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Wiring the BUS

3208 Views 9 Replies 7 Participants Last post by  dwb

I am creating a new DCC layout -( essentially 2 loops each around 15m running length) and being new to DCC an wondering about the correct specification of wiring for the BUS. I've read Brian Lambert's info ( which was pretty helpful, but am wondering what the 'minimum' wire specification is for the Bus and the Dropouts.

I'm thinking of using 1.0mm twin and earth solid copper cables for both - this is mainly because I have a spare 50M roll of it to hand. Brian Lambert recommends 1.5 or even 2.5mm cable - so am I risking anything by using smaller/thinner?. Even with DCC I probably only plan to run maybe 4or 5 trains max concurently.

Could I use a lesser/smaller wire for the dropouts ?. again I have rolls of very thin cable (don't know the spec) which I have used for wiring points motors, and this would seem a lots easier to solder to rails than a large thick piece of copper from the twin&earth.

Would appreciate your thoughts - thanks in advance.
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Bus wires the bigger the better (within reason) Droppers of course can be smaller. So for a 5amp system ideally you should have 7-10 amp cabling as a bus.
Some people may think this is overkill, but for the sake of saving pennies on cable I'd rather have the capacity.
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Hi, you asked about bus wiring etc.

Take a read of the wiring advice at You'll find lots of information, and if you have any specific questions, feel free t oask on this forum or direct.

Please note I always quote "ideal" specs for wire - a slight compromise, especially in using finer droppers, won't hurt as long as the length is kept less than 12" - its much more important that you can easily make a tidy solder joint to the rail!

I have used 1mm wire for part of the layout, fiddle yard, but have used 2.5 for the main station area. I think that the larger sizes stop the risk of over heating and maybe a fire if the wire passes through the baseboard. For droppers I have used 7 strand fine telephone/computer cable from a length of scrap network cable that I got when the office I worked in was being re-wire for a new network, the old was going free so I had about 100m in short 8/10m lengths. As this has 9 wires and an earth I have over 1000m of coloured wire for droppers, points etc.

So far every thing works OK and there is no signs of voltage drop.

hope that helps

mike g
At the risk of being shot down and/or flamed I just do not understand the "out of a skip/left over from work" principles.

People are willing to pay a couple of hundred pounds for a control consul, invest several hundred on locomotives & rolling stock & then begrudge spending around £30 for a couple of 100m coils of 2.5mm single flexible stranded cable to make a really nice job of it - maybe it's the fact that it does not show unless you look under the boards.
I think the BUS is very important. I have seen fragile BUS wires that contribute to the bad functioning of some layouts.

This is what I use. Perhaps a little OTT, but I am vvery happy with the result and I have no voltage drop over the layout.

Conductivity problems between loco and track and the track pieces themselves are what plague a layout and give quite a bit of grief. I'll feel better knowing that the signal is being properly conducted to all corners of the layout.

I have soldered feeder wires directly to each piece of flexi-track. This will later help with block control should I implement it. I grind down a patch under the rail - removing all oxidation. I tin and then solder on a set of wires.

I lay the track with two feeders adjacent to each other, preventing too many connections to the DCC BUS.

All my red wires are to the front of the layout. Keep it simple - no reversing modules are needed anywhere on the layout except at each return loop on either end of the dog-bone. As a 'red' rail will bend around and touch a 'black' rail, the reversing look sorts that out.

I join all track with insulated rail joiners.

I group feeders together and connect them to the DCC BUS using this type of connector:

The DCC BUS itself is low resistance (6mm²) speaker wire that should maintain a good DCC signal all around the track. I use a continuous wire from one side to the other. That is why these connectors come in handy - they allow me to add feeders wherever I want without cutting the copper. I just trim back a bit of the insulating plastic, drop in the wire under the screw, replace the screw, tighten and add the cap that prevents splitting.

The DCC BUS is just under 20 metres long and it works fine with my Lenz LZV100 command station roughly in the middle. If I need to add a booster later, I can either split the Main DCC BUS into two sections or add another under the baseboards.

Here is my DCC RRampMeter Showing a nice and steady 16 volts at my command station:

It sometimes flutters to 15.9, but doesn't go below that.

On the other side of the layout:

This photo is taken about 10 meters away (along the track). It shows that my oversize BUS wires and feeders do the job perfectly. No voltage drop over this distance.

To check the layout with a load, I added a load to the RRampMeter in the form of a halogen bulb connected to the output terminals. The bulb had a current draw of 1.75 amps. The RRampMeter measured 15.2 volts DCC at the command station and 15.2 volts at the same distant point 10 meters down the track. So again the BUS does it's job perfectly.
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That's a new one Doug I've never seen that type of connector before, what's it English.
In south Africa we used bare copper earth wire about 7mm dia as a bus, with a clearance of 70mm between bus wires there was never a problem. This is commonly used for house earth wire, and is cheap, due to high level of Electrical storms each house is wired with it's own RCD. If you use multi strand droppers, you don't even need to solder to the bus, without intervention they never come loose. Just wrap your colour coded (red or black) dropper end, suitably stripped around the bus ensuing a tight wrap-around. Naturally this type of bus is best suited to those using a rigid baseboard. IE non portable.
Here's another fallacy soldering your droppers underneath the rail is neater and better practice- total rubbish just solder to the outside of the rail, it gets covered with ballast anyway, so why make a rod for your own back. Just tin the end of the dropper, using the pliers make a small 90 degree turn and solder this to the side of the rail - a perfect connection every time, easy to change if needed.
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The nice thing about that connector is that you don't have to cut the wire, just bare a little of the insulation. It is called a "Borne de raccordement" (here in France). Legrand makes it. They come in different sizes. Good for thick wires. Link to a shop selling them online: here.
thanks for all those responses: those LeGrand connectors look great - but I can't find any locally (Uk, Hertfordshire) - so will stick with soldering feeder-drop wires on to the bus.

Which brings me to a follow-on questions. What is the 'established' for laying tracki and soldering drop-feeds. Do people lay the track and THEN solder drop wires in place (and drill holes through the baseboard),
Do you solder drop wires to each piece of track before assembling the layout (assuming you have the luxury of a 'blank sheet of paper' on which to build.

I am currently doing the latter - but progress seems very slow and I still have the small problem of manouvering the wires out of the way to allow the track to lay flat, and then bending them back into place and working out the correct place for each hold to be drilled.

thanks in advance for help (again)
QUOTE What is the 'established' for laying tracki and soldering drop-feeds

Read this entry in my blog for how I do it. I have droppers on every track section and insulate every point. I have been asked about that last /point/ before and if you hop over the asymmetric DCC thread, you will read that I think I have just had a bonus from going to this extra bit of trouble.

I am pretty sure Doug has an entry in his blog too.

There are many different ways of laying track which work. Once you are sick to death of reading about how other people do it, choose the methods that suit you and you should be fine.

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