DC common rail refresh

[budinoh]

Please refresh my mind. I am at the wiring portion of my layout and have a question. I once knew the answer but now I don't. I am doing DC with common rail. I will have 3 controls. We shall call them A B C. I have single pole rotary switches to route power to my 45 blocks. Do I run 1 common bus line all the way around and run feeders to the non-insulated track? Then do I connect the negative line from A B&C to the one bus line? How does that line work for that? I can't for the life of me remember. I can do reverse loops, switch motors and block detection in my sleep and can't remember something this simple.

 

Thanks,

Jeff

[Train Modeler]

I did this years ago and have forgot too.   Here's a good link from the NMRA on the subject.

http://www.nmra.org/beginner/wiring.html

Richard

 

[rrinker]

 Simple solution - don;t use common rail. Then there's nothing to consider. Even in the days before DCC, I gapped BOTH rails and ran TWO wires to the selectors. Sure it's more wires, but it's also intuitively obvious and nearly impossible to mess up.

               --Randy

[ajkochev]

What you described is what I did on my layout a few weeks ago.  Made a common wire to one side and connected the other side to various insulated blocks(13 in my case) after going through push button switches. 

Unless you are only planing on one power pack or cab EVER you do not need to worry about polarity.  Polarity is changed by the direction switch on the pack itself so the common rail will be ether positive or negative depending on its position.  If you plan on using more than one power pack or cab then things get more complicated as you will need to isolate both rails on a collection of blocks to prevent a short from two different packs.

My layout is a small shelf switcher and modular and splits in two sectons to store in a cupboard.  I've wired mine so they can be daisy chained and work as one layout or a second pack can be added and each module acts as its own layout with the three tracks that cross to the other side having all rails isolated.

 

HTH

[Texas Zepher]

budinoh

Please refresh my mind. I am at the wiring portion of my layout and have a question. I once knew the answer but now I don't. I am doing DC with common rail. I will have 3 controls. We shall call them A B C. I have single pole rotary switches to route power to my 45 blocks. Do I run 1 common bus line all the way around and run feeders to the non-insulated track? Then do I connect the negative line from A B&C to the one bus line? How does that line work for that? I can't for the life of me remember. I can do reverse loops, switch motors and block detection in my sleep and can't remember something this simple.

1.  Yes on the common bus & feeders.  2.  No, one wire from each block to the center of the rotary.  Then one wire from each power supply to each of the three rotary switch terminals A, B, and C respectively.  Basically the selector chooses which control is connected to which block.   You are right - simple.