Positive and negative

[simon_young]

Positive and negative

Can I ask what is probably a stupid question.

I am new to model railways and was wondering, on a DCC setup which track is positive and which is negative?

The connection to the track are always connected via black and red connections, red being the B connection and black the A from the controller, can I assume that B is positive?

[Fishmanoz]

Hi Simon, a DCC signal is a pulse width modulated square wave at a frequency above 10kHz. As such, each track goes from positive to negative at that frequency. Consequently, neither track can be considered either positive or negative. 

[poliss]

The red and black wires are only there to make sure that if you add extra power feeds you connect the same coloured wire to each rail. There's no such thing as positive and negative in DCC, but if you mix up the wires when putting more track feeds in you will get a short circuit.

It's the same with DC too. Positive and negative change when you change the direction of the locomotive.

[simon_young]

Many thanks for the information.  I will be putting a bus system under my board and will make sure all track feeds return to the same point, one on the red side and the other on the black

[walkingthedog]

Here's a useful hint. Put a piece of red tape on one side of a wagon and a black piece on the other side if you wish. Put the wagon on the track and push it round/along the layout. Always put the red wires the same side as the red tape and the black ones the same side as the black tape. Don't take the wagon off the track in case you put it back round the other way. 

[RB51]

This, or the red pen mark beside the track, is a good idea Simon, you would be surprised how easy it is to get mixed up. R-

My apologies WTD - I seem to have replied to you instead of Simon. Thanks Hornby for the ability to edit. 

[walkingthedog]

What you've done is correct Roger. You've quoted me and added your idea. 

[Teedoubleudee]

I've just finished wiring my new layout which is a simple oval with a passing loop. I just followed my own rule of Red to outside rail(s) and Black to inside rails(s). I used some spare household 2.5mm cable for the track bus and connected it like a ring main so hopefully no voltage drop on that lot! The only soldering I've done is to the drop wires at rail end and fish plates, all other connections are by screw terminals. Just tested it with an analogue controller and all OK. Next job is to wire in the point motors and live frogs - then connect up to DCC.

[simon_young]

Many thanks for your help, I will do that, it makes sense

[Yelrow]

Hi, simon unless you have a huge layout, many of us would say, that a bus is not necessary, and i for one dont have any problems,  running 6 locos and several points  It is a lot of work, john

[RDS]

I totally agree.  

I have had up to 10 loco's working at the same time with 4 concentric loops, 24 sets of points and a turntable, all from one track connection to the outer loop.  On one of the sidings, the power has to pass through 15 sets of points and it works perfectly.

[idlemarvel]

In general I agree with rds and yelrow.  There is a lot of fuss made about having to have a power bus which is not necessary for most domestic layouts.  My current layout is 7'6" x 4'3", basically two loops, four sidings, eight points (all insulfrog), five locos and I have one power feed (4A) and use point power clips (R8232). 

There are reasons to have multiple power connections.  One is if you suffer from short circuits on insulfrog points.  The cure for this is insulated rail joiners / fishplates (R920) at the toe end of the points which does necessitate multiple power connections.  Another is if you can't bring yourself to use point power clips as they spoil the scenic effect.  Or if you use electrofrog points to minimise the dead sections over points (all Hornby points are insulfrog).

[Rog RJ]

I have an 8ft by 4ft two track oval with sidings  and when I first got my DCC set I tried to run it with just one power feed and connecting wires from outer to inner circuit and some point clips too.  It was OK for a couple of days (it was all new track) but trains soon started to slow down in two or three places for no obvious reason.  Fitting extra track feeds to the areas where the slowing effect happened cured the problem.  I still don't have a full bus set up but there are a lot more track feeds now than when it was first set up.

It's lucky that I don't have my track ballasted which makes it easy to add track feeds if I need to but if it was ballasted it would be much more difficult.  I would say fit as many droppers/track feeds as possible and provide a bus for the most reliable running, especially if your layout is permanent and ballasted.

[Yelrow]

my layout is also 8x4' 5circuits with 14points, not fixed down,as i like to play ,and. Been like this since march. never cleaned track, no slowing problem, but I do have a 4 amp transformer, john

[poliss]

If you don't mind soldering, then it won't hurt to add extra power feeds. Lots of people don't use a bus on their layouts and don't have any problems, but others do have a problem.

[walkingthedog]

You can never have too many feeds whether DC or DCC. Costs next to nothing and improves your soldering skills. 

[Yelrow]

wtd  does not do the table tennis table any good looks like woodworm. the more serious point is that a lot of people change their layout often. I still make weekly adjustments. i would be for ever soldering, and unsoldering.   If hornby thought track needed soldering together  they would supply it in the set, surely. John

[morairamike]

For those who do not run a set up on the best dining table or the table tennis or the baby changing table or the kitchen worktop or the lounge floor or the dressing table, then relying on fish plates for the transmission of power is to be honest asking for trouble. OK you may not need to solder a pair of wires to each bit of track but some of us did and do. The result is NO POWER DROP OUT on any part of the layout. There is no way that the fishplates on a track will give 100% power transmission for ever. The addition of  ballasting introduces moisture which finds its way into the small gaps and will cause corrosion overtime and temperature change causes movement of the track.

So if like me you wish to wire up a power bus under the base board then do so, and then solder a pair of wires to every rail then do so, we live in a free country no one dictates what you do with your layout, like I say IT'S MY RAILWAY and I'll build and run it like I want to.

[idlemarvel]

I don't think anyone here has said you shouldn't have a power bus, only that you don't necessarily need to.  As you say quite rightly it's a free country and your railway.  Undoubtedly the more power connections the better, but there is a price in terms of time, effort and materials, not to mention soldering skills which not everyone has.

[Teedoubleudee]

My take on this is, is that it's a whole lot easier to include the  extra drops at design/build time rather than wait for problems to occur later and have to fix them once the layout is complete and access is, at best, limited.

[Yelrow]

Hi,there are two camps, involved here,those who build , model scenery,and wish perfect permanent. Running, that's fine, each to their own.  Then there is me, and probably others who get as much pleasure from constantly changing their layouts. I did my scenery thing with modroc and chicken wire years ago hello hello hello with my kids, and now, enjoy chopping and changing. my dcc and dcc layouts, barely go 10 days, without  tinkering, with sidings etc, or as more ebay track bargains, arrive, adding on points. if I had soldered all my tracks, I would still be laying them, I only fix track next to points. I run 2 n gauge tracks, 2 TT tracks, 3 three rail circuits, and ,6  2rail dc  , not to mention my Dcc layout. at Age 71, I would be in my dotage by the time I had soldered every rail.  Would it run better, of course it would, would I get any more pleasure from it, definitely not, I would be  too busy trying to unsolder, in order to try something new. that's the joy of the hobby, we are all individuals, eccentric, certainly, me, definately, just ask my wife, john

[idlemarvel]

Agreed yelrow.  I must completely rebuild my layout at least once a year and tinker with it every couple of months..

Good to hear that at age 71 you do not consider yourself in your dotage!:-)  Hope for us all (myself a mere 59).

[RB51]

Very good John - a very "positive" post, and very inspirational to any faltering souls I hope. Certainly me (not faltering but always boosted by such positivity). R-

[poliss]

If I was going to change my layout often, I would buy the track that's speacially made for the task.

[Teedoubleudee]

Do you think we should put our age in our signature ;-)

 

TWD (70 1/4)