Newbie in DCC

Discussion in 'DCC & Electronics' started by Railroy19, Apr 23, 2006.

  1. Railroy19

    Railroy19 New Member

    Hello to all fellow trainzers. My first post on this forum.
    I have just rewired an existing N Gauge layout of mine. After reading lots of information on the wiring for DCC forums. I ran a new set of bus wires 14 gauge all around my layout and dropped all new 18 gauge feeders from the tracks about every 3 feet or so, that was fun! sometimes I had a tough time getting up from under the table:)
    I used a home made tester hooked up to the track to be sure I did not cross any feeders to the wrong bus wire, that worked very well. I tested evrything out and the wiring is fine.
    I was very happy that it worked all so good. Now I thought to myself with all of this great wiring of heavy gauge wire the system will work real good. Which by the way does work great. I have the NEC Pro system 5 amps. My layout is L shaped about 17 feet by 22 feet.
    Now my question is how come you need such big wire for a bus system when the connectors to the command station are only like a 28 gauge telepnone wire size??sign1
    Thanks for reading this.
  2. Harold Cole

    Harold Cole Member

    It is because of voltage drop,the bigger the BUSS Feeder Wire the less voltagedrop from the source of power.
  3. pgandw

    pgandw Active Member

    It's the amount of current going through the wire that determines the wire size. Your command station bus uses low current digital signals, so doesn't need heavy wire. Your track bus is both the digital signal to the decoder and the power for the locomotive, lights, sounds, etc. Minimum wire size for 5 amps is 20 gauge. But that assumes a higher voltage drop due to the resistance of the wire than we want for reliable operation of our DCC trains. If you were never going to use more than 5 amps on the layout 16 gauge wire would be sufficient. Some also say feeders every 6 feet is sufficient. The problem with wiring overkill, just like benchwork overkill, is that nobody knows exactly where the "line of death" is - how close can you cut it without having problems occur. And nobody wants to be the experimental guinea pig either.:)

    yours in wiring
  4. Railroy19

    Railroy19 New Member

    Thanks guys
    I just thought the heavy wire connecting to such a small connection did not seem right.
    I'm used to heavy screw on connections of DC power packs.
    I just hooked up my reversing module and I'm really impressed with the smooth operation thru a reversing loop. Great new technology. Now I have to figure out how to get my two new engines to run at the same speed. This should be fun.

    Thanks again.
  5. GeorgeHO

    GeorgeHO Member

    You need a bus wire big enough to carry all the current used by all the locomotives and lighted cars on your pike. The smaller feeder wires will only be hooked up to a few locos. It's like the plumbing in your house, your bathtub only needs a small pipe to supply it, likewise the kitchen sink and the clothes washer. If all three are being used at once, then you will notice a decrease in pressure (current) unless the pipes supplying them are big enough to handle the load. And the pipes suplying your house must be far bigger, big enough to supply your neighbors also. In addition, as already pointed out, the smaller the wire the greater the resistance. What that means is that smaller wire is heating up and using/wasting electricity over its whole length which leaves less electricity for your locos the further you get away from the power pack, but the larger wire will deliver almost all the electricity to your trains.
  6. Railroy19

    Railroy19 New Member

    Thanks George

    I see that I now have a lot to learn about DCC. This forum has lots of great information on trains and operating systems.
  7. lester perry

    lester perry Active Member

    I like the question and don't get the answer. I noticed also that the terminals on the power supply were very small. The wire going from power supply is about 18 gauge maximum. I cant fit any larger into the terminals. Then I step up to what I run to layout. How does enough water get through small pipe to fill the large one? I am not having any problems but I don't get it.
  8. Railroy19

    Railroy19 New Member

    Hi Lester

    My thoughts exactly its like hooking up a three inch water pipe to a half inch water line just the reverse of logic to me. Although it works fine the way it is.

    In ventilating systems the main ducts are larger at the unit and smaller at the outlets.
  9. Railroy19

    Railroy19 New Member


    Sorry posted twice:oops:
  10. lester perry

    lester perry Active Member

    After reading you original post again it sounds like you are speaking of the wire going to the controller, I am speaking of the wire going to the track. Which are you trying to find out about ?
  11. Harold Cole

    Harold Cole Member

    The longer the run of wire the more voltage drop,so if you have 50 or 60 feet of 18 gauge wire,you start with 14 volts by the time you get to the end of the run you might only have 11.5 volts.This is a fair amount of voltage drop ,so the bigger the gauge of buss wire you run the less amount of voltage drop.The smaller has a certain amount of resistance over a long run, so the bigger the wire the less resistance and less voltage drop.Several less volts can make a big difference.Running 4 of 5 HO engines could be pulling 3 to 4 amps at a 14 volt source with a big wire buss,but with an 18 gauge at the same 14 volt source it could be pulling 5 or more amps,and with 12 to 14 volts this could cause problems.
  12. Billy Youll

    Billy Youll New Member

    I'm sorry If I sound a little slow but as I'm very new to DCC can you please clear
    something up for me I only run a short 0n30 line which I ran with dc up till now
    I'm about to start up with DCC (I opened the box of my new Empire Builder to day)
    so could I run my DCC outfit with my old light weight wiring or should I pull It all out
    and rewire in the same way Mr railroy19 has done
  13. Nazgul

    Nazgul Active Member

    BILLY, If you had no problems with dc, you should be ok. Before I yanked the wires, I would try it. The worst thing that could happen is you will have power droppage at your furthest points. If this is the case, then rewiring will be needed. It wont hurt to try.

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