# DCC with Digitrax, Wiring How to.



## Massey

Hey Guys. Many of you know I am building my home layout now. I thought this was a good time to go over some basic DCC wiring and if there are any questions please feel free to ask.

First off I am using Digitrax devices in this how-to mainly because that is what I own and what I am most framiliar with. Other systems connect in a similar fashion.

The equipment we will be discussing today is the Digitrax DCS 100 (DB150 is similar), The PS515 5 amp SELV power supply, PM4/42, and the PS12 (12V 300ma power supply)

A couple of terms that should be mentioned here. 

1. Common rail wiring: This is where one rail throughout the entire layout is electrically the same at all times and is tied to one pole of the DC power supply, usually the negative. This setup should not be used in DCC systems.

2. Power District: An electrically isolated area of track that runs on it's own power booster or power manager. If a short occurs in one power district it will only effect that district and not the entire layout.

3. Programming Track: A seperate track or isolated area of track used in the programing of decoders. 

4. Power Manager: A device that works with the Command Station and Booster of the DCC system to manage power and help isolate short circuits.

5. Command Station: The brains of the DCC system. The command station can have the throttle or booster or both built in.

6. Booster: A device in the DCC system that takes the signal packets of the Command Station and adds them to the power going to the rails. 

7. Thottle: The device used to control the trains. The Throttle can be, tethered, radio, infra-red, or part of the booster.

8. Power Supply: Electrical device that transforms 120V household power into lower AC or DC power that can be used by the DCC system or other accessories.

9. Auto Reverser: A device that will reverse the polarity of the rails to allow things like loop backs and wyes where normally the track configuration would lead to a short circuit. The auto reverser can be part of a power manager like the PM4/42 or a stand alone device like the AR1

OK now that that is out of the way lets get started.

First off the Command station. In this case here we are going to be using the DCS100 found in the Digitrax Super Chief sets. This is a full command station and booster built into one unit. It has a power interface plug, 2 loconet jacks and 2 toggle switches. Here we are mainly going to discuss the power interface plug since that will be common to all scales.

In the picures below I have labed the different wires of the plug with different colors for easier viewing.

You will see 7 ports on the plug each will secure a wire with a screw on the top of the plug.

From left to right the connections are this:
Power 1 
Power 2 
Programing track Rail A
Ground
Programing track Rail B
Rail A
Rail B

For small layouts and simplified wiring with no power manager or reverser, and no programing track you simply need to run a wire from the Rail A and Rail B terminal to the tracks. One to each rail and it does not matter which one. Then wire the output leads from the power supply to the Power 1 and Power 2 terminals. This is as simple as it gets folks you now have DCC wired to your layout. See the picture below










For a more advanced setup using The PM4/42 Power manager see below.

Massey


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## Massey

*DCC with Power Management*

Lets kick this up a knotch here and lets talk about power management. Digitrax has 2 different but nearly the same power managers out there right now. The PM4 and PM42. They are basicly the same unit with the PM42 having a faster processor and a couple of different settings. The PM4 can be upgraded to the PM42 by simply replacing the processor chip with the updated version. This is available from Digitrax for about $10 at the time of this writing. 

Now Why would you want power management? On a small layout or loop of track you would prolly not need it but on anything larger than a 4x8 or even some 4x8s depending on the complexity of the track plan you may want to add a power district or two. Lets talk a minute about the pros and cons of power managment.

Pros.
1. Troubleshooting power issues is simplified.
2. A short circuit in one district does not effect other districts
3. Dedicated circuit breakers protect both the locomotives and the Boosters. (PM4/42s have this feature, other power managers may as well but you would need to check manufacturer's specs, not all power managers do)

Cons.
1. Higher expense.
2. More complex wiring.

IMHO the pros easily outweigh the cons. I have ran layouts with and without power managers and it is much nicer when a power manager is in place.

The PM4/42 is actually 4 seperate power managers or 4 auto reversers in one package. You can set it up with any combination of power manager or auto reverser you desire up to 4 sections. The PM4/42 can also be used with up to 4 boosters at a time. I am not going to go into detail here on how to wire the PM4/42 for each operation or configuration you would have to refer to the manual that came with the unit for that information. This unit can use the loconet for programing or is capable of running on any manufacturers DCC and DC system as a stand alone unit. If this unit is used with DC the layout must NOT use common rail wiring. 

Wiring the layout discribed in the last section was pretty simple. This is not much harder, it just takes a couple of extra steps. First off you need to decide where you want each district. (reverse loops later) Once you decide that then you need to isolate both rails parallel to each other, so that the wheels of the train cross both gaps at the exact same time. This can be done by using plastic rail joiners, or even simply cutting a gap in both rails. Just make sure that the gaps are close together so that the trains wheels cross them at the same time. Next it is time to feed power to the PM4/42.

On the bottom of the thread here I have drawn a simple schematic of the PM4/42's wiring. This just a basic wiring plan with one booster and 4 districts/reverse loops. I did not go into detail with the jumpers or what pins are for what, again refer to the manual for that. The PM4/42 needs to be supplied with it's own power. A small power supply like the Digitrax PS12 or another similar unit that will provide adequate power can be used (refer to the manual for the power supply needs). Next we need to add the booster to the mix. Remeber we used Rail A and Rail B terminals to go to the rails in the last post? Well this time we are going to feed those into the inputs of the PM4/42. Now you are ready to feed the power to the tracks. On the outputs of each channel of the PM4/42 is a Rail A and Rail B. It is required that you keep these aligned for power districts to prevent short circuits when running between power districts. I use a red for A and white for B wires to help me keep track of which is which. If when testing you find that you did get a set mixed up dont worry just swap the wires and you will be good to go. The last thing you need to do is attach a wire from the "Ground" terminal of the DCS100 to the proper pin on the PM4/42.

To wire a reversing loop it is the exact same method, but you need to take a couple other things into consideration as well. The PM4/42's terminals will need to be wired for reversing operation (refer to the manual). The entire area to be reversed will need to be isolated and it must be longer than the longest train you plan on running through the loop. (a wye that is just designed for one engine at at time only needs to be an inch or so longer than the engine but a reverse loop that is part of the main line will need to have the entire train in the loop to prevent shorts). Check the simple schematic I drew below for more information










Massey


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## Massey

*Advanced programing track*

OK now for the programing track. There are basically 4 ways to do this. 

The first is the most basic way. No dedicated programing track, all programing done on the main. This is all well and good except that for some programing functions only the engine being programmed can be on the rails. If not then all decoders on the tracks will receive the same instructions such as road number. This is not practical for large layouts but may be fine for smaller layouts with only one or two engines at any given time.

Second, is a separate dedicated programing track not attached to the layout. This works well for quite a few situations, and the programing track can be unplugged and put away when not in use.

Third, a completely separate DCC system on some test track. This is usually not worth the money unless you do lots of engine repair.

Forth is isolating a small section of track on the layout and using a DPDT switch change the rails between normal DCC and Programing track. This method I am going to explain in more detail.

In order to use the 4th method you need to isolate a section of track longer than the longest engine or decoder equipped car you plan on programing. Just like with the Reversing loop or Power district you will need to have the gaps in the rails directly across from each other so both wheels of the engine cross the gap at the same time. This is to prevent the command station from taking damage if you short the rails while in programing mode.

Once this is done you will need to wire the rails to the common terminals on a DPDT switch. Do not use a momentary switch in this location, if you do you will have to hold the switch over the entire time the engine is being programed. Some programing can take a few minutes to finish such as adding sounds to a programmable sound decoder. Next choose one side or the other and attach the Rail A and Rail B wires so that when the switch is thrown their way they will make contact with the left and right rails of the layout. Make sure that you keep the polarity the same as with the rest of the layout, just like you did with the Power districts. And last but not least run 2 new wires from the program track terminals on the Command Station to the last 2 terminals of the DPDT switch. That's it! now when the switch is thrown to DCC mode the engine will travel on the tracks just like normal, but in program mode the engine will accept programing instructions with out effecting the rest of the layout. This also provides a safety by not letting programing signals to effect all engines on the layout. The image below is a Schematic of the typical DPDT switch and a layout of the terminals of the typical DPDT switch. I will have to put a disclaimer in here: Always check the schematics of the switch you purchase, don't assume the layout of the terminals are all the same and that they are the same as I drew up. I simply drew a "typical" switch layout.










Massey


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## xrunner

Massey said:


> Hey Guys. I thought this was a good time to go over some basic DCC wiring and if there are any questions please feel free to ask.


Good thread - I'm in the process of learning all this stuff right now. Here's a couple of questions. 

I have read the manual for the DCS100 and the manual simply says to hook it to a "power supply". I thought huh - it doesn't come with a power supply? What power supply? AC or DC ... what current does the power supply have to provide? The terminals don't even have polarity shown. What power supply is it hooked to?

I want to use stationary decoders for my turnouts and control them from the controller, but how does one keep track of the position of the turnouts? I thought surely the decoder would provide a connection for an LED for an indicator, but digitrax decoder didn't have such an LED connection. Does the controller tell you which way the switch is thrown?


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## Massey

I will discuss the Power Supply and decoders here in a post or 2 bear with me I did not pre write this before posting so I am making it up as I go, based on notes in my head!! 

Massey


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## gc53dfgc

Massey, 
you better get the other two reserved threads done quickly otherwise you won't be able to edit them and will have to have Anton edit them in from other posts like what i am having to do on my DCC installs thread.


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## Massey

xrunner said:


> Good thread - I'm in the process of learning all this stuff right now. Here's a couple of questions.
> 
> I have read the manual for the DCS100 and the manual simply says to hook it to a "power supply". I thought huh - it doesn't come with a power supply? What power supply? AC or DC ... what current does the power supply have to provide? The terminals don't even have polarity shown. What power supply is it hooked to?
> 
> I want to use stationary decoders for my turnouts and control them from the controller, but how does one keep track of the position of the turnouts? I thought surely the decoder would provide a connection for an LED for an indicator, but digitrax decoder didn't have such an LED connection. Does the controller tell you which way the switch is thrown?


The DCS100, and DB150 I know for a fact can use either a DC or AC power supply. With my setup I have a PS515 SELV powers supply. This is a 120V input with a 15V/AC 5 amp output. It is made by Digitrax and can usually be purchased for around $40-$60 Ddepending on your local hobby shop. The DCS100 and DB150 can also use a DC power supply but I dont know what the max output ratings are, the manual that comes with the sets will have that information. I am not sure of the power requirements for the DCS50/51 (Zephyr set). 

The stationary decoders come with different features just like mobile decoders do. Some do have LED outputs and some dont. The screen on the throttle will give you an indication of the decoders last "known" position by indicating a "t" (thown) or "o" (open). If you use Digitrax stationary decoders that have the Loconet function you should get the correct information about the decoder if the throttle is plugged into the loconet or if you have a duplex throttle. If they dont use the loconet and only recieve information from the rails then the command station can only "guess" the position of the decoder by the last instruction sent to the decoder. 

Some switch motors have outputs to wire LEDs to. This if you ask me is more accurate than the decoder giving the information. The decoder only tells the switch motor to do its thing, if you manually move the switch motor for some reason the decoder will not know. The switch motor on the other hand will know it has been moved and the outputs will be realigned to show the right LED based on the switch position. 

I hope this helps.

Massey


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## norgale

I guess I'll just have to buy some of this equipment and try this out. It's still complicated when your just sitting here reading this and not ever even seen one piece of this equipment. If this was all rods and wheels and gears and belts or chains I could understand it. Once the activity goes into a wire or a little box I'm lost. I mean digital watches cause me to have nightmares so you can imagine what I'll be going through with this. Maybe it's easier to understand when your actually working with the equipment. We'll see. Pete


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## Massey

Dont worry Pete I will be posting a few pics of some actual setups. I have my DB150 setup for my test track and my DCS100 is going to go on my shed layout. Stay tuned for some real pics of a real setup.

Massey


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## deboardfam

I agree with norgale.. hard as crap to understand when you dont know model numbers or have the equipment. LOL but a great write up. 

I definately learned a lot though... I think I am going to go with a seperate small piece of programming track just right above my zephyr board or something or if I can find a nice place to tuck it on the layout. We will see.

So I got the basic wiring.. my layout is going to be decent sized.. will I need an additional power pack to spread out the power or will just running extra leads off the zephyr to different points in my layout spread the wealth so to speak.


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## NIMT

deboardfam,
What do you call a decent size?
Regardless of how big your layout is you need to run buss wires and put drops off of the tracks about every three feet give or take.
When running your buss lines never loop it back to itself start at one point and end at another!
When you need to add more power you are going to need a Booster to supply more power to your layout. Run it then upgrade when you need to.


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## deboardfam

NIMT, it is going to be a 3x8 V shape roughly (as of now, thats the plan, N scale)

So wire 1 to 2.. then 2 to 3.. and so on then just leave the last one terminating?


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## NIMT

3 x 8 in N is a good size but you won't be out doing the DCC unit that soon!
Buss wiring example







Same rails always stay the same color or polarity.


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## deboardfam

It will be a 3x8 V.. so will have a 3x8 sheet on one wall.. then a 5x8 sheet on the other.. So not huge. Will be a good setup for N scale.


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## bradimous1

I am not sure if this thread over simplified this, or if it was just done that well. I don't have DCC or know that much about it... just a simple DC guy I am... but this makes me want DCC. Until I read the problems that deboardfam is having getting everything programmed.


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## deboardfam

brad.. my problems are just due to my newbness. LOL
The atlas engine I bought doesnt have specifics on the decoder plus I was just messing with it a few mins. Not fully tried to program it yet. 
If your getting into the hobby now, DCC is the way to go in my opinion.


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## bradimous1

deboardfam said:


> brad.. my problems are just due to my newbness. LOL
> The atlas engine I bought doesnt have specifics on the decoder plus I was just messing with it a few mins. Not fully tried to program it yet.
> If your getting into the hobby now, DCC is the way to go in my opinion.


have had a DC system for a little over a year now and love playing with it. should have my new, improved table finished this weekend, at which point I can start laying my new track... once the track is laid, I am thinking of going to DCC.


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## deboardfam

My 4 year old can run my zephyr without issue. He watches the engine, when the "front light" is on it goes frontwards when the "back light" is on it goes backwards. Thats what he calls it and how he knows lol.


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## bradimous1

that is awesome... I can't wait for my son to be old enough to run the trains


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## xrunner

Massey said:


> The entire area to be reversed will need to be isolated and it must be longer than the longest train you plan on running through the loop. (a wye that is just designed for one engine at at time only needs to be an inch or so longer than the engine but a reverse loop that is part of the main line will need to have the entire train in the loop to prevent shorts).


Massey, please clarify - why does the reversing section in a mainline need to be longer than the longest train? Using n scale, there is no rolling stock that can cause a short - they all have plastic wheels. So, it seems to me that the section only needs to be a little longer than an engine in any case.

Thanks.


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## NIMT

xrunner,
The problem comes into play if you have lighted passenger cars or if you have and engine on the head end of a string and an engine trailing.


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## JohnAP

Also, all rolling stock do NOT have plastic wheels. A lot of my N scale cars have metal wheels and I'm slowly but surely upgrading ALL of them with metal wheelsets and micro-matic couplers.


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## xrunner

NIMT said:


> xrunner,
> The problem comes into play if you have lighted passenger cars or if you have and engine on the head end of a string and an engine trailing.


For people still learning about reversing sections, it might be better said this way -

"The entire area to be reversed will need to be isolated, it must be longer than the longest train you plan on running through the loop if there are any rolling stock with metal wheels/lights or trailing engines"



Edit: Also, I just realized, what difference would it make if the reversing section was just a little longer than one engine, and the train had several cars or even one car and then a trailing engine? Why would that even cause a problem?


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## NIMT

Xrunner, You are exactly right on the reversing section being either long or short! It will work as long as it is as long as the longest engine consist.


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## manchesterjim

Good stuff here Massey...Thank you! :thumbsup:

Is there somewhere in the DCC section I can look that addresses wiring for a turntable and the resultant sections?

What I'm saying is that I haven't drawn it out yet, but it seems that the turntable or the spur tracks from it might need reversing....(I could be wrong on this)

I ask because I'll be installing a turntable as part of my yard layout modules. 

Thanks!


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## Massey

yes a turntable will need reversing. The wiring schematics I drew out above will work for the autoreversing of a turntable so long as you use the turntable's tracks as the ones that get reversed.

Massey


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## manchesterjim

Massey said:


> yes a turntable will need reversing. The wiring schematics I drew out above will work for the autoreversing of a turntable so long as you use the turntable's tracks as the ones that get reversed.
> 
> Massey


Thanks Massey.....that answers the question, and I happen to have a PM42 with a spare section....I'll set that up as the AR for the Turntable.


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## Massey

Make sure to follow the wiring directions as the PM42 has totally different wiring for autoreversing as it does for short protection.

Massey


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## kursplat

sorry i missed this thread earlier...with everything i've read on DCC this makes it very easy to understand what all the pieces are for :thumbsup:
the gap thing in the rails for isolating blocks bothers me. electrically i would like the gap to be wide enough that the wheels don't touch both ends at the same time, (seen too much electrical stuff blow up over the years  ), but i realize _that's_ not going to work. so does the fault protection just cycle the power off for a split second as the wheels touch both sides? does the controller even see a fault? is dumb luck someday going to cause me to stop an engine with the wheels resting on both sides of the gap and leave me all 

thanks


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## Massey

leaving an engine on both sides of a gap is not a problem. Now having 2 engines running into the same reversing section at the same time from different directions is a problem and yes a short will occure and your short detection/ fault system would activate. Your reversing loop track should only be made to ever have one train in it at a time to prevent this from happening. The PM42 is designed not only for the auto reversing but also as short circuit protection to do 2 things. First keep all engines not in the effected area running with no notice of the short. 2 protect the command station from damage. most command stations have some type of short tollerance built in but when the command station takes the short it effects the entire layout. 

Now if you have an engine parked across a power district block and a short happens in one of those blocks then yes the short will also pass through the engine parked on the gap an that would then trip the fault protection in the second power district. This once again is not that big of a deal since the fault detection is taking the hit and saving the booster or command station. 

Does this help clarify how things are protected?

Massey


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## Massey

Oh and when we say the reversing section should be longer than the longest train that will use it, that is so that metal wheels dont cross the gaps on each end at the same time. Also gaps should be parallel to each other so that the wheels bridge the gaps at the exact same moment, if not then shorts can occur.

Massey


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## kursplat

sounds good Massey, thanks


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