# Bus wire and Atlas Selectors



## Jeff Louthain (Feb 2, 2015)

I have an old n-scale layout that runs around a twenty three by fifteen foot room. It is about 2 1/2 feet wide through out. I run mostly DC equipment but have recently added some Broadway Limited dual mode engines. I have a single main line with three rather long passing sidings. It takes three trips on the main line to return to station from which you start. I have many selectors in use to create many blocks along the route along with multiple power packs. I want now to run a bus wire around the entire layout. My question is this-- can I merely have one bus or do I have to run separate bus wires to each of my blocks (atlas selectors). Sure hope someone can help!


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## traction fan (Oct 5, 2014)

*DCC?*



Jeff Louthain said:


> I have an old n-scale layout that runs around a twenty three by fifteen foot room. It is about 2 1/2 feet wide through out. I run mostly DC equipment but have recently added some Broadway Limited dual mode engines. I have a single main line with three rather long passing sidings. It takes three trips on the main line to return to station from which you start. I have many selectors in use to create many blocks along the route along with multiple power packs. I want now to run a bus wire around the entire layout. My question is this-- can I merely have one bus or do I have to run separate bus wires to each of my blocks (atlas selectors). Sure hope someone can help!


Jeff;

If I understand your question, the short answer is, yes, you would need separate buses for each block. However, you may not need any buses at all. If your layout works well, without obvious slowing of the trains when they get far away from the power pack; you probably don't need bus wires. You can read the long answer below for a more detailed explanation.

If you are switching over to DCC for your whole layout, then you can set all the block selectors to the same setting and connect the DCC system to the two rails. DCC doesn't require blocks, though they can be used to operate signals and as "power districts."

On the other hand, if you want to be able to run DC sometimes, and DCC others, then it is important to wire up a toggle switch to connect the layout to either DC, or DCC, but never both at once. (That could damage the DCC system.)

If you just want to keep running DC locos with the blocks, then don't wire a single pair of bus wires for the entire railroad. Doing that would connect all the blocks into one big continuous block, and render your selectors useless. 

I'm not sure which control system you plan on using, DC or DCC.
I strongly recommend the latter, for its several advantages; one being wiring simplicity. Two wires total! One to each rail from the DCC controller, that's it! Part of the switch to DCC would be installing decoders in as many locos as you plan to operate. However, this could be done gradually, as time and money permit.

The only reason for using bus wires at all is the voltage drop on very long lengths of track. If your present layout runs well on DC, then you probably don't need bus wires. If the trains slow down noticeably when they get far away from the power pack, then bus wires (one pair for each block) might help. You can try this using your present DC system. Install a pair of 14 gage wires in one block to test. Drop a smaller 22ga. wire every six feet from each rail, down to that rail's bus wire. Then run a train, and see if the speed stays more even than before the bus wires were installed. If it does, then you can do the same thing on the other blocks, just don't wire two blocks together.

If there's no change, then you can forget bus wires.

When you do go to DCC, then the buses could be connected to each other, or not, if you plan to use them for signals or power districts. There are several good books on DCC available. This response is already quite long so I won't go into how those two things work. You might also look at the control section of this forum.

good luck;

Traction Fan:smilie_daumenpos:


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## Jeff Louthain (Feb 2, 2015)

*Atlas selectors*

Thanks for you reply! I plan on remaining with DC. The only reason for DCC for me is the sound onboard and these Broadway Limited dual mode engines give me that. I have tried DCC and get power drops all the time ( probably bad track laying not sure) and after talking to many DCC users it seems like most use a bus wire on each section of track for this very reason. So that is why I want to try using a bus for these Broadway limited dual mode engines. You say I need a bus wire for each block but with each selector having four blocks on it still need help on the block wiring (selector) to the bus. Would you have a common rail of the bus connected to the selector with the other bus wire having four separate connections to the selector thus keeping the four blocks separated?


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## traction fan (Oct 5, 2014)

*Don't bypass any gaps*



Jeff Louthain said:


> Thanks for you reply! I plan on remaining with DC. The only reason for DCC for me is the sound onboard and these Broadway Limited dual mode engines give me that. I have tried DCC and get power drops all the time ( probably bad track laying not sure) and after talking to many DCC users it seems like most use a bus wire on each section of track for this very reason. So that is why I want to try using a bus for these Broadway limited dual mode engines. You say I need a bus wire for each block but with each selector having four blocks on it still need help on the block wiring (selector) to the bus. Would you have a common rail of the bus connected to the selector with the other bus wire having four separate connections to the selector thus keeping the four blocks separated?


 Jeff;

The answer to your latest question depends on whether you are using common rail on your whole layout, or not.
If your blocks are divided by gaps, or insulated rail joiners, in BOTH rails; then no, you would not have any common rail, or I should say "common bus wire." Any time you wire around an insulated boundary between blocks, you have defeated the whole purpose of isolating the blocks. 

I'm not familiar with the Atlas selector. I guess it has four, electric, slide switches, but I don't know if each switch breaks both wires, to both rails, or only one wire, to one rail. If the latter is the case. then you probably have block insulators in only one of the rails, not both. That would mean that you are, indeed using common rail. 

The easy way to think of bus wires is as rails, "in a parallel universe." Electrically, each bus wire is a parallel path for electricity for the rail it is connected to. All the bus wire does is provide a low resistance, and more reliable than rail joiners, way of providing power to a particular rail. 
Therefore, if your layout is wired for common rail (One of the rails, that has no insulated gaps/joiners) Then the bus wire for that one, common, rail ONLY; could be one, continuous, wire.
On the other rail ( the one with insulated gaps) You need to have a bus wire parallel to, and connected to, each one of those rails. You can't run any bus wire across any gap.

hope that helps you;

Traction Fan:smilie_daumenpos:


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## Jeff Louthain (Feb 2, 2015)

*Common rail*

Thanks again for your help! I do indeed have a single common rail throughout my railroad and now feel comfortable with a single bus wire running all around track with many feeders from the bus to the common rail. Anxious to see if that alone improves operation but I bet I will also have to add bus lines to each independent block. The Atlas selector is what I believe to be four single pole double throw slide switches -up for A position, down for B position, and middle position being off( useful to distribute power between two cabs as well as four blocks). Again thanks for your help and wish me luck. Jeff Louthain


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