DCC Feeders and Bus Wires

[davefoxx]

Forum,

I've gotten to the point that I can no longer continue to run my DCC layout on two wires.  Obviously, the coin trick fails at the far end of the layout.  So, I need to start dropping feeders and running the bus wires.

Anyone got any tips for running wires on a DCC layout?  Do I need to be concerned about ganging bus wires together, thereby causing some sort of signal noise in the wiring.  I'd like to keep the wiring neat, but that would mean wires are tied together.  Do I need to twist pairs of wires?  Am I worried for no good reason?

Thanks,
DFF

[davefoxx]

Ooh, another question: What is the best way to run the bus wires?  The obvious answer is the shortest run that catches all of the feeders, but I recall reading somewhere that the bus wires should not be a loop.  Is this correct?  My layout is a roundy-round, but should I avoid the temptation to just parallel the bus wires to the track plan.

Thanks,
DFF

[dnhouston]

The bus wires should not be a loop, that is correct.
If it were me, I would mount the Command Station in a central location and send out two (2) sets of bus wires following the track plan in each direction, that way the feeder wires are as short as possible.  I keep the bus wires slightly separated, but that is more for ease of soldering, although I believe I read somewhere that they should not be twisted together (I could definitely be wrong there).

I'm sure the DCC experts will be chiming in shortly

[Philip H]

Since i have a more shelf type layout, i've got a 14ga twisted wire bus following the front edge of the layout all around.  i used screw terminal strips at the separation points between layout sections so if it needs to come apart its easy. Feeders are mostly 20gauge stranded wire, tied to the bus with suitcase crimp connectors.  my longest feeder is about 18 inches.  and just because I'm that anal  :face palm: I've started collecting fat plastic bread tabs to use as wire labels.  write the data on the blank side, slip the wires in, and go.

[Scottl]

Is the twisted bus purposeful?

[C855B]

I don't think there's much to be concerned about. If you're talking 50' runs we'd want to consider twisting, which would then also mitigate the issue of tightly bundling. Under 50', whatever gets it connected. [To dnhouston's point - whoever advised on "not twisting" is... well... misinformed. Twisting provides significant resistance to transient noise and especially externally-induced noise. If you do any work with ethernet or telephone wiring, you'll know that pairs are twisted, for this reason.]

I wouldn't loop only out of general principles (looped runs are harder to trace for debugging), making the break at the furthest point from your power source. The "furthest point" advice is just so we don't do something like have a big, long bus following the mainline and ending near where we started. Within reason, and neatness, you want to keep the bus runs shorter rather than longer. Looping around to follow your track in a single big broken loop makes the single wire run twice as long as it would be if you had two runs from the source in a "V" arrangement. It's the unnecessarily long runs that aren't your friend.

Philip has a good game plan. I'm ambivalent about suitcase connectors, but that's just me since I'm beyond obsessive about wiring neatness and it's hard to keep things neat with these lumps every few feet.    Electrically and mechanically they're fine, and easy. Just be sure to use the 3M-branded versions.

[davefoxx]

Thanks, guys!  It sounds like I might want to move my command station, but it is conveniently located near an outlet.  However, now that I think about it, there is another outlet near the water heater, and that one would eliminate an extension cord crossing an aisle.  That cord is not a problem for me (usually), but I cringe when my two-year-old daughter comes in the layout room and does laps under the layout.

My original plan was to fish bus wires inside the HCD, but now that I have more than one HCD and fishing wires really makes for hard-to-trace wiring, I'm going to bag that plan.  I may even go back and remove the wiring for the Hex Frog Juicers which are buried inside the original HCD and are not color-coded very well (they didn't have to be but are the same colors as those I'll be using for the feeders and bus wires).  But, that can wait for me to install the bus wires and feeders.

DFF

[mmyers]

Twisting of bus wires doesn't need to be considered until you get out to 30 or so plus feet of bus. Of course when lengths get out to 50 or so feet the recommendation is to add another booster and power district. At that point bus length starts all over again from the second booster. Consider an oval of track with its bus wires and feeders. Maybe the bus doesn't loop but the oval of track does and it is a conductor just like the bus wire. And the rails aren't twisted either.

Martin Myers

[peteski]

I also think that twisting the DCC bus wires is overrated. Twisting is important for low-level signals (such as Ethernet or telephone) but for a high power bus with very slow bit rate carried by the high current power signal) it is not needed.  Yes, the rails are not twisted either.

[Scottl]

This point was what I was thinking as well.  Some of the bus currents are in the amp range, so the noise should be minimal even over 10's of feet.

I only raise it because some people use Romex 14 or 12 ga house wire for the bus which is handy and robust.  It is definitely suitable for the loads of DCC on even the largest layout (15 or 20A), but of course, is not twisted (although I guess you could...).

[John]

Dave .. don't over think this.  Your layout is a couple of doors .. go to wall mart and pick up some 14 guage red and black wire in the automotive section .. its about 20 feet per roll ..  then get yourself some 20 - 22 guage for the drops. 

Run the main buss down the middle of each door -- connect them all together in one spot .. run a connection to your DB and then drop some feeders every few feet.

Most people over engineer this electrical stuff ... were not building a MILSPEC layout ..

[davefoxx]

Haha, John!  This is exactly what I did this afternoon.  I'm not finished with all of my drops, but I have enough that the layout is up and running again.  First, I moved the command station and tore out all of the old wiring.  The command station is now located under Raeford and plugs into an outlet near the water heater.



Like you recommended, I ran bus wires right down the length of both doors, so it's probably twelve or fifteen feet long.  I used terminal strips to anchor the bus wires at each end of the doors and to jump between doors, allowing me to disconnect the wiring with a screwdriver, if I ever separate the doors.  I've got a couple drops for feeders and have installed new feeders to three out of four of my Hex Frog Juicers.







Thanks for your help, everyone!  I needed the inspiration to tear out and start anew.  Sometimes, it's hard to go backwards, especially when that takes the entire layout offline.

DFF

[C855B]

... I only raise it because some people use Romex 14 or 12 ga house wire for the bus which is handy and robust. ...

This is where I draw the line. Romex in non-110V/220V casual applications is just asking for trouble... not with the 12V stuff, but in the lesser, "off-label" use of it possibly creating confusion with normal household wiring nearby. If that's what ya' got to use, OK, the wire itself is perfectly fine... just strip the jacketing off.

John has it right -  I had forgotten that Dave's RR was two HCDs. Twin conductor automotive cable and call 'er done. But rest assured that bus wiring on the GC&W will be twisted. LOTS of experience on this end chasing RF-induced gremlins from haphazard power leads. Granted, that was from installing and maintaining 2-way radios, but nonetheless it was something I learned 35 years ago as "best practice". Twisted power pairs also tend to route neater and bundle better.

[Scottl]

How can using Romex in low voltage applications cause trouble in a layout?  The worst case is you assume it is 120V and handle with due care. 

[C855B]

Other way around. Over the years I've seen enough sloppiness in layout settings to surmise a layout in a garage where the layout has Romex and the garage has exposed Romex and the layout is fastened to the garage studs. So you see a random hunk o' Romex running somewhere... is it live? Or Memorex? And are you sure?

Not to mention I've also seen N-Trak modules with 110V daisy-chain wiring using Romex. Again... 12V, or 110V?

Romex to me says "Danger Will Robinson", and I will continue to rail against its use for 12V MRR wiring.

(Being immersed in serious electrical wiring the past couple of years has given me an understanding of why electricians are so grumpy. If you browse D-I-Y forums and the topic turns to a wiring issue, within one or two posts there's always an electrician flaming about never-do-that, why-the-hell-are-you-messing-with-it, call-an-electrician-before-you-kill-someone. Never fails. )