DCC Bus wiring

Hi Noel,

I'm not ure what you mean by the ring being cut but this is how my bus wires make their way around the layout following the centre of the main runs of track , the ends of the wires left open as can be seen at the top of the plan.

Ah, whether to Ring or Radial the bus, that is the question? Sounds a bit like Shakespeare

Ring is a complete loop of wire that is joined together at the ends of the wire run and has normally a smaller single wire linking the ring to the feed connection terminal place (You cant normally get both ring wire ends into the terminals of a DCC unit!) Two single wire rings are run around the layout to make a DCC bus.

Radial is a wire run that starts at the power source and runs out to the furthest point and does not return back to the source. Again it may be necessary to use a slightly smaller wire to connect onto the DCC unit at the beginning of the radial wire, due to terminal size on the unit. Two radial wires are run out and used as the DCC bus. The place where the input feed to the radial bus is connected doesn't always have to be at one end, it can be connected anywhere along its length wherever convenient.
Convention in electrical theory seems to like the ring, as this will help split the load and any fault currents flowing. Cost of ring v radial may also be smaller thing to be considered, as more wire is normally used in a ring.

Using a radial DCC bus is normally considered to be the way to wire a DCC layout. But there is no reason a ring can't be used if wished. If you do opt for a Ring, joint the ends of the ring wires into a pair of 15amp terminal blocks. Then, if later, you do have power problems, its very easy to open the ring up into a radial by unscrewing the terminal blocks grub screws and removing the two pairs of wires - Do put either terminal blocks back onto the ends of all the four wires removed or tape them to prevent any possible short circuits occurring.

The main thing is don't skimp on the wire gauge used. Solid copper wire in 1.5mm is about the minimum and 2.5mm better. If you need flexible wire (portable layouts etc) then 32/02mm or even 50/02mm are good sizes.

Happy New Year

*** Flashbang, you said:
"But there is no reason a ring can't be used if wished."

Generalisations are dangerous. In truth as I said in this case no big deal but in general its not advised to make a ring at all. As a layout grows ring type busses will create problems that do not need to exist.

Again on a smaller layout a single direction "long wire" bus isn't important, but "safest best practice" is globally recognised to be a T shaped bus with the command centre at the approximate mid point.

Its always best to simply stick to best practice as there are so many skill variances and because of progressive small errors made accidentally by modellers who are rarely wiring experts. Doing so minimuses the chance of problems. I have fixed problems with many client layouts by changing such minor things... which can have major consequences.

Also... In all cases, things that are not important on smallish layouts become problem issues with growth... when the need to do things such as either properly separating or twisting bus wires and the adding of suppression/termination filters to the bus become important.

There is no need to look at solid copper and there is absolutley no benefit vs stranded - in fact given the lack of proper tools and the need to be very careful to not nick solid wire and weaken it, use of stranded wire is usually best for the average modeller.

Once layouts grow above the average, wire sizes of 6mm in square area become necessary. The sizes we are talking here are only really OK in the case of small to medium layouts. Even in that case. 1.5 is way, way to small for other than a shunting plank, and 2.5 the recommended minimum. Even 32/.2 is actually on the small size but mentioned as it is the most common easily available reasonable cost wire.

Bigger is always better every time (The real world practical limit is - how big can you and your soldering Iron still consistently solder well). This is all about voltage drop and inductance related issues and the like, nothing at all to do with current carrying ability.

Richard

Learnt a lot more about how my bus works here thanks Richard

A tip with the bus is cut lots of pieces of heatshrink and put them on the bus wires for any extra feeds in the future i may want to add as the track isnt complete yet ......... heatshrink is cheap and you always have shrink ready to go on the bus wires this way.

Blimy.....Sorry I made any posting!
I feel like a good ticking off has been made!
Those were my views, it may not be yours of course, that's life!

Aren't most circular layouts rings in effect via the rails! Especially where insulated frog points are used.

6mm2 as a DCC bus is surely a bit OTT (well a lot actually!) If you have to use 6mm2 conductors your DCC layout needs urgently to be split in several smaller power districts to help reduce power usage and improve the short circuit path.
Trying to run two 6mm2 wires around the underside of a layout would a bit like wrestling with a snake! This is the wire that is used and suitable for powering domestic electric cookers and smaller electric showers!!

Ironically 32/02mm2 is rated at 10 amps. Which is equivalent to approx 1.0mm2 solid copper wire. Note; some suppliers down rate 32/02mm2 to 6amps. 1.5mm2 solid is rated 15 amps while 2.5mm2 is rated at 20amps. These are continuous maximum power ratings, not short circuit ratings which are much higher.

Using solid conductors as the DCC bus on a fixed layout does offer easier wire stripping where dropper wires are to be connected onto the bus mid run etc. The only "Tool" needed is a sharp knife - Stanley or craft. Trying to remove insulation from stranded wires mid way is harder to do and risks the knife blade digging into the strands and breaking them, where on solid wire the blade slides (or slices along) smoothly along the inner copper wire. Soldering the connection is best, but where it's not practicable or easy to carry out the use of 15amp terminal block connectors could be used. I dislike the use of 'Snap Lock' connectors on flex bus wires as these actually can cut through the copper wires inside the insulation without the installer being aware.

Happy New Year

*** No, I wasn't ticking anyone off, just stating it as I see it. I never have a go at anyone for the sake of it.

I see posts like your initial post (and follow up post) all the time and I do appreciate you meant well BUT I'm afraid your logic just isn't right with regard to DCC wiring. This sort of thing is my business and I advise and consult on it all the time, often fixing problem layouts simply by reverting to the sort of standards I mention.

Re your comments on wire size relativity you have to ignore issues like amperage and the like. This is not a simple linear ohms law issue in any way.

You are dealing with a high frequency assymetric square wave which has characteristics that are not the same as conventional DC or AC wiring. Any compromise will progressively create power delivery problems AND affect the quality of the DCC signal. DCC is quote robust but it has limits, and staying with a good set of standards assures good results.

For example, if you do not either separate separate bus wires by a reasonable amount or twist twin wire on a long DCC bus then you will end up with significant levels of inductance between the wires which will in itself create enough resistance to drop voltage by about 20%. You can see something of this effect just by taking a roll of twin wire with nothing connected either end and no power connected either - use a meter set to ohms and you will get a valid reading - which is created by the fact the two copper wires are closely adjacent to each other.

(In extremes its a huge problem... for example in a powered situation, if high power cables used in mains power wiring / concert audio setup are left coiled for example, the load which is created by the inductance of the wire can generate enough heat to cause a fire - it has been the cause of many fires where cabling for a concert etc has been left coiled / not been properly laid

6mm is not at all over the top for a long bus. It is critical to use heavy wire (appx 10 gauge) on a large layout. Ask any of the many large layout owners / larger club layout builder who thought they could get away with less and ended up having to re-wire.

NO, Layouts are not a ring unless they are a simple train set oval, which is too small to worry about these issues. Every point/turnout is a break as is every isolating gap.

Using a knife of any kind on wire is always bad practice... period.

It is worse for an amateur on solid wire as a single nick will create a vulnerable fracture point. Losing a couple of strands in stranded wire is acceptable in comparison. Strippers are cheap and will do the job properly.

Again, if you use the correct clamp type IDC connector (each cable size has its own specific need) AND the correct crimping tool they are 100% reliable - it is the low cost universal types which do as you say especially when simply clamped with the wrong tool. I rarely use them though as I too prefer soldering.

Regards

Richard

QUOTE (Flashbang @ 1 Jan 2009, 03:37) <{POST_SNAPBACK}>Blimy.....Sorry I made any posting!
I feel like a good ticking off has been made!
Those were my views, it may not be yours of course, that's life!

Aren't most circular layouts rings in effect via the rails! Especially where insulated frog points are used.

6mm2 as a DCC bus is surely a bit OTT (well a lot actually!) If you have to use 6mm2 conductors your DCC layout needs urgently to be split in several smaller power districts to help reduce power usage and improve the short circuit path.
Trying to run two 6mm2 wires around the underside of a layout would a bit like wrestling with a snake! This is the wire that is used and suitable for powering domestic electric cookers and smaller electric showers!!

Ironically 32/02mm2 is rated at 10 amps. Which is equivalent to approx 1.0mm2 solid copper wire. Note; some suppliers down rate 32/02mm2 to 6amps. 1.5mm2 solid is rated 15 amps while 2.5mm2 is rated at 20amps. These are continuous maximum power ratings, not short circuit ratings which are much higher.

Using solid conductors as the DCC bus on a fixed layout does offer easier wire stripping where dropper wires are to be connected onto the bus mid run etc. The only "Tool" needed is a sharp knife - Stanley or craft. Trying to remove insulation from stranded wires mid way is harder to do and risks the knife blade digging into the strands and breaking them, where on solid wire the blade slides (or slices along) smoothly along the inner copper wire. Soldering the connection is best, but where it's not practicable or easy to carry out the use of 15amp terminal block connectors could be used. I dislike the use of 'Snap Lock' connectors on flex bus wires as these actually can cut through the copper wires inside the insulation without the installer being aware.

Happy New Year

According to all my IEE (electrical engineering) books and a quick look at Wikipedia a Radial circuit is (copied from their site)
"A radial circuit is one where power is transmitted from point to point by a single length of cable linking each point to the next. It starts at the main switch or fuse and simply terminates at the last connected device. It may branch at a connection point"
http://en.wikipedia.org/wiki/Electrical_wi...radial_circuits

All your house lights are normally wired via one or more Radial circuits - e.g. Supply (Fuse or MCB) to first light fitting then onto the next and so on until the last fitting is reached. &#8230; Actually this is identical to wiring a radial DCC bus on a layout!

I'm finding all this rather unecessary as nothing constructive is now forthcoming - just what appears to be a lot of waffle.
I would like to suggest this thread be closed??

QUOTE (Flashbang @ 1 Jan 2009, 18:09) <{POST_SNAPBACK}>I'm finding all this rather unecessary as nothing constructive is now forthcoming - just what appears to be a lot of waffle.
I would like to suggest this thread be closed??

Why close the thread ? constructive advice has been given by two experts in the field of DCC to the original question whch will hopefully help Noel in his layout.

The ''waffle'' as you choose to phrase i found very informative to those not in the know thus increasing knowledge of a bus wire in this case.

I think I a bit more bafled than when we started but I take in Richard comments and thanks to all for there help
Yours Noel

QUOTE (1ngram @ 27 Jan 2009, 15:20) <{POST_SNAPBACK}>When you guys speak about a bus wire here are you talking about a single cable and if so how are you connecting the droip wires from the track to it?

I had surmised the 'bus wire' as being a succession oif wires from terminal block to terminal block where the individual drop wires drop to the terminal block and are connected there to an end of each piece of bus wire (if you can understand me) as I did with wires to my old dc layout and then back via other terminal block junctions with other drop wires back to the power source. Yes? No?

And if I use stranded wire for the bus wire for a layout 16 feet long over 4 boards each 4 foot long I need a what? - 32 strand wire?

My boards need to be take-downable as A and D form fiddle yards for C and D on my Russian layout and C and D are the fiddle yards for A and B on the GNSR.

Hi 1ngram,

Combined with the diagram i put on post #2 of this thread and the excellent advice Richard has provided the setting up of a DCC bus has dropper wires added from the rails to the bus wires thus ..... soldering track is not difficult with a few simple tools, where the wires are to be affixed remove a few sleepers then turn the track over run a file next to the last sleeper wipe the rail clean and apply a little flux with a paintbrush get a hot up to temperature iron (i use an Antex 25Watt ) and your solder tin the end of the iron tip with solder and touch the rail you should hear it sizzle and see the solder flow onto the rail as soon as you hear the sizzle or the solder flows remove it work quickly as too much heat will melt the plastic sleeper.
Repeat for the other rail....... now prepare your wire by stripping the insulation nearly as wide as the gap between your two rails twist the wire so all the strands are together then flux and tin with solder just eonugh solder to cover the wire ...... with a pair of pliers bend the tinned part at a right angle at the top of the insulation you stripped and squeeze on the wire to flatten it.
Apply a little more flux to the rail and wire and hold to the rail wipe the iron tip clean pick a little solder on to the tip and apply it to the wire and rail again until you feel the wire move down to the rails and hear the sizzle hold in place for a moment, with wire cutters trim the overlong wire and file up to the inside edge of the rail and you will have a good solid joint, where the wires are to be joined to the bus use heatshrink to cover the join.

I have done a drawing with paint i hope explains it

*** My mistake - that should have been "or separate the two separate wires by about 100mm or more"

Regards

Richard

QUOTE (Richard Johnson @ 28 Jan 2009, 00:36) <{POST_SNAPBACK}>*** When I talk about a "Power bus I am talking two wires. This can be twin or two separated wires.

In order to reduce inductance either twist the twin wire about 4 turns per foot or separate the two separate wires by about 10mm or more.

Yes, 32/.2 is about as small as it should ever be. It should be as continuous as possible with the droppers/feeders connected at regular intervals.

Richard