Boy Do I Need Help

Discussion in 'HO Scale Model Trains' started by bspun2, Mar 6, 2007.

  1. bspun2

    bspun2 New Member

    Well guys this is really bad i got this 7ft x 12ft train table I have my track laid and all the switches wired but not the track. I just bought the MRC Prodigy Advance DCC System.
    But I still want to wire my train to run analog. My ? is how? I'm trebbley lost.I sepperated all the side track with the plastic rail joiners. "when i say all the track i meant from loop to loop" I have 22 turnouts that are insulated from the next section. What do I need to do where the power is reversed?
  2. The Atlas Twin or Selector will allow you to choose the polarization (sp?) of the track. I'll post a pic tomorrow, when I'm not posting from my WII. sign1
  3. dsfraser

    dsfraser Member

    To begin with, DC and DCC are fundamentally incompatible. DC is Direct Current. DCC is Alternating Current. If you put an ocilloscope across the track, DC i a flat line where DCC is a classic sine wave. Those systems that suggest you can run a DC locomotive on a DCC circuit do so by breaking the AC into chunks, and only feeding current to the DC locomotive on the "uphill" side of the sine curve. This is very hard on the motor, and something I would caution against.

    Reliable DCC operation requires very good trackwork, and very good conductivity, which means lots of feeders and clean track. This sounds onerous, but it also has great advantages. It is not necessary to split the layout into blocks with insulators. It can all be one big circuit. You park a locomotive with the decoder, not by shutting the power off to the piece of track the locomotive is sitting on. You don't have to worry about reversing loops, because the decoder will "decode" which half of the AC it needs to maintain motion. There is an extra level of complexity in learning how to use DCC, an additional cost in equipping all your locomotives with decoders, and your trackwowrk has to be solid, but overall the wiring of the layout is very much simpler.

    With DC, you have to insulate, isolate, and power every separate block of track. You need a battery of DP/DT switches to turn power off and on to each block. You need a diagram to figure out which switch works what. Some will say that's where the fun is, figuring out why your locomotive stalls or arcs on a switch, but I'm not one of them.

    If you wire your layout for DC operation, when the time comes that you make the change to DCC, you'll end up ripping out all the DP/DT switches and tying the wires into two bundles, + and -. All your insulators will be redundant, in fact will inhibit conductivity, and should properly be replaced with metal connectors for more reliable operation.

    When I find the time, my old DC layout is on it's way out the door. I have to put decoders in twenty-odd locomotives, but my new layout will be DCC from Day One (Digitrax Zephyr).

    If you're just starting out, I'd urge you to choose DCC, which is the way of the future, and wire your layout accordingly. Go buy a used laptop and incorporate it into your system. Install block detectors, program it so that your locomotives will stop if there's an open switch leading to an oncoming train. Use it to set your signals to green or red, depending on other traffic. Use it to drop crossing gates. DCC adds so much to the realism and enjoyment, it's hard to summarize in a couple of paragraphs.

    Do some reading. I spent a year researching DCC and various systems before I chose to go that route. There are several DCC forums on Yahoo and elsewhere with many knowledgeable people. Check them out.

    In any case, to answer your specific question, "What do I need to do where the power is reversed?", you have to ensure that the direction of DC current in the loop matches the direction of the incoming train. Then, while the locomotive is in the loop, you have to change the polarity of the DC current in the outgoing track with a DP/DT switch. (DP/DT = double pull / double throw — get em at Radio Shack, or use Atlas switches).


    Scott Fraser
    Calgary, Alberta
  4. Jim Krause

    Jim Krause Active Member

    I can tell you what we do with our club layout to make it DC operational for use with a coin system for the museum visitors. Remove the DCC components and wire up the three mains to DC power supplies. Of course all we have then is continuous running on three separate loops, turned on and off by the money machine.
  5. MadHatter

    MadHatter Charging at full tilt.

    Hi bspun2 & dsfraser

    The above is only true on a smallish layout. If you have two yards for example it is recommended that you isolate the two because if a short occures in one of them you will find the fault quicker because trains only stop at that one yard.

    When you isolate the sections/yards on your layout these will be known as power districts.

    I suggest find a friend whos has a digital system and ask for his/her manual also operate with it a bit so you can get a feel for it.

    I recommend the Digitrax Zephyr because I have always found useing Digitrax items easy to use.

    The Zephyr has another one up above the rest- you can attach two smooth control
    (no pulse power) DC controllers to the system and program them to act as digital controllers, with the exception of not being able to control the funtions such as sound, lights, etc.
  6. Torpedo

    Torpedo Member

    A bit of contradictory advice here. First you say rip out the blocks and get rid of the insulating gaps, then you say install block detectors, which require insulating gaps and blocks. :oops: Could be a little confusing.

    DPDT (the "/" is generally not needed or used) stands for double pole double throw, not double pull double throw.
  7. pgandw

    pgandw Active Member

    Hey guys, read the original post. The OP states he has a Prodigy Advance DCC and wants to run analog (DC) as well.

    Point: Prodigy does NOT support DC operation under DCC control (zero-stretching of Digitrax and others). So layout must be wired to switch from DC to DCC operation, but NOT both simultaneously.

    First, to switch back and forth successfully between DC and DCC is going to require knowledge of the decoders in your locomotives.
    • You cannot run non-decoder equipped locomotives on Prodigy DCC. So any locos without decoders must be removed from the layout when running DCC.
    • SOME (most newer) decoders will automatically sense whether DCC or DC is in use and configure themselves automatically to run under the system in use.
    • SOME (many older) decoders cannot be run on DC. These locomotives must be removed from the layout when running DC.
    Next issue is your existing insulated rail joiners. The plastic insulated rail joiners are notorious for not holding track in mechanical alignment. Unless they are needed because you have "power routing" turnouts, it's best to replace as many of the plastic rail joiners with metal as possible. Most folks cut gaps in the rail using a tiny saw or Dremel wheel. The gap is filled with a piece of plastic glued in place and filed to shape to prevent the rails from creeping.

    In the interests of keeping things simple, I recommend no gaps or insulated rail joners unless needed for the turnouts. However, this does restrict you to one locomotive with DC operation. But the point of DC analog operation should be to tide you over until all your locomotives have decoders. The advantages of running multiple trains with finer control using DCC will make you want to change to pure DCC as quickly as you can.

    If you insist on 2 train operation on analog DC, you will need to do the whole block wiring thing, insulating both rails at every block junction. DCC does not tolerate common rail wiring very well, hence the need for insulating both rails.

    To use either DC or DCC, you wire your track to the center terminals of a DPDT toggle. The DC track power goes to the terminals at one end, and the DCC track power goes to the terminals at the other end of the toggle switch.

    Multiple power districts are not necessary for the size of layout you have. They can be handy at a later date once you have learned how you will use your layout. A derailment and resulting short causing the whole layout to shut down is not a bad thing on smaller layouts! But if you put in block wiring, you already have the ability to isolate various sections of track in DCC for trouble-shooting.

    One other issue about dual mode operations - lighted locomotives and cars. DCC generally provides a higher track voltage than DC. Lights set up to work on DC may blow quickly or have much shorter life spans on DCC.

    If managing these issues seems too confusing, I recommend you get and study one of the books on model railroad wiring. Or just forget about analog DC operation, and enjoy your new DCC unit.

    my thoughts, your choices
  8. bspun2

    bspun2 New Member

    well that makes up my mind. I'm going 100% dcc sounds like it will be easier to wire.
    thanks guys
  9. dsfraser

    dsfraser Member

    Torpedo, if you read it carefully, I say that for DC operation, you need to split the layout into isolated, insulated blocks. Afterwards, when moving to DCC, these blocks are redundant and can be merged.

    MadHatter makes a good point — nothing ever works as planned, and being able to isolate particular sections of the layout does make troubleshooting much easier.

    Fred makes some very good points too, particularly to get a good book on wiring. It can get very complicated, and as you become more knowledgeable and more sophisticated in what you want to do, understanding the principles and establishing a system for wire colours and labelling will save you much grief in the years ahead.

    And I'm glad you've opted to go with DCC. It has "inner bigness" that will allow you do what you want for now, and can grow as you expand your model empire.

    Scott Fraser

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