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DCC bus wire (again - sorry)


FinnerZ

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I would not recommend using mains wire as it tends to be too stiff and inflexible.

I use 32 strand x 0.20mm Equipment Wire (32/0.20) for the Bus and 16 or 24 strand x 0.20 Equipment wire (16/0.20 or 24/0.20) for the droppers. I connect the droppers

to the Bus Wires with Scotchlok IDC connectors as these do not require you to remove a section of insulation on the wire to make a connection and a Power connector or rail to connect the dropper to the rails. Ensure that you maintain the polarity when connecting

to the rails, as the rails are live at all times on a DCC layout. An alternative is to solder the dropper witres to the rail and the Bus Wires.

I wire my Bus as a ring main so that the power on has to run half the distance to the furthest point on

the Layout and reduces any voltage drop caused by resistance in the wire. Staring at the controller, going round the layout and returning to the controller connections.

I use a Grey (for the White stripped Black wire) and a Black Wire. Use the same

colours for the dropper wires than there will be no confusion when you are wiring the layout.

If you are going to solder the dropper wires make sure that you tin (with solder) the wires and rails where you are going to make the connections. Then heat

both the rail and the wire when making the connection.

Some DCC modellers will say that you do not nedd such heavy gauge wire, but I maintain that using thse gauge wire reduce the voltage drop and ensure that all sections of the layout receive sufficent

power to run a reliable DCC Model Railway

I purchase my wire from CPC http://www.cpc.co.uk in 100 metre reels or you can purchase it in cut lengths from Maplin (there prices tend to be expensive).

For more information on DCC wiring go to this

link:

http://www.dccconcepts.com/index_files/DCClayoutwiringwire.htm
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I've already started to use the panel pin idea in a video by Teleman (I'll put the link in another post as they take a while to be cleared if they have a link) and despite not even being 16 yet have a collection of mains flex that I'm planning to use for

this purpose. I just wanted to find out if this was suitable, as I have quite a long layout with old track so the best electrical connection is needed. Where do you get the IDC connectors from because I could attach them to the pins and then into the wire

which I could run next to it. I know what you mean about polarity problems - I've started putting the pins in some of my simple sidings and it's already getting hard to find them, let alone match up polarity.
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I have a question re these bus wires: I have tested my reasonbly large layout with a voltmeter all over it with just one power source to the track and it seems fine everywhere.

This got me thinking that this bus wire malarky is more to improve the

DCC signals to the loco's than power to the track.

Anyone got any thoughts on this?
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He is another link to wiring a DCC Buson a NMRA site:

http://www.gatewaynmra.org/dcc/powerbus.htm

The Scotchlok connectors are available from CPC:

http://cpc.farnell.com/3m/a-560b/3m-scotchlok-connectors-10-pack/dp/CB13438?Ntt=scotchlok
or

from Halfords.

CPC's price is £2.12 for 10 inc VAT for 10 to 90 connectors and £1.79 per 10 for 100+ , breakeven point is 80 connectors (if you want to buy more than 80 it is cheaper to buy 100).

Polarity of the connections to the rails is vital

to prevent short circuits.
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That sounds right to me. I found there was little problem (other than track cleanliness) with my layout when it was DC but the problems only started when it was DCC, showing that the signal is all important. In my layout I had a bad responsive loco that

would move back and forward fine, but just not when I wanted it too - it was still getting power fine.
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You have to remember with DC you are only running one train on the track at one time, but with DCC you are running multiple trains on the same line. If you are running DC trains on a single track, you probably use blocks with their own power supply.

Try

puting 3 or more DC trains on the circuit and see what the voltage drop is.
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Yes - well I will check out the voltage drop over the weekend with three loco's running. But I don't intend to run droppers to every rail - as I mentioned, the main problem I have intermittently is poor signal caused by dirty wheels and track. When I clean

everything it runs fine.

But its all good fun!!
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  • 2 weeks later...


Phil: When you measured the voltage around the track - how many locos did you have MOVING (ie consuming power) on th e track near where you were measuring

the voltage?
If none were oving, then a voltmeter should NEVER show a voltage drop at a distant place UNLESS ther is a very bad joint somewhere!!
HOWEVER - when more than 1 Amp (for example) is running in the wires, then the resistance of the wires WILL

produce a noticeable voltage drop in distant parts.
The spec says dcc should always be above about 7V (so as to be able to run a 5V processor on the chip) - although many newer types will accept lower, this is not a good idea to rely on!
Try remeasuring

your voltage drops with either a moving loco, or a sound loco at the distant part.
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This subject - as the title suggests- has been discussed may times before. But there is no 'definitive' answer as the size and requirements of layouts differ (as does scale)

When analogue: only 1 loco ran on any 1 piece of wire. It probably had

no sound, and maybe only a headlight. The average power consumption (overall heating effect) via that wire was even lower, as it would only be used when th eloco was in that specific section.

Once Digital: There may be more than 1 loco in 'the section'

powered by that wire - it may have sound, and be pulling coaches which are constantly lit. There is an overall requirement for GREATER power capability. [Aside from the issue that dcc's flexibility may encourage more use of the model railway ]. If this connecting

wire is 'the bus' wire; then it may be carrying the current for the WHOLE layout, and to the furthest part: it should be capable of doing this with minimal loss.

When considering using 'mains' cables or FLEX for a layout, it is common to note the 'current

rating' eg 3A.6A,13A,30A etc: but this is quoted, from a safety point of view, for the likely heating effect, when the cable/flex is buried in a wall, and being used to power 240Vac equipment- although a relationship to 1ow-voltage use may be drawn. Cable

is rigid-core, and flex is multi-strand and more easily flexed 8-)
When using 'mains' cable within a layout, it should be used in such a way as to ensure there is NO CONFUSION between mains and low voltage use! eg the outer sheath stripped.

I admit

to using '6A flex', in its sheath, within my layout - but it has NO MAINS WIRING within it/ 'above loor level'. I use Black, White and Gold coloured outers to distinguish differing dcc busses (and coloured tape markings). I use 'figure of 8' 'loudspeaker/hi-fi'

flex for 16Vac (white+black stripe) and 12V (red and black) 'high current' flex for those busses. When I first went digital, with Zero-1, I used '30A' T+E stripped from its outer running beneath the layout: but found this stiff and inconvenient for 'plug'

type connections I use now. I used a mixture of 2-pin DIN and now 'Wago' connector blocks for board-to-board connections ('pernament' loft layout and portable layouts) - I prefer these to screw-based terminal blocks etc.

The Voltage Drop Test and the

Safety (Cutout) Test:
It is important that the finished result provides enough power with minimal voltage drop to the furhtest part, when UNDER LOAD - ie with MOVING LOCOS consuming power.
(A drop of about 2Volts from NO LOAD is probably okay).
The

RESISTANCE of the wiring must be low enough for a short-circuit on the track to trip the track output of the controller/ section cutout: The larger the layout, OR the higher the power capability of the controller!! - the LESS the resistance needs to be.
Therefore

what may be acceptable on an ex-analogue layout, now powered by a 'starter' 1-2A dcc controller may continue with the old wiring - passing the tests above; BUT if a 4-5A controller is used - DO CHECK that the wiring is sufficiently low resistance that the

CONTROLLER can CUTOUT on a short-circuit applied across the rails ANYWHERE.


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Hi stevecamden,

Wiring every rail to the bus is usually an overkill especially if you ar talking of standard lengthh rails, but you should consider adding additional drop wires at regular intervals and especially one at the furthest point from the

controller.

You should also check each rail joiner to ensure it is a tight fit, as these are often a problem. The finger test can tell which joints need tightening. If it's warm, then tighten it, if it's hot, you have a problem and it should be replaced.

Relying totally on rail joiners to pass current from one rail to another, on a DCC layout, is not a wise idea.

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  • 2 weeks later...
I've think I understant these but I just want to make sure. Does it have two sections for the two wires, and then you use pliers to squeeze the connecter and it will break through the insulation and make a connection? Is this about right?

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Hi Finner,

The scotchlok connector slips over the bus cable and you close the connectot and lock it. The drop wire is fed into the connector in the hole below trhe bus wire, as far as it can go. Then you use pliers to squeeze the metal IDC connector

until it is level with the plastic shroud. This IDC connector cut through the insulation on the bus wire and the drop wire and also slightly into the copper wires, thereby making the connection. Make sure the end of the dropper wire passes into the connector

beyound the metal IDC connector.

Each Bus wire needs a seperate connector
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  • 4 weeks later...

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