How to Wire A Model Railroad


Proper wiring is an essential component of a working model railroad. Here you will learn how to correctly wire a model railroad, regardless of which specific layout you are planning to operate under.

The simple method to wire a model railroad is when it consists of a transformer with two wires that will only work for an oval measuring 40-60″ in length. Voltage drops that occur from over distance and with multiple locomotives running simultaneously call for DC or DCC wiring methods to be utilized.

The following topics will be discussed in the sections below: tools and materials needed, wire types and sizes, how tracks are wired and why specific methods are used to wire a model railroad. Keep reading to learn how to make your model railroad come to life.

How Do You Wire A Model Railroad?

Before you get going, it’s recommended that you draw out a design on paper. You can find instructions for filling out a wiring diagram here.  If you are a beginner, you are encouraged to scroll through the section below, where you can review some of the fundamentals of wiring a model railroad.

Step One: A Review of Electronics

In the succeeding sections, you may notice some terms that you are unfamiliar with. The first step to properly wiring a model railroad is a brief refresher course on electrical terms. If you are already well-versed in the world of electrons and circuits, you can skip this first section altogether.

 

  • Open Circuit
  • Closed Circuit
  • Short Circuit
 

A path through which electrons flow

An uninterrupted path (i.e., a switch)

Electrons are flowing (i.e., a switch is on) Electrons bypass the device being operated

Circuit Breaker Prevents devices from becoming damaged in a short circuit by automatically shutting the power off
Voltage The force causing electrons to move
Current The rate of flow for electrons in closed circuit
Resistance Holds or slows down the flow of electrons
Transformer Supplies voltage to the circuit
Resistor A device that applies electrical resistance
Incandescent Lights Able to take both AC & DC voltage, can be plugged into either terminal (positive or negative)
LED Lights, contain two parts:

  • Long Lead
  • Short Lead
Can only take DC voltage, can last a long time if paired with the right resistor

Plugged into positive terminal

Plugged into negative terminal 

Capacitor Devices holding a charge even when the power supply is off
Potentiometer Increases the resistance with the turn of a dial, suitable for dimming lights

Another critical thing to remember when you wire a model railroad is Ohm’s Law, as this will help ensure that you are using the right parts. The equation is commonly expressed as Voltage= Current/Resistance.

Purchase A Multimeter for Troubleshooting

A multimeter (aka an electric test meter) is a must-use tool for anyone working with electricity, including model railroad builders. These instruments allow you to measure current, resistance, and voltage. There are several possible scenarios during this process in which you will need to do a little troubleshooting.

Here  are some examples of troubleshooting you can do with a multimeter:

  • You wired a circuit, but the device won’t operate: Test voltage from the transformer outward.
  • Trains are not running smoothly: You should test track voltage at various points, where voltage may be lost to track or connect resistance.
  • Testing for the occurrence of short circuits

For instructions on using a multimeter, you are certainly encouraged to view the owner’s manual for the specific model you purchased. You can also find more detailed instructions on how to use a multimeter in model railroad applications.

model railroad wiring
David B. Photo

Managing Wires: How Do You Organize Wires in A Model Railroad?

It’s easy to become over-ambitious and not plan things out ahead of time. The consequence of this is that the wires become a jumbled mess as you begin to expand your operation. Give any model rail hobbyist plenty of free time and space, and their imagination is bound to run wild. 

This is a big part of what makes this hobby so fun, but it is important to remember the importance of proper organization. Here you will find some guidelines for how to keep your wiring organized:

  • Drill holes in the table’s joists: You can always staple the wires to the joists, but this can make it too easy for someone reaching under the table to grab the wire inadvertently. A simple solution to keep the wires better organized is to feed them through holes in the joists directly underneath the track above.
  • Consider using an extruded foam base: This hobbyist came up with an idea to feed their wires through the extruded foam, allowing them to work on wiring while sitting on a stool.

How to Avoid Short Circuits in Your Model Railroad

With proper setup, you can avoid causing short circuits. If these occur, you will have to spend a bunch of time troubleshooting to find the problem area. 

  • In a model railroad track, one of the rails acts as a positive wire and the other acts as a negative wire.
    • The transformer is connected to the positive terminal.
    • Your power pack’s negative terminal is connected to the opposite rail, which carries electrons back to the power unit.
  • Use red wires for the positive wire and black for the negative wire.
  • Use a manual toggle switch to reverse the polarity for a reversing loop isolated from the mainline track.
  • Separate mainline tracks and isolated loops by using rail gaps—plastic rail joiners between the tracks.

Bus vs. Star Distribution: What’s the Difference?

As soon as you start researching the topic of model train wiring, you will hear the terms “bus” and “star.”  Don’t worry if this sounds confusing; it’s a pretty straightforward process:

  • Bus: Long, medium, or heavy-gauge wire is strung under the layout, from the transformer terminal blocks to the rest of the track; drop-off wires are connected to accessories (like lights, signals, etc.)
  • Star: Large gauge wire is strung and run to strategic distribution points (called Hubs) under the layout. Drop wires progress outwards to accessories so that the wiring layout resembles a star.

Which wiring distribution is better? Neither the star nor bus distribution is better than the alternative in general. Still, there are certain situations in which you may find it advantageous to use one over the other.

 

Bus Star
Good for maximizing track power Works well if you have several accessories
May cause radio interference in a command control system Easy to work in variable power points where tracks and accessories are powered differently

How Do You Wire Switches/Turnouts in Model Railroads?

In model railroading, you will often hear switches being referred to as “turnouts”. This helps avoid confusion with actual electrical switches. Regardless of which terminology you choose to use, these parts of the track layout come with special wiring considerations. 

The frog is the part where the two tracks join together. Before completing the wiring process, you should take notice of the different types of turnouts used in model railroads:

  • Insulated frog: Plastic is placed between the two rails to separate the metal pieces from each rail. This technology prevents short circuits from occurring.
  • Powered frog: Wing rails are connected to the guard rails, and both tracks are metal in the spot where they join. The benefit of these is that you won’t need to install rail gaps for the branch, and you won’t need to install a separate electric switch to turn the branch track on and off. 

As a result, these two different types of switches are wired differently. In insulated frogs, the switch will exist as a small gap where the train wheels will not be powered. You will hear turnouts being referred to as “DCC-friendly” or “Electrically Reliable.” These are insulated frogs, where each switch-point rail is always the same polarity as the adjacent track. You can learn more about the intricacies of wiring turnouts here

wire a model railroad
David B. Photo

What Materials Do You Need to Wire A Model Railroad?

Several tools and materials are required to wire a model railroad. Continue below to learn about which kinds of wire and which tools may be necessary to get the job done.

What Kind of Wire Do You Use for Model Railroads?

Model railroads typically use one of two different types of wire— solid or stranded wire. It’s up to you which type of wire you want to use. There are advantages and disadvantages to each type of wiring.

 

Wire Type Pros Cons
Solid  Flexible, not as easy to break/cut with repeated bending  Can be more difficult to keep organized
Stranded Easy to connect to screw terminals, less susceptible to short circuits since it won’t easily wander off to the opposite terminal Breaks easier if bent repeatedly

Pay special attention to the wire gauge selection. The wire gauge directly impacts the amount of resistance in the wire. Improper sizing means that specific devices within your track will not work as they usually should.

Here are some guidelines for proper wire gauge sizing:

  • For track power bus: 14-gauge wire or stronger (Smaller gauge numbers indicate a stronger wire.)
  • For feeder wires: 18-gauge wire

What Tools Are Needed for Wiring A Model Railroad Track?

The wiring process is made a lot easier if you use appropriately sized tools for the job and ensure that you have all the tools on hand before you start the project. Here are the tools you are likely to use during the process:

 

Analog (DC) vs. DCC Wiring in Model Railroads

The primary difference between DC(a.k.a Analog) and DCC is that the former relies entirely on voltage and polarity to move the train. At the same time, DCC wiring supplies a constant level of power to the track. If this is your first model railroad, please be advised that there are aspects of DCC wiring that make it more complex. 

For one thing, it will be difficult to circumvent the need for soldering to be performed somewhere along the way. The section below serves as a guide to the fundamentals of how model railroads are wired. You are encouraged to review these before you start making purchases so that you know which materials and tools you will need.

Analog Method- Block Wiring

This type of method involves the separation of different sections of the track via the use of rail gaps, or narrow gaps cut through the metal rails. This allows you to operate two trains off of the same setup. You can even have two operators standing side-by-side, each holding its control panel that is connected to its locomotive.

Materials needed:

  • Rail gaps
  • DC power packs
  • Control panel with a toggle switch
  • Slide switches
  • Multiple transformers (if you want to run more than one train)
  • An automatic block detection device (to automate the use of specific accessories)
  • Terminal strip

Even though the various sections are isolated, the track will still look indistinguishable from a continuous track. The locomotives can be moved from one block in the track layout to another via a toggle switch.  Note: You cannot operate two different locomotives on the same block at the same time. 

How Do You Wire Blocks in Model Railroads?

If you want to operate two trains simultaneously, you will need to construct at least three separate blocks of the track. You will give yourself even more flexibility if you can manage to build more than three blocks. 

  • Plan a layout: The simplest schematic includes a simple oval
  • Make sure that you have enough toggle switches: Each block will need its SPDT toggle switch. You might consider going with an SPDT switch that doesn’t connect power in either direction (if you are constructing sidings where trains are being parked).
  • Use a bus for the common negative wire: Run the bus wire all around the bottom of your track layout. (This is usually done underneath the plywood base of the track.)

 

    1. It’s best practice to install one track feeder for every 3 feet of track.
      • Feeder wires become necessary due to the anticipated voltage drops along the course of the track.
    2. Attach each track feeder to the bus via the use of a terminal strip.
    3. Connect each block to its toggle switch by using a feeder wire.
    4. Place rail gaps in alternating blocks. The rail not containing any gaps is called the common rail. This way, you won’t have to purchase pricey DPDT switches.
  • Connect tract terminals to the power packs: A cab-control layout works the easiest with identical DC Power Packs.
wire a model railroad
David B. Photo

Wiring A Reverse Loop

Things will start getting a little more complicated if you construct a reverse loop. The advantage of reverse loops is that they make it possible to change a train’s direction as you please. Without a reverse loop, wire, or turntable, the only way to change direction is to put the train in reverse.

Here is why it is more difficult to wire reverse loops:

  • You need a special electrical circuit to prevent a short.
  • You need to cut gaps in both rails; the standard rail method won’t work.
  • You need to change the polarity for the two rails in both the reverse loop and in the block of track that comes before the reverse loop.

This entire process can be made a little easier if you can get your hands on a selector, like the Atlas 215 Selector Switch. This consists of 4 separate SPDT slide switches. The selector has screw connections and can be used in conjunction with two power packs to operate four track blocks. 

How to DCC Wire A Model Railroad

The difference between DC analog track layouts and DCC layouts is that a DCC system continually supplies power to the entire track and all of its accessories. With this technology, you can move more than one locomotive on the track at a time without having to separate into separate blocks in the way that you would with an analog setup.

Here the materials that a DCC track typically requires:

  • DCC power bus wire
    • A stronger wire is needed to handle the amperage.
    • 14-gauge or stronger is the standard. 
    • Red and black coated wires to separate positive and negative terminals 
  • Feeder wire to connect to the bus wire
  • Command Center/Booster: typically provides power for the entire track layout.
  • There are decoders in each locomotive.
  • Tools:
    • Wire strippers
    • Soldering Iron (25W or stronger)
    • Multimeter
    • Drill bits
    • Scratch Brush
    • Pliers
    • Suitcase-style connectors
    • Insulation tape or heat shrink

Getting Started- Find Your Multimeter

You should make sure that you have a working multimeter before you get going. Checking for short circuits along the way is recommended. Otherwise, you will be running the risk of causing a short circuit that may be difficult to locate later on. 

wire a model railroad
David B. Photo

Here’s why this is so important, particularly in DCC layouts:

  • An uncontrolled short has as much power as a 60-watt light bulb.
  • There is a zero-tolerance for transient short circuits; the booster trips and shuts down rapidly.
  • As such, finish checking for short circuits before you connect the booster.

What Does A Booster Do in A DCC Layout?

Boosters are devices that take instructions from the command station and create a digital signal sent out to the track. Not only does the booster need data from the command station to function, but it also needs a source of power.

The booster is responsible for converting either DC or AC power from the outlet into a DC power source that can run the track. As mentioned in the section above, it also protects against short circuits. Boosters will typically deliver 4-5 amps of current, but some deliver up to 10.

If you need more than one booster, you will need to divide your track layout into separate power districts. This detail is also significant: always use boosters with the same current rating. For example, there is no case where it is acceptable to have an 8A booster in one district and a 5A unit in another.

Fitting Locomotives with Decoders

Every locomotive within a DCC setup needs to be fitted with a decoder device that is programmed to accept signals from the power or control unit. You can find decoders online, along with instructions for how to install them. This is a good resource for step-by-step instructions.

How to Wire A DCC Power Bus

The power bus is the wiring underneath the main track. Connected to the power bus are various track feeder wires that become necessary due to anticipated voltage drops across the track. You will need a wire that is strong enough to deliver enough voltage across the entire layout. Wires that are 14-gauge or stronger work the best for DCC systems.

  • Don’t connect the booster until every portion of the layout has been tested for short circuits.
  • You can run the wire under the table or above, as discussed earlier in this article.
  • Make sure that you are using the proper red and black wires. Red= positive, Black=negative.
  • You can keep wires organized under a table by drilling a set of holes in the table joists and feeding the wires through.
wire a model railroad
David B. Photo

Connecting Feeding Wires to The Rail

The most versatile way to add the feeder wires to the track is by soldering the wire to the rail. This requires a fairly robust soldering iron (25W at the very least). This soldering iron kit would be suitable for these purposes.

Here is how to solder the dropper wires to the rail:

 

  1. Use a half-round or square needle file to clean the rail all way down to the shiny bare metal, removing all oil and debris contamination 
  2. Drill a hole through the roadbed next to the rail to bring the wire up from below the track.
  3. Use No.22 copper wire for the initial track feeders.
  4. Apply a small amount of rosin flux and rosin-core solder.
  5. You can find more specific guidelines and instructions here.

Connecting Feeder Wires to The Track Bus

To wire a model railroad using a DCC layout, it is considered best practice to install a feeder wire for every rail (measuring 3 feet in length). The feeder wires don’t have to be of the same gauge strength as the power bus.

Method 1: Suitcase Connecters

To cut down on the amount of soldering needed, you can simply connect the feeder wires to the power bus using suitcase connectors. These come with marked ports for both the positive and negative wires, making them simple to use. The installation process will require the following tools: either a crimper tool or slip joint pliers

 

  1. Slip a suitcase connector onto each power bus wire (1 connector to the black wire, and 1 wire to the red wire)
  2. Connect the appropriate feeder wires to each suitcase connector.
  3. Suitcase connectors will typically have a window you can peer into to ensure that the feeder wire is fully connected.
  4. Clampdown on the suitcase connector to close it, using either a crimping tool or slip joint pliers.
Method 2: Soldering the Wires

Alternatively, you can solder the joints. To solder the dropper wires to the bus wires, you will need a soldering gun that is strong enough for the job, at least 25W. Soldered connections can be made on either the outside or the bottom of the rail.

Note: Soldering will involve the use of hot material that may drip on your clothing and skin. You are encouraged to wear protective clothing, such as long sleeves and pants. Safety glasses also may be necessary if you are working underneath a table. 

wire a model railroad
David B. Photo

Here is how you can splice the ends of the two wires together:

 

  1. Use a wire stripper to strip off the ends of the wires being connected.
  2. Place a section of shrink tubing over the end of one of the wires past the section you stripped off.
  3. Wrap the bare ends of the wires tightly around each other.
  4. Move the heat shrink tubing over the connection while the solder is still hot.
  5. You may use the side of the soldering iron to heat the shrink tubing if the joined ends are not hot enough.

For Sectional Layouts: Install Breakpoints Between Sections

If you choose to wire your entire DCC layout continuously, then you won’t be able to unplug any sections from the wiring bus. If you think that you will ever need to remove any sections from the layout, you will undoubtedly need to install breakpoints.

To install breakpoints, you will need:

  • Power plug connectors 
  • Your soldering equipment
  • A wire stripper

Start by stripping back the red and black wires and then solder them to create a firm connection. After this, things should be simple and straightforward, as these one-way power connectors have a marking for the black wire.

Connecting the Booster to The Power Supply

It cannot be overstated how important it is to never wire boosters in parallel. This is an excellent way to fry your boosters and therefore render them useless. Specific instructions for wiring your booster, as well as adding other boosters to the layout, should be found in the instruction model for the model you purchased.

Final Thoughts

In summary, there are two methods commonly used to wire a model railroad:

  • DC Wiring (also called Analog)
  • Trains operate based on voltage and power.
  • To operate two trains or more at once, you need to construct separate blocks powered by their own DC Power Packs.
  • DCC Wiring (Digital Command Control)
  • Constant power is delivered to the tracks.
  • Source of power: A bus wire running underneath the entire layout.
  • Wire gauge size: 14 or stronger to deliver consistent power through the entire track.
  • Feeder wires should be connected to every 3 feet of rail.

 

Josef

Lifelong Rail Enthusiast and Owner of Worldwide Rails

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