Converting to DCC

== The Basics of Converting to Digital Command Control ==
This article assumes that:
# You have read the DCC Tutorial and optionally the Introduction to DCC so that you understand the basic principles of DCC;
# That you have selected a DCC system, which you may or may not have purchased it yet; and
# You have read the Wiring Your Layout article.
=== Overview ===
For small layouts simply disconnect the analog power pack and hook up the two wires to the DCC system's . It should be noted, that this is the most basic way to get your track running on DCC. 
If the existing layout uses multiple , the conversion is a little more complex. First, all DC (analog) power supplies must be disconnected from the track. Then, all connections to the track will go to one or more .
After you have connected DCC booster(s), you'll need to go through your layout's track work to ensure your booster detects short circuits. If there any reversing loops, you'll need to ensure that those are handled properly. This is easily done with the .
If you're impatient and want to get your locomotives running on DCC before you've converted them all you can set up your layout for Mixed DCC and Analog Operation.
The more wiring topics, see the Wiring for Digital Command Control portal.
==== Safety ====
In contrast to traditional direct current systems, the Digital Command Control booster provides significantly higher power output, reaching up to 10 amps. This is a substantial increase compared to the typical direct current (or analog) setup involving multiple power supplies, each with a maximum output of one or two amps. Consequently, a short circuit can cause rapid and extensive damage.
Many older direct current/analog layouts were constructed in stages using a diverse range of wires, colors, and techniques, resulting in numerous splices and connections. This configuration can pose significant challenges during troubleshooting and may necessitate replacing the wiring as a more suitable upgrade option.
Sloppy wiring practices can lead to new problems, such as poor operation, burnt-out decoders, short circuits causing damage, and even runaway locomotives. Therefore, it is better to rewire the layout, document your work, and use adequate wire sizes for the task.
When converting to DCC, the first and most important step is to verify that the wiring is capable of handling the increased power capacity available. Light gauge wire is not suitable for this task. Additionally, check that any toggle switches or other wiring devices are capable of handling the increased current capacity of the DCC system. In most cases, the toggle switches should be removed as you control the trains with DCC, not the layout.
As a general guideline, the main source of power to the track, the TRACK or POWER BUS, should be at least 14 AWG. Larger wire gauges are always preferred. For drops to the track, 18 to 22 AWG is sufficient. Short lengths of lighter gauge wire will be adequate if you need them to connect your track bus to the booster. Please note that larger scales, such as “G,” can require significantly larger wire gauges, 12 to 8 gauge is not uncommon, as 10 to 20 ampere boosters are often used.
For added assurance, test your track wiring using the Quarter Test. If it fails, identify and resolve the issue.
=== DC/Analog combined with Digital Command Control? ===
In the early days of Digital Command Control (DCC), the capability to operate both Digital and Analog simultaneously was deemed essential. This feature is known aszero stretching. However, its use is strongly discouraged as it can rapidly overheat any DC locomotives on the track.
With the advent of affordable decoders that are easily installable, zero stretching is no longer necessary. Many local hobby shops offer decoder installation services if required.
==== Using DC and DCC systems ====
Never connect the two control methods simultaneously. An accidental connection of the high current DCC signal to the DC trackage can cause significant damage. If analog control is desired, create a single connection point for DCC or analog control, ensuring only one can be active at a time.
Some DCC accessory devices, like Auto-Reverse units used with a reverse loop, can be damaged by DC voltage. It’s not worth the cost to forget to remove them from the layout when using DC power.
=== Power Supplies ===
While it is possible to disconnect your analog throttle/power pack and use it as a power supply for your DCC system, it is generally not a permanent solution. The typical power supply used for an analog layout will not provide sufficient voltage or current for satisfactory operation. Avoid using a power pack with Pulse Power.
Obtain a power supply with the appropriate voltage and current ratings for your system. Refer to your owner’s manual for recommended power supplies, or check the minimum and maximum voltages and whether you require a Direct Current (DC) or Alternating Current (AC) input. In some cases, either type of input will suffice. For current, ensure that you have at least the current rating specified by your booster. While larger high-current power supplies may not be an immediate expense, additional amps are not a significant concern. However, using a high-current booster designed for large-scale locomotives on smaller scales can pose potential risks.
=== Common Rail Wiring ===
Implementing DCC can pose challenges, particularly when the entire layout is wired as a single electrical circuit, commonly referred to as Power District. While this approach may seem straightforward, it can lead to complications. Additionally, it becomes problematic when reversing loops or tracks intersecting each other. For these reasons, it is advisable to avoid “Common Rail wiring.
==== Power Districts ====
This is the DCC term for blocks used with Cab Control and other methods of running multiple trains. Power management devices with circuit breakers allow electrically separate track sections (districts). If a short occurs, only that district is affected, while other trains keep running.
=== Phasing ===
Phasing is crucial when using multiple boosters. Each booster has its own isolated track segment called a Booster District.
To verify phasing, use a DMM on the AC Volts Range. Place probes on either side of the gap and read the voltage between the booster districts. It should be zero. If there’s a significant voltage, the boosters are out of phase. When locomotives bridge the gap, they’ll cycle endlessly if they have Auto Reverse. Disable Auto Reverse to prevent that. Correcting the phase relationship between boosters will prevent this.
Connect a heavy gauge return wire between the boosters as per the manufacturer’s instructions to allow return currents to pass through this route instead of your throttle network wiring.
==== Reversing Sections ====
A reversing section is created when a track loops back onto itself, and the right rail becomes the left. Manual methods like switches or automatic reversers are used to handle this. Gaps must be cut in the rails to eliminate shorts. The loop must be large enough for the entire train to fit within the gaps.
See the Reverse loops page for more details.
=== Turnouts ===
One issue is that the Switch rails must not be electrically connected. If so, a metal wheel can bridge between the Switch and Stock Rail, creating a short. Older turnouts were constructed this way, which can cause problems with DCC systems.
Most commercial turnouts are “DCC Compatible,” with mechanical issues that are easily corrected. Power routing turnouts can cause problems if the point rails which make up the frog are not isolated from the downstream track, allowing the two phases to short.
To avoid this, use “DCC Friendly Turnouts” or modify those that can be modified.
==== Key Points====
# Electrical Isolation: Switch rails must not be electrically connected to prevent shorts caused by metal wheels bridging between one and the adjacent stock rail.
# DCC Compatibility: Most commercial turnouts are compatible with DCC systems, but mechanical issues may need correction.
# Power Routing Turnout Issues: Power routing turnouts can cause problems if the point rails are not isolated from the downstream track, leading to shorts between the two phases.
=== Conversion Devices ===
Several devices are available to assist you in the conversion process. Please note that some may not longer be available. 
* Lenz manufactured a device designed to protect equipment when Direct Current (analog) was used on the layout at the same time as your Digital Command Control system. This device, the LT100 Digital Circuit Breaker, is wired in series with your analog throttle. One LT100 was required per throttle. The device disconnected analog power to that block when a Digital Command Control decoder equipped locomotive crossed the gap. Otherwise, a short would occur and damage would follow. Once the entire locomotive was in the block, the Digital Command Control signal was disconnected and the analog throttle took over, for seamless operations. As many modellers have completely embraced Digital Command Control, Lenz no longer offers the LT100 Digital Circuit Breaker. Read the manual for the LT100 here.
* If CV 29 is set correctly for Alternate Power Sources, a multifunction decoder should work on direct current. The danger of setting a decoder for alternate power sources is possible loss of control. On a layout that can be powered by Digital Command Control or Direct Current (by disconnecting one power source and connecting another) all the locomotives can suddenly accelerate if the throttle and block switches are not set correctly and direct current is applied to the tracks. Many modellers set the decoder to NMRA Digital Command Control Only operation to prevent a runaway should the decoder encounter a corrupted Digital Command Control signal and switch to Analog operation.
* Some analog power packs with a pulse power mode can damage or destroy a DCC multifunction decoder. Other decoders may behave erratically.
=== Other Considerations ===
==== Occupancy Detection ====
If you have a functioning signalling system, some consideration is needed here. For DCC, a complete rethink and reconstruction may be needed, but if it uses optical methods independent of the track, there should not be too many issues. 
=== Accessory Decoders ===
Accessories, like turnout motors for animation and switches can be hooked up to accessory decoders. This allows you to control your switches and animation through the DCC system.
==== Motive Power ====
One of the initial steps in converting your layout to DCC is to install a multifunction decoder in each locomotive you intend to operate. This is another advantage of DCC: the multifunction decoder provides complete control over the vehicle’s performance, which can be customized to your specific requirements.
You do not need to convert your entire fleet, and it is unlikely that you will. Select the locomotives you want to run and gradually expand your DCC-equipped fleet over time. Some locomotives may be challenging to convert, and those can be moved to the display track or sold, similar to how a real railroad operates.
Analog conversion is useful if you install decoders but do not yet have a DCC system in place. Once you have completed the conversion, consider switching the decoders to NMRA Digital Only operation to prevent runaways.
# Multifunction Decoder Installation: Install a multifunction decoder in each locomotive for DCC control.
# Fleet Conversion: Convert locomotives gradually, focusing on those intended for operation.
# Analog Conversion: Useful for decoder installation without a DCC system, with the option to switch to NMRA Digital Only for safety.
==== Must I Rewire My Layout to Eliminate Blocks? ====
;No. You can just set all the blocks to select the same cab, and install your DCC system in place of that cab.
:Be sure to disconnect your analog control system before doing that. Never attempt to run analog and DCC at the same time. Bad things will happen no matter how cautious you are.
Some features like reverse loops still require gaps in the rails, but the feature can be automated with a DCC Auto Reverse unit.
If you are converting from direct current (analog) to Digital Command Control, a thorough review of your wiring is in order. See the article on Converting to DCC.
==== My Turnouts are not Compatible with Digital Command Control ====
There is no real issue with turnouts and Digital Command Control. All of your trackwork should have no issues with DCC. The problem with switches is short circuits. DCC boosters will react much faster to a short than an old analog power pack would. Check your turnout geometry with an NMRA gauge for proper clearances, and make any modifications needed.
See the articles on turnouts for more information. There are also articles on the popular PECO Insulfrog and PECO Electrofrog and how to make modifications if needed, which also apply to other commercially available switches. There is also an article about the new PECO Unifrog.
==== The Cost of Converting My Motive Power Fleet for Digital Command Control will be Too Costly! ====
;No one says you have to convert your entire fleet of locomotives to Digital Command Control immediately.
As you’ll see below, you only need to convert those you use frequently. It might not be the most cost-effective option to convert some older locomotives, and others might have mechanical issues that need to be fixed first. But hey, you can always expand your DCC locomotive fleet as time and money allow.
There are also a bunch of well-detailed, smooth-running commercial DCC locomotives available that come with DCC already installed and ready to run on your DCC layout. And guess what? Some of them even have sound on board!
Some modellers decided to make the switch to DCC and organized their locomotive fleet in this way:
# Locomotives they had no attachment to. These would not be converted to DCC, instead they would be sold off.
# Locomotives they liked. Some may not be possible to convert. Decisions were based on desire to keep the locomotive and ease of conversion. Some would be converted to DCC operation, those where it was not possible or too difficult would either be moved to category 1 or become display models.
# Locomotives they wanted to keep and could be converted to DCC.
During this process, the fleet would often be reduced, and the money from selling extra locomotives helped pay for the conversions and buying new DCC-equipped locomotives. Plus, they got to add some super detailed locomotives to their roster!
==== Sound is an Unnecessary Expense! ====
Some modellers don’t care for sound and prefer silent trains, but this is one of those things where many people will say that once you have a sound locomotive, it totally changes the game. It’s always a hot topic for discussion.
==== Digital Command Control Will Be Obsolete Soon! ====
The purpose of the NMRA DCC Standard was to establish a standardized protocol that would alleviate the confusion inherent in the command control market. DCC technology is not poised to become obsolete in the foreseeable future. The standard is defined at the rail level, not at the throttle or decoder.
Command control systems have emerged on the market in recent years that are not DCC compatible. While these systems may offer intriguing features or engaging user interfaces, they are also proprietary, requiring their own hardware and software. The path to DCC adoption was paved with noble intentions, but many modellers invested in commercial command control systems only to find their investment rendered obsolete when the manufacturer or importer ceased operations. Consequently, command control systems did not gain widespread popularity until the advent of the NMRA’s DCC Standards.
Similar to the early days of television, where competing standards existed, the industry thrived once the compatibility issue was resolved. An NTSC color set from the 1990s could be transported back in time to the 1950s and function seamlessly. A black and white set equipped with vacuum tubes from 1961 would have continued to operate until the day analog broadcasting ceased. (The experience outside of North America would have been different.)
The Internet operates in a similar manner. While it is constantly evolving with new services, the underlying protocols have remained largely unchanged for decades, enabling innovation while maintaining compatibility with all equipment and services.
== Available Videos ==
The DCCWiki has a number of curated videos available.
These videos may be helpful: 
* Overview of Basic DCC Systems
* A comparison of Digitrax and NCE Throttles
Category:DCC
Category:DCC_Tutorial