Bus Wiring question.

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I guess I need the really begginers version of help. I am building my first layout and of course have decided to go DCC. I have purchased the Digitrax Zephyr and am currently trying to transfer my design from paper to foam board. Still need more track and turnouts.

Anyhow, my layout will be 7'4" by 11' and be in the shape of a square doughnut (with an open area in the middle for access). I will have a mainline running around the perimeter of the layout and another that parallels the outer track on one long side and is about two feet from it on the other (a smaller, tighter loop), a passing track, a few sidings and a few spurs. My question is how do I run the bus line under the layout to supply power to all these areas?

Do you run one long bus wire and snake it around to cover all the areas or is it better to run a short bus to a terminal strip and then run bus spurs (if there is such a thing) up either side ot the doughnut? I know that the bus should never form a closed loop, but besides that I have never really seen a discussion on a web site or a book on how to run bus wires with respect to it's position to the track above. I thought I understood that generally the bus wires should run directly beneath the track above and if this is true how do you run it under numerous but somewhat spatially seperated track segments?

I hope that is clear enough to understand. I have been trying to figure how to do this for quite some time; looking for answers in many different places.

Any help would be appreciated. Thanks

-- Ken Keifenheim (kmkeifenheim@amerion.com), March 07, 2005


I have added a section on bus routing on my webpage. I will be adding drawings in the next few weeks.

The URL for this new addition is at:


-- Allan Gartner (wire4dcc_admin@comcast.net), March 09, 2005.


The center of the star can be a terminal strip. It could also be a collection of solder joints. I do, however, recommend a terminal strip. If you have problems and need to disconnect things, you will be really glad you used a terminal strip.

Note that there could be another star on the arm of your main star. Remember, there are no hard rules about how to wire. To a large extent, your wiring can mimic your track plan. In my first diagram (at http://www.WiringForDCC.com/track_2.htm#a40) there is a stub siding. You could consider this a mini star with only 1 new arm.

I suggest that you do run your booster to a terminal strip and then branch off from there. If for no big electrical reason, it is just easier to wire your layout this way.

When creating blocks, yes, you need plastic joiners so that your track electrically mimics the wiring breaks.

One last thing, I suggest you make a buzzer (seen at http://www.WiringForDCC.com/track.htm#a1) and use it as you wire. This will help you avoid making mistakes.

Good Luck!

-- Allan Gartner (wire4dcc_admin@comcast.net), March 10, 2005.

You can wire your main the way you suggest. Anything that will help divide your layout should you run into a problem is a plus. Check out the drawing that goes with the wiring overview at:


You can run 1 long "main bus" and then subdivide into "sub buses." You can use a light bulb as shown, a switch, or an electronic circuit breaker to limit any problem that may occur to that particular sub bus.

Does it make sense to make a separate block for a siding? It depends. I do on mine, but I'm using block detection and I want the dispatcher to know if the siding is occupied. If I wasn't using block detection, would I still do it? Probably not. It's only 1 piece of track. More likely than not, if you develop a problem with your trackwork, it will involve a turnout. Not too many problems develop on a straight piece of track.

-- Allan Gartner (wire4dcc_admin@comcast.net), March 10, 2005.

Your layout is small enough that " long bus run" wiring issues are NOT going to be a problem. I say wire it the best way that makes sense for you to be able to install it and support it.

You may want to think about creating some power districts to partition the layout electrically to facilate maximum reliable operation. Perhaps put the main line on one block and the yard in another. If you have more than one mainline, put that one one on its' own district too. For the time being, you can use kill (on-off) swithes in series to isolate the power. Electronic circuit breakers would be nice, but the Zephyr may not put out enough power to allow most of them to work.

If you plan to do signalling, there may be more considerations about block wiring. However, for a layout this size, it may not be practical. I would have the signals indicate switch position instead.

From a "purest" wiring point of view (given the lack of real issues here), it would be best to run the wires following the track directly over it so the feeders are short. Run each track bus run back to central location near the booster so that you can centralize all you power equipment in one place. Use barrier terminal blocks. I would place the kill switches or what ever protective device here.

I would run 16AWg - 18AWG clear speaker cable wire where it is easy to keep the wire identification/colors straight to tell you which wire goes to which rail. Typially one wire is a different color or there is a color strip on one wire. On the other hand, common Lamp Cord also has wire identification but requires good eyes to see the wire markings molded into the insulation of idential color. In other words, there is no color key. If you working with less than bright light conditions, do not use it. I would assign one wire to be the rail closest to the the center of the layout. That will make it easy to figure out which wire goes to which rail unless a wye or reverse loop is involved.

Since the wires are in pairs, there is minimal cable managment issue in terms of keeping the wire pair close to each other. You can make track feeder connection by cutting the wire and using twist caps. Keep you color code straght.

Hope this helps.

-- Mark Gurries (gurriesm@macconnect.com), March 08, 2005.

I forgot to mention a few things. (Im getting old!)

Please refer to the following new section for more information about bus wiring.


-- Mark Gurries (gurriesm@macconnect.com), March 09, 2005.

Thanks this is exactly what I am looking for. Your new sections and diagrams are a great help to an electronics novice like me.

When you refer to the "star" method for splitting up the bus line, is the center of the star a terminal strip?

Do you run the main bus to a terminl strip (or block, not sure of the correct terminlology) and then branch off other busses from there?

When speaking of creating blocks on the layout I assume you would need to electrically isoloate each block of track from all the others with some type of plastic rail joiner?

-- Ken Keifenheim (kmkeifenheim@amerion.com), March 10, 2005.

Wow, you are taking care of many of the questions I have had for some time. Thank you very much!

I have a couple questions on breaking the layout into blocks. If I have a long mainline that I wanted to break into four seperate blocks and feed each block off the same bus line, does it make sense to run the bus to a terminal strip and the end of each block and then continue the bus from that terminal strip to the next block and another terminal strip etc. I am thinking you can then disconnect the bus from the strip starting from the end to look for problems or shorts if they occur. I think you were trying to say that in your last E-Mail.

Also, if you have a mainline and a siding track next to it that has feeders from the same bus, does it buy you anything to create a seperate block for the siding?

Thanks again for your help, I'll quit bugging you after this.


-- Ken Keifenheim (kmkeifenheim@amerion.com), March 10, 2005.

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