Wiring for two cab control

Discussion in 'HO Scale Model Trains' started by felliott, Nov 6, 2008.

  1. felliott

    felliott New Member

    would like some ideas about locating blocks and wiring for cab control.
  2. 60103

    60103 Pooh Bah

    I use what was called a "X section" a lot. Sample: at a passing siding, the siding and main between the turnouts make 2 blocks that can be selected by cabs. The turnouts are connected to whichever block the turnout is pointed at, and a distance behind the turnout as well. This lets you select the block, drive the train in, drive the other train in and drive both out without resetting the main line. You could run like this with the X section going halfway to the next siding. Or add more blocks if you run a lot of trains.
    (Of course, I haven't done all mine this way. :curse: )
    X sections are great at crossovers and yard throats.
    I think double ended siding should be made into blocks with the gaps as close to the turnouts as possible. I've worked areas where the gaps were halfway down the siding and kept running into problems.
    Long runs with no turnouts may need to be blocked at reasonable distances.
    And for various reasons you may want to end blocks in the middle of crossovers or any place where turnouts go frog to frog. You'll be putting electrical gaps there anyways.
  3. MasonJar

    MasonJar It's not rocket surgery


    Do you have a diagram of your layout or are you looking for "general rules of thumb" in planning for two cab wiring?

  4. pgandw

    pgandw Active Member

    My rules of thumb for blocks:

    1. Any continuous run (oval, dog bone, figure 8, etc) where one train may be following another should have at least 4 blocks for the 2 trains.

    2. Each passing siding should be a separate block, with gaps at the clearance points of the turnouts, as was pointed out in another post.

    3. Each branch or spur where a locomotive or train could be operated independently, or where one may be parked while another goes by, should be a separate block.

    Block wiring on a small layout for true 2 train independent operation is a hassle, as is operating such a layout. Block toggle flipping becomes the focus instead of operating the trains. In such situations where you are truly operating 2 trains independently (separate throttles and operators), I recommend DCC.

    If you are just having one train run continuously unattended while you switch an area with the other, then block control is more reasonable.

    Larger layouts with more than 2 trains running independently should be DCC is starting from scratch. Wiring a larger layout for block control with 3 or more trains is not a trivial undertaking. Adding walk-around control adds to the complexity of coordinating block power assignments.

    my thoughts, your choices
  5. MasonJar

    MasonJar It's not rocket surgery

    Thanks Fred! Great insight and rules of :thumb:

  6. Santa Fe Jack

    Santa Fe Jack Member

    I am having a lot of fun managing the block-wired DC layout I have built. The wiring was a big project, and the operations can be challenging, but it is part of the fun for me.

    So, I just finished (in October) the wiring of the layout, with 11 blocks, 4 cab controllers (two dual MRC transformers), and indicator LEDs to show which controller is connected to which block. There are several sub-blocks, too, where power for a piece of track (a siding or stub) can have power switched off. There are two bits of track that can be switched to the block at either end, to aid in turntable operations.

    With the 4 cabs cross-wired to the 11 blocks, the wiring is complex, but it all works wonderfully!

    I know I need to update the web page referenced in the sig. Once I do, it will show all the blocks needed.

    If you want any help in how to do this, let me know. I've got all the logic worked out.
  7. Santa Fe Jack

    Santa Fe Jack Member

    I got a PM from someone trying to add a new block of track to an existing layout, using two controllers. I'll post an answer here for the benefit of others:
    First, there is the consideration of whether or not you are using common rail wiring. I will assume for now that you are not.

    So, you have two wires (leads) coming from the rails on your new block of track, and you want to connect these to the four wires from your controllers (two wires from each controller, aka cab). What you need is a dual-position dual-throw toggle switch (do a Google image search on "dual-position dual-throw" if you want to see some). these are also called dual-position dual-pole toggles. The toggle has six terminals on the bottom, which are in two rows (hence dual throw) of three. In each row, the center terminal is the one that gets switched to one of the other two. So the center terminal is the one that goes to your track block. Decide which row of three is to be positive and which negative, and wire the center terminals to your track block, and each of the other pairs to one of the controllers. Now, when you flip the toggle, it will connect the track to one controller or the other. If you get the ON-OFF-ON toggle, it will also have a "dead" middle position, which can be useful if you want to have no power to the block.

    If you are using common rail, it is simpler, since you need only a single-throw dual-position switch. This connects the powered rail to one or the other of the positive terminals on the controllers. The negative terminals on the controllers get tied together with all the common rail leads on the layout. Again, wire the center terminal to the block, and the other terminals to the controllers.

    Now, here's a cool enhancement to consider: If you have common rail, you can use a dual-pos dual-throw switch to good advantage. Use the one throw for the track power, and use the other to switch accessory power to a pair of indicator lights, showing which of the power packs is supplying power to your block. Using lights of different colors (LEDs are great for this) makes it really spiff. The power comes from the accessory terminal, or other power supply (I use a simple 12v supply), and gets wired to the center terminal. The two indicator lights get attached to the outer terminals, and then to ground.

    I hope that gets you where you want to be.


    Now, for the more adventurous, here's what I have done: I have four controllers switched to eleven blocks. That is, each block can run from any one of the four controllers. For this, I needed a rotary switch, so that I get four positions. In the end, I got a 6-position rotary, so that I could include a "dead" position at each end of the switch, where there would be no power to the block. Since I am using common rail, I could have used a single-throw 6-pos rotary switch, but RadioShack has these nice dual-throw 6-pos ones that will serve well, and will provide another service: I used the second throw to select 12v power to one of four LEDs (four different colors), corresponding to the four power packs. So now I have a red, blue, green, and yellow controller, and when a given block switches to one of them, it also switches on the appropriate LED to show which controller is powering each block. This is very very nifty, since I can see at a glance which controllers are powering which parts of the layout. So, I end up with 11 rotary switches on the control panel, each with a set of four indicator LEDs. And it works like a dream! The wiring was tedious, but so worth it.

    BTW, I have entered this layout in MRR's track plan contest. Wish me luck!
  8. cidchase

    cidchase Active Member

    Those little Atlas books at the Hobby Shop are worth their weight in gold if you have not much wiring experience!:)
    And not expensive! :thumb:

    One of them has a good dual cab, common rail layout diagram.
  9. felliott

    felliott New Member

    Thanks to all of you who answered my question about identifying blocks!!!!F Elliott

Share This Page