DCC Impulses - Layout Wiring

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DCC Impulses column - MRH Dec 2011

 

 

 

 

 

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jarhead's picture

Super Article

Thank you for your article but I am confused. You mention that the feeder wires and the main buss wire should be solid core instead of stranded wired. I thought that DCC worked better with stranded than solid core. Is this wrong ?

Nick Biangel 

joef's picture

Solid or stranded?

I'm not Bruce, but for a given wire size (12 gauge for instance) the wire is equivalent in its ability to transmit electricity.

In other words, it doesn't matter. While Bruce may insist on solid wire, I can tell you my Siskiyou Line uses stranded wire for the bus and feeders, and my 20 year old layout runs fine on stranded wire.

To some degree it's personal preference. I prefer stranded because it's easier to route and the smaller gauges of stranded wire don't break as easily if it gets moved around accidentally.

I'm sure Bruce has good reasons for preferring solid wire - so based on who's reasons you like best, go with that recommendation.

Joe Fugate
Publisher, Model Railroad Hobbyist magazine

Joe Fugate's HO Siskiyou Line

JamesS's picture

IDC's vs. solid or stranded

I plan on using IDC connectors for my feeder/bus connections.  Does solid or stranded make any difference

when using them?

 

James

JamesS

Milwaukee  to  Lac du Flambeau

17' x 20'  HO with RailPro

solid versus stranded...

There's two reasons we don't use solid wire on Aircraft.

The first reason is obvious - it breaks easier within the plastic dielectric and then you don't know where it's broke.

The second is not so well known.  It's called "Skin Effect."  And this basically means the all your charge flows on the outer surface of the conductor, and very little to nothing on the inside.  So we use stranded wire.

I dare say we need more experiments before we have a decisive decision on this matter...

I think the biggest negative of stranded is "opperator error."

If you make a crimp connection with stranded wire or use a screw and terminal connection, it is essential that you solder the end of the wire to make it a solid wire.  Who ever takes the time to do that?  The problem is that the individual strands from stranded wire will push out of the way and get loose from connections.

joef's picture

Or use spade crimp connectors

If you make a crimp connection with stranded wire or use a screw and terminal connection, it is essential that you solder the end of the wire to make it a solid wire.  Who ever takes the time to do that?  The problem is that the individual strands from stranded wire will push out of the way and get loose from connections.

Or use spade crimp connectors like I do. They're fast, economical, and quite effective at solving this stranded wire issue:

Shameless plug - these and many more time and money-saving tips are in my Siskiyou Line video volume 3, priced super low right now as part of the "Deal of the century" video sale.

Joe Fugate
Publisher, Model Railroad Hobbyist magazine

Joe Fugate's HO Siskiyou Line

Wire and connections

There will be hours of comments over wiring DCC and some will be right, some will be OK and some will be in left field.

My experience is shared and this is what I did and had ZERO issues, and a few notes of WHY.

12 awg stranded bus wire: THHN, comes in various colors and easy to work with. Available at Lowes and Home Depot. Stranded will go thru bench work much easier.

20 or 22 awg solid wire for feeders. Solid makes it easier to solder to rail. The skin effect and other reasons wont matter in short runs, normally less than 12 inches.

SOLDER CONNECTIONS: I solder every connection, crimp on lugs get crimped AND soldered. I solder the feeder to the buss wire too. 

COLOR CODE: Make one and stick to it no matter what. Wire is pretty cheap in the long run, colors help with keeping things from becoming a rats nest, and NEATNESS COUNTS!

NOTEBOOK: Make a notebook on your blocks, colors used and any special connections you have made. You remember them now but what about in three years getting ready for visitors and you cant remember why the red, blue and purple wire are connected under the yard....

When I first started reading posts about DCC wiring, somehow it became this magical, complex and crazy maze. Strange when one of the early "sales pitch" for DCC was simple wiring. It can become a huge mess if you dont plan, think about what is really needed and make good choices from the start.

"Wiring for DCC" is a very good website and he covers most any topic you want to argue about.

One person tried to tell me DCC wouldnt work if you use green wire! Funny, in all my electronics experience I didnt know electrons had favorite colors....

 

Randy McKenzie
Virginia Southern - Ho triple decker 30x32

Digitrax Zephyr, JMRI
On Facebook:  http://www.facebook.com/groups/485922974770191/

Based on the north end of the Clinchfield.

Learn something new everday!

"One person tried to tell me DCC wouldn't work if you use green wire! Funny, in all my electronics experience I didnt know electrons had favorite colors...."

Maybe his "green wire" that didn't work was solid copper oxide?

JeffShultz's picture

Green wire

In my experience (Telecoms wiring with some limited rewiring of my house as well), green is predominately used as grounding wire.... I'm thinking if you ground your power bus, it's not going to perform well.

Jeff Shultz

MRH Technical Assistant

 

Just what I wanted for Christmas!

I haven't even finished the first page and I'm writing to say thanks for a great article.  It's clear and comprehensive and offers exactly the information I need to avoid mistakes.  I'm one of those who will be retiring soon and starting over in a new house.  For various reasons, my reboot will mean shifting from N to HO and from DC to DCC, so I'm spending the intervening time reading and planning.  The various Kalmbach books are of course most helpful, but this article is a great condensation, restatement, expansion, and fresh perspective on the topic.  Worth the price of my subscription--oh, wait...  <g>

Bruce Petrarca's picture

Solid or stranded

Nick -

You've gotten a bunch of data from various folks here.

Let me take a minute to explain myself.

It is easy for folks to latch onto an idea and make it a bigger deal than it really is. Skin effect is one of these issues. Yes, alternating current runs on the surface of wires. At the frequencies encountered in DCC, the skin effect is about the same as 14 AWG solid wire. That's why I suggest that for district buses. Skin effect will push the current flow in 12 AWG solid wire to the surface, so that it will have about the same losses as 14 AWG solid. (Calculated skin effect is 0.7 mm radius, or 1.4 mm diameter - 14 AWG is 1.6 mm in diameter.)

By going to stranded wire for the 12 AWG runs, you get two benefits:

1) easier to twist

2) reduced losses due to skin effect vs. 12 AWG solid.

I recommend solid wire for the feeders for the ease of wiring already mentioned.

As for the comment about aircraft wiring, I sincerely hope my layout doesn't shake and flex like an airplane! And, as I mentioned above, skin effect kicks in at about 14 AWG solid at DCC frequencies.

As I said in the column, there are a bunch of theories out there. What I am presenting is consistent and works. If you mix concepts, you might have a gap in your coverage! Kinda like having two insurance policies on your car. You might pay too much for duplicate coverage or you might have something that neither policy is covering.

Bruce Petrarca's picture

Who ever takes the time to do that?

Russ -

If you look at figure 7 in the article, you will see that the spade lugs on the booster bus were crimped to the stranded wire and then solder was flowed into the joint.

Takes just a minute and eliminates a BUNCH of issues.

So, I guess I can say, "I do!"

skiloff's picture

Tail light bulbs

Bruce, in the Q&A section it mentions that you don't recommend the tail light bulbs for short management, while your publisher does.  I use the tail light bulbs but I'm wondering your perspective on it as to why you don't recommend it out of curiosity.  I still only have about 18 feet wired in right now and if you have a convincing argument for me, I might switch, though it has worked well for me to this point.

Dave

Contemplating
HO Scale '70s/80s era
GMT-6

yeah, there is that myth...

When I first started reading posts about DCC wiring, somehow it became this magical, complex and crazy maze. Strange when one of the early "sales pitch" for DCC was simple wiring. It can become a huge mess if you dont plan, think about what is really needed and make good choices from the start.

And then I look under every DCC layout that I have ever seen, and there's still enough wire under there to make any Wirephobe go bonkers!

No matter how you do it, good grounding Electronics principles will be the boon to ANY Electrically operated Model railroad!!!

I had not noticed that detail in the pic, Bruce.

"If you look at figure 7 in the article, you will see that the spade lugs on the booster bus were crimped to the stranded wire and then solder was flowed into the joint.

Takes just a minute and eliminates a BUNCH of issues.

So, I guess I can say, "I do!"

So many people think that a crimp connector just needs to be crimped to get a good connection.  I learned doing transport refrigeration repair for over 30 years that if I was using an insulated crimp connector, I had better solder the end of the wire before crimping; and if I was using a non-insulated connector like Joe showed on his layout, to do it exactly like you do.  If you don't solder, it may seem to work, but like you say, you are leaving yourself open for a bunch of issues.  It is amazing to me how those individual strands of wire will work themselves around to get loose!  Sometimes I think they are little Houdini's!

Kevin Rowbotham's picture

Snubbers

Another good read Bruce!  Thanks for sharing your years of experience with us here at MRH.

I'm using Digitrax on my railroad.  I can easily add snubbers with parts on hand even though I have not experienced any issues to date.  With a pinch of prevention being worth a pound of cure, the snubbers seem like a good precaution on my busses.  Would you agree?

Edit:  Oh yeah, I crimp AND solder too!

~Kevin

Appreciating Modeling In All Scales!

Skin Effect

I did some quick research on skin effect.

The result is, that at the DCC frequencies, there is little or no difference in skin effect between stranded and solid wire of the same gauge.

Terry

Bruce Petrarca's picture

Tail light bulbs

When Charlie asked me to comment about the subject at hand - auto-reversers not tripping when they were downstream of circuit breakers - I commented off-hand about not being a fan of bulbs. I didn't expect that to "make the cut", but it did.

Okay, I'm out of the closet on this issue now!

One of the first uses I saw for bulbs was to wire them in series with the power applied to a turnout. This mitigated the issue with some of the turnouts that didn't behave well with DCC short-circuit management. Saved some folks reworking turnouts that were already installed on the layout. When a flange made quick contact between the rails, the bulb took the load and the booster would not shut down. I think this is a fine use for them - keeps folks from having to rip up and rework lots of turnouts. However, IMHO, when such a turnout fails, it should be replaced with a "DCC friendly" unit without the bulb.

NCE has suggested their use in conjunction with their EB-3 circuit breakers. Wire a bulb around the EB-3 so that some current would flow even when it was open, to reduce the start-up load on the EB-3 when the circuit closed. Why have the EB-3 in that case?

So, what I see is the bulb as a crutch, fixing design issues - or as a diagnostic tool, not to be left on the finished layout. I don't see its place as a "new design" item.

I don't like the underside of my layout lighting up when I short out! Our club layout has Sonalerts on the circuit breakers, so everybody in the room knows when someone derails! Gee, I don't need a neon sign (slight exaggeration), too! That said, I'm working on the South Bend IN section of the PCMRC (http://www.pcmrc.org/) layout. I'm installing a lighting bus (DC power that is only applied when the DCC track power is active) to power the lighted buildings (LEDs). So, when you short out in South Bend, the loss of track power will drop the relay that is providing the lighting and the town will go dark. Is that subtle enough?

Bruce Petrarca's picture

Snubbers

Kevin -

Good man: crimp and solder!

My most extensive experience with snubbers is on mixed Digitrax and NCE O-scale layout. The original system was a Super Chief radio. When the owner wanted more power, we added an NCE booster. The layout has two decks in a 16 x 85 foot building. There are two booster districts and several track districts. He also has a star-wired turnout bus with three ends. He was having issues with his DS-44 stationary decoders loosing their addresses after a booster got tripped. (It was tripping because he had cross wired a couple of track districts and a short took down the booster, not the circuit breaker.)

So, we added about 15 snubbers - one to the end of every bus on the layout. The problem with the DS-44s seems to be gone.

That all said, if you aren't having any issues, I'd leave well enough alone. If you do have some unexplained gremlins biting at some point in time, they are cheap and easy to add and just might fix the issue.

Bruce Petrarca's picture

Skin Effect

Glad you agree, Terry.

Bruce Petrarca's picture

Turnout bus addendum

Something that I didn't mention in the Turnout bus section on page 49:

If you don't wire the stationary decoders directly to the booster, but instead put them down stream of a circuit breaker, you can have a disaster.

Imagine this scenario. You have your turnouts positioned other than where they are on power up (position B). You have a short in the district and the circuit breaker shuts down power to the track and to the stationary decoder. When power is reapplied, the stationary decoder moves the turnout to the "normal" position (A). You come down the track expecting the turnout to be in position B and it is in A! Derailment! Corn-field meet! OUCH!


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