Spuring DCC Power

I think you'd probably do better taking the feed from your command station (is that with a transformer? mine isn't) that goes to the rails to a terminal block and splitting it to go to the rails from there.

Ian J.

As Ian says, take your feed to a terminal block pair (chocolate block) and then you can take it to as many points on your circuit as you wish but do ensure the feeders go to the same rail each time! This will overcome most poor rail connector contacts.

Peter A

Normally you have a pair of bus wires under the layout. The DCC command unit is directly connected to this. As a rule of thumb you have droppers from your bus to the track every yard or so. If you have complex track work with a lot of turnouts you will need droppers more frequently. To test if you have enough droppers do the coin test. Deliberately short out the track and see if the DCC control unit indicates a short,this is normally a buzz or several buzzes which will continue as long as you have the coin on the track. If it dos'nt or the responce time isnt immediate then add more droppers. The reason why we want an immediate responce is that shorting for what ever reason (the most common being a derailment of some kind) can cause damage to wheels and turnouts if not detected immediately.

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In message , Richard Willcox writes

Just the type of information that puts the over cautious off DCC altogether. I just love the last sentence. Love the reply-to address though. How apt :o)

None of this is at all necessary if the layout was/is correctly wired for DC to start with.

Quaint idea to say the least.

Absolute rubbish.

Cheers.

So tell us why you think it's absolute rubbish, then maybe you'll be taken seriously.

Everything Richard says is spot on.

MBQ

In message , " snipped-for-privacy@hotmail.com" writes

I think it is absolute rubbish because one of the tests that your DCC system is working properly is what our friends in the US call the "quarter test" and what I have seen referred to in the UK as the "50p test". The idea is that with the DCC power on, you deliberately short-circuit the track with a coin of the said value. There is no damage to anything, no matter how you arrange the short-circuit, because the DCC electronics detects the short circuit and turns the track power off immediately.

If you do get damage when performing this test, then your DCC equipment is not working properly, or your wiring has too much resistance in it, causing the DCC equipment not to detect the short. In either case, you should do something about it, because your setup will have failed the "quarter/50p test", and should not be used until it passes it.

Not everything Richard says is spot on.

Richard was describing the same test and explaining why DCC systems require such fast cut out (the multi-amp capability of a booster could damage wheels or track if a short were allowed to persist). The "do something about it" if the test fails is to add more droppers, just as Richard said.

Which bit of what he said isn't spot on?

MBQ.

In message , " snipped-for-privacy@hotmail.com" writes

Er, um, yes.

Rule 1: always read the message carefully before replying to it.

I am most interesting in what people have written in respone to my post, I have also investigated a bus system the Express Models sell (or rather a package of components to make the bus up) and I am now wondering if the following is possible, or what the situation i will lay out below creae a short:

I have a Square layout, with a hole missing i nthe middle, I am now considering running the two wire main bus under it, but, if I was to connect it into a complete loop, and have my Command centre feeds connected to the bus by droppers, or, would that short?? Would I have to not complete the full circuit of the bus and just connect one end of the bus to my Command Centre track feeds.

Diagrams would be so much better here - but I appeal to your imaginations! :-)

TIA Graham

I've learnt by experience not to use my email address on public forums have you ?.

Are you a DCC novice, or simply just a knocker who knows no better. I've been using DCC since 1994. On small layouts maybe a bus isnt totally neccesary provided power can be reticulated around the layout. On large layouts bus are a necessity.

Just about every book written about DCC quotes this test, do you have any practical experience of DCC ? Clearly you have yet to get past the energy saving clock work stage. You clearly lack practical experience of DCC. It's simple practical but does require an IQ >75 so I guess this rules you OUT.

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It would not short, it would be just like the ring mains in your house.

In message , Richard Willcox writes

Never had the need, Always used my real identity since the days of the Micronet and [Yuk] Viewdata systems, although I don't run a Redmond operating system on line and spam and dross have never been a problem. I also have nothing to hide :o)

Interesting. I have been designing [very] long range RF based telecoms equipment for over 35 years. Taught [engineers] for five. Currently employed [avoids boredom] as a consultant by a large [the largest] UK communications monitoring group.

I'm not sure what you mean by bus in this context. You seem to have problems with terminated feeds, rings? Booster stages and relay links. I assume that you know the difference.

Yes, and particularly the simple telemetry protocol upon which the current system is loosely based. I note that you have read 'just about every book written about DCC. That's why we consider ourselves qualified is it? :o)

:0o) Love it.

Unlike you Richard I have no need to pontificate in groups to impress others. I don't have to make money out of the unwary and foolish novice hobby user either. I actually have a great deal of 'real time' experience of the underlying system protocol that results in what you refer to as DCC. It might just possibly have escaped your attention that Digital Command Control extends far beyond playing with trains. It becomes very interesting when NBRF generated over long distance.

I am currently playing with a fifteen foot N-Gauge layout running DCC by RF hand controller [using a modified Roco unit] and the results are so far quite promising. Only 26 sets of points and 4 operational locos but [fingers crossed] no problem with DFE or crosstalk yet using the handheld unit. Unfortunately plugging in the laptop to the unshielded transmitter under the home workshop conditions is producing all sorts of nasty sprogs. Had to revert to foil screening to experiment. I Chose N-Gauge for proximity purposes and using run of the mill hook up wire without screening.

As for your attitude to criticism Richard it's well summed up by my colleague here this morning after reading your posting. Quote = "A real Dick masquerading as Noddy. Sounds about right. Not worth a response".

Unfortunately and apologies. I just couldn't resist it :o)

Happy to take this communication to E-mail if you are interested in the RF aspects of my little project.

Cheers.

Many Thanks Ian for your information.

Does anyone have any experience with the DCC Power Bus "Kit" that Express Models sell - that they would like to impart to me here please :o)

TIA Graham

Personally, I would avoid them. Just string your main feeders around the layout then use a pair of automatic wire strippers such as 86-0390 from

to open a gap in the insulation wherever you want to connect a dropper to feed a piece of track. Solder the dropper to the exposed bus wire.

Normally you would use wire strippers to completely strip the end of a piece of wire but they work equally well in breaking and pulling apart the insulation anywhere on the wire.

MBQ

What relevance does that have to DCC?

Which system protocol is that? The DCC protocol was invented for, er, DCC. Granted, once you've settled on using a half duplex serial bitstream all such protocols are broadly similar with packet framing and error checking, etc. becoming mere details. The DCC protocol is not rocket science, you don't need a great deal of 'real time' experience to understand it, and how it works.

Richards post was, in any case, referring to effects of the physical layer, not the underlying protocol.

But we are specifically discussing NMRA DCC as used for "playing with trains".

You still seem unable to back up your originall rubbishing of Richard's post with any *facts* as to why what he said was wrong. Until you do, your contribution is totally worthless.

MBQ

Wow! The guy only expressed his POV however misinformed. However iam intrigued by the use of SPROG when referring to square wave induced interference. When did it migrate from child or novice to the world of glitches?

Peter A B Sc ,Dip Nuc Tech + added star in pure bullshit. Control Engineer to the uninterested.

Hi Graham and Ian,

Following below is a reply to a member of the Yahoo DCC group with reference to wiring the DCC bus as a ring main from Richard Johnson of DCC Concepts. It may answer some of your questions.

Eddie.

Devils advocate as ever :-). If you have no problem now you probably won't get one...

However you are simply wrong about the track being a ring - it is not... nor is a rail the same as wire... if it was, droppers would be unnecessary.

Most importantly, you haven't made any sort of "ring" of your track unless you have no points and no isolation gaps at all. (even an insulfrog point creates a break in a rails continuity) The recommendation to not ring the main and to terminate the bus is a good one, and it is NOT an urban myth at all...

The ring has no effect on shorter layouts / smaller layouts but as the layout grows larger there ARE problems developed by creating a ring. These have been discussed ad nauseum on many lists and it is clear that once the layout grows beyong the average size it is unwise to ring the main.

The conventional wisdom is to use a bus that radiates in a tee or similar fashion from the boooster, with the booster in the centre. the time and cost to do it this way is no different to making a ring, and experience says that while some layouts may have no problem with a ring, some DO... so why argue the point anyway.

Especially as it is also clear that a terminated bus has a clearer waveform than a non-terminated one - a very good reason NOT to loop the bus as you cannot terminate a ring. If you looked at the size of the spikes created by every slight short on the layout you'd never question this, and installing the suppression created by the termination clearly works to reduce these as well as cleaning up the waveform, meaning longer decoder life and less chance of things such as missed or misinterpreted commands.

My counter agrument, put simply:

I have never seen a runaway or a control problem with a layout wired with adequate droppers and a terminated power bus. I have seen AND FIXED several larger layouts with constant problems where wiring was inadequate, used ring mains and did not terminate the bus.

These layouts also had a mysterious problem of decoders failing in use after several months and point motors changing themselves due to confused data or interference on the bus. These same layouts ceased to exhibit the problems after the bus was corrected (all had ring removed, all terminated, one had the bus re-routed to stop crosstalk between power bus and other wires... and of course termination was installed.

NOT creating a ring is simply best practice and there is absolutley no benefit in creating one, so why cause confusion by seeding doubt on what has been learned over a decade or more of DCC operation. I therefore highly reommend that a ring main is not used, and terminators are installed as a matter of course (we are talking a few pence only for the resistor and capacitor, so why NOT do it).

Its not necessary for us to agree, diverse opinion is part of life...

This is simply what I have learned from a long period of research and seen/done with my own eyes and hands. Putting this approach into practive worked without exception and the improvements carried out had results that were clear and unambiguous.

If you do not wish to follow the same path then that's your choice and I wish you well - this is a hobby, not a religion!

I simply recommend to all DCC'ers **that it is the safest, best and most reliable method, **that doing it costs no more,**That is no more difficult and CAN result in a problem free and pleasant DCC experience.

So why NOT do it?

Kind regards

Richard

I read this group daily but have hardly ever posted. Where am I making money out of the foolish and unwary ?. What are you brewing up there in your attic ?? ;=0 what ever it is stay off of it for a bit, it's affecting your judgement . You may have vast experience in other fields but little practical experience of DCC.

I don't have an attitude Roy, & BTW keep your colleague off the brew as well.

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What we've used in the past as bus wire is 5mm bare copper earth wire. This is one of the cheapest cables around and used extensively in South Africa due to the earth leakage system used there to protect against the heavy lightening storms on the Highvelt. There's no problem using unsheathed cable, obviously you need a gap of 60 -70 mm between them. With my last layout I commenced soldering droppers to the bus, obviously this requires a large iron (125 watts) with this size cable. Latterly droppers were simply stripped at the end and pulled tight and wrapped around the bus. No ill effects were found over a four year period. Droppers never became loose and the layout performed exceptionally well.

know of at least four other layouts employing this system of bus two of them much larger than my former layout. I'm not advocating this method under British conditions, but just demonstrating there's are plenty of ways of achieving the same thing.

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