Wiring for DCC

[tstage]

I posted this over at the Bachmann forum but I'd like to get your input into this.

I just purchased the Bachmann EZ Command DCC System for my layout. I'm fairly happy with it but I, for sure, will be looking to upgrade to a more sophisticated and expandable starter system, like the Digitrax Zephyr or the CVP EasyDCC, in th futue. For now, it's quite adequate and my feet are "getting wet". [:)]

Presently, I only have two wires that feed power to the track of my 4 x 8' layout - the same wires that I was using to run it on DC. I'd like to start wiring the layout legimately for DCC. What I'd like to know is this: Can I take the small 20 ga. wires that came with the EZ Command System and just hook them into the 12- or 14-ga. power bus wires without running into any current problems?

I want to have track feeders running every 2 or 3 feet from the bus wires. It just seems strange and counter-intuitive to me to go from (in a sense) "feeder" wires (from the EZ Command unit) to larger power bus wires, back to smaller track "feeder" wires. Does that make sense? I'm guessing that, sense it is such low current, it really won't make much difference. That's what one of the fellas on the Bachmann forum seemed to confirm. Still...I ask the question.

Thanks for chiming in Randy! [:)]

Tom

[BRVRR]

Tom,
Since you are rewiring for the future, I would wire the buss directly to to the DCC unit/command station. On the 4x10' BRVRR, the DCC buss wires connect directly to my Zephyr. I don't know what type of connections you have on the Bachmann, but I would recommend you do the same. If not use connecting wires the same size as your buss. Just one less future problem to deal with.

[RMax1]

I've run mine into into Atlas connectors #205 and then to the feeders. I believe that I am running 14 guage wire between the connectors as the main bus line. I'm able to turn off and on seperate areas of the track ie sidings and main line with a flip of the switches. So far it works good and allows me to lay out non DCC equipment without the power being there. With 40 or so locomotives I haven't quite decided which ones to convert first. The DCC runs into the first connector and from that connector 14 guage wire runs to the next bank of connectors and so on down the length of the layout. I've got 3 DC power packs that are going to be used for lighting, undertable switches and other accessories. The lnly length of thin wire is from the controller(couple of feet) and from the connectors to the feeders.

RMax1

[tstage]

Allan,

I understand you. That's the problem with the Bachmann EZC. It has a single "stereo"-type jack in the back (that the connector fits into) then splits off from there and attaches to each rail of the track.

I'd prefer to keep the bus wires 12- or 14-ga, with the feeder wires 18- or 20-ga. I was just wondering if that 1 o r 2 foot of 20 ga. wire coming out of the back of the EZ Command unit and hooked into the bus wire might forecast any bad weather ahead.

Here's what Jim wrote me on the Bachmann forum:

----------------------------------------------------------------------------------------------------------------------
Author: Jim Banner (---.ss.shawcable.net)
Date: 02-15-05 19:53
Scale: General

Suppose your small wire is 20 gauge, which has a resistance of 10 milliohms per foot and your bus wire is 12 gauge which has a resistance of 1.6 milliohm per foot (a milliohm is 1/1000 ohm.) Further, suppose you use 4 feet of small wire (1 foot between the EZ Command and the bus, and 1 foot for each feeder.) Then suppose your bus is 100 feet long. So - total resistance from your EZ Command to a locomotive at the far end of the layout is 20 + 20 +320 = 360 milliohms. Voltage drop at 1 amp is a negligible .36 volts.

Now suppose you had used the small gauge wire all the way. Then the total resistance would be 2040 milliohms, and the voltage drop at 1 amp would be 2.04 volts. This is enough to dim the lights somewhat and slow the trains.

Thirdly, lets suppose you used 12 gauge wire all the way. Then the resistance would be 33 milliohms and the voltage drop would be .33 volts. This is not much better than the first case considering the trouble of trying to solder 12 ga. wire to the rails.

Based on this, yes, it would be worthwhile to use heavy bus wire for long runs even if you have to use lighter wire for short distances at each end.

-Jim-
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Agree or disagree? Thanks!

Tom

[simon1966]

When I first got my Zephyr, for my medium size layou, I initially just hooked it onto some typical feeder wires that I then soldered to my bus wire. This was only temporary until I built a shelf to mount it on and then connected to the bus directly. I have to say, I did not notice any difference in performance, but at the time was only runnin 2 loco's max.

[rrinker]

You can certainly tie the small wires to the heavy bus and not really have a problem - it's only a short distance. If this sort of thing was a problem, you'd also have to solder #12 to your track instead of using #20 feeder drops.
A pleasant discovery was that the screw terminals on my Zephyr actually can take a #12 wire. But, to break my layout up into power districts, I am planning on using Tony's PowerShields. The terminals on those (actually holes, you solder the wires on) can't take a #12 wire. I built a mounting board that is hinged under the layout to put the PowerShields on, and there will be short drops of whatever the biggest wire they can handle (I think #14) to terminal strips. There, the #12 busses will tie in.
Bottom line, a short drop of smaller wire won't hurt, and since there is an absolute maximum of 1 amp from the EZ-Command, there won;t be any problem. The voltage drop will be negligible at that current load over that short a distance.

--Randy

[tstage]

Okay, so the consensus is that, because of the short distances, the smaller 20-ga. wire coming off the EZ Command to the 12-ga bus wire is not really a big deal.

Now, that leads me to my second question. What configuration is the best way to lay the bus wire underneath my 4 x 8' layout. For ease of explaination, here's a pic of my current layout :



I'm trying to make sure that two things don't happen underneath the layout:
1) All 20-ga. rack feeders stay under 3'
2) There isn't a high concentration of track feeders in one place - e.g. a yard with several switches

So, do I just follow the track? Do I sort of start from the outside and spiral inward? Can I branch off the main bus (with another 20-ga. bus branch) in order to reach my yard?

Forgive me my ignorance. These probably are rather stupid and mundane questions to the rest of you who are much more electrically savvy about these things. I'm understanding the wiring part; it's the configuration that I don't remember seeing anyone explain in detail in any of the books that I've read.

Thanks!

Tom

[rrinker]

Follow the main line around the loop. Run two branches off to follow those yard tracks and the interchange. Assuming the connection to the DCC controller will be on the side facing the viewer there, closer to the wall where your parts box is sitting, I would run counter-clockwise around the layout, and where the yard and branch interset, tap more #12 into th e main #12 and parallel those tracks, right below them. If the taps for the yard and interchange would be near or at the end of the main loop, just tap those busses from the other side The idea being all the way around is about 24 feet, and you don;t want the yard bus to make the whole thing even longer.

I ran my feeders in two parts, each goes halfway around, but my layout is 8'x12', not 4x8.

--Randy

[BRVRR]

Tom,
I can't argue with the math. The small connecting wires will likely be fine. With DCC and wire size, bigger is always better has been the mantra since I switched to DCC two years ago.
As far as how you run your bus, I would run it under or just inside of the mainline, counter-clockwise from the command station. I doubt if any feeder will exceed 20-inches or so. You can run the extra bus for the yards and sidings if you like (More, bigger, better), but the 4x10' BRVRR's bus seems to work fine, routed just inside of the inner main.

[tstage]

BRVRR,

I understand you so far. Your power bus runs CCW to your command station and is routed on the inside of the inner main. Okay, that makes sense.

Now, I'm fairly sure of the answer to the following question but I have to ask the question anyhow: Is it important that the bus "always" running parallel to your track or can it just run parallel "sometimes".

For instance, it's easy to run wires parallel to the track when you track is running straight. It's more difficult when you track is curving around. So, when you are following a curve with your power bus, do you follow it making 90-degree turns. Does that make sense?

If you look back up at tje picture of my layout: the back side of the layout is curved, like one side of the number "8". Instead of following that curve the whole time, can I just run the bus in a straight line from one end of the layout to the other - as long as I have feeders attached to the track every 2 or 3'? After that, in order to follow the track as it makes the 180-degree turn to go the opposite direction, can I just turn 90-degreees, run the bus for 3' or so then turn 90-degrees again to makle my 180-degree turn?

I am guessing that this would be okay but I had to ask anyhow. I've seen plenty of pictures about how to attach the feeder to the track and the feeder to the bus. I don't remember ever seeing a diagram how closely the bus should follow the track from underneath. Am I correc in stating that, ideally, you want the least amount of bus wire that will adequately power the most amount of track, in the shortest distance?

Anyhow, thanks for being patient with me on all this. I'll probably think of other questions. I do have the "Easy Model Railroad Wiring" book by Andy Sperandeo. I think I'm just going to go back and read that from cover to cover so that I can get a little better aquainted/educated on electrical principles and ideas as they relate to MRRing.

Tom

[rrinker]

My corner wires go at 45 degrees - I drilled holes in the joists to run the wires through, so there are two holes on the joists at the corner, since it's two different table sections. The wire naturally takes the angle between the two holes, although I don't pull it all really tight. It's not hanging in floppy loops, either. Just a little slack to ease working with it.

--Randy

[BRVRR]

Tom,
My 12-Gage buss is connected directly to my Zephyr, I left about 1 1/2 to 2-feet of slack for my movable drawer which holds the command station and two MRC 1300 power packs connected to the jump ports. I coiled the slack by wrapping it tightly around a broom handle. The bus then runs clockwise just inside of the inner main line (BRVRR is double tracked main) from the middle of the front (south) long edge of the train table. On the end (west) It makes an 90 goes about 2-feet, makes another 90 and runs under the inner main on the backside (north) long edge of the table. At the other end (east) it makes a 90 goes about 2-feet makes another 90 and returns to the center of the table where it is terminated. The ends are taped and stapled to the table frame. I drilled 1-inch holes through the frame members to pass the wires. (Both wires through the same holes). The wire is not too tightly draped through the frame members, but not sagging either. I connected track feeders (20 or 22 gage) with suitcase connectors to the bus and soldered the other end of the wire to the outside of the track. One feeder every 4-6 feet. I have 9-isolated sidings for cars and locomotives controlled with Atlas Connectors.
I have had no problems with the power bus since I installed it about a year and a half ago. I don't see a problem with allowing the buss to 'wander' a little. The important thing is to keep the feeders to the shortest length practical. I have changed some of the sidings, eliminated a couple and relocated a few. The suitcase connectors make that easy. Take the link to my web site and press the Layout Button once you are there. The photos and the text should make most of what I said here clear. If not feel free to ask.
Good Luck!

[tstage]

Allan,

Thanks for the info. So, if I understand your description of the direction of your bus, your layout is a 4 x 10' "L" and your bus makes a giant "incomplete" loop around the inside of your main of your "L", where it terminates close to your command station. This that correct? I do understand that keeping the feeders as short as possible (or at least under 3 feet) is desirable.

A note of clarification: Allan, you originally mentioned that your bus went CCW around your layout. Your last post you changed it to CW. Is it CCW?

Thanks again for helping me with this. [:)]

Tom

[BRVRR]

Tom,
I was suggesting that you run your buss CCW under your layout. That suggestion was based upon the location of your controls. It doesn't really make any difference, however.
The BRVRR is a 4' x 10' rectangle, the DCC buss runs CW. It is an 'incomplete' loop under the inner main.

[rrinker]

Although, Allan, you might be basing THAT on my ASSUMPTION of where Tom is putting his controls - I don't think that was confirmed.
But which direction it goes really doesn't matter. The little electrons in the wire couldn't care less, besides thaey are changing direction at a relatively high frquency anyway with DCC power.
I will stand up here and say that I absolutely, totally DISPISE any form of crimp-on connector. Yes, I terminated by bus wires with spade lugs so I could ocnnect them more easily to terminal strips - crimped, but ALSO soldered. My feeders, they are ALL soldered to the bus. My wire stripper (the squeeze kind with the clamp, NOT glorified wire cutters with a notch) makes short work of peeling back a short section of insulation on the #12 wire whwre a feeder needs to connect, even in the middle of the wire. Plus I use #20 wire for the drops, and I haven't seen a tap connecter YET made to have a #12 feed with a #20 tap. They're all #12 run with #18 as the minimum tap. Sound sliek al ot of soldering, but around the one completed loop on my 8x12 layout, it was less than 30 solder joints for all the feeders to the bus, and that's with feeders on EVERY rail joint.
If you don't have a stripper like this, get one. They make quick work of stripping any wire from about a #10 down to a #24. With a little practice you can usially manage with one hand. Squeeze, squeeze, squeeze, all the feeders have their ends stripped. Have to be alittle more careful on the bus, just a light squeeze. Wrap the stripped feeder around the bare section of bus, tightly. Quick hit with the soldering iron (I used my bigger 40 watt one for this. But a nice 100-150 watt soldering gun will also work great here, just bulkier to handle) and it's all done.

--Randy

[BRVRR]

Randy,
I stripped the buss ends of the feeders for about an inch, doubled the ends back on themselves to make them thicker and then pushed the end into the 'suitcase' connector. The 'tug test' and ohm meter confirmed a solid connection. To each his own.

[Leon Silverman]

Randy:
One word of caution about the squeeze stripper you mentioned ( I assume this the type that has been advetised on TV). They are advertised as being able to strip up to four wires at a time.
This is true only for the smaller gauges. I used it to strip some 12 gauge romex wire when I added some outlets to my room. It handle a single wire with no problem. It fell apart when I attempted to strip two wires simultaneously.

[rrinker]

Nope, this is not the type advertised on TV, this is a heavy duty tool I got at Home Depot. It wasn't cheap, but worth every penny. There's no way it could do more than one wire at a time, unless they are all different sizes. There is one wide clamp part, but the blade that does the actual stripping has a series of holes for different wire sizes. No way could you even attempt to do 2 wires of the same size, there's no place to put them.
This is a HEAVY tool, solid metal, no cheap plastic stuff. Strips #12 as slicker than, well, you may have heard the one about owl excrement combined with grease... [:D]

--Randy