I’m ready to wire up my layout for DCC. I have a small folded dog-bone and a small stub end yard. I really don’t see the need to have more than two power divisions - loop (& spurs) and yard. My DCC system should be powerful enough without the need for a separate booster for one of the divisions.
I know the track should be electrically isolated (with insulated rail joiners or a gap) but does that mean I need to isolate the main bus?
OK, I think there are a few different concepts getting confused, so I’ll take a stab at this.
Between normal feeders, of which you may have many (every six feet or so seems a common practice) you need no gaps in anything, rails or bus. Since you are only planning on using one booster, you don’t technically need any gaps anywhere, unless there’s a reverse loop involved. If you want to divide that one power district into ‘train blocks’ to help in short management, then you need gaps. Look at this link for a description of one way to handle this: http://siskiyou-railfan.net/e107_plugins/content/content.php?content.13
Unless you do something like that you really have no need for gaps, since a short anywhere on the booster is going to take everything down anyway.
Jeff,
Hmmmm…
So you have one “common” bus (red in your diagram) that despite the gaps “connects” all the power divisions.
The other blue bus has an automotive bulb between it and every green feeder. When a shot happens within a power division - something happens to the bulb. I imagine it doesn’t blow out.
When you have a short in the ‘train block’ the higher current is enough to light the bulb, and the voltage drops over the bulb, and limits the current through the short to around 2 amps. some people don’t like the idea, and would prefer a breaker, but those are considerable more expensive. I’ve thought about it, and it seems the bulb should work pretty well. Of course you still want to clear the short as quickly as possible. Here is a thread with considereable discussion of the concept, and DCC in general:
http://www.trains.com/TRC/CS/forums/467762/ShowPost.aspx
By the way, I can’t take credit for the previous link, it is Joe Fugate’s website. A pretty good read.
Hi. If you still would prefer to “isolate” two main operating “blocks” (for want of a better word), the yard and then the rest of it as you imagined earlier, you could just add two sub-buses.
It’s okay! It is easy to visualize… your main bus comes off your power unit. Two heavy wires go to a central point at your layout, or run for several feet along a bench type.
To that, you add two separate heavy wire pairs, but separated (not “gapped”, just separated by distance from each other) so they they serve as a platform for other smaller wire feeders up to the rails. This second set of pairs, perhaps near each end of the layout, are what is called sub-bus(es).
If you have that okay, what this allows you to do is to only solder one (1) bulb in series into the sub-bus before the first set of feeders that come off it and rise up to the individual rails. Instead of putting a bulb into each set of feeders, more costly and time consuming, and more to fix if it goes wrong, simply use the limiting bulb for the entire “block”. That way, you only need the one, and when it serves its purpose, your other “block” won’t be affected.
Just a thought.
BTW, you may still have to cut gaps in each end of some sidings between two oppositely facing turnouts if the turnouts feed power into the siding. You sometimes get a short, depending on which point is against which stock rail. First time you think you have it all done correctly, and you power it up, if it gives a short indication, consider sidings with turnouts at each end as one of the possible solutions. A tip - each time you complete a section of track, power up and watch for short problems in your trackwork. If it all goes up over three weeks and then you power up, where will you look first?
And, yes the bulb does not blow, it lights up very brightly and says, “Hey, over here!” You don’t
Simple answer: if you willh ave 2 power districts, then you will have two sections of bus. The bus as well as the track needs to be isolated at the dividing point between the power districts. WITHIN a power districts you do not gap the rails, unless you want to install block detection.
–Randy