Wiring for Digital Command Control
Summary: Wiring for DCC isn't as complicated as some would have you believe, but it is a very important component to the entire Digital Command Control Experience. Good wiring is essential for reliable operation with Digital Command Control.
Due to the large number of related topics to wiring, this article is meant as a jumping off point to other articles. Brief summaries of each topic, with a link to the primary article for more detailed information.
Whether you are starting your first layout, or converting an existing layout, this is a good place to start.
DCC Wiring Topics
- Wiring tools - First things first. You'll need some basic tools. Some simple electrical tools can be made for a few dollars that can save you hours of time and less frustration while wiring your layout. Always keep in mind that you do not buy tools, you invest in them.
- Wiring Complexity - Wiring for your layout can be as simple or as complex as needed or desired for a given level of capabilities expected from the layout.
- Wiring Color Code - It's best to develop a colour code when you're just getting started. However, it's important to stick to it! This article explains picking a wire colour code as well as wire sourcing to help you stick to your code.
- Wire Sizes and Spacing - Are these wire sizes overkill? How far apart should the bus feeders be? Answers to these, and more questions.
- Wire Types - Selecting the correct type of wire is important for the reliability of the DCC signal on the track.
- Voltage Drop - Model railroads have low tolerance for voltage drops throughout the layout. Be sure to use the proper wire gauge and feeder spacing.
- Do I Need to Twist the Bus Wires? The question everyone asks.
- Wiring Tips and Tricks
- Block detection - Block detection is a method for detecting rolling stock within a given section of track with the use of stationary decoders.
- No common rail wiring - In wiring for DC (analog) operations, modellers usually had a wire that was common to all blocks, in other words the rail it connected to was ungapped over the whole layout. Don't do this for DCC!
- Reverse sections - Although the electrical phase on the rails does not control the direction of the loco, you still have to deal with reverse sections on your layout. If the track turns around back onto itself, the right rail will come in contact with the left rail which will cause a short circuit; the same as placing a metal object across the rails.
- Turntables - Wiring turntables
- Turnouts - Wiring turnouts
- Crossings - Wiring diamond crossings, single and double slips, scissor crossings, etc.
Notes about Direct Current (Analog) Operations
- Conversion to Digital Command Control involves upgrading the wiring to Digital Command Control's requirements. If the plan is to convert to Digital Command Control in the future, wire the layout for Digital Command Control from the beginning.
- 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, was 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.
- You can read the manual for the LT100 here.
- If CV 29 is set correctly for Alternate Power Sources, it 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 decoder.