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My First & Last Layout Project - Physical Progress at Last!!


cctransuk
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I am - after some fifty years procrastination, about to embark on what will be my first - and last - substantial model railway.

 

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NOTE : This is the final iteration of the layout design - it was originally intended to incorporate cassette units in the fiddle yard.

 

 

I intend to use common return cab control, via two adjustable voltage regulator or H&M Walkabout controllers; (A & B). Each of the baseboards, (shown edged in thick blue in the drawing), will be hinged to the wall so that they can be individually raised at 45 degrees to permit under-baseboard work. (This is an essential requirement once you reach the age of 70+)!

 

To permit the hinging, inter-baseboard wiring is to be avoided except at the rear, adjacent to the wall and hinges. It should be possible to run bus wires along the back edge of the baseboards, with slack inter-board links to allow for raising individual boards.

 

Each electrical section will have a two-way, centre-off switch mounted locally at the baseboard edge, so that it can be driven by either of the two controllers. The four edges of the baseboard nearest to the centre well will each have a pair of sockets for the controllers to be plugged into, corresponding to the two controllers A & B.

 

Point control will be mechanical from locally sited baseboard edge slide switches, which will also determine frog polarity.

 

Track will be Peco Code 75 bullhead in the scenic upper half of the layout, and flat-bottomed track for the lower, fiddle yard half.

 

Now I understand that cab control involves a common return serving two or more controllers, with separate feeds to the other rail, which is divided into sections that can be switched between the two or more controllers. My deduction from this basic understanding is that, on the DC side of the controllers, it will thus be necessary to have two individual DC feed bus wires - one for each controller; and one common DC return bus wire.

 

However, I am somewhat less than clear how things would work with the low voltage AC feed from the two, separate mains transformers - it is my understanding that there have to be two completely separate transformers, rather than two low voltage outputs wound onto a single transformer core.

 

Can the low voltage AC feeds from the separate transformers have a common return, or must they have entirely separate feeds and returns? The answer to this will determine whether I need three or four low voltage AC bus wires.

 

My current wiring convention for my test track is to use five pin DIN plugs to connect walkabout controllers to the baseboards - two pins for low voltage AC input to the controller, and two pins for DC output to the track via section switches. I wish to perpetuate this convention on the new layout.

 

I apologise for asking these very basic questions, but I have never before, in the last fifty years, needed to do anything more complex than to wire up a single test track board!

 

I would be very grateful for comments, criticisms and corrections concerning the foregoing - I would like to get it right first time, given the rate that time flies by nowadays!

 

Thanks in anticipation,

John Isherwood.

Edited by cctransuk
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You should not need to apologise for asking questions. None of us knew anything before we learned it for the first time.

I learned a lot from others at a club. This is unavailable to most of us right now, but this forum is a great sort of virtual club.

 

When using common return, it helps me to think of voltage as potential difference. We use 0v as a convention to make calculations easier but we could use anything.

Assuming we consider the common as 0v, the 'live' rail can be anywhere from 12v to -12v.

With common defined as one of the rails, the low voltage AC feeds must be kept separate, so you will need 4 wires, not 3. A transformer with 2 secondary windings is fine because they are electrically isolated from each other.

 

You may find wiring each board a bit tedious, but you will feel it is very worthwhile if (when?) you need to change/add/repair something underneath.

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15 minutes ago, Pete the Elaner said:

You should not need to apologise for asking questions. None of us knew anything before we learned it for the first time.

I learned a lot from others at a club. This is unavailable to most of us right now, but this forum is a great sort of virtual club.

 

When using common return, it helps me to think of voltage as potential difference. We use 0v as a convention to make calculations easier but we could use anything.

Assuming we consider the common as 0v, the 'live' rail can be anywhere from 12v to -12v.

With common defined as one of the rails, the low voltage AC feeds must be kept separate, so you will need 4 wires, not 3. A transformer with 2 secondary windings is fine because they are electrically isolated from each other.

 

You may find wiring each board a bit tedious, but you will feel it is very worthwhile if (when?) you need to change/add/repair something underneath.

 

Thanks for that - greatly appreciated!

 

Tedious I can do - lying on my back inside a kitchen cupboard carcase, dripping hot solder onto me is, nowadays, a step too far !!

 

That is why I will have seven , well separated, labelled, substantial bare bus wires along the back edge of the underside of each board. The bus wires on each board will be linked by slack jumper cables. A standard seven-core jumper cable with plugs and sockets at each end, with a couple of spares as insurance, should do the trick.

 

All control within an individual board - two-way, centre-off section switches, and mechanical point actuation / frog polarity slide swiches - will be locally located on that board.

 

The controller interfaces (A & B) between the low voltage AC supply bus wires and the low voltage DC traction bus wires will each be capable of being plugged in at any of four pairs of locations.

 

Please - input from any wiser heads than mine; (and there are many!); will be gratefully received.

 

Regards,

John Isherwood.

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I think there may be some confusion of terms. 
 

Cab control in DC involves a system whereby track sections , typically forming a route from the train start position to its destination , are switched to ONE dc controller.  There maybe many controllers and many track sections but the principle remains the same.
 

this is the opposite to the more simplistic solution of fixed dc controllers switched to fixed sections of track whereby there are “ bridging “ points where the train has to straddle two control zones. 
 

neither of these solutions out of the box need separate Isolated AC Power supplies or common return wiring , ( there are some advantages of isolated power supplies in this sceanario. ) they can all be run on a common DC power feed. Proper cab control can be wired using a common track feed but that’s not necessarily the classic MR common return  

 

Classic common Return means that wiring can be minimised and completely separate return currents. Run back to their respective power sources , hence with isolated supplies even currents of opposite polarity can return to their respective power supplies , ie one section /controller can be opposite polarity to the other but the common return still works 

 

this needs isolated power supplies otherwise the current may flow via a wrong return route ( amongst other things , like double voltage risks ) 

 

 

 

 

Edited by Junctionmad
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Hi John,

 

I wish I had used your tilt-up baseboard idea when I built mine about four years ago. As soon as I hit 70 my knees started acting up something 'orrible :)

 

Common return means fewer wires. At section breaks you only need one IRJ instead of two which I think is more than enough reason for using it. As Junctionmad says it is possible to use common-return with a single DC power supply but it does not sound like that's what you want to do.

 

The AC feeds to your controllers have to "float" with respect to each other. That means they either have to come from the secondaries of separate transformers or they have to be independent secondary windings sharing a common primary winding. The important thing is that there cannot be any electrical connection between the AC secondary windings. You will have to run independent AC pairs to your controllers.

 

I hope I have answered the main thrust of your question.

 

Cheers,

Andy

 

 

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@cctransuk Good luck with the layout, especially with the wiring as my first big layout of the 60s was wired up with 5 independent controllers with common return - Codar 2000s (remember them?). They, too, had to have separate transformers. It was the control panel that was the most difficult to wire up. The layout was abandoned in the 70s (blame it on fast women and slow cars). The next, and final layout will be DCC (am I allowed to say that on your topic?).

 

Cheers,

 

Philip

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1 minute ago, Philou said:

@cctransuk Good luck with the layout, especially with the wiring as my first big layout of the 60s was wired up with 5 independent controllers with common return - Codar 2000s (remember them?). They, too, had to have separate transformers. It was the control panel that was the most difficult to wire up. The layout was abandoned in the 70s (blame it on fast women and slow cars). The next, and final layout will be DCC (am I allowed to say that on your topic?).

 

Cheers,

 

Philip

 

All,

 

Thank you for your respective inputs - much appreciated.

 

What I conclude is that my (very) basic understanding of cab control and common return - foraged from innumerable sources over fifty years - is essentially correct; (miracle)!

 

I think that the way forward is to use 'chocolate block' connectors to support the seven bare copper bus wires, under the slightest of tension; with plug and socket jumper leads between individual boards. With locally sited section switches, no sections spanning adjacent boards, and on-board point control, no other inter-board wiring or mechanical connections should be needed.

 

This implies no centralised control panel as such, but with several sockets for plug-in controllers around the layout, there should be flexibility as to control position; albeit at the expense of some initial movement around the layout whilst route-setting. (Got to get the daily exercise somehow)!

 

Effectively, there will be several independent layouts butted together to form a circuit, each with their own section and point control switches, but with the ability to control a train around the combined layout from one or other of two controllers.

 

I'll let you know if the theory works in practice!

 

Thanks again,

John Isherwood.

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1 hour ago, Philou said:

Just the one thought regarding a non-centralised control system - will you not have a lot of moving around dealing with sections and point control?

 

Yes - but at my age, indoor exercise is positively encouraged!

 

(Anyway, with a well-oiled office chair on castors, getting around could be positively exhilarating!

 

Regards,

John Isherwood.

 

 

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No need to use common return with cab control  I don't and using separate feed and return for each will make your task easier, you will need Double Pole switches.  I use double pole rotary switches.

I use OnTrack hand helds which have din plugs as standard, DIN plugs fall apart.   Fortunately they only need three pins so I substitute Stereo Jack plugs, the same trick works for Morleys.

If the baseboards hinge up just run the wiring along the wall and lead it onto each baseboard separately. wires will twist happily along their axis almost indefinitely without breaking.

I have used rotary switches to select any one of four controllers, to several power districts for want of a better description sub divided by isolater switches for sections.  I wish I  had used 6 way as I now have seven controllers,  but 6 is the largest singe bank commonly available.   An off position is handy.  

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1 hour ago, DavidCBroad said:

No need to use common return with cab control

 

Hi David,

 

Quite true, but unless you happen to enjoy using a lot more wire, cutting a lot more rails and soldering a lot more connections what would be the point?

 

Many people have benefited from using common return for, as far as I know, at least sixty years. I'm not aware that any of them have so far detected a fatal flaw but I'm always interested to hear if there are any.

 

Cheers,

Andy

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Just now, AndyID said:

 

Hi David,

 

Quite true, but unless you happen to enjoy using a lot more wire, cutting a lot more rails and soldering a lot more connections what would be the point?

 

Many people have benefited from using common return for, as far as I know, at least sixty years. I'm not aware that any of them have so far detected a fatal flaw but I'm always interested to hear if there are any.

 

Cheers,

Andy

Hi Andy.   

I originally wrote that I started off with common return and found some really strange unexpected problems, shorts mainly, but trains moving when they should have been isolated.   I deleted that bit as I was waffling but I found  mixing common return with live frog Peco points straight out of the box, unmodified meant adding extra isolators and feeds and even microswitches.   Abandoning common return certainly helped fault finding

I worked out what was going wrong eventually, I have been doing car electrics for 40 odd years and used to do domestic wiring until the early 2000s so I'm not a beginner, but I decided it was easier to wire each controller separately, It is more wire but I pay so little for wire that its not an issue, but it is extra work and extra switching needing Double pole switches not singles, its just for me the trade off between more work and less snagging  vis a vis less work and more sorting problems  come down on the side of more work and less unforseen snags. 

We have 7 controllers in use,on a 24 X 8 OO layout with three levels and branches.  one double Morley , two OnTrack, and 4 Hammant and Morgan  Safety Minor Variable transformers. 3 can each be connected to 98% of the layout,  1 other can operate 100% of the layout, 3 others including the Morley only operate their station area or branches.  To put the icing on the cake we don't actually operate the layout in the way I originally envisaged

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Best we do not turn this into a debate about the virtues or otherwise (yet again) regarding CR.  John seems to have a good handle on it and it's his layout. We might want to be supportive rather than try to impose our particular opinions on the subject.

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I'm using cab control and common rail with 4 controllers.

One thing is that I'm using household insulated wire to take the current around the layout -- what we call lamp cord. I found that I could get several colours of thick wire at the hardware store.

With common rail you can run locos across blocks which are assigned to different controllers as long as the direction switches are set the same way

 

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Years ago, I asked one of the Westford Model Railway builders why they did not use common return wiring.  He said they had unexplained shorts on common return.   I followed that advice and have never regretted it  and never had an unexplained short.   

 

 

 

 

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3 minutes ago, 4901 said:

Years ago, I asked one of the Westford Model Railway builders why they did not use common return wiring.  He said they had unexplained shorts on common return.   I followed that advice and have never regretted it  and never had an unexplained short.  

 

Many of us have been using common return for at least sixty years without the slightest problem, but as I said, John seems to be quite happy to use CR. Short circuits are easily explained regardless of whether a layout uses CR or not.

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1 hour ago, 4901 said:

Years ago, I asked one of the Westford Model Railway builders why they did not use common return wiring.  He said they had unexplained shorts on common return.   I followed that advice and have never regretted it  and never had an unexplained short.   

 

An unexplained short means that whoever wired it up was unable to troubleshoot their own work.

It is not black magic or the fault of common return. It is usually caused by sections being too large & loops which end up getting fed from the wrong direction.

Making sections as small as possible is a principle I follow. This will ensure that I know where sections are being fed from, reducing the potential for a short & allowing troubleshooting to be much easier should an problem occur.

 

This is nothing to do with common return though.

The only issue I would have with common return is the possibility of someone unknown using the layout & connecting a pair of controllers fed from the same transformer winding- maybe a club layout or one which gets sold on.

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4 hours ago, 4901 said:

Years ago, I asked one of the Westford Model Railway builders why they did not use common return wiring.  He said they had unexplained shorts on common return.   I followed that advice and have never regretted it  and never had an unexplained short.   

 

 

 

 

Common Return works very well, UNTIL one of the key rules get broken. As Peter the Elanor says, it's usually caused by someone connecting something to a transformer winding belonging to something else. Everything appears to work, until a combination of controllers settings (i.e. one forward, another reverse), then you get a mystery short, which can be difficult to find.

If you only use INDEPENDENT transformer windings, there should be no issues.

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9 minutes ago, kevinlms said:

Common Return works very well, UNTIL one of the key rules get broken. As Peter the Elanor says, it's usually caused by someone connecting something to a transformer winding belonging to something else. Everything appears to work, until a combination of controllers settings (i.e. one forward, another reverse), then you get a mystery short, which can be difficult to find.

If you only use INDEPENDENT transformer windings, there should be no issues.

which of course comes back to John's original question...viz

I have two controllers which are fed from independent transformer wiring. Because of cab control, some sections link to one controller and some to the other. All the sections are connected by CR. So that means that one transformers wiring is linked via the common return to the other transformer wiring. Why does that not cause a problem?

Ian

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5 minutes ago, ikcdab said:

which of course comes back to John's original question...viz

I have two controllers which are fed from independent transformer wiring. Because of cab control, some sections link to one controller and some to the other. All the sections are connected by CR. So that means that one transformers wiring is linked via the common return to the other transformer wiring. Why does that not cause a problem?

Ian

 

Why does that not cause a problem?

 

Because the two outputs from two transformers are isolated from one another.

 

 

Pete the Elanor answered that very question.

 

With common defined as one of the rails, the low voltage AC feeds must be kept separate, so you will need 4 wires, not 3. A transformer with 2 secondary windings is fine because they are electrically isolated from each other.

 

If you have Common Return on the DC side, you CANNOT use Common Return on the AC side. This is where people make basic mistakes and introduce shorts.

 

You can test for shorts between 2 different power supplies yourself. Take 2 C or D size batteries (easier to handle, no technical reason) and a couple of 1.5 volt lamps, with wires attached to each lamp. No matter which way you turn the batteries around - plus to minus, plus to plus or minus to minus, you won't create a short. You will only blow the lamps if you connect it across BOTH batteries plus to minus at once - which still isn't a short, it's over voltage as far as the lamps are concerned, but not to the batteries!

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Try to imagine that each controller's output is floating. It is not tied to ground, or the mains or any other controller. The transformer ensures that. Connecting one leg of its output to another controller via the common rail just means the whole lot is floating. But if you have a common transformer winding then the controllers are connected in two places:- before the electronics and after. Effectively a short circuit. If that doesn't help please feel free to ignore.

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I do not propose to address the question you asked and comment on cab control/common return as that is an established and well understood system of control  and others have already discussed this . 

 

My comment is on your proposal to have so many hinged baseboards.  I am 70 myself in a few months time and have already had one knee replacement and the other will probably need doing too before many years, so I do appreciate the difficulties.  I cant kneel on the knee that has been done.  I find that whilst I can still get down there, it's a b*gg* trying to get climb back up again and need something solid and substantial to grab so I can haul myself up..   Especially irritating when I only want some tool that I didn't anticipate and put down there first.  That and where do I put my inflexible legs so that I can get to an angle where I can work comfortably on whatever bit needs doing.  One tip is that I have found a mechanics' creeper very useful. 

 

The problem I anticipate with your approach is the sheer number of board joints which have to align precisely if you are to have reliable running.  Hopefully your woodworking skills are far better than mine, but I have always had problems with alignment.  Portable layouts often get good joins with precision dowel arrangements to force boards to align exactly, but they work by sliding boards together laterally not dropping them vertically.  All your boards have to align at both ends, not just one, which will increase the difficulty.

 

You seem to have avoided the fundamental error of putting pointwork across a joint but I still foresee other issues. 

My objective when designing a layout to fit over joins is

  • to minimise the number of joints, consistent with the practicality of moving the boards
  • to minimise the number of tracks across each joint
  • to avoid joints on sharp curves as far as possible
  • even with straight track, to try to cross at 90 degrees rather than on a skew.

Could you reduce the number of track joints by bolting some of the boards together permanently?  I am thinking particularly of the number of tracks in the fiddle yard.  Of course you can't carry that to extreme or it will be too heavy too lift. 

Do your boards need to be rectangular?  What I am suggesting is that the corners be cut diagonally with a triangular bit fixed one to the adjacent board on the short wall, the other to the board on the long wall.  You probably can't do that with the turntable corner and you might have to adjust slightly the position of a few points. but I think it should reduce the number of tracks crossing at a skew.

 

On the plus side, I don't see problems with electrical connections between boards, as you don't need plugs and sockets.  It is a permanent layout so you can wire across the joints and all you have to do is leave enough loose flexible cable to allow the hinges to move, as you have recognised.

 

In order to fold up the boards for attention, you need not only to remove rolling stock and any loose scenery but also ensure that you don't have fixed scenery, signals and the like which would be foul of the wall in the raised position.  Even if you don't have to lift to the full 90 degrees, this problem is worse near the hinged edge of the board, which is of course where most of your track lives,

 

How do you intend to hold the boards in raised position?  Something like a series of car bonnet stays ?  Whatever you devise, it has to hold reasonably firmly as you don't want the board to move as you screw something onto it.   I would recommend doing as much as possible of the under board work before hinging to the wall.  AT least during construction, it may prove easier to do some of this by unscrewing the hinges and turning boards upside down after track laying.

 

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On 03/09/2020 at 10:25, Michael Hodgson said:

I do not propose to address the question you asked and comment on cab control/common return as that is an established and well understood system of control  and others have already discussed this . 

 

My comment is on your proposal to have so many hinged baseboards.  I am 70 myself in a few months time and have already had one knee replacement and the other will probably need doing too before many years, so I do appreciate the difficulties.  I cant kneel on the knee that has been done.  I find that whilst I can still get down there, it's a b*gg* trying to get climb back up again and need something solid and substantial to grab so I can haul myself up..   Especially irritating when I only want some tool that I didn't anticipate and put down there first.  That and where do I put my inflexible legs so that I can get to an angle where I can work comfortably on whatever bit needs doing.  One tip is that I have found a mechanics' creeper very useful. 

 

The problem I anticipate with your approach is the sheer number of board joints which have to align precisely if you are to have reliable running.  Hopefully your woodworking skills are far better than mine, but I have always had problems with alignment.  Portable layouts often get good joins with precision dowel arrangements to force boards to align exactly, but they work by sliding boards together laterally not dropping them vertically.  All your boards have to align at both ends, not just one, which will increase the difficulty.

 

You seem to have avoided the fundamental error of putting pointwork across a joint but I still foresee other issues. 

My objective when designing a layout to fit over joins is

  • to minimise the number of joints, consistent with the practicality of moving the boards
  • to minimise the number of tracks across each joint
  • to avoid joints on sharp curves as far as possible
  • even with straight track, to try to cross at 90 degrees rather than on a skew.

Could you reduce the number of track joints by bolting some of the boards together permanently?  I am thinking particularly of the number of tracks in the fiddle yard.  Of course you can't carry that to extreme or it will be too heavy too lift. 

Do your boards need to be rectangular?  What I am suggesting is that the corners be cut diagonally with a triangular bit fixed one to the adjacent board on the short wall, the other to the board on the long wall.  You probably can't do that with the turntable corner and you might have to adjust slightly the position of a few points. but I think it should reduce the number of tracks crossing at a skew.

 

On the plus side, I don't see problems with electrical connections between boards, as you don't need plugs and sockets.  It is a permanent layout so you can wire across the joints and all you have to do is leave enough loose flexible cable to allow the hinges to move, as you have recognised.

 

In order to fold up the boards for attention, you need not only to remove rolling stock and any loose scenery but also ensure that you don't have fixed scenery, signals and the like which would be foul of the wall in the raised position.  Even if you don't have to lift to the full 90 degrees, this problem is worse near the hinged edge of the board, which is of course where most of your track lives,

 

How do you intend to hold the boards in raised position?  Something like a series of car bonnet stays ?  Whatever you devise, it has to hold reasonably firmly as you don't want the board to move as you screw something onto it.   I would recommend doing as much as possible of the under board work before hinging to the wall.  AT least during construction, it may prove easier to do some of this by unscrewing the hinges and turning boards upside down after track laying.

 

 

Firstly, the baseboards will be built by a professional, and he is well aware of the need for consistency and rigidity.

 

Secondly, once the wiring, etc. is completed, I envisage clamping adjacent baseboards together using bolts and wing-nuts in close-fitting holes, so as to avoid differential movement between boards. Thenceforth, any work below a baseboard will simply require the removal of four bolts so that the board can hinge up.

 

The baseboards will be supported by kitchen unit carcases, with kitchen wall cupboards above, which will restrict the angle to which the boards can be raised on the two long sides of the layout. However, it will be relatively simple to support the raised boards with some form of attachment to the cupboards.

 

Lighting for the baseboards will be LED strips mounted beneath the wall cupboards, with LED downlighters elsewhere.

 

 

18905529_BASEUNITS.JPG.cd938f567da8ab43542b01de7682a632.JPG

 

47736060_WALLUNITS.JPG.2c173ebd9c270a919b052a7228e9cc4c.JPG

 

 

I may well use plugs & sockets on the inter-baseboard jumper cables, simply so that an individual baseboard can be disconnected and raised up for problem isolation purposes.

 

John Isherwood.

Edited by cctransuk
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there is an excellent description of common return here https://rail.felgall.com/crw.htm

 

it should be pointed out that as was incorrectly  mentioned  , is that common return only ever related to the DC side of the controls ie from the outputs of various DC power sources ( which could be transformers etc . It never applies to anything AC ( normally , though common return to isolated power supplies can of course return AC currents ) 

 

it should be pointed out that today many DC power sources are switched mode power supplies rather then transformer rectifier systems and many SMPS systems have DC negative bonded to mains earth , so that common return can’t be achieved 

 

the types that have no earth pin clearly are isolated and can be used 

 

With modern dc controllers there is no reason why a given rail can’t be a common rail for a given set of section switches and all dc controllers fed from a common DC supply 

 

the issue arises at controller boundaries where a dissimilar polarity  is selected 

 

however good dc can control eliminates that issue because the train should never need to cross a controller boundary to complete its journey 

 

I recently planned out a conversion to cab control for a large dc loft layout. The main issue is to ensure that any given track section couldn’t be switched to two controllers at once , this required interlocking logic on the mimic panel to achieve this. (Mechanical “ radio “ buttons could also be used ) 
 

In Johns case there seems to no protection against switching a track section onto multiple controller busses AFAIK 

Edited by Junctionmad
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