Maybe a silly question but ?

[Ian White]

Hello All

 

so many years ago when I had a train set , there was no such thing as DCC , So I'm a total beginner on this , I keep hearing about this bus wire do I need it or can I do without it ? 

 

Thanks, Ian

[BoD]

If you are convinced that your fishplate joins are 100% reliable at all times across the whole layout then arguably you don't need a bus wire. (Notwithstanding that you may need additional feeds depending on points etc).

 

However, perceived wisdom and experience shows that for DCC bus wires with regular feeds to the rails, often referred to as droppers, provides much more reliable operation.

[Ron Ron Ron]

Hello All

 

so many years ago when I had a train set , there was no such thing as DCC , So I'm a total beginner on this , I keep hearing about this bus wire do I need it or can I do without it ? 

 

Thanks, Ian

 

 

Hello Ian

Don't worry, there are no silly questions.

 

Think of a "bus" like the ring main in your house.

In the ring main example, it takes a power supply and distributes it around the home.

Sockets and outlets are connected to it at convenient points and it's a reliable way of providing a good power supply around the home.

 

I don't intend to baffle you with jargon, but bear with me for a moment....

With a DCC controlled layout, there could be several different types of bus being used, depending on your needs and the sophistication of the layout and control layout.

e.g.

Power Bus - which can take the form of a Track Bus (to feed the rails) or Accessory Bus (to feed optional accessory decoders and other modules).

Cab, Throttle or Command Bus (various terms for the same thing) - used to connect handsets and other control/input devices to the DCC Command Station.

Control Bus (Power Station Interface) - connects the Command Station to external Boosters (Power Stations)

Feedback Bus - used by some systems to feedback signals to the Command Station from modules or detectors on the layout.

There's even a Layout Control Bus in development.

 

Enough of the blurb...

I strongly suspect that you are probably reading/hearing about a Power Bus (Track Bus).

All it is, is a simple pair of wires that runs around a layout (it can be laid in various configurations) and is connected to the track at various places.

The Power Bus is used to carry the track power and embedded DCC signals that are output from the DCC system and feeds it to the rails at various connection points around the layout.

It provides a more reliable, robust and consistent supply, rather than just relying on a single connection point and transmission around the layout only via the rails.

 

Some people just connect up to their track at a single point and rely on the rails; but unless you have the smallest and most simple of layouts, it's generally considered wise to use such a Power Bus in order to save a lot of frustration and hassle resulting from a poor DCC power supply on the layout.

 

I hope that answer isn't too convoluted or confusing?

Don't hesitate to ask further questions. The folks here are very helpful.

 

Links to on-line information and recommended books, can be found in this RMweb thread.......

 

http://www.rmweb.co.uk/community/index.php?/topic/114222-best-book-for-complete-beginner/

 

 

 

.

[Stevelewis]

Its  a  matter  of  whether  you  feel  competant  to  solder  a  lot  of  dropper  wires  from  the  track  to  the  underboard  BUS  wires.  ( or  you  could  use  lots  of  PECO pre wired  railjoiners but  that  would  cost)

 

I have  used  digital  for  many  years  ( since '97)  on various  layouts  indoors  & outdoors  I have never  used   Bus bars.

Infact  the  concept  was not  aired for several  years  after  I started in Digital

 

I  become  aware of  the  concept  when a supplier  of  DCC equipment no longer in the  busuness  offered   rolls  of  adhesive backed copper  tape  which  was to be  stuck under  the  base   board  as  a  Bus  sytem allowing the droppers  to  be  soldered thereto!

 

As  an example  I had   an approx 20 X12' 00 layout  in a double  garage  for  around  12  years   double  track  looped  8 track plan  with  a  goods  yard, loco shed  and  a branch to a terminus  at  the  end of  the  building approx 24 ' long ( obviously  the  car  never  got  a  look in)

 

That  layout  had  3  main digital feeds  and a small number of minor  feeds  which  were taken as  spurs from  the main feeds,  The  layout  worked  well for  around 12 years until we   down sized

  ( Bad  move  that  my  advice  is  try to avoid  downsizing  not  enough layout  space!!)

[Ron Ron Ron]

....I have  used  digital  for  many  years  ( since '97)  on various  layouts  indoors  & outdoors  I have never  used   Bus bars.....

 

....That  layout  had  3  main digital feeds  and a small number of minor  feeds  which  were taken as  spurs from  the main feeds,.....

 

 

Steve, that sounds to me very much like a Power Bus, in some form or another?

 

 

 

.

[Stevelewis]

Steve, that sounds to me very much like a Power Bus, in some form or another?

 

 

No  not  at  all,  simply  taking a  spur  for  example  from  a  main  feed to one  of  the  feeds  to  the  2 main lines  to  the  far  end  of  the terminus  track work  around 20' if  I remember  correctly.

 

The  whole  layout  in  question  was  a  looped  8  format  double  track main line  ( looped  8 =  a figure 8  but  one loop of  the  8 looped  over   the  other by means  of  gradients    to give on overall length of  run on the  main  circuit) I used 3 boxes x 25  yards of  Peco  code 100 so if  you consider  that   using  droppers   on  all that  track  or  even   some  of  it  would  have  meant  a rather   large  amount  of  soldering!!

 

In fact  the  layout  was  started before  I went digital in around '97  at  which time  Power Buses  had  not  even been discussed as far  as  I know

.

[PaulRhB]

A simple DCC setup can do without a bus wire and feeds to every piece of track as long as the fishplates are snug. Worth having feeds from the main bus wires to each rail fairly often though as the bigger bus wire keeps the signal 'clean' and stops voltage drop. Rails and fishplates aren't as reliable as an unbroken wire with droppers soldered to it

Here's a couple of diagrams I did for the G scale forum showing basics.

 

For a larger layout requiring more power you can split it up in to power districts by adding a booster, or several, so there's always enough amps for all the trains if your basic system isn't powerful enough. In OO I reckon on half an amp when running per loco or allowing an amp per loco if sound fitted. This is more than the majority draw but gives a nice margin

[Ron Ron Ron]

 

Steve, that sounds to me very much like a Power Bus, in some form or another?

 

 

No  not  at  all,  simply  taking a  spur  for  example  from  a  main  feed to one  of  the  feeds  to  the  2 main lines  to  the  far  end  of  the terminus  track work  around 20' if  I remember  correctly.....

 

That is effectively a Power Bus, albeit one with very few connections to the track work.

Some may argue that it's not a very efficient or effective configuration for a Power Bus though.

 

 

 

.

[bigP]

--

[Ian White]

Sorry Chaps , I've not been too well , so please don't think I was  being rude by not replying , Thank you very much for the info , I'll have a good read over the weekend  

 

Thanks again , Ian

[RAF96]

If I can just revert to simple basics, good though the previous advice given has been and certainly the OP should read up as advised.

 

The track is your primary electrical circuit before you start adding droppers and linking to and fro etc. As stated if your rail joiners are snug then your primary circuit will be satisfactory to run trains. Train sets and home layouts have been running this way for decades and many still run on the simple premise of using a single connection to the controller.

 

For many folk this is enough until the trains start to stutter when usually the soldering iron comes out and a separate bus is retro installed.

 

At the first sign of unreliability of the track only bus system, I apply the thumb test. Run your thumb round the live circuit noting if it gets hot at any rail joint. If so then you have a slack joiner and if you can snug it up a bit with a flat bladed screwdriver or similar you will likely restore integrity of the joint.

 

Once you have read all about the other track wiring methods then it is your hands how simple or complex you feel you need to go on your layout.

 

I have three loops, some sidings and loop to loop to loop points, all fed from a single connection to the controller. I have also connected loop to loop to loop in four places round the layout. Everything runs fine except the 0-4-0s wont creep across the insul-frog points which I put up with to avoid the complexity of converting to electro-frogs.

[14Steve14]

A model railway club local to me made an exhibition layout that used DCC and did not have a power bus. There was only two power feeds from a chockblock connector where the controller feed was split. The layout relied solely on fishplate connections and point blades. The layout worked faultlessly for days at exhibitions and they never had any trouble with it.

 

There is also loads of ways to wire a power bus and there is no right and wrong way to do it, as there is no right and wrong materials to use. Have a read of all the information on the internet, and pick the bits you want to try and experiment. I wrote a basic DCC power bus wiring page for my website based on all the different information I found on the internet and used to make a working layout. Customers find it helpful and many have built layouts using that information.

 

There a few simple things to remember when wiring a power bus. Keep any dropper wires as short as possible (under 9 inches). Use large enough power wire for what you need the layout to achieve. If you are only having one loco running at a time and 2 others stood stationary, use a smaller wire. If you have lots of locos and 4 or 5 running use the largest wire you can get. Try not to make the track and wiring into a complete ring. Put in a break somewhere. Put power into this broken ring in the centre to reduce voltage drop at the outer reached ends. Finally make sure you test the protection built into your controller before putting any locos on the layout. Do this by causing a short in several places and see if the controller reports an error or shuts down.

 

I hope this in some way helps you with your DCC wiring worries.

[Crosland]

I have to take issue with there being no right or wrong way. There are certainly wrong ways to do things. relying on fishplates is one of them. Anecdotal evidence of one layout that never had a problem does not make it a right way to do it. I can give plenty of counter examples.

 

It all boils down to the question: What is the "best practice"?

 

You have your requirements backwards.

 

The number of locos being operated is a secondary consideration when choosing suitable gauge wiring for the power bus. 

 

The primary consideration (the only one really) is that the wiring can handle the fault current that the booster is capable of sourcing (may be 5 or even 10 Amps for larger systems) in such a way that the boosters cut out mechanism is not compromised. So long as you are not using wet string as your bus wire, even the physical extent of the layout has minimal bearing here, unless you are VERY well endowed with space.

 

If you take 16/0.2 as the starting point and work upwards based on the above requirement, then voltage drop will be minimal under normal operating conditions.

 

Doing the short test only after wiring the layout could be very disheartening in the event of a failure.

 

Regarding droppers, it's all well and good saying keep them short but you need to understand the reasoning, and should state it so that others can make an informed choice. The bus is itself merely a dropper from the booster to the layout. The key point is that it is desireable to use much thinner wire for droppers, to make connection to the track easier. This is where voltage drop comes in to play but, again, only under fault conditions. The thinner the wire, the shorter the droppers need to be. A few inches would be appropriate for 1/0.8 hook-up wire, for example. Nothing magical happens at 6 inches or 9 inches (stop sniggering at the back).

 

Similarly there is no need to avoid connecting the bus in a ring. It happens every time a loco bridges the rails between the two ends. No one has yet managed to come up with a plausible theory for avoiding rings, once other wiring best practices are covered.

[14Steve14]

I have to take issue with there being no right or wrong way. There are certainly wrong ways to do things. relying on fishplates is one of them. Anecdotal evidence of one layout that never had a problem does not make it a right way to do it. I can give plenty of counter examples.

 

It all boils down to the question: What is the "best practice"?

 

You have your requirements backwards.

 

The number of locos being operated is a secondary consideration when choosing suitable gauge wiring for the power bus. 

 

The primary consideration (the only one really) is that the wiring can handle the fault current that the booster is capable of sourcing (may be 5 or even 10 Amps for larger systems) in such a way that the boosters cut out mechanism is not compromised. So long as you are not using wet string as your bus wire, even the physical extent of the layout has minimal bearing here, unless you are VERY well endowed with space.

 

If you take 16/0.2 as the starting point and work upwards based on the above requirement, then voltage drop will be minimal under normal operating conditions.

 

Doing the short test only after wiring the layout could be very disheartening in the event of a failure.

 

Regarding droppers, it's all well and good saying keep them short but you need to understand the reasoning, and should state it so that others can make an informed choice. The bus is itself merely a dropper from the booster to the layout. The key point is that it is desireable to use much thinner wire for droppers, to make connection to the track easier. This is where voltage drop comes in to play but, again, only under fault conditions. The thinner the wire, the shorter the droppers need to be. A few inches would be appropriate for 1/0.8 hook-up wire, for example. Nothing magical happens at 6 inches or 9 inches (stop sniggering at the back).

 

Similarly there is no need to avoid connecting the bus in a ring. It happens every time a loco bridges the rails between the two ends. No one has yet managed to come up with a plausible theory for avoiding rings, once other wiring best practices are covered.

 

 

Point me to a page of information that best describes best practice then. Others will also be able to read it, and maybe then people will start only wiring a layout that way. So called DCC specialists cant agree on what is the best way to wire a DCC layout, and many of them conflict with each others views. Brian Lambert has different ideas to Mark Gurries, and they are both different to Nigel Burkins ideas and methods. Your model railway club may wire layouts totally different to my local club, but that does not mean that any of them are doing it right or wrong or even following best practice. They are doing what works for what they want.

 

I am sure a kid with a train set that his or her dad has just bought will have all the knowledge to wire a full DCC bus under their layout. It wont happen and the only way they can get a train set to work is to apply power through fishplates. They wont have a power bus and they wont know what a dropper wire is. Their train set will still work, and they will be very happy with it. If there was a correct way of wiring a layout or even a simple train set then Hornby who sell these starter kits should include all the wire needed to make a power bus. It wont happen.

 

Every one has a different opinion and way of wiring DCC layouts. I try to explain to my customers or anyone else, in as simple way that most will understand, the way that I did it, and I have no problems. You have to remeber that many people are new to this hobby, and dont understand terminology so it has to be kept simple.

[Crosland]

Point me to a page of information that best describes best practice then. Others will also be able to read it, and maybe then people will start only wiring a layout that way. So called DCC specialists cant agree on what is the best way to wire a DCC layout, and many of them conflict with each others views. Brian Lambert has different ideas to Mark Gurries, and they are both different to Nigel Burkins ideas and methods.

 

Add Alan Gartner and you have a full house

 

I don't think there will be much difference in the principles applied, but I haven't compared sites line-by-line. The application of those can vary.

 

Your model railway club may wire layouts totally different to my local club, but that does not mean that any of them are doing it right or wrong or even following best practice. They are doing what works for what they want.

I don't have any issue until such people start making claims that wiring with wet string, or not using resistors with LEDs, must be OK, because it works for them. They wouldn't be interested in best practice if you slapped them in the face with it