DCC Bus questions

Discussion in 'DCC & Electronics' started by josef86, Aug 7, 2007.

  1. josef86

    josef86 TrainBoard Member

    I have an nscale layout that is being upgraded to dcc. I'm not sure how to run the bus lines. I as thinking of using 16 awg (or do you think 14 awg is better?) for the bus lines. Feeders will be 22 or 24 awg. Would stranded or solid core be better? thanks. I have an idea how to run them but I'm not sure where to start or stop them.
  2. jlbos83

    jlbos83 TrainBoard Member

    As far as the size of the bus wires, it depends on how long they are going to be. So it depends on the size of the layout. You can't go wrong with 14, and it is easy to come by. But 16 will be fine if your layout is smaller rather than larger. Stranded or solid doesn't really matter. Stranded can be easier to work with, as it bends more easily. Electrically it doesn't matter, so choose what works best for you. As far as where to start and stop, again it depends onthe layout. The objective is to minimize the length of the run from your booster to any point on the track. Think about that and work from there. If you post a pic of your layout design someone would probably make suggestions.

  3. GM

    GM TrainBoard Member

    Wiring for DCC


    Point your browser to Mark Gurries DCC Presentations. Then select DCC Wiring for an exhaustive dissertation on the science of wiring for a DCC layout. Mark covers all of your questions and more.

    Towards the end of the PDF file you will find a very easy to read discussion of the subject of selecting wire size for buss lines and feeders.

    I hope this helps.
  4. josef86

    josef86 TrainBoard Member

    I will have to check that out. Its a 4x10 layout. Its a single mainline, but is looped around in such a way to simulate double main. It has changed so many times, before I found a design I wanted to stick with. The pictures I have show this.


    If could likly draw it out if it would help. One of the picture shows 4 track wide. Two of them are Eastbound and two are Westbound. (eletrically speaking).
  5. jlbos83

    jlbos83 TrainBoard Member

    At 4x10 16 gauge would most likely be fine. Remember, the bus does not have to follow the rails, and there can be more than one coming from the booster. One idea would be to run a spine across the middle of the layout the short way, and then three or for double ended lines off of it a foot or so apart. Then just put feeders from the track to the closest pair of bus wires. No place would be more than about 6 inches from a bus, and no bus would be more than about 9 feet long, at the very most.

    Ignore the dots, they just get things lined up.

  6. josef86

    josef86 TrainBoard Member

    Okay, I will do that.
  7. josef86

    josef86 TrainBoard Member

    Okay, I read everything and I have a couple of questios to make sure I read it correctly. If I choose to twist my bus cables I would be twisting the commen and main bus cables.

    I am using red for main and black for commen. Or I guess we can call it a rail and b rail buses. So A is red and b is black. I would be twisting the red and black togather? (I would assume it the same idea as network cables having twisted pairs).

    Now the real question I have is how do I terminate the end of a bus? Are the ends of the buses (Red and Black) connected by a RC coupler? Or did I mis understand that.

    From what I can tell DCC to need extra attention to detail then dc layouts.
  8. mfm_37

    mfm_37 TrainBoard Member

    Twisting the red and black bus wires is not really necessary on your layout. Won't hurt though. Red for Rail A and Black for Rail B is a good choice, NTRAK uses the same color code and it matches NMRA color standards for decoder rail pickup. Be careful that you follow each rail especially when the main loops back.

    No need to terminate. Just tape the ends of the bus wires to keep them from shorting or connect them to the last feeds on the run. Good advice previously to locate the booster as close to center of the bus as possible. Keeps voltage drop to a minimum.

    Not really. It's still two wires connected to two rails, same as always. Reducing voltage drop and using enough feeders is good for analog and DCC.

    Martin Myers
  9. Gats

    Gats Staff Member TrainBoard Supporter

    Red and Black or A/B for the DCC bus is fine. As long as you connect the track feeders the same, ie red to outside rail, throughout the layout so you don't have any shorts. For the bus I would twist them 6-8 times per metre for good measure. It doesn't need to look like a plait and if it's untwisted for 1/2 metre don't worry overly.

    For the length of run indicated I don't see the need for a RC coupler. From what I understand it's needed for long runs where the possibility of 'ringing' or an echo is increased causing commands to become garbled and rejected.

    Josef, look at it as more attention to detail for less overall wiring. ;)
  10. josef86

    josef86 TrainBoard Member

    I have started with the feeders. By doing the feeders first I can make sure I keep their lenght down. I remembered that in one place two of the tracks have a different polarity then the two tracks next to them. My booster is about as close to the center as I can make it.

    I need to go out and by some 16 awg for the buses. My main priority at this time is to get all the power wiring done. So I can move on to the detection stage using CTI products.

    Thanks for all the help.
  11. bradb

    bradb TrainBoard Member

    Posi-Locks and pre-made (cheap) module wiring?

    Hey all!

    I'm building a modular N scale Layout, with 2 modules 1'x4', one corner module that's 2'x2' (actually cut like the Ntrak corner modules) and maybe 1 or 2 1' modules attached at each end, basically in an "L" formation.

    I'm building a point-to-point switching layout (a variation of 'Union Freight') and am just about finished with the modular benchwork. I want something kinda portable but not compatible with any current standards.

    So while I was looking around gathering parts to wire the bus for DCC, I found http://www.posi-lock.com/posiplug.html.

    Has anyone used them? Sounds simple and easy.

    I was thinking of using them in combination with pre-made 6' lengths of stereo cable from radio shack (a red/black cable with male RCA connectors on one end, female RCA on the other).

    If I used that with posi-locks, my wiring would be very fast and easy (well, after I solder the feeder wires). Since the track plan is fairly simple, the bus will probably go straight down each module.

    So... do you think this is a viable solution? Any suggestions on things I missed or maybe a better answer?


  12. L Lee Davis

    L Lee Davis TrainBoard Member

    To lessen the confuseion think RED RIGHT RAIL. See photos hope they help.

    "Still Training After All These Years"

    Attached Files:

  13. L Lee Davis

    L Lee Davis TrainBoard Member

    Brad, Very cool site I will have to give them a try.

    "Still Training After All These Years"
  14. kiwi1942

    kiwi1942 TrainBoard Member

    DCC wiring

    Very New to DCC and wiring, "downunder"

    changing over to DCC and would like to know what diameter of this supposedly BUS WIRE(12-14 AWG) and Droppers (18-22 AWG)

    Layout Home Version 10ft x 6 ft, adding modules to 30ft x 10ft, inbetween the Home version, there is going to be 3 modules 8ft x 2ft, of which will be Straight tracks, each modules with have D plugs and IDE cable to join from one to the other and at the joins and now with the BUS, I am thinking of having bigger plugs to make the joint, with perhaps RCA plugs

    thanking you
    Last edited by a moderator: Jul 27, 2008
  15. mfm_37

    mfm_37 TrainBoard Member

  16. kiwi1942

    kiwi1942 TrainBoard Member

    DCC wiring


    Thanks very much
  17. NorsemanJack

    NorsemanJack TrainBoard Member

    Then you need to be sure to twist your wires the opposite direction! :D

    Or, did you mean, "downunder" the layout?

    But seriously, with respect to the question of BUSS gauge, my round the walls layout uses 16 gauge lamp cord for the buss, but since it creates a complete loop, doesn't that give me the equivalent of two 16 gauge wires? Actually, it's all DC today but will soon be DCC.
  18. Gats

    Gats Staff Member TrainBoard Supporter

    Maybe someone with more experience will chime in here, but I don't think a complete loop for the power buss is a good idea. There could well be an echo created in the data stream which will confuse the decoders. DC hasn't the problem since there is only voltage involved.
    I would recommend a command station to end point/s (star) arrangement.
  19. NorsemanJack

    NorsemanJack TrainBoard Member

    If the track creates a complete loop, than a loop is unavoidable. After all, the buss is only a mirror of the track circuit.
  20. Lownen

    Lownen TrainBoard Member

    I've run DCC on continuous loops in both HO and N scale layouts with no problems. I've done loops so big that they needed multiple feeders. And of course the sidings and spurs needed their own feeders as well. Everything ran fine. The only isolated sections of track were the reverse loop and the programming track. And my programming track is a siding that I can switch between DCC operations and programming.



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