Wiring

Discussion in 'HO Scale Model Trains' started by Prof1000, Mar 5, 2008.

  1. Prof1000

    Prof1000 New Member

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    Hi Folks

    On my layout I have a 6 track yard that is wired with two cad atlas controllers. It runs off off a dual power pack. The main line is powered by walk around set up. My question is I have a track from the main line going into the yard and I have it insulated with one plastic rain joiner. I have not turned on both power sources at once as of yet. I am wondering if I need to insulate both rails on the line going into the yard. If not will it cause a short on one or both power packs. Thanks for the help.

    Brian
  2. RusticBob

    RusticBob New Member

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    You must always insulate both rails to prevent any cross feeding into a DC power pack. To use multiple Packs on a section of track... One at a time... Place a selector switch between the packs and the track. DPDT switch will allow 2 packs, and rotary selectors will allow additional. Both + and - leads must be switched. I am sure someone has a simple schematic for this. Hope this helps.
  3. MasonJar

    MasonJar It's not rocket surgery

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    You cannot use common rail wiring schemes with more than one power pack. If two packs were to ever feed one block, you would have a bit of a problem :eek:

    You must fully insulate each block (i.e. both rails) and uses DPDT or rotary switches as per Bob's post.

    Andrew
  4. steamhead

    steamhead Active Member

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    You CAN use common wiring with two power packs AND use common rail wiring....I wired my previous layout like that and ran it for 12+ years....To isolate the blocks you need only one insulated rail joiner (except for special track conditions such as reversing loops, live frog turnouts, etc.). You also don't need DPDT switches, a SPDT/Center-Off switch will work just fine....
  5. MasonJar

    MasonJar It's not rocket surgery

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    Gus...

    I stand corrected...! Can you show how this is done? I think some sort of diagram is what Brian is after...

    Andrew
  6. steamhead

    steamhead Active Member

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    Hi...I'll try coming up with one tonight...scan it at work in the morning, and post it....(If I remember how it was done....):mrgreen:
  7. Ralph

    Ralph Remember...it's for fun!

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    I was going to say that it wasn't necessary to insulate both rails. Electrical wiring is not my favorite part of the hobby so I use Atlas selector switches for block control. I have two power packs. The layout is wired with a common rail and the other is divided by insulated rail joints into blocks. Works just fine with trains traveling on different blocks controlled by different power packs in different directions. Like I said, I'm not electrically minded, but I would have thought a series of DPDT switches would be needed if not using the Atlas selectors.
    By the way, you guys who insulated both rails, I assume you have to provide feeders to every block? Probably not a bad plan in any case.
    Ralph
  8. 60103

    60103 Pooh Bah

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    The wiring depends on how the dual power pack is wired inside. I both cntrols come off the same transformer, you need to wire everything separately because you can short from one to the other by changing the reverse switch.
    If the pack has separate transformers, it's like having 2 separate power packs.
  9. Ralph

    Ralph Remember...it's for fun!

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    There you go David.
    Ralph
  10. steamhead

    steamhead Active Member

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    OK...Here's the sorry diagram I came up with.....:oops:

    At the top are power packs A and B. One of the terminals from each is joined to a common wire (RED), which will go directly to the COMMON RAIL. This rail has no gaps other than those that may be needed for track situations where a short may "naturally" occur due to the track configuration.
    The other terminal from each pack (BLUE and ORANGE) will be wired to one of the outside terminals of the SPDT/Center-off switch. The center terminal from each switch (GREEN) will go to each isolated rail in each block (1,2,3,4). The switches should be CENTER OFF so you can turn the power off to each block and park locos there while not in use.

    Please note David's comment above...This can only be done if the power packs each have their own (not shared) transformer.

    Good luck...!!!

    Attached Files:

  11. Spawn of Chaos

    Spawn of Chaos Member

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    Better pic than I could come up with. And that looks like it should work.
  12. RusticBob

    RusticBob New Member

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    I found this at NMRA site... My confusion is cleared... Unless as mentioned the cabs draw from the same transformer...

    "You may think that with trains running in the opposite direction would cause a short as you will have both positive and negative current running in the common rail/wire at the same time. This is not the case as all electricity returns to its own source. So the negative electrons from Cab A will not interfere with the positive electrons from Cab B as they are two separate sources."
  13. Prof1000

    Prof1000 New Member

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    Still Not Sure

    Hi Guys:

    Thanks for the advice but here is a diagram of what I am thinking of doing. I have the yard running on an dual power source. Now I want to run the main line on a walk around. I wonder if when the front wheels of a locomotive are on the main line and the rear wheels are on the dual power source of the yard will there be problems. I have included a diagram hope you can help. Thanks.

    Brian

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  14. steamhead

    steamhead Active Member

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    Hi...I take it this walk-around is a portable throttle that has its own power source..?? So all told, you have three power packs..?? You say that you have the yard running on a dual power source...Are both sources wired to the yard or just one..?? If both, how are they wired..?
    Let us know...I'm sure some one can come up with a solution....
  15. pgandw

    pgandw Active Member

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    If the dual power pack is an MRC, it does have 2 transformers, and can be used with common rail. Other brands of dual power packs may or may not have 2 transformers - that is the key.

    The guiding principles for DC block (or cab) control:
    • only one train/locomotive in any block. A train or locomotive straddling 2 blocks should have its controlling power pack connected to both blocks.
    • a power pack or throttle should be able to follow the train where ever it goes on the layout, with blocks being selected to allow keeping control of the train.
    • only one train/locomotive per power pack/throttle.
    You need to set up a way for the walk-around and the yard throttle to both be selectable in a zone of block(s) where the hand-off from one throttle to the other will be done. This can be done by adding another set of block toggles (the SPDT in the diagram) to select between the yard throttle and the walk-around for those blocks where the hand-off will be done. Where you are handing off control, you must stop the train and switch the block to the other throttle. The common rail can be linked to all the common of all 3 power packs/controllers.

    hope this helps
  16. Prof1000

    Prof1000 New Member

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    Thanks Guys

    Yes Gus the yard is wired with a tech11 2800 dual cad using atlas controllers. The walk around has its own power source. I was thinking that once the train leaves the yard and the front wheels are on the main line just over the plastic joiners then I will turn the power off on the yard tech11 and turn on the power for the walk around that would work would it not. Thanks again.

    Brian
  17. Prof1000

    Prof1000 New Member

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    Wiring a Puzzle

    Hi Guys:

    Yes I have three power packs. The yard is wired with a tech 11 2800 dual cad. That is controlled by atlas controllers. The main line is to be run with a walk around that has its own power source. I was thinking of having the train run out of the yard and when the front wheels cross the spot where the two plastic rail joiners are I would turn off the power to the yard and turn on the power to the walk around and it would take over. Is this a good solution. Thanks.

    Brian
  18. steamhead

    steamhead Active Member

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    Hi....Do you really need two packs to work the yard..?? The proper solution would be to have the yard powered as one (or several) blocks off one pack and the walk-around, and have the walk-around as the other cab to run the mainline once you've cleared the yard. You wouldn't have to mess with switching power off or on when you leave the yard....Plus risking the engines if they were to get the output of two packs, even momentarily...
  19. lester perry

    lester perry Active Member

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    from your diagram it appears to me that you will need a double pole double throw switch wire yard to the center contacts and one power source to each of the 2 outside contacts. whe you are going into the yard you will run main and yard from one power source the walk around. once in the yard stop flip the switch changeing power to yard from the walk around to the yard power so the 2 are sepated
  20. pgandw

    pgandw Active Member

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    Brian

    What you are proposing will not work.

    Insulating both rails in one place does you no good. As soon as the first locomotive wheels span the insulated gap, you have 2 throttles controlling one train. The situation continues until all the locomotive wheels are across the insulated rail joiners. While the locomotive is spanning the insulated joiners, a "fault" current that is proportional to the voltage and polarity difference (if any) between the 2 power packs is flowing through your locomotive wheels and frame. The current will be high, basically limited only by the capacity of your power packs. Your power pack circuit breakers may or may not trip, depending on how they are wired and which leg of the circuit the power pack bridging is occurring in. If the power packs put out enough current, you can ruin your locomotive and/or the power packs.

    This is the reason for the rule that a train is never in 2 electrical sections of track fed by different power packs at the same time.

    This is also why, that if you want to transfer control of the train from the yard throttle to the walk-around, you need to set up an electrical block, insulated in at least one rail at both ends of the block. This block must be able to be selected between the 2 throttles - just like your yard blocks. I do recommend - but it is not required - stopping the train in the block while you shift controllers. If you don't stop the train, there will be a jerk while power is shut off momentarily, and then comes back on at a slightly different voltage on the other throttle.

    Ideally, you will block out your main line with the Atlas Selectors, just like you did with your yard. One of the yard throttles and the walk-around can be selected to control a train anywhere on the main.

    hope this makes sense