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Discussion Starter · #1 ·
I am building a new layout and using DCC for the first time. I have, so far, one loco that I bought fitted and one older one to which I had a decoder fitted. They both work well and I am impressed with the slow running I get.

One problem,, my locos are set so that 'Forward' is out of the station and 'Reverse' the opposite. Occasionally when I first turn the controller on the locos will start to move in the opposite direction to that selected. As soon as I stop and then start them again, everything reverts to normal. Except once when the newer loco was being driven in 'Reverse' direction out of the fiddle yard, without me touching the controls it stopped and started moving in the opposite direction???

Any suggestions please?
 

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You don't say what type of dcc controller you are using or, perhaps more importantly, what make your decoders are. When you say that you have set the direction to be 'forward' out of the station does this mean you have reversed the direction of travel by adjusting cv#29 on each loco's decoder or is it some sort of adjustment on the controller?

If it is the latter and you have reversed forward/reverse in your controller settings then try putting that back to normal and changing cv#29 on each loco (if you haven't already changed this for direction of travel just read the current value of cv#29 add 1 and reprogram it.) . If that doesn't fix the problem then come back and give us a bit more information.
 

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Discussion Starter · #3 ·
Thank you for a prompt reply. I am using a Digitrax DCS 52 controller with an additional Digitrax UT6 throttle. The built in sounddecoder is in a Roco BR 233 diesel loco and is 'specifically adapted' for this loco type but it doesn't say what sort of decoder it is. The other was installed in an old DC Roco 212 diesel by a local model shop. I would need to check with them for the decoder details.

I'm still wrestling with the basics at present - I find the handbooks extremely complicated and not well written - so haven't got as far as CV29 yet. When I say 'my locos are set' I mean simply that when I placed them on the track the first time and selected 'Forward' they moved out of the station and vice versa so I stuck with that.

When I switch on the controller and start running, nineteen times out of twenty the loco moves in the direction selected. The twentieth time it moves in the opposite direction. Stopping and starting again usually clears the problem for that running session. On one occasion I had selected 'Forward' and the BR233 moved in the correct direction but after a couple of seconds, without any control input, stopped and moved in the opposite direction. Again, stopping and restarting cleared the problem.

Thank you in advance for any assistance.
 

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Assuming that "forwards" is clearly understood to be the "front" of the loco. Which in a diesel is "cab number 1"....

Then, slight randomness in direction might be due to DC-running still being enabled, and possibly address-zero biasing in the DCC signal (two different things).

Digitrax manuals were written by a network engineer in 90% techno-gobble. They're the worst thing about Digitrax!


First, in the DCS52, address-zero biasing (or allowing a DC loco to run (badly) on your DCC system)....
Ensure that (a) you never use address zero (and if there's an Op-switch in the manual to turn it off, do so).
Ensure that (b) you've not accidentally used a Jump-Throttle connection when you didn't intend to (jump throttle feature is another one of those "good idea 20+years ago, now well past its sell-by date" ).


Then, in the Locos sort out CV29 so DC running is disabled. See this page I wrote a dozen or so years ago to explain CV29, and how to work out the value you need to set.
Read the values you currently have back from the programming track first.
RailCom is of no use on the Zephyr system so may as well be switched off (RailCom would require a pile of additional non-Digitrax hardware - I do have such hardware, and an earlier Zephyr model).



- Nigel
 

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A couple of things.

Firstly, if you can read the value of cv#8 that will tell you what decoder is fitted. If you refer to this list it will tell you which value of cv#8 refers to which decoder:
https://www.jmri.org/xml/XSLT/pages/DecoderId.html

It sounds like you may have some wiring issues which could be fooling the decoder into thinking it's running on dc. I'd try disabling dc running on the decoder. This may help or it may show up other problems but it's a good starting point. To do this it's another cv#29 change. Look at this page which has a calculator for cv#29 values:
http://www.2mm.org.uk/articles/cv29%20calculator.html
Unless you are using long addreses (higher than 127) then all you probably need here is 28/128 Speec Steps selected which will be a cv#29 value of 2. Give that a try and see how you get on.

I'm sure that @Nigel2001 will be along shortly with some helpful advice. He's the expert on this subject.
 

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Discussion Starter · #6 ·
Gentlemen (and lady if she's listening), many thanks for all the info. It was a bloomin' sight simpler 20 years ago (my last layout) with a DC controller. There again, the trains didn't run nearly as well. I really am impressed with the slow-running on my locos, very important as my layout is a shunting layout.

I will set to and work my way through the tips and info you have both provided. Its about time I learnt properly how the system works. A virtual pint to you both!! Many thanks

David
 

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...my locos are set so that 'Forward' is out of the station and 'Reverse' the opposite...
There's a fundamental point that first needs to be clarified.

In DCC, movement direction is defined on the locomotive, and has no reference to fixed locations on the layout. As Nigel wrote, normally on single cab diesels this means the cab end leads when forward is selected. If you pick the loco up and turn it around on the track, it will still move forward - cab end leading - but now going in the opposite direction along the track.

Side issue.
...Digitrax manuals were written by a network engineer in 90% techno-gobble. They're the worst thing about Digitrax!...
And how. Now twenty one years past, my first survey of 'what's what in DCC systems' followed my standard practise in all technical gear acquisition: obtain the manufacturer documentation. I discarded Digitrax as a contender on one brief read of their documentation: most likely incompetent.

It's entirely up to you, but I would return the Digitrax gear for refund if that's possible. There is now a plentiful choice of superior alternatives, and some have clear and simple documentation.
 

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Discussion Starter · #8 ·
I don't think I made my point very clearly. My BR 233 loco has a cab at each end. The first time I ran it I placed it on the track, selected 'Forward' and accepted the direction in which it moved. Nothing more complicated than that

As to DCC controllers I wanted a controller that would run perhaps 8 or 9 engines ( but at most two at a time) I wanted one with a proper throttle (not a wheel) and direction controls and that offered smooth slow running. My points are controlled entirely separately. The DCS52 seemed to fit the bill and so far it has apart from this occasional directional confusion.

The manual is not easy to follow, i find those written in US English rarely are.
 

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A shot in the dark here, but quite apart from the excellent advice from Nigel, could the shuttle function be coming in to play? This is really aimed at Nigel because he knows more about this.
 

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As others have already indicated, 'forwards' in DCC is relative to the 'front' or 'no.1 end' of a loco, not to its orientation on the track.
This is a key difference between DCC and DC: in DCC you drive the train. In DC you drive the track.

Regarding the directional issue reported by the OP, this sounds very similar to a problem that used to exist on ZTC systems where the system appeared to 'forget' the current direction setting of a loco.
In ZTC, it was actually a programming error in the command station. I don't know whether they ever did fix it, but it was caused by an integer value being used to represent the speed of a loco. A positive speed was forwards and a negative speed was backwards. In other systems, a specific separate bit was used to indicate direction.
The problem with ZTC was that when speed was zero, there was an issue of what directional messages were sent to a decoder, remembering that when coming to rest, a loco would have had a an absolute value which was reducing to zero. The problem was when it got to zero, it didn't know from which direction it had been coming: there is no such thing as +0 and -0 and the system always resorted to the assumption of +0. The effect was that a loco running in reverse and stopping would stop and the lights would switch direction. If running forward and coming to rest, there wasn't a problem.

The user of a system experiencing such problems cannot fix it. It sounds to me like Digitrax is having a similar problem. Unless the firmware can be updated, my advice to the OP would be to junk Digitrax - there are several European offerings which are way way better.

Having re-read the OP's comments, I'm wondering whether there is a problem at all now ? Was it just that the OP wasn't aware of direction being relative to the front of a loco ?
 

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The built in sounddecoder is in a Roco BR 233 diesel loco and is 'specifically adapted' for this loco type but it doesn't say what sort of decoder it is.
Very likely a Zimo decoder, as they are factory-installed in Roco sound models. Probably a MX645P16, as Roco still uses PluX16 interfaces in those models. More information can be found here.
 

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And how. Now twenty one years past, my first survey of 'what''s what in DCC systems' followed my standard practise in all technical gear acquisition: obtain the manufacturer documentation. I discarded Digitrax as a contender on one brief read of their documention: most likely incompetent.

It's entirely up to you, but I would return the Digitrax gear for refund if that's possible. There is now a plentiful choice of superior alternatives, and some have clear and simple documentation.

I'd say that Digitrax gear is fine compared to most makers, just the documentation. You can be critical of many maker's DCC documentation; quite a few omit various key details in an attempt to be "easier to read". Whereas it is (just about) all in there with Digitrax, just hard to read. There are plenty of big complex layouts using Digitrax' hardware, so it works technically.


There are a few European brands of DCC system which have advanced a fair bit from the 1990's technology which most US brands are using. For example, Roco. Though not without some problems: it has just issued an (automatic) update for Android and Apple devices which rendered the screens blank-white (ie. useless to run anything). A rapid new update followed about a day later.


- Nigel
 

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As others have already indicated, 'forwards' in DCC is relative to the 'front' or 'no.1 end' of a loco, not to its orientation on the track.
This is a key difference between DCC and DC: in DCC you drive the train. In DC you drive the track.

Regarding the directional issue reported by the OP, this sounds very similar to a problem that used to exist on ZTC systems where the system appeared to 'forget' the current direction setting of a loco.
...............

The user of a system experiencing such problems cannot fix it. It sounds to me like Digitrax is having a similar problem. Unless the firmware can be updated, my advice to the OP would be to junk Digitrax - there are several European offerings which are way way better.

There is NO PROBLEM with direction control in Digitrax. It doesn't have the awful bugs which plaged ZTC systems.

Sheesh - why do people feel a need to trash systems they don't personally like ?


The Digitrax Zephyr is a perfectly good, stable, control system. I've had one for 17 years. I've also used, extensively, most of the other makers on the market. I'm the lead tech support for several large layouts, which cover most of the main system makers. As a system to drive a handful of locos on a modest layout, the Zephyr is a sensible choice of system.



- Nigel
 

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I don't think I made my point very clearly. My BR 233 loco has a cab at each end. The first time I ran it I placed it on the track, selected 'Forward' and accepted the direction in which it moved. Nothing more complicated than that

As to DCC controllers I wanted a controller that would run perhaps 8 or 9 engines ( but at most two at a time) I wanted one with a proper throttle (not a wheel) and direction controls and that offered smooth slow running. My points are controlled entirely separately. The DCS52 seemed to fit the bill and so far it has apart from this occasional directional confusion.

The manual is not easy to follow, i find those written in US English rarely are.
The Loco, BR 233, if you look carefully at the side lettering, will be labelled "1" or "2" at each end. (its clear on the two liveries I looked at on line). The end with the "1" should be the "front" and that is the direction which will be "forwards". Pick the loco up, turn it round, and forwards will still be the end with "1" on it.

That's a fundamental thing with DCC - forwards is relative to the locomotive.
With steam locos its usually obvious; chimney at the front. With diesels and electrics, you quickly learn the visual differences. On the BR233, there's a clear difference in the roof outline, the large plain bulge with three fans behind is towards the rear, and there are other visual clues.

The decoder in the loco is, if factory fitted, (as indicated above) most likely to be a Zimo, which is about as good as you get from any decoder supplier. You may wish to turn off RailCom in the decoder, as well as DC running in CV29.
RailCom is of no use to you with the Zephyr system without spending quite a bit of money on more kit (and RailCom generally is of questionable value for most layouts even if the control system supports it).



As I have indicated in the thread above, the Zephyr is fine as a controller. There is nothing wrong with it, it doesn't have weird bugs which some other now defunct devices (ZTC) experienced. It will do all the things you've listed and more. Anything else you were to buy would have its own set of minor difficulties as you learn to use it. And may have cost considerably more money and still have difficulties.



- Nigel
 

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Discussion Starter · #15 ·
Thanks for all the info. I shall work through all the tips, I'm sure the answer will be there somewhere. Part of the problem is that I'm returning to modelling after 15 years and I'm not familiar with a lot of the technical terms. I did some research before buying but had no idea until I opened the manual how complex DCC systems are and the incredible list of variations available.

The Zephyr works well at the simple level I'm looking for and gives very sensitive control. I can easily couple up to a rake of coaches without moving them at all.

As with all technical manuals they need the engineers/designers to write them and then they should be obliged to run them past Joe Average to see which bits are hard to understand and then rewrite them. I have often found this with manuals in US English. (Although someone told me recently that there is the Queen's English and there are mistakes!!) I bought a Kadee electronic uncoupler recently and in one paragraph it gave two different voltages as the minimum required. I had to go to Kadee to get the right answer.

Hey-ho, its a great hobby, keeps me off the streets.
 

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There is NO PROBLEM with direction control in Digitrax. It doesn't have the awful bugs which plaged ZTC systems.

Sheesh - why do people feel a need to trash systems they don't personally like ?


The Digitrax Zephyr is a perfectly good, stable, control system. I've had one for 17 years. I've also used, extensively, most of the other makers on the market. I'm the lead tech support for several large layouts, which cover most of the main system makers. As a system to drive a handful of locos on a modest layout, the Zephyr is a sensible choice of system.



- Nigel
The Zephyr was my first system also and after ploughing through the manual several times while trying to sort it all out it suddenly becomes clear what they are trying to say, it is logical in an odd way, but for sure the system itself is stable, strong and reliable…..it worked on my 2mm Japanese layout for years and then played well enough for running and installing sound on my 7mm Heljan Diesels (which everyone said it wouldn’t have the power to do so, no issues), in fact the only reason I changed was when I wanted to build my present layout in 4mm and DCC had moved on with many more functions and I wanted to control the points with DCC and a mimic panel, so upgraded with an ECOS.

But the Zephyr is not being thrown out just yet, it makes a good stand by for testing away from the layout.
 
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