PJ_model_trains Posted March 8, 2014 Share Posted March 8, 2014 IF YOU ARE INSTALLING DCC INTO YOUR LAYOUT THERE ARE 3 AREAS YOU NEED TO CONSIDER 1 - Cable size for your droppers 2 - Cable size for the wire from your controller to the DCC Bus 3 - Cable size for the DCC Bus The details below have been prepared, with the help and expertise of many, to help you get started with your model railway using DCC. The wires are the minimum sizes recommended subject to your layout size. (see below) You also need to consider what type of DCC Bus you want to install, it doesn't matter which you choose, they all work well, it is personal choice and down to layout shape. The different types of DCC Bus are; Radial, Ring or Star circuits, you can find out more about these at this web site. http://www.brian-lambert.co.uk/DCC.html#Comparison ITEM 1 & 2 Cable size for your dropper wires & cable size for the wire from your controller to the DCC Bus These wires do not have to be as heavy as the wire for the DCC Bus but, they can be if it is easier for you. It is however recommended, to prevent damage to terminals of controllers that use always use the flexible wire provided by the manufacturer between the DCC Bus and the controller, this is sufficient. ITEM - 3 Recommended minimum cable size for the DCC Bus RECOMMENDATIONS FOR CABLES SIZES TO USE FOR A DCC BUS SUBJECT TO LAYOUT SIZE Here is a guideline: Please, DO compromise as little as possible! Suggested minimum requirements Small: Up to 8’ x 4’ (2400x1200) , or shelf type layouts. 16 Gauge Definately no less than…. 20 gauge Use: 1.0mm2 domestic property lighting cable Medium: Say up to full room layouts 12 x 20 (3600 x 6000). 14 Gauge Definately no less than…. 18 gauge Use: 1.5mm2 domestic property lighting cable Large: Over 12 x 20, club layouts, very long layouts. 12 gauge Definately no less than…. 14 gauge Use: 2.5mm2 ring main domestic power socket cable for layouts Although these figures have a built in level of safety please use them as guidance as minimum wire sizes to use. Multi-strand cable can be used The formula for calculating cable size being... ((R * R) * Pi) * strands = mm wire thickness Pi = 3.14159265 R = radius of each wire Strands = number of strands in each cable, 1 for solid, 32 for 32 strand cable etc. For more details see heading 'Your Example' above. ADDITIONAL RECOMMENDATION: DCC CIRCUITRY It gets quite technical on inductance problems with DCC circuitry but concludes the best solution to minimise this is to use separate cables twisted together at 12 turns per meter or more, and it prefers star wiring to ring, with terminators. ADDITIONAL RECOMMENDATION: DROPPER WIRES TO DCC BUS Another subject of heavy debate but here are a few brief guidelines. Brian Lambert and other technical people who are considered to know what they are talking about, recommend one dropper to every rail in your layout. It is clear from discussions in the forum some get away with a lot less than this so we do need to look at why the specialists say this. The reason is because you need an even distribution of power around all of your layout, the second reason is because fish-plates/rail-joiners are a weak connection yet are expected to transfer power from one rail to the next without any drop in current supplied. It has been suggested that one pair of droppers every other length of standard track is probably a reasonable option as the chance of failing or weak fish-plates is unlikely to be either end of a rail. Having said that it also depends on expansion and contraction which is what the fish-plates are for and how many times rails have been put together and taken apart, every time it is done there is a definite risk of weakening the join and reducing the current that passes across the fish plate. For the same reasons as stated above it is not advisable to solder droppers direct to fish-plates, you would be in effect soldering to the weakest link. Good luck with your layout. SHOULD ANYONE HAVE ANY QUESTIONS ABOUT DCC BUS OR ANY OF THE ITEM LISTED HERE *** PLEASE DO SO IN A NEW THREAD *** Link to comment Share on other sites More sharing options...
Blackbird Posted March 9, 2014 Share Posted March 9, 2014 Thanks to PJ_model_trains, for listing a 'guide' to DCC bus mains. There is nothing wrong with the parameters suggested, If a busmain is REQUIRED. The title: IF YOU ARE INSTALLING DCC INTO YOUR LAYOUT THERE ARE 3 AREAS YOU NEED TO CONSIDER. implies that; if running DCC, a busmain is required! This is incorrect. It imposes an additional encumbrance on entrance to DCC control to model railways. They are NOT A REQUIREMENT, they are an addition, IF required! Basically. you can operate a DCC layout without the additional complexity of busmains using the basic Hornby, (or other compatible make track) (Hornby haven't yet recommended the use of busmains) Busmains overcome the 'possible' deterioration of track joiner connections, the rails (NS) have an adequate current capacity for the (average) moderate sizes layouts. Busmains provide the extra security for large, long term layouts. The frequency of droppers is only relevant to the condition of the track joiners, (one per rail implies that all track joiners are defunct) The principle of busmains is sound and the previous listed cable sizes more than adequate, but they aren't allays required for DCC operation! Don't put prospective DCC operators or entrants to the field off with the additional complexities of Busmains. Link to comment Share on other sites More sharing options...
PJ_model_trains Posted March 9, 2014 Author Share Posted March 9, 2014 Blackbird said: Thanks to PJ_model_trains, for listing a 'guide' to DCC bus mains. There is nothing wrong with the parameters suggested, If a busmain is REQUIRED. The title: IF YOU ARE INSTALLING DCC INTO YOUR LAYOUT THERE ARE 3 AREAS YOU NEED TO CONSIDER. implies that; if running DCC, a busmain is required! This is incorrect. It imposes an additional encumbrance on entrance to DCC control to model railways. They are NOT A REQUIREMENT, they are an addition, IF required! Basically. you can operate a DCC layout without the additional complexity of busmains using the basic Hornby, (or other compatible make track) (Hornby haven't yet recommended the use of busmains) Busmains overcome the 'possible' deterioration of track joiner connections, the rails (NS) have an adequate current capacity for the (average) moderate sizes layouts. Busmains provide the extra security for large, long term layouts. The frequency of droppers is only relevant to the condition of the track joiners, (one per rail implies that all track joiners are defunct) The principle of busmains is sound and the previous listed cable sizes more than adequate, but they aren't allays required for DCC operation! Don't put prospective DCC operators or entrants to the field off with the additional complexities of Busmains. Thanks for your comments Blackbird. I must say I do not take credit for this, it is the work of yourself, Fishy, Raven Electric, Brian Lambert and others. All I have done is collated them to create a new thread with facts for beginners so that when a question arises, 'what size cable should I use for DCC Bus', all we need to do is point them to this thread. The above does not say a DCC Bus is necessary see, ADDITIONAL RECOMMENDATION: DROPPER WIRES TO DCC BUS, but does give reasons why it would be wise to consider doing so. Should a person having considered the risks of not having a DCC Bus then that is their decision, on the other hand should they decide to install one, the table of wire/cable sizes is there to help. All we have done collectively is debated at great length, what the experts say, what we know (meaning those with electrical knowledge and/or experience) and provided a few facts to help the new comer to the hobby. We are aware a few members have not installed a DCC Bus and have not yet had any problems, Hornby are aware of the technical recommendations for the DCC Bus and the discussions on the forum, they have decided to leave it to the individual to decide, I think we have all done our bit here and should now do the same. May be Hornby have not recommended the DCC Bus because they do not manufacturer or sell any part of it, we do not know, it is probable but again, we do not know. All we know is they have left it to the individual to decide. Should anyone enquire, 'what size cable do I need for a DCC Bus' any member of the forum can now refer them to this short, factual thread. It is the work of many, designed to help the new comer get started with their hobby and enjoy model trains as much as we all do. The link is https://www.hornby.com/forums/hornby-forums/hornby-digital/6592/ SHOULD ANYONE HAVE ANY QUESTIONS ABOUT DCC BUS OR ANY OF THE ITEM LISTED HERE *** PLEASE DO SO IN A NEW THREAD SO AS TO KEEP THIS THREAD AS SHORT AS POSSIBLE *** Link to comment Share on other sites More sharing options...
RDS Posted March 9, 2014 Share Posted March 9, 2014 Blackbird said: ... They are NOT A REQUIREMENT, they are an addition, IF required! ..... Don't put prospective DCC operators or entrants to the field off with the additional complexities of Busmains. Well said! Exactly the point I have been trying to make as well. Link to comment Share on other sites More sharing options...
Fishmanoz Posted March 9, 2014 Share Posted March 9, 2014 And to again acknowledge the source of the information in PJ's post so we can avoid any suggestion of plagiarism, the content of his post from ITEM 3 to 'Your Example' above is taken directly from the technical advice on the DCC Concepts website, as is the figure of 12 turns per metre for twisting the bus wires. Link to comment Share on other sites More sharing options...
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