Wiring Info

Wiring Notes

Compiled from notes given at a NMRA Convention

Pictures and diagrams are still to be added to this page

Used with permission by MRRC

Build a Short Detecting Beeper BEFORE You Start Any Wiring;

This recommendation is the first in the track wiring section. If you wait until you find out you have shorts, it's too late. Don't wait until you wish you had made one of these. Do it now. It only takes a few minutes and a few dollars to put together and will save hours of debugging .

Buy a 273-059 buzzer from Tandy and a 270-325 9V battery clip [JayCar & Dick Smith have equivalents]. And, of course, a 9V battery. Attach this instead of a booster to your track while doing all wiring, any wiring error that you make that results in a short, will cause an immediate beep.

You will need to move the beeper to each booster district as you wire. Alternately, if you have a team wiring several districts at once, temporarily jumper the main booster feeders together so only one beeper is needed. Clip to the track with alligator lips. Be sure the boosters are not connected to the track. I cannot emphasize this enough. The booster will appear as a short to the beeper. Nothing but the beeper should be attached to the track.

Identify your track in some way.

DCC track power is a form of AC but electrically behaves like DC, keep thinking of it the same way as you did with DC. You still have two wires and you need to know which is which. This is especially important topside. With your winding every which way, it's easy to loose track.

Call them "+" and "-", "A" and "B", whatever you like. Avoid "inside" and "outside" rail because unless you have a simple oval, chances are your inside rail will become your outside rail at some point.

Attach Your Feeders With Screws Terminals or by Solder.

If you have a short that is troublesome to find, you will be able to disconnect the feeders. Otherwise you will have to start cutting your carefully soldered wires. I've seen this happen more than once, I'm afraid, I prefer soldered connections, too. But here, soldering will work against your troubleshooting efforts but there are ways. [refer divide and concur]

Good track connection and practice

Make sure you lay your track and join rails together in a manner that you think is the right way.

Some people don't like to solder too many pieces of track together due to expansion considerations. You definitely need to consider the temperature swing in your layout room. Is it in the house or out in the garage? So after deciding what your track laying practices are going to be, follow these basic rules:

Every piece of track should be wired to something. That can be another piece of track or a wire. The wire can be a feeder or a jumper from the adjacent rail. DO NOT count on a metal joiner to carry power to the next rail. It WILL let you down eventually.

Insulate both rails directly opposite between booster districts.

Insulate both rails between reverse sections and ensure that the joints a adjacent to each other. You need a solid short circuit to trip the auto reverse units that are offered by MRC, Lenz and particularly with Auto Reverse between boosters.

Divide and Conquer Bus Feeder Problems.

Consider dividing any individual bus into a series of zones that can be switched off. This allows you to quickly isolate the section of trackwork that is creating the problem. This means that one of the bus can be cut and linked via switch to the to the feeder. The switch can be located just under the rear of the fascia out of site.

To run the layout just turn on all the switches to a trouble check , turn them all off and then turn them on one by one, its that simple.

Running multiple bus's to remote points of the layout back to a switch panel can create what we were seeking to remove in the first place.

Do Not Have a Common Rail or Common Wire Between Booster Districts.

NO! - Shorts could result if either booster is set to auto reverse. When running a large layout all the power used by the boosters will have to be returned via a single wire. A couple of 5 amp booster can create 150 watts of power and with light wiring and or a dry joint there is a fire risk.

QUESTION: How do I handle a Simple Reverse Loop or Wye?

A simple reverse loop or Wye is one that connects to your main trackage through only 1 track.

A simple reverse loop or Wye can be automated simply using multiple boosters or a auto reverse module. This will allow you locomotives to smoothly travel from through the reverse loop.

The only problem with this arrangement is that only one locomotive can be cleared at a time, so if you wire this feature to more than one reverse loop and two locomotives arrive at the same time a short occurs one locomotive will have to be cleared manually.

Remember that all locomotives in the reverse loop remain direction and speed independent and this allows you to use the reverse loop as a functioning parts of the model railroad - no lost real estate.

QUESTION: Why use two or more boosters?

This requires we look at current thinking on how to use multiple boosters. Traditionally boosters are added as required and generally hooked them up in series i.e.. chained one to the other In practice these is a problem , if a short occurs whole district stops and the failure of a single booster will stop the whole railroad as it effectively isolates a section of the railroad.

Systems wired in parallel [side by side] to increase reliability. Wire a layout so that booster 1 controls the main and booster 2 all the yards [Refer fig 1], we can see that problems in either area is now isolated. If a additional booster are required ,the main is split onto 1 & 2 while the yards would be wired to 3 & 4.

Yards are one area were a separate booster offer the maximum benefit due to the high number of movements.

This arrangement makes trouble shooting boosters easier, just flip wires and if the problem changes zones, the problem lies in the booster, if not it lies in the layout.

Now the addition of more boosters offer not only more power but increased reliability.

QUESTION: How do you wire a dogbone layout?

These is no wrong way with DCC but there are better ways. If you wire the track on the two straight as a A & B - A & B that is you create a reverse loop at each end of the layout you will save a lot of time latter. Why you ask, we could wire the layout as a continuous loop and avoid that problem. Well yes , but you will then create a reverse loop anywhere you try to cross from one track to the other.

Now DCC makes this easier but it is a case of working smarter not harder. Study Fig 3 and then convert it to a simple loop and you will see what I mean [Thanks to the NMRA Modular Group]

SUGGESTION: Wiring - Develop A Colour Code - And Stick To It!

You can source good quality wire from any electrical wholesaler in your area.

If you use the bare copper wire as part of your feeder system, be careful it doesn't contact anything that is grounded to your home wiring. Worse, beware of contacting any other voltage sources - such as the wires going to your booster power transformer.

If you are installing a dedicated programming track and is switch as per the System One manual remember to run feeder from the programming track in a different colour code to the normal track code. If you were to feed the power from the bus into the programming input on the Command Station you will damage the unit.

SUGGESTION: How often should I place a feeder ?

As stunning as it may sound , the nickel silver rail, which we regard as a good conductor is actually a poor conductor. Alan Gartner's DCC site has a excellent explanation so use the web.


The best way to look at the issue is to realize copper has 1/100 the loses that nickel silver rail has for a equivalent cross section.

After reviewing Alan's notes and after speaking to other modelers who have used DCC for 20+ years, it is the copper that runs the railroad and just solder every piece of track regardless of length - that as simple as it gets.

Question: What is the best way to setout the wiring.

In my opinion the principle problem that can be created by the layout is the noise generated by the activity on the layout.

This noise is I believe the principle reason why one layout has no problems and another unexplainable problems.

This noise generated has three principle sources, Track, Power and Command Bus.

The noise on the command bus is created simply by the action of multiple throttle just begin plugged and unplugged. This can also be exacerbated by the style of plug used. This is a problem for the manufacturers to handle and there is little that we can do to alter this.

Track generates it noise by our trains simply moving, points begin opened and closed. Here we have more opportunity to help quieten this down.

Anything that creates arcing, even if you cannot see it should be reduced.

Ensure that locomotives have GOOD pickups. This means wipers on all pickups wheels, hardwired to our decoder. Look at motors, paying particular attention to the commutators. Clean commutators, check brush tensions and contact on the commutator. A little Conducta Lube on the commutator and track helps here.

With points DCC Friendly switches are the best way to go. If you have already wired the layout consider power routing the frog and stop using the blade as a open air switch.

The final item is the two bus's and here we have some real opportunity to prevent all this noise begin amplified in the wiring.

With digital signals in commercial plants they will expend vast amounts of money to separate power and signal. On the model railroad all track and wiring will act as a antenna radiating noise in a uncontrolled manner.

We cannot prevent all noise but we can help prevent it getting into our command bus. With the flat cable simply twisting the cable a few times between plug points greatly improves it ability to reject radiated noise or just replace with CAT 5.

Installing the communication bus to the front and the power bus to the rear will help prevent the two interfering with each other.

I do not like solid wire because of it ability to act as a antenna. As a bus I prefer a twisted 7 core wire to help with noise rejection and a minimum 2.5mm cross section [12g].

Feeders should be 0.5mm [16g]with a maximum length of 600mm. Under no circumstances would I consider 20g wire of any type.

Were possible the feeders should be run at 90 degs to the power bus.

Above all ensure that there are no shorts in any part of the layout. Just because the layout dose not shut down dose not mean they are not there.

Question: Were do I put my Command Station

On both the Master Series command stations and the System One command Station, the dual ports are actually a single port. They are tied pin to pin inside the command station. That "built in" simple parallel bus splitter was removed from the Power House pro due to lack of front panel space. Hence the reason it is perfectly valid to use a telephone splitter.

For those a little more technically interested.......

The basic rule is this. The closer two devices are to each other that talk to each other, the less chance of noise being a factor in the reliability of the communication. It like two people trying to talk to each other in a crowd of noise. The further apart you are form each other, the harder it is to hear each other.

From a electrical point of view there are several advantages of putting the command station in the middle of the linear terminated bus.

1) From a voltage drop standpoint, each leg handle less Cab supply current which simply means less voltage drops.

2) From a command station signal transmission standpoint, noise is reduced since noise on one leg will not crossover easily to the other leg. This essentially means the bus is split into two separate legs in this phase of communication. Since the command station is fixed in position relative to the bus. This benefit remains constant

3) From a command station signal reception standpoint, there is some improvement in that the distance between the active cab to the command station has been cut in half or less helping to reduce noise. But some noise from the remaining portion of the leg past the command station is still seen by the command station.

The noise issue varies from cab jack to cab jack since there is always some variable distance from the active cab to the command station. It still much better than a command station being at the end of the line opposite of the cab!

What is a DCC Friendly Turnout/Point?

Atlas is a good example of a DCC friendly rail switch. (Note: This does not mean that the Atlas is the best DCC friendly switch. It is a good example of a rail switch that is not power routed and is wired in the manner I suggest.)

By attaching the stock rails to the point rails, a short by the wheels or the point's to both stock rails is now unlikely. This alteration also eliminates the joiners between the closure rails and the points from being a potential lost of contact with the power bus.

Power routing of a isolated frog, and ensuring a hard wired stock rail and closure rail combined with a power routed frog.

Commercial points hinge point rail to the closure rails and are in time a major source of poor power deliver through a point less than reliable.

What is Power Routing?

Power routing was popular in DCC block control. It was a way for using specially built rail switches to turn the power on or off to a siding or yard track automatically. No additional switches or wiring was necessary. Given that DC block operations required control panels and lots of switches, you can see the appeal, especially where a yard was involved.

On a rail switch, you must power route the frog or electrically insulate it.

The task of as point is to change direction of the locomotive not act a electrical switch so the need to be employ a device designed to do the job - a switch - the electrical kind.

The switched power routing the frog can be implemented in any one of a number of ways.

Built into the switch machine like a Tortoise or NJ International.

Built into a ground throw like some made by Caboose Hobbies.

A micro switch you add like with the Switchmaster switch machines when used with a Rix bracket

A device a manufacturer intends you to add to their switch machine like those made by Atlas, Peco, etc

The important thing is that the switch is flipped at basically the same time the points flip.

Tortoise Owners: The Tortoise switch machine's contacts are rated at one amp. The Switchmaster on a Rix Rax II bracket with industrial micro switches. You will need two switches as these will changeover before the point has begun to move - instant short.

DCC Friendly Rail Switch Solves the Problem of Shorting When Using Auxiliary Contacts!

If you are using ground throws, you can use a switch built into some of them, or you can add a micro switch. Burying a micro switch is more work, but the switch will last practically forever.

For electrically powered rail switches, it is common practice to use contacts built into the switch machine or add a micro switch if no contacts are available.

If the modeler counts on the manufacturer supplied point wipers (look at a Shinohara or Peco.

FOR EXAMPLE) to power route the frog, the modelers knows eventually these will fail and power routing via contacts or micro switch will be necessary.

If the modelers adds the contacts or micro switch, a short may occur if the micro switch or contacts switch when one of the point rails is still contact with wrong rail. So the model is forced to disable the wipers on the rail switch to eliminate the potential of a short.

With DCC friendly rail switches, the point and the stock rail are at the same potential so there is no potential of a short. Point wipers or not, there is simply nothing to worry about!

Power Route ONLY the Frog.

One way to make troubleshooting easier, is to limit how far reaching trouble can be. Power route only the frog. At worst, the rail switch itself.

Points Rails are not a good way of routing power to the closure rails.

Jumper the Point & Closure rail.

This is best done at the time of installation. You can jumper using a small piece of 30 gauge wire but these tend to break or inhibit the operation of the point rail.

I have found that spot soldering a piece of 0.008" phosphor bronze wire [CMA at our web site] about 40 mm [1 3/4"] long at each end between both has enough flexure to not effect point operation but ensure reliable contact.

Don't Power Route ANY Sidings. Not Even Single Stub Sidings.

Some of you want to power route stub sidings - don't!. You need power to talk to a locomotive and if you do this you effectively isolate the locomotive from the command station.

Run two feeder wires to that stub siding just like you are going to do everywhere else - no exceptions.

Owners of Existing Layouts.

DCC friendliness is desirable, but not essential. If you have an existing layout, you need not consider uprooting your rail switches to make them DCC friendly. Depending on the make of rail switch, the degree of effort may vary. Evaluate the situation based on your ability to do the job successfully without doing harm to your rail switches. For the moment, don't worry about DCC friendliness. Definitely forget those that are hard to reach or in tunnels.

What do you do if you forgot making your rail switches DCC friendly?

Solder jumpers from each closure rail to it's corresponding point rail. This ensures good electrical contact as the years go by. This will also prevent the hinge point from becoming a hot spot should a short occur.

Do this even if you have a rail switch that wipers that bring electrical power to the points from the stock rails. Sooner or later, this will also become a spot of poor electrical contact or a hot spot during a short.​