Train Control Introduction (Analogue DC, Digital DCC, RC)

Latest update: 11 June 2016

There are a few different ways to control your model trains. In general, you’ll hear about three categories:

  • Analogue / DC
  • Digital / DCC
  • RC
  • Live Steam – not covered on this page yet, will be added in the future!

There’s also the question if you’ll be using battery or track power to power your trains. Usually, ‘Analogue / DC’ and ‘Digital / DCC’ use track power, while RC uses battery powered locomotives.

This page provides an overview of the three categories, more details can be found in the corresponding sections about each category (linked at the end of this page).

A Standard Loco:

The schematic below shows how your locomotive comes out of the box (usually). The locomotive picks up power from the track (using the wheels and pickups to do so), and has some simple onboard electronics to drive the motor.

Train Control

Analogue DC (Track Power):

The situation pictured below describes how a standard analogue DC system works. A DC speed controller supplies power to the track. Depending on how much voltage there is on the track, the locomotive will run faster or slower.

Train Control

You can only control one train per ‘loop’ of the track, unless your layout is divided into separate loops or sections. You will need a controller for each section or loop, or you need to use some more advanced electronics to for instance create an automated station circuit where two trains start and stop automatically.

Pros & Cons:
+ ‘Old’ technology –> Reliable, ‘just works’
+ Cheap
– No individual locomotive control
– Lighting appears dim at lower speeds, and turns off when locomotive is standing still
– Limited sound functions (if any)
– Lots of wiring required for complex layouts

Bottom line: By controlling the power on the track, you can control the trains.

Digital DCC (Track Power):

A digital system in a model railway context, is generally referred to as ‘DCC’.  DCC stands for ‘Digital Command Control’ and is a standard for a system to operate model railways digitally. The DCC standard is defined by the NMRA and is used to describe almost any kind of digital system used in model railways.

A DCC central station modulates the voltage on the track to encode digital messages while still providing electric power. The voltage on the track is a bipolar DC signal, more specifically a modulated pulse wave. Depending on the length of the time the voltage is applied, a ‘0’ or ‘1’ can be represented.

DCC Signal

Each locomotive is equipped with a decoder, which can ‘read’ the signals from the track. Each decoder has its own unique number. For example: an NW2 diesel loco carries number 2 (programmed by the user), and a SD-40 diesel loco carries number 40. I want to run the NW2, so I select the #2 on the screen of my controller. The controller then talks to the central station which then tells the NW2 to move. The central station unit knows the NW2 carries a decoder with number 2, so in order to talk with the decoder, the central station will modulate the signal on the track to carry the number 2 by using a combination of digital 0’s and 1’s. The decoder in the NW2 knows he is addressed and will then perform the desired actions, while the SD-40 does nothing as it only listens to the number 40. This is a simplified example, in reality it’s a lot more complex than this.

Train Control

Not only locomotives, but also switches, signals, uncouplers and other accessories may carry their own decoder. This way, every single item can be adressed and controlled by the DCC central station.

Schema DCC Basics
Schema DCC en” by PRZ (JPEG version), WhiteTimberwolf (SVG version) – JPEG version. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

The way these communications happen (choosing addresses, which action a locomotive has to perform etcetera), is standardized in the DCC standard. This way, a digital central station from for instance Massoth may communicate with an LGB or ZIMO decoder as long as both conform to the DCC standard.

Pros & Cons:
+ Control every locomotive individually
+ Lighting and sound can be switched on even when locomotive is standing still
– Expensive
– Learning curve

Bottom line: Track power is always on. Each item on your layout has an address number. By entering this number in your controller, only that one locomotive, switch or whatever is controllable on its own. All other items stay still.

Battery Power?

Battery powered trains do not depend on the rails to supply power to the locomotive. The idea is simple: put a battery in a locomotive, a motor controller and an RC (Radio Control) receiver.

Using a handheld controller, you can control your trains without worrying about poor track contact. However, space inside a locomotive usually is limited so fitting a battery and the control electronics inside can be difficult. Many people use for instance a boxcar where they store the batteries and control electronics. The idea is that you don’t have to modify your locomotive that much, and you can fit larger batteries (meaning longer running time).

Train Control

Pros & Cons:
+ Independent from track power
+ Ideal for small to medium size layouts
– Batteries take up space, possibly not enough room in locomotive
– Limited running time

RC (Battery Power & Track Power):

I mentioned an ‘RC receiver’ above… In an RC system, you can have one or more handheld controllers, which send their commands over the air to the RC receiver inside a locomotive. This way, train control is completely independent from the track, which is different from DC and DCC as those systems control locomotives via the rails.

There are a lot of RC systems available, many of which are proprietary systems and therefore difficult to use with other systems. While most RC systems rely on using battery power, some also use track power to power the locomotives.

Many RC systems use the 2,4 Ghz frequency, which means you might suffer from interference from nearby radio sources (phone, Wi-Fi, microwave, Bluetooth …). The motors and electronics inside your locomotive cause interference as well.

Pros & Cons:
+ Independent trom track
– Limited range
– Radio interference

Bottom line: RC means controllers communicate with your locomotive over the air using radio waves. Trains are powered by either track or battery power, the latter being a more common choice.

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