DCC Bus Wiring and Multiple Baseboards

[Art Dent]

Hi

 

I’m fast getting to the point where I’m about to lay track and the DCC buses in my loft layout.

 

DCC controller is NCE Powercab with SB5 booster.

 

I have a 50m reel of 2.5mm2 mains wiring for the DCC bus - the layout will incorporate a double-track loop around the ends and sides of a loft approximately 40ft long and 16ft wide (12m x 4.8m) iirc. 

 

The mains wiring ring will be stripped of its outer grey sheath and the bus wires twisted approx once every 6-10 inches.

 

The track will be laid on multiple baseboards - around the 2ft x 4ft (600 x 1200mm) size of the 9mm thick mdf boards that make them up.

 

The idea is for the DCC bus to run up both sides of the loft with the DCC control station/booster situated at one gable end of the loft.

 

My query concerns the passing of the DCC track bus (and separate accessory bus) between one baseboard and the other.

 

The layout isnt intended to be dismantled but if it would be a simple matter to include connectors - without paying too hefty a penalty in terms of voltage drop - then that would be my preferred option. 

 

A final query. I think that both DCC buses on either side of the loft need to be separate - forming a ‘Y’ shape from the command station/booster - rather than a loop (or ‘O’ shape) - and include terminators. 

 

That is correct isn’t it?

 

Art

[JST]

Personally I wouldn't bother with the bus connector idea if you don't intend to dismantle the layout. If you did change your mind it would be easy enough to cut the bus wires and then put connectors in when you rebuilt it.

 

My bus is arranged in the same fashion as you intend and it works fine. I have to say though, I had a couple of data signal issues until I added bus terminators.

[Gordon H]

The inclusion of connectors will allow far easier fault finding by enabling the isolation of individual baseboards.

[HLT 0109]

Art,

 

By the time you have ballasted the track and got your scenery in, you may find that the boards are stuck together, making it difficult to dismantle the layout - in which case having inter-board electrical connections becomes a waste of effort.  If you want to maintain the possibility of separating the boards, I think you would have to complete track laying and scenery on each board individually, as I am doing in my portable layout.  I have not tried dismanting a permanent layout but I imagine it is difficult to cut the track accurately without damaging the scenery and structures.

 

Harold.

[RFS]

I had a similar situation although with a smaller loft - about 33'x9'. I decided not to worry about dismantling because, quite simply, the layout is designed to use the space available and, if dismantled, is most unlikely to fit anywhere else. So not only do wires pass direct between boards but the track is laid across the joins too. 

 

If you haven't built the boards yet I would recommend 9mm Birch Ply rather than MDF: it's less than half the weight and is very rigid.

 

If you are going to use a single booster then you're going to have a very long bus. There's a recommendation that bus length should not exceed 30ft from the feed, but even with your booster at one end your bus is going to be up to 60ft in each direction. You might need to consider two boosters.

 

It makes no difference whether the bus is a U-shape or a ring. Your trackwork is a ring anyway, so even if you carefully isolate each half of the bus (with IRJs above as well) you'll still get a ring when locos with multiple pickups cross the join. What is important though is to wire in reasonably-sized sections to make fault-finding a bit easier. 

Edited May 25, 2019 by RFS

[WIMorrison]

I am working on the theory that if I do move house again (unlikely) then it would be an opportunity to build a new layout that would fix all the issues in the current track layout - Mind you I have said that 3 times now and I still haven't got the perfect track layout - but the next layout will have all the problems sorted

 

Basically if you want to make it portable for the future then you need to build it like an exhibition layout and cut the track and scenery as you build it, almost impossible to do later, therefore I don't bother.

[RFS]

7 minutes ago, WIMorrison said:

I am working on the theory that if I do move house again (unlikely) then it would be an opportunity to build a new layout that would fix all the issues in the current track layout - Mind you I have said that 3 times now and I still haven't got the perfect track layout - but the next layout will have all the problems sorted

 

 

 

I think there are many of us, me included, who have the same thoughts!

[beejack]

If you go down the route of two sets of bus wires then get a couple of EB1 Circuit breakers or similar and electrically isolate the two halves of the layout with insulated rail joiners, that way you can tell which half has a short.   Don't put one on the accessory bus as unless the short is on this bus it will allow you to still change points etc.

 

As for the connection between boards, why not just leave a little extra wire at the baseboard joint then should you have issues with shorts or wish to separate the boards you have the ability to add connectors at that point. 

You could always terminate the bus into 15 amp strip connectors at each end of the boards, and use a short bringing wire to connect the boards together.

 

 

[Marcus-Jay]

I am in the process of adding an O16.5 Narrow gauge to an existing O gauge layout.  It's only a loop track with a pair of passing loop stations and a couple of sidings. However, it is a 30m loop!

The O layout was originally a portable, but has not moved in the decade or so since installation! So we are adding with the intent of making it easy to break up should it ever be required, thinking it will add cost today but save it further down the line. 

In the spec, we have added in a 'baked bean tin' sized loop of the bus wires at each baseboard joins. Although we won't cut it at this stage it will give us plenty of leeways to add connectors in the future.  For our bus wiring, we're using Brimal 32/0.2 which we will strip back and add smaller droppers to each of the individual track sections.

[Crosland]

19 hours ago, Gordon H said:

The inclusion of connectors will allow far easier fault finding by enabling the isolation of individual baseboards.

 

This ^^^

 

Also, if you decide not to include them and think you might add connectors later, ensure you leave enough slack for cutting, stripping, etc.

[dasatcopthorne]

I always understood that the Bus must not go round in a loop and meet itself.

 

Am I wrong?

 

Dave

[WIMorrison]

What does the track do on a roundy, roundy layout?

 

the fact that it is on top of the board and bus underneath doesn’t make a difference to the electrons

[Junctionmad]

On 26/05/2019 at 14:17, dasatcopthorne said:

I always understood that the Bus must not go round in a loop and meet itself.

 

Am I wrong?

 

Dave

Yes 

[jpendle]

With decent connectors there shouldn't be much voltage drop, if you are concerned then just double up the number of connector pins used to cross the baseboard joins, this will halve the voltage drop.

 

BTW I use Wago Levernuts on my N Gauge DCC layout, they look to be around 25p a time in the UK and come in 2, 3, or 5 way versions, they are mains rated so should be able to cope with DCC.

 

The beauty of them is that you only need a pair of wire strippers to use them, and they and the wire in them can be connected and disconnected multiple times.

 

The 3 and 5 way versions are especially suited to DCC bus wiring.

 

Regards,

 

John P

[Crosland]

On 26/05/2019 at 14:17, dasatcopthorne said:

I always understood that the Bus must not go round in a loop and meet itself.

 

Am I wrong?

 

Yes, but you are not alone, unfortunately.

[Art Dent]

Thank you folks for the replies.

 

The layout is on multiple 2ft x 4ft basbords as I mentioned in my OP, I currently have five built and the mdf to make three more.  The intention was to have the layout able to be taken apart, but it is unlikely that it will be moved and as RFS mentioned, even if moved it would be unlikely to fit anywhere else.

 

The track feeds are going to be protected by a Power Shield - probably a PSX-4 - splitting the layout into four “districts”.

 

I was wondering about the length of the track and consequently the bus wires, so may get a second SB5 booster and put one on one side of the loft and split it into two districts with a PSX-2 and do the same on the other side.  The accessory bus won’t have a circuit breaker.

 

i was considering using two centrally-located 4-way metal earth terminal blocks on each board to allow for easy connection to the bus wires and distribution of the dropper feed wires around the board but that would possibly mean that some droppers would be around 18-24 inches long. Is that too long?

 

If that idea turns out to be a non-starter (comments welcomed) then adding a “baked bean tin” sized loop of wire at each entry point to a board would allow for a board to be ‘removed’ should the need arise.  That’s a great idea.

 

Thanks for the input so far,

 

Art

 

[RFS]

I use these metal earth terminal blocks extensively and they certainly simplify connecting up multiple dropper wires. You should have no problems with 18-24 inch dropper lengths but best to use 16 x 0.2 wire for these. I actually use DCC automation so one rail of each block is connected to 8-way occupancy detector modules. Wires from these to the rails can be up to 6-8 ft long and I've had no issues at all with 16 x 0.2 wires for these. It's best to use a dropper for every piece of track so that you are not solely relying on rail joiners to manage the electrical connections.

 

As far as circuit breakers are concerned, if you have a short in one section they ensure that trains in other sections keep running. This may or may not be what you want. If, like me, you're the only operator you may prefer a short to stop the whole layout so that you are free to deal with it. Might be different on a club or exhibition layout, for example. In which case you could have a single circuit breaker feeding multiple sections through DPDT switches, so you can isolate each section to help find an unexplained short. The accessory bus can still bypass the CB. 

[Ron Ron Ron]

1 hour ago, Art Dent said:

......I was wondering about the length of the track and consequently the bus wires, so may get a second SB5 booster and put one on one side of the loft and split it into two districts with a PSX-2 and do the same on the other side. .......

 

 

Art, you can't use a second SB5.

If you did find that you needed a 2nd booster, then you would need to add the NCE DB5  (some other brands can work too).

 

Just for clarity (apologies if you know this)....

 

The PowerCab is a complete DCC system contained in a handset.

Apart from being a throttle/cab, the PowerCab handset contains the system command station and booster.

 

 

The SB5 SmartBooster is not just a booster. 

It also contains a replacement command station, which takes over the command station duties from the one fitted inside the PowerCab handset.

With the SB5 connected, the PowerCab's internal command station and booster are disabled...and therefore redundant.

 

You can only have one command station in a DCC system.

It's the hub and central brains of the system.

Therefore, you cannot use more than one SB5 in the system.

 

If you require any additional boosters, NCE provide the matching DB5, which is a "dumb" booster (i.e. half of an SB5 without the command station bit).

 

Again, apologies if you already know all that.

 

Ron

 

 

.

 

 

[Ron Ron Ron]

2 hours ago, Art Dent said:

.....I was considering using two centrally-located 4-way metal earth terminal blocks on each board .....

 

35 minutes ago, RFS said:

I use these metal earth terminal blocks extensively and they certainly simplify connecting up multiple dropper wires. .......

 

I've also used some metal earth terminal blocks.

May I suggest that these are fitted inside matching terminal block covers, to protect them against any inadvertent contact that might cause a short, electric shock or electrical damage.

The covers and cover boxes are cheap as chips to buy.

 

 

 

.

[John K]

Point me at some blocks and covers please Ron.

Thanks

John K

[peach james]

The answer is as always, it depends.

 

Long Marton is wired into Cinch Jones connectors, with the intent that the majority of it is portable.  It doesn't mean it moves around much, but when I need to get to say, the plumbing in the walls, I can take it apart, and move it out of the way...

 

Using terminal strips would to me, seem to be a perfectly appropriate way of dividing the layout into sections.  That, or even the loop of wire as mentioned.  The one thing I wouldn't do is have the wire tight at each set of joints...

 

Having it even crudely sectionalized like Long Marton can make fault finding MUCH easier.  

 

Some sections of Long Marton are up to 24' from the booster that powers them, so probably more like 30-40'.  I tend to use 14 AWG wire (15A capacity, if you want to think of it that way...) to limit voltage loss.  It's when you get to things like 22 AWG that voltage loss and current capacity becomes an issue.  I melted (!) a truck on a lit passenger car, so yes, the physics of it do require passing the short circuit test...

 

I don't anticipate that the full amount of Long Marton would be salvageable if I moved house, but the major chunks would give a vast start to building a new layout.  I probably would do something different, but it would all depend on space available.

 

James

[Art Dent]

Hi John

 

i don’t know about the covers to which Ron refers but this is the type of earth terminal block I was referring to

Earth Terminal Block (eBay UK link)

 

Like you I’d appreciate Ron providing a link for those. 

 

Art

Edited May 30, 2019 by Art Dent

[Ron Ron Ron]

   

 

 

[Ron Ron Ron]

RS

TLC

Screwfix

Toolstation

 

etc, etc.

 

 

.

[Art Dent]

8 hours ago, Ron Ron Ron said:

 

Art, you can't use a second SB5.

If you did find that you needed a 2nd booster, then you would need to add the NCE DB5  (some other brands can work too).

 

Just for clarity (apologies if you know this)....

 

The PowerCab is a complete DCC system contained in a handset.

Apart from being a throttle/cab, the PowerCab handset contains the system command station and booster.

 

 

The SB5 SmartBooster is not just a booster. 

It also contains a replacement command station, which takes over the command station duties from the one fitted inside the PowerCab handset.

With the SB5 connected, the PowerCab's internal command station and booster are disabled...and therefore redundant.

 

You can only have one command station in a DCC system.

It's the hub and central brains of the system.

Therefore, you cannot use more than one SB5 in the system.

 

If you require any additional boosters, NCE provide the matching DB5, which is a "dumb" booster (i.e. half of an SB5 without the command station bit).

 

Again, apologies if you already know all that.

 

Ron

 

 

Hi Ron,

 

I did know this but then promptly forgot, so thank you for the reminder. I blame age!

 

Indeed the ‘S’ of SB5 means ‘smart’ and the ‘D’ of DB5 means ‘dumb’, the ‘B’ meaning ‘booster’ and the 5 referring to the 5A capacity.  Some folks may not realise that. 

 

I may may see if the SB5 can cope on its own first - but that is after track-laying has commenced. 

 

Regards,

 

Art

 

Trying to type this on an iPad mini and it is a PAIN!

 

Thanks for the pix and suggested outlets : )

Edited May 30, 2019 by Art Dent