Large Scale Train Control Systems – Introduction

Last Updated: 15 August 2021

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

Analogue / DC
Digital / DCC
RC
Live Steam – not covered on this page yet

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 a brief overview of the different systems, and some pros and cons on each of them.

Track Power <> Battery Power?

Track Power

Most locomotives are track powered by default. This means the track is ‘Live’, in the sense that the rails are powered by an external power source. The locomotive then has some kind of mechanism to pick up the power from the track: either via the wheels, or via extra pick-ups. Additionally, the locomotive has some electronics onboard to drive the motor to get your train moving.

Track power is a great option and has many advantages, but also a major drawback that might push people towards battery power operation: track maintenance. It’s important to keep the rails clean to guarantee power pick up so the locomotives keep running smooth. If the rails are dirty, the ride will be jerky (especially on lower speeds), or locomotives might even come to a standstill.

Locomotives are powered by the track, but can be controlled in two different ways: via the track (‘DC’ or ‘DCC’), or via onboard electronics (‘R/C’).

Pros & Cons:
+ Easy to operate: lay down some tracks, hook up to a power source, place your brand new locomotive on the rails, and you’re good to go
+ No need to worry about charging batteries
– Ride quality depends on the power pick-up, which requires (a little) maintenance
– Traditional ‘DC’ control for track power works great but is limited in features, and the upgrade to more advanced ‘DCC’ control costs you some more (time & money!)

Battery Power

When converting a locomotive to battery power (or buying a battery powered locomotive from the factory), the locomotive contains everything it needs to run. Track power pick-up is irrelevant, and the track is considered ‘Dead’. Most track sections are brass or stainless steel because they’re great for outdoor use because of their sturdiness, but if you’re running battery powered locomotives only, in theory you could run on plastic track.

Onboard, the locomotive contains a battery, and some control electronics to drive the motor, and then some more electronics to allow the speed and direction to be controlled (see ‘R/C’).

A drawback is that 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). Of course, your locomotive is now very dependent on that piece of rolling stock, leaving you with less flexibility about what you want to run with it.

Pros & Cons:
+ Track is ‘Dead’, thus you don’t need to worry about track maintenance as much
+ Conceptually very simple
– Most locomotives come with DC and/or DCC electronics by default, which you’re paying a premium for, but you don’t need those
– You need to convert locomotives
– Batteries take up space, and there’s possibly not enough room in the locomotive
– Limited running time

Control Systems

Track Power – Analogue DC

A ‘DC’ speed controller supplies power to the track. Depending on how much voltage there is on the track, the motor inside the locomotive will make it run faster or slower. Direction is also controlled by the polarity of the DC power applied to the rails.

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. Each locomotive on the track section will respond, unless more complex wiring is introduced to create separated track sections.

Track Power – Digital DCC

The ‘DCC’ (Digital Command Control) standard is defined by the NMRA and is used to describe almost any kind of digital system used to operate 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.

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 a decoder with number 2 (programmed by the user), and a SD-40 diesel loco carries number 40. Let’s say I want to run the NW2, so I select the #2 on the screen of my DCC controller. 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.

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.

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
+ Accessory control
– 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 other item is controllable on its own. All other items do nothing.

RC (Radio Control)

In an RC system, you have a handheld controller which sends its commands over the air to an 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.

The RC receiver inside the locomotive do not really have an ‘address’ (like they have in a DCC system), the receiver specify a certain frequency channel they can be operated on. Your handheld controller then has the option to switch between those channels, targeting the desired receiver/locomotive. So if an RC system is described as having 8 channels, it means you can operate up to 8 locomotives with it.

Most RC systems rely on locomotives using battery power, but it’s also possible to still use track power to power the locomotives.

There are a lot of RC systems available, many of which are non-standardized, proprietary systems and therefore difficult to use with other systems.

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 from track (when using battery powered locomotives)
– Limited range
– Radio interference

Bottom line: R/C 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.

Large Scale Train Info

Some potentially useful info about the world of Large Scale trains (G Scale, 2m Scale, 1 Scale)