DCC - wiring my layout?

Sarah, from experience, I would recommend breaking your layout up into sections. You can feed them all from the same wire and they can all carry the same electricity. The day you will thank me is when someone puts a loco or wagon on the track with a short circuit in it, and you can't figure out where the short is located. Having a few sections lets you diagnose where the problem might be.
 
Fred2179G said:
Sarah, from experience, I would recommend breaking your layout up into sections. You can feed them all from the same wire and they can all carry the same electricity. The day you will thank me is when someone puts a loco or wagon on the track with a short circuit in it, and you can't figure out where the short is located. Having a few sections lets you diagnose where the problem might be.
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Greg Elmassian said:
I suggested that on another thread Fred, and was told the layout was too small to do that.

Fred, I am with you, I have seen first hand how frustrated people have gotten when they cannot find a short.

Greg
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I think you will find that Sarah has mentioned problems with wiring in the past and a simple set up with just one section and perhaps a second feed as this will be a relatively small layout should work fine for her.

As for the reverse loops if she uses them!!!
 
Returning to the subject of "Wiring my layout". I am committed to DCC. So with 4 locomotives I'm quite content to learn what I can.

So, a question, please?

My layout comprises basically a circle (for want of explaining the ins and outs). Within this circle are 2 return loops.

There are at the moment no isolating fish-plates.

Ignoring the point-work and the return loops and just accepting that one rail goes all the way round on the outside and the other rail on this track-work whilst being part of the point-work does not come in contact with the other rail. Should I be able to run a locomotive all the way round, please assuming the points are set to do this?

Second part of my question is, if I then switch one of the points on the outside circuit will it create a short?

Thanks,

Sarah Winfield
 
@Sarah Winfield Have you posted a track plan or photo anywhere for use to see? (Sorry if you already have, I must have missed it?)
If you have LGB points these are not a "live frog" design, they will not cause a short when you throw the point. In fact they are wired so that both routes are permanently live so without isolating joiners anywhere you would have already encountered a short if there were the potential for one in your track plan.
 
You must understand electricity and positives and negatives are like a black art to me.

So, if I have just 2 wires feeding my track, one, say the positive, on the very outside rail and the other, say the negative, on the inside rail, will everything inside the outside rail be negative?

I'm just trying to get back to something I understand.

Sarah Winfield
 
@Sarah Winfield Need a track plan really to comment. For a simple oval then yes you're right, but in your previous post you mentioned "return loop"s?
 
Sarah, draw a rough sketch of your layout on a sheet of paper, drawing in both rails in two different colours (say, one rail in red and the other in blue). If you just draw a simple oval, then at no point will the blue and red rails meet - even if you did a figure-eight design using a crossover in the middle, the crossover is designed so that the two rails never actually touch each other. But now draw a reversing loop, a balloon shape where the track goes from a point, turns back on itself and re-enters the other leg of the same point - as you draw the two rails, you will see that the blue and red rails meet each other as the line comes back into the point. That is where you will have a problem, and that is why even with DCC, reversing loops need special treatment (usually a little magic box that gets over the problem for you).
Sorry if that sounds basic (I'm not meaning to be patronising, honest!) but you did say that you were having trouble grasping the basics of polarity..... drawing it out will, I hope, make it much easier to grasp.

If you can draw your intended layout plan and the blue and red rails NEVER meet, then you are good to go! :)

Jon.
 
Sarah Winfield said:
You must understand electricity and positives and negatives are like a black art to me.

So, if I have just 2 wires feeding my track, one, say the positive, on the very outside rail and the other, say the negative, on the inside rail, will everything inside the outside rail be negative?

I'm just trying to get back to something I understand.

Sarah Winfield
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For the time being until you get Reverce Loop Modules do not connect the tracks that join these reverce loops as you will get a short till the Isolators come. My diagram shows where these Isolations need to be. The outer loop will then work fine.

To try to understand things for you think of your layout as having an inner and outer rail.

This will get swopped in the reverce loop.

Just follow the outer rail along the section that forms the reverce section and you will see that it joins the inner rail at the other end of that section. You can do this with your finger on the track.

Bang short!
 
Good morning from a sunny south coast.

Hopefully you will find a rudimentary sketch of my outdoor layout. It is made up of solely R1 curves and points.

The house is on the LHS and the shed located in the recess.

Coming to the information you have imparted so far, if none of the point switch rails are touching the outside rail then I could run an engine? As soon as an outside point is switched to direct my locomotive off the outside track that will create a short? (At the moment the passing loop on the LHS hasn't been installed.

Thanks

Sarah Winfield
 

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Sarah Winfield said:
Coming to the information you have imparted so far, if none of the point switch rails are touching the outside rail then I could run an engine? As soon as an outside point is switched to direct my locomotive off the outside track that will create a short? (At the moment the passing loop on the LHS hasn't been installed.

Thanks

Sarah Winfield
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Sarah, without isolating sections/fishplates you will have permanent short circuits regardless of the direction that the point(s) are set.
LGB points have brass strips underneath that feed all rails at all times.
 
Ah, now I understand, I think!

So the outside rail isn't totally isolated from the rest of the rails even if none of the switch rails are in contact with it? Is that a fundamental fact, please?

If all the rails are live why don't I get a short all the time?

SW
 
Sarah Winfield said:
Ah, now I understand, I think!

So the outside rail isn't totally isolated from the rest of the rails even if none of the switch rails are in contact with it? Is that a fundamental fact, please?

If all the rails are live why don't I get a short all the time?

SW
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I may have confused you a little.
I hope this diagram, with the under point brass strip connections shown as thin wires, may help. The frog is brown as it's plastic.
The welded ends of the brass strips sometimes fail. Also with previously owned track previous owners may have cut/removed them to provided for isolation where required. This may explain the lack of a short if you have made a reverse loop.

temp point.png
 
going back to my concept of outer and inner rails and Neils excellent diagram. All rails are live but with AC the cincept of Positive and Negative is nit quite the same but is so in principle. Look at my partially updated view if your layout
0D440C56-B628-41AA-B986-0A48F8F9D051.jpeg
Here I have shown outer as red and inner as green. With simple sidings and LGB points all is well. Only at reverce loops do things go wrong as shown where the Red and Green Rail ATTEMPT TO JOIN EACH OTHER AT THE TOP OF the DRAWING. The yellow Isolators will stop this problem. You also have the same problem on the loop (not the proposed one) at the left but here you have 2 problems or return loops. Draw coloured lines as I have done to understand the issue.

So now with this plan you have in effect 3 reverce loops! Suggest that on that loop you loose the right hand rail and make the siding point off that reverce loop as close to the diverging point before it as possible.
 
Thanks guys, I can at least see how a short would occur.

a) Do I put isolators on each rail?
b) Does it have to be each end? Could I not simply put the isolators in the centre of that run of track?
c) Could I put one isolator on one rail at one end and the other on the other rail at the other end?
d) Since putting isolators means there will be no power between them does it mean putting new connections into the track between each yellow isolator? (Subject to what you say about b) and c)) Presumably this is where DPDT switches come in?

Sarah Winfield
 
The problem with a reverse loop is that you need a completely separate section isolated at both ends otherwise you'll get an instant short as the wheels cross the isolating joiners. So the usual approach is to create a section which must be as long as the longest train you're going to run, and isolate both rails at both ends as JonD has indicated. Within that section a feed wire is required to each rail.

For DC this separate power feed goes to a DPDT switch to swap the polarity. You set the switch to match the polarity of the track you're entering from. You drive the complete train into the section (in case any stock also has metal wheels), stop the train and change the DPDT switch then drive train out of the other end of the reverse loop - you have to turn the knob or set the direction opposite to what it was!

For DCC an electronic reverse loop module can be used which does the job of the DPDT switch for you automatically. It detects when the train first enters one end of the section or the other(when it crosses the isolating joiners) and rapidly sets the track polarity to match. As the train drives out of the section over the other joiners it swaps the polarity to match that end. Because DCC controls the train direction via the decoder (not by the track polarity), the loco just carries on. Arguably it is better for the system to use train detectors to recognise when a train is about to enter or exit the switched section, rather than relying on detecting and reversing the short circuit across the isolated joiners. Some reverse loop modules support both methods.
 
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I appreciate your help, thanks. You must excuse my problem in getting my head round these reverse loops.

I can't afford to buy the special modules at the moment but how many of the modules would I require for my layout please?

The RHS loop has been marked in yellow to show where the isolating joiners go on the red and green rail. Is this also where I need to put my DPDT switches please?

Do I connect them across the yellow join, please? Presumably power from the controller is fed to the centre connections of the DPDT and the outside connections go the each side of the isolating joiner?

Thanks,

SW
 
Sarah Winfield said:
I appreciate your help, thanks. You must excuse my problem in getting my head round these reverse loops.

I can't afford to buy the special modules at the moment but how many of the modules would I require for my layout please?

The RHS loop has been marked in yellow to show where the isolating joiners go on the red and green rail. Is this also where I need to put my DPDT switches please?

Do I connect them across the yellow join, please? Presumably power from the controller is fed to the centre connections of the DPDT and the outside connections go the each side of the isolating joiner?

Thanks,

SW
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Sarah, I recently posted this vid somewhere else but cannot point you to it so have linked it again for you. For the purposes of your understanding, though this is a Triangle the Track to the right is in effect the Reverce Loop Section. You need both rails at each end isolated.

Till such time as you can afford a Module you can Isolate the Rails at each end or just have them as short dead end not connected sidings and all will be well.

If you get an LGB Module the Double Isolating Sections sort out all those issues and the wiring just a link from your Controller is sorted via those. In my setup I have used the Double Isolating Track at one end where the Track Feeds come feom the Rail itself. The other end I used a single Isolator and a short Single Isolating Track.

A Massoth set I think has the two isolating sections and track clamps that you can do all the wiring to/from.


In the vid as the Loco passes over the Isolations you can just about hear the click of the relay in the Reverce Module changing the polarity of the Reverce Section as necessary for the correct end of the Recpvecing Section.

Note that the Loco does nit give a hoot which way or side rail it gets current from and just keeps going. So long as there is not a short this is the case.

I am not sure how many Modules you would need, if you continue with the 3 reverce loops possibly 2 at least. But 1 may be ok for the two Reverce Sections so long as 2 trains are not trying to reverce sections at the same time. Any expertise on this please?
 
Yes, you can get by with one autoreverser for more than one reverse loop as long as nothing can be in both loops at the same time.

I don't know what stuff costs over there, but autoreversers are inexpensive and easy here, but I don't want to argue the point I know will come up... here in the US everyone use the ones that are simple, sense the short and reverse.

Apparently there is a strong opinion over the pond that this is bad, causes issues and you need the more complex and expensive autoreversers that use sensors/switches/extra track sections.

$53 here https://tonystrains.com/product/dcc-specialties-psx-ar-power-shield-auto-reverser-circuit-breaker/

All the major clubs and everyone I know use these, they are the best, there are cheaper ones.

Greg
 
Sarah Winfield said:
The RHS loop has been marked in yellow to show where the isolating joiners go on the red and green rail. Is this also where I need to put my DPDT switches please?
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No the DPDT is used with the power feed wires to the track

Presumably power from the controller is fed to the centre connections of the DPDT and the outside connections go the each side of the isolating joiner?
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No. The power from the controller (or from the track outside the reverse loop) goes to one side of outer teminals on the DPDT and is then cross-wired to the other outside terminals. This is what reverses the polarity when your throw the switch from one side to the other. The centre terminals go to the track.

Here's one of many sites which illustrate how it's done.
https://www.heathcote-electronics.co.uk/reverse-loops.html

I would recommend a centre-off DPDT, that way you can park and switch off a train in the isolated section of you wish.
 
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