliable operation. If the locomotive can’t pick up the DCC signal or power to operate, you’ll have stuttering locomotives leading to frustration.

DCC User Advantages

•More fun

•More features

•Runs your locomotives directly, not your track

•More prototypical operation

•New technology continuously being developed appeals to new modelers

•Easier to run multiple trains

Helpful DCC Books and Links

Practical Guide to Digital Command Control - Larry Puckett

Carstens Publishing – ISBN 978-1590730126 M.S.R.P. $24.95

DCC Made Easy: Digital Command Control for your Model Railroad - Lionel Strang

Kalmbach Publishing – ISBN 978-0890246160 Out of Print

Price Varies

Basic DCC Wiring for Your Model Railroad – Mike Polsgrove

Kalmbach Publishing – ISBN 978-0890247938 M.S.R.P. $15.95

The DCC Guide – Don Fiehmann


Helpful DCC Books and Links continued

http://www.ncedcc.com http://www.digitrax.com http://www.lenzusa.com

http://www.modelrec.com http://www.esu.eu/en/start/ http://www.soundtraxx.com

http://www.cvpusa.com http://www.bachmanntrains.com

http://www.qsisolutions.com http://www.tonystrains.com

http://www.carstensbookstore.com http://www.kalmbachbookstore.com

http://www.litchfieldstation.com http://www.ulrichmodels.com

http://www.jmri.org

DCC Projects & Applications – Mike Polsgrove


DCC Projects & Applications Vol. 2 – Mike Polsgrove with David Popp


QUESTIONS

Thanks for Coming – Enjoy the show!

Introduction to Digital Command Control

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