DCC Wiring Confused

T

tinbasher

New Member
Sep 6, 2004
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Kelowna,B.C. Canada
Hey Guys, New to this DCC thing and it has me a bit confused. I've purchased a Prodigy Advance system and now want to start wiring new layout but I am a bit confused about power districts/blocks and the easiest way to go about it. I am attaching a copy of my layout and would like to get some helpful hints from you guys as to what to watch out for on my layout.

The graphic doesn't show the siding or yard yet as they have to be finalized but still I am ready to get my feet wet with the wiring. What I really need is for one of you to push me in. The layout size is 21'x14'. I have concerns in regards to having my bus wires longer than 30' as per www.wiringfordcc. More to follow, just wanted to get this puppy barking!:thumb:
 

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You do have a reverse loop on the right side - I can't tell if there's a turnout in the middle at the top or what. I would first locate and attend to the reversing loops using an automatic reverse loop controler then decide on how many and where you want the power districts. It will depend mostly on how much power you intend to have and how many trains you will be running at once. Once that is done, you can optimize the system for run lengths possibly even having to relocate your command center (I know I wound up moving mine from my original intended location)
 
Thanks Jerry, Heres how I kind of envision the power districts. But is it that critical that the main power bus remain under 30 ft. If I were to add terminal blocks would that lessen the amount of inductance in the wire or possibly twist the wire or even yet terminate the wire as per www.wiringfordcc/track_2.htm.
 

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Here we're talking length without mentioning wire gauge. Using larger (lower numbered) wire will allow for longer runs. I'm using #12 stranded and have runs (out and back) to about 64'. I don't think (don't really know) that terminal blocks will eliminate potential inductance but twisting will. I twisted all my cables before installing on the layout.
 
Greetings :)

tinbasher said:
I'm using #14 solid core and #20 for feeders Do you think that should be alright? Jerry, how to you terminate the ends of your bus wires?

Thanks

Lorne
Click to expand...
All this bus wire stuff can get a bit complex and really its all a peace of mind thing.. ie do I know I am going to be alright? :)

Heres the way I approached the whole problem... Yes I wanted to have blocks, so that I wouldn't take down the whole layout with a short, but they were organised operationally.. ie a block for the yard, one for the station, one for the industry exchange etc.. These are all next to my DCC Pack in a corner of the railway room. From there, each has a bus running around the room to where that block is located. That runs into a set of terminal strips, which distribute the power to the track in what a network person would call a star configuration.

As to did I have enough power at the end of a run... I had no idea, so I went back to basics.

Connect 2 wires to your DCC pack.. run them as a twisted pair to the furthest point of your layout... solder them to a piece of track.. make sure wires are straightish, not looped over each other... power up DCC pack and drop a quarter onto the rails.. if you get instantaneous shut down and beeps then you have no problem.. if not.. put in bigger wires :)

Currently I have a run of approx 60 feet from the booster with no problems. I couldn't tell you what guage wire it is, just a bit bigger than the one I first tried :)

There are no terminators or anything at the end of the bus.. just 2 wires running to terminal block then to track.


Hope this helps..

Regards
 
I'm not using terminators (at this time) either. So far the only "problem" I had was erratic performance from a TTX PS Rev but that was solved once I wired in adequate feeders.
 
The number of power districts will depend on how many trains are you going to be running on your layout at once. If you're only going to be running, say, 4 at once, then you probably only need one power district.

Locate your reversing loops, isolate the tracks according to the instructions that came with your set and install automatic reversers or boosters. It looks as if you've got two reversing loops - one on each loop. And possibly a couple more around your crossover. If you've got lots of sidings in one spot, you might want to move one of those power districts into that yard and add those long runs of mainline to the nearest power district. Again, the consideration is how many trains will you be running at once over that part of the layout that is in that specific power district.

Your track power buss is simply two wires which circle underneath your layout in close proximity to your tracks (or in close proximity to your power district). If you read your manual it will say something like "... use a minimum of 18 gauge wire for your track power bus". Most people up to 14 or 12 gauge wire. The wire can be solid or stranded. You're using 14 AWG for the power buss and 20 AWG for the track feeds which should be more than adequate. I belong to a module railroad club Ottawa Valley HOTRAK and our power buss runs are much longer than 30 feet with 14 AWG wire.

To terminate the ends of the track power buss, simply put some shrink tubing or electrical tape over the ends. Don't solder the ends together, ie don't solder the black wire to the white wire! You'll be cooking pancakes!

Every 3 feet or so, drop a pair of track power feeds down from the tracks and connect them to your track power buss. Soldering them and then shrink tubing is the best way to do it. Or use some liquid insulation to cover the joint. For some wiring techniques, visit my website, click on DCC and then select the subject on the track power buss. Don't use mechanical connectors to connect the track feeds to the track power buss. Things like terminal blocks and snap connectors result in voltage loss. Soldering is the best way to go.

More important, what kind of turnouts are you using? Some turnouts, like the old Shinohara's were nightmares with DCC. Others, like the Peco Insulfrogs were a dream. The key is to isolate the frog from the rest of the turnout so it doesn't short. WiringForDCC tends to overkill things quite a bit so I would visit other websites and see what they have to say, especially when it comes to modifying turnouts.
 
The power district simply allows you to run a lot more locos on your layout. It has everything to do with the capacity of your command station/booster, which is discussed under Laws of DCC on my website (Click on DCC from the index and then Laws of DCC).

There are two limitations to your command station/booster. The first is the number of "slots" or locos that your command station can handle at one time. For example the Digitrax Zephyr can handle 11 locos, the Empire Builder 22, the Chief 122, the Atlas Commander 7, etc.

The second is the power available from your command station or booster. Assume each locomotive draws 0.5 amps and your command station/booster is rated at 5 amps. The math tells us that you can run a maximum of 10 locos at one time on your layout (0.5 amps x 10 locos = 5 amps). If you put an 11th loco on your layout, you will start to blow a fuse. At least in theory.

One way to overcome this limit in power (amps) is to add a booster. A booster is simply a command station/booster which is configured to simply act as a booster. And then we isolate the track controlled by this booster from the track controlled by the first command station/booster. When we isolate the track controlled by the command station/booster, we have a power district. When we isolate the track controlled by the booster, we have another power district - a total of two power districts on the layout.

Assume your booster is 5 amps and your locos draw 0.5 amp each. Applying the same math, we can run 10 locos on the second power district. So, on our layout, we can run a total of 20 locos at once - 10 on the power district controlled by the command station/ booster and 10 on the power district controlled by the booster.

However, we have to make sure that we don't have too many locos in one of the power districts as we will now exceed the current draw (the amps) in the power district. For example, assume you have 10 locos in Power District #1, each loco draws 0.5 amps and the capacity of the command station/booster is 5 amps.

We now run an 11th loco into Power District #1. This 11th loco draws 0.5 amps so we now are pulling a total of 5.5 amps out of the command station/booster (11 locos x 0.5 amps = 5.5 amps). We have now exceeded the capacity of the command station/booster and we will start to blow some fuses.

Of course, there' another question to answer and that is how many slots do you have on your command station. Obviously, if you have an Atlas Commander, which has 7 slots, or a Digitrax Zephyr, which has 11 slots, you won't be able to run 20 locos on your layout. But that's another story.

And what is the likelihood you will ever run more than 10 locos at once that draw 0.5 amps each on your layout. If you're running Athearns, they draw a lot of current (but certainly less than 0.5 amps), and if you're running Atlas or Kato's, they don't draw anything near 0.5 amps each.

So, you have to take a look at a number of things before you decide to create power districts and invest in boosters. It all depends on how many locos you're going to run on your layout at once and how much amperage each one of those locos will draw.
 
This is an interesting thread, particularly to DCC wannabees like me.
Three questions:
1) Under what wiring conditions does inductance become a problem, leading to the need for twisted pairs??
2) Is track cleanliness more or less of a problem with DCC? I've read opinions both ways.
3) Are certain switches (turnouts) recommended for DCC, or not recommended? (Further to RailwayBob's comments above)
 
i'll tell you something about clean track, it makes everything on a dc layout work much better, goo-gone is a great solution, i found it at aa local hardware store, just whipe down the rails with some on a rag and then again with a dry rag to get the access, to clean wheels use a piece of paper towl and some of this goo-gone, set it on the track and put the front or back wheels spin on it, works great.
 
The track cleaning has been answered so I'll attack nos 1 & 3.
1. Twisting avoids "crosstalk" between parallel cables. If you only have one, it's not a problem. But for most, with main bus, power district busses etc there is chance of crosstalk that the twisting avoids.
3. Turnouts with isolated frogs and point rails that are not connected to each other are highly recommended for DCC. The idea is to eliminate the possiblity of a wheel bridging gaps and causing shorts which are more disasterous in DCC than DC.
 
In our module railroad club, we run over 400' of modules, with 7 boosters and one command station at a time. We have never had any problems with inductance.

If you're using sound decoders, then clean track is a must as any break in power to the decoder interrupts the sound. Sound decoders are less forgiving than your regular decoders. And clean track should be a must on any type of layout. Stay away from plastic wheelsets on your cars. They'll spread the gunk throughout your whole layout. Clean your loco wheels frequently and your car wheels regularly. There is a product called Goo-Gone which some people use on their layouts. However, there is a lot of controversy over its use. Better yet, a bright-boy or sanding block over the tracks is even better. It's just that DCC is less forgiving about dirty track than the old analog was.

For turnouts, you need an insulated or isolated frog. The best are Peco Insulfrogs, Atlas Customline. Peco Electrofrogs can be easily modified. Walthers has a new Shinohara turnout which is advertised as "DCC Friendly". That is, it has an insulated (plastic) frog.

The old Shinoharas don't have an insulated or isolated frog. Therefore, you have to isolate the frog by cutting gaps in the rails just beyond the frog. You may have to trim the copper wiper that allows the switch points to make contact with the rail. Better yet, stay away from them if you can. If you can't, you don't have to butcher them as described in WiringForDCC.

And do not, I repeat, do not, use automobile tail light lightbulbs when wiring up any of your turnouts! The command station/booster is designed to shut down when there is a short (like when you run a turnout). The Digitrax system beeps about 3 times and shuts down. That's a signal to you that's something is wrong (usually, you've run the turnout). The shutdown is to protect your system. You want to hear those beeps. Installing lightbulbs bypasses that protection.
 
Thanks for the very useful DCC information Railwaybob.
Over the last several days I've tried to access your website www.railwaybob.com by clicking on your link or by entering the address on my browser, without success. I hope the problem is temporary?
 
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