The big BUS debate

Rail rider,

Some good additional questions.

the following is my working practice for a medium sized or larger layout:
it is only one solution among many.

As I have designed, rebuilt and upgraded most parts of my layout; the only thing left from my first system is the power bus, which I got right first time. (nothing else i might add!)

You buy lots of plastic chock blocks and cut them into fours.

Don't put them below your layout but above it. Cover with a back drop later. People with bad backs please take note!

Arrange them with the intention of having a horse shoe of wire (main ring)around the whole layout.

The gap I have between each block is about three feet (see what you think). No need to stretch the wire too tight a modest washing line is best. You pull when you solder remember.

Top wire is red, second wire down is black.

This is your main 'power bus' and is conneceted to any dcc amp( Hornby or Lenz or Digitrax) on the market.

Now next wire down is yellow and the one below can be black.

This bus is your 'assecory decoder bus' and is attached to a transformer like the Lenz TR100. (i'm sorry but as you progress - yes - you need two transformers)

This method will not let you down, and is highly flexible. Better to wire around an assecory decoder bus once at the very beginning; this will allow you to place the decoders near the section of track being built no matter how you design things.

This system will not let you down and will grow with you.

TVBG

RE: Two transformers above;

After I had posted this I looked at the Hornby 2006 which arrived today.
Hornby say about the Elite:
'the Elite is supplied with a 4amp transformer which is capable of providing... power to run ...eight locomotives. The transformer supplies 3 amps to the track and 1 amp for accessory control.'

Nice system and saves you thirty quid on the Lenz.

TVBG

A BUS is a transporter for the DCC data.

It connects your DCC command unit to the track. It does this with two wires. That's where the 'two wires' comes from. In this case, it is a pair of cables, commonly coloured red and black.

To make the connection better, one adds feeders to more than one place on the track. In fact, it is better to add a feeder (dropper) every metre or two. To do this, it is practice to run a thicker pair of wires around your track (under the baseboard). and connect your feeders to this wire. The BUS should not be looped, but terminate with a resistance. The command unit can be in the middle of the BUS to avoid signal loss.

That's the DCC data BUS, you can also have, if your system has the capacity, a feedback BUS and extra power feeds (not called a BUS) for accessories and stationary decoders.

I have under my tables:
- the DCC data BUS
- a 16V AC DCC accessory and decoder power feed
- a 12V DC lighting circuit and other 12 V accessory power feed
- I will add a DCC feedback BUS at some later point

Doug,

Thanks for correcting me. I have indeed called the two 'power' wires for the accessory decoders a 'bus'. If its improper I would edit it as 'accessory decoder power sub- system'.

mmm

In fact, perhaps, Doug you name it, and i will use that term in future so as to avoid confusion. I must confess both systems only have a name when I need to attach something to them!

Also, the red and black bus we are talking about is also surely a 'power' as well as a 'data' system. The bus to the feedback system is properly only a 'data' system. For what its worth I changed to green, to wire these modules on my layout.These feedback decoders are then powered by the system above; which Doug will name correctly for me.

If this info is to be used, it is important not to confuse new users and we must try to use the terms used in wider electronics.

Thanks for the feedback

TVBG

QUOTE (Rail-Rider @ 18 Jan 2006, 13:58)THE Bus?
Here we hit maybe THE fundamental problem for beginners!
Mention of busses immediately makes it apparent that DCC may not be as simple as just buying a digital controller, a chipped loco or two, plug in and go. Sure, it CAN be, but the sheer volume of enquiries about busses and wiring is a dead giveaway that it is not really that simple in practice. If it were really that simple, those bus and wiring queries would have no need to exist!

To which, I must add and heavily emphasize that this topic is not aimed at someone making a fresh start with a clean slate (though it might be useful anyway), but is squarely aimed at modellers with well-established layouts who are contemplating its conversion to digital.

For these people, and there are probably thousands of them, it looks more and more certain that a simple 'two wire' setup just won't be adequate.

How to convert an existing DC layout to DCC;
1. Disconnect DC controller
2. Connect DCC system to wher you just removed the DC controller from
3. Turn all isolation sections so that all of the track is live
4. Turn on power
5. run trains

I could probably include a step 2a. Install decoders in your loco's, but as you don't have to do this with all your loco's before using them on DCC (with most systems) I left it out.

We were told, "all you need is two wires to the track", so why all this talk about 'busses' and wiring? Should we now forget the idealised 'TWO WIRE' principle as being far too simplistic for anything but the simplest layouts and therefore inadequate for converting anything more complex? You can forget it if you like, but there are only 2 wires from the system to the track no matter how big or small a layout is.

What, exactly, is a bus?A BUS (note capitalised) is any wire or multiple wires which has multiple connection points along its/their length. Think of a water pipe with several taps along it, that's a pretty fair representation of what a BUS is.

HOW MANY buses are needed?In DCC terms there are 2 BUSes, the track BUS, and the communications BUS.
What are the differences between busses? Why is a bus needed - what is it used for?
1.The track BUS - this is the 2 wires that come from the digital system and connect to the track at various places. This BUS is made up of 2 wires, one for each rail, as there is only 2 rails on a length of railway track you only need 2 wires for this BUS.
2. The communications BUS (Com BUS)- this BUS is made up of 4-8 wires and is what the throttles are connected to. This BUS allows the throttles and other devices (such as accessory decoders and block detectors) to communicate with the Command Station so that they are not only receiving commands but can also send back messages to the rest of the system. You can even eradicate this BUS almost completely if you use a system with wireless throttles.

Unfortunately it's not quite that simple, XpressNET isn't capable of handling all the device on your layout, so any system which uses XpressNET (Hornby, Lenz, Roco, ZTC) also has a 3rd BUS (the feedback BUS), this additional 2 wire BUS makes up for the missing functionality of XpressNET. There are also some systems which have the same problem as XpressNET systems, however instead of adding a 3rd BUS they simply don't have full functionality, have a look at the DCC systems Comparison Table and you will see these systems marked with a 'No' in the feedback column.

How do we know which bus people are talking about?In general when people are talking about 'the BUS' they are refering to the track BUS.

Lisa
Absolutely correct and expressed in simple to understand words (I hope its understandable by all?)

I touched on BUS wiring etc on the DCC forum today. See the item headed 'Wiring for DCC' where my offering is.
Hopefully my newly ordered DCC system is now winging its way across the Atlantic to me? So i'll be right in there BUSsing and CVing away!!!!
Brian

I'd probably call it 2 spare wires that I don't use
Seriously I've always drawn power for accessory decoders from the track, I've never had or seen the need for a seperate power supply for them.

That would explain why the LS150 is so cheap then!

BUS -a BUS (note capitalised) is any wire or multiple wires which has multiple connection points along its/their length.

You just need to give it a name like Accessory Power BUS?

You see, people, it really did need touching on didn't it.

Brian, your post/topic is linked to up there - thanks for making it.

I will now sit, watch and cogitate for a day or so again.

A DCC accessory or module may be a stationary point decoder, a signal decoder a feedback module etc. Some of these devices need power and or a DCC signal.

They can take the DCC signal from the main track BUS and they don't interfere with the DCC signals for the trains. They need their own 16V AC power so an accessory power feed. A BUS transports data, so a power feed is not really a BUS.

So the Lenz LS150 takes a DCC signal from the track DCC signal BUS (JK) and a 16V AC power feed (~).

I honestly don't know if these terms are 100% right. There is no DCC dictionary. Don't get any ideas Lisa

Doug:

I know what to call it but for the sake of friendship I won't Moving away from the Lenz/Digitrax debate, what then do Canbus users have ? do they need a feedback whatsit ?

Doug,

1.I called The two wires running around my layout from amp to track via droppers the 'Power Bus'.

2.I called the two wires running from transformer to a row of stationary decoders an 'accessory power bus'.

On Lisa's definition this is ok (see above).

On my definition this is ok (obviously).

You say it is not, and then say your not sure because there is no dictionary of terms. If you are not sure you are 100% correct; How do you know i'm a 100% wrong? I might be or I might not be, but how do you, Doug the Mod, know ?

Doug I will not chase you on this anymore. When we first start on dcc we all become a little OTT in our excitement. I think you have just got carried away a little in manual land. If you read the post again; all i was trying to do, was pass on an idea for a flexible system that I paid dearly for in time and effort and has worked for me over the last couple of years.Looking at where you are you might like to try it.

Do not be too pendantic in you role as mod here; rubbish the content by all means if it is a bad idea? Remember, a power bus can be called 'twat knickers' tomorrow if thats what we all agree upon and all understand was formaly called a power bus!

Hand shakes at dawn?

TVBG

Let me tell you that as someone looking to start in DCC I thought that I had the bus issues sorted before I read this thread but now I am mightily confused.

I understand exactly what a bus is & I accept that you can have as many buses as you like each of which connects to its own outlets - be they track power, signals or whatever else BUT I am now totally confused about how many wires I need to thread around my new layout.

1. I hope we would all agree that I need a track power bus and that this is 2 wires of different colours to aid identity that are connected regularly to the track so that one rail is always connected to one wire & the other colour wire to the other rail. Basically the connections from this bus to the rail should ideally be such that there is a connection to each rail between every rail joiner - eg onto every piece of track. I have learnt that the bus should not be a ring circuit but needs to terminate. I guess that in a tailchase layout for that to mean anything the track must not be a ring circuit either and must thus have insulated joiners that correspond with the break in the power bus.

2. Now it gets complicated. Some of you are telling me that I can take power for accessories from the track & some of you say not & thus that I nees a separate bus. I am totally at a loss to know whether the control signal for these accessories comes down the track bus or down the accessory bus or whether I really need one. 2 more wires.

3. I now come to the feedback bus the necessity for which seems to depend on the brand of DCC that I buy. Lenz & its cronies need such a bus whilst Digitrax does not. As I haven't decided which system to buy yet & I may change my mind that is 2 more wires. I assume that this bus needs connecting to something but I am nor sure what. If guess it is just accessories rather than the track & I am sure that I will need to make it easily accessible for that extra accessory I will buy that they haven't even invented yet.

4. As I might like to do something else on my layout like put lighting into buildings I need a separate power supply for that as well. 12v & 2 more wires & again easy access to put extras onto it in the future.

The way I count this I need to run 4 buses and thus have 8 wires. There may be others that I haven't thought of yet. When I started this I would never have imagined that I would need more colours that my electrical wholesaler can supply but it appears that I do.

How am I doing?

Chris

QUOTE (Doug @ 18 Jan 2006, 20:39)I honestly don't know if these terms are 100% right. There is no DCC dictionary. Don't get any ideas Lisa
Spoilsport I was actually thinking of doing that.

QUOTE (ChrisE @ 18 Jan 2006, 23:27)Let me tell you that as someone looking to start in DCC I thought that I had the bus issues sorted before I read this thread but now I am mightily confused.
Don't worry, they've almost confused me too.

QUOTE 1. I hope we would all agree that I need a track power bus and that this is 2 wires of different colours to aid identity that are connected regularly to the track so that one rail is always connected to one wire & the other colour wire to the other rail. Basically the connections from this bus to the rail should ideally be such that there is a connection to each rail between every rail joiner - eg onto every piece of track. I have learnt that the bus should not be a ring circuit but needs to terminate. I guess that in a tailchase layout for that to mean anything the track must not be a ring circuit either and must thus have insulated joiners that correspond with the break in the power bus.
OK, you've got this mostly worked out, however there is no reason why you can't have aring circuit, the need to terminate this BUS is an age old myth which comes up from time to time, ignore it and build a ring main like the rest of us.

QUOTE 2. Now it gets complicated. Some of you are telling me that I can take power for accessories from the track & some of you say not & thus that I nees a separate bus. I am totally at a loss to know whether the control signal for these accessories comes down the track bus or down the accessory bus or whether I really need one. 2 more wires.
It would seem that some of the cheaper accessory decoders need a seperate power supply rather than using the track power, avoid these decoders and you won't need this extra BUS.

QUOTE 3. I now come to the feedback bus the necessity for which seems to depend on the brand of DCC that I buy. Lenz & its cronies need such a bus whilst Digitrax does not. As I haven't decided which system to buy yet & I may change my mind that is 2 more wires. I assume that this bus needs connecting to something but I am nor sure what. If guess it is just accessories rather than the track & I am sure that I will need to make it easily accessible for that extra accessory I will buy that they haven't even invented yet.
You can avoid this extra BUS by buying a system from CVP, Digitrax, NCE, or Zimo, these are all top notch systems which you pretty much can't go wrong with. If you want to complicate matters then buy an XpressNet system (Hornby, Lenz, Roco, ZTC) and add 2 more wires to your list.

Come to think of it, I don't think ZTC has a feedback BUS, it's just missing a chunk of functionality.

QUOTE 4. As I might like to do something else on my layout like put lighting into buildings I need a separate power supply for that as well. 12v & 2 more wires & again easy access to put extras onto it in the future.
You can run your lights from track power, I do.

QUOTE The way I count this I need to run 4 buses and thus have 8 wires. There may be others that I haven't thought of yet. When I started this I would never have imagined that I would need more colours that my electrical wholesaler can supply but it appears that I do.
How am I doing?
Actually by your reckoning you need 5 BUSes, you missed out the Com BUS which the throttles plug into. However DCC only requires 2 BUSes;
The Track BUS
The Com BUS
Extra BUSes are only required to make up for a deficiency in either the system or the accessories you connect to it. This all comes down to which system you buy, and which accessories you buy, you pays your money and you makes your choice. However you definitely don't need more than 2 BUSes on a well designed DCC system.

A lot of it is just people being anal, myself included. There is this desire to tinker and over-engineer more that any real need of the equipment.

BTW,

You might want to consider another electrical wholesaler.