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.
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.
