DCC Track Wiring

[menacesco]

Being new to digital I am struggling to find the correct way to wire up my layout for DCC. The problem is that I get a short circuit when trying to cross between two ovals. All my points have been made live as I believe this is the correct way of wiring for DCC and I have tried using insulated fishplates between the crossover points to no avail. I suspect I need a reverse module unit but I am unsure how this should be wired. I have attached an image of the layout.

/media/tinymce_upload/b8f144914abfb91342896c8a9fddb155.JPG

 

[Chrissaf]

Menacesco,

Thank you so much for including the photo. That really does help us to help you, I wish more Newbie posters were this helpful. There is no part of your layout design (presently) that I can see that requires a Reverse Loop Module. I can see in the 7 o'clock position a R8201 Link Wire Kit with one of the power clips currently disconnected. This is almost certainly the source of your short circuit. If you still have the 'short' circuit with the R8201 disconnected as shown in the photo, then something else is amiss.

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Download my 'Getting Started with Track Extension Packs' PDF document from the locked thread at the top of the forum General Section and have a look at Page 15

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The R8201 will introduce a short if reversed wired. My document Page 15 explains all.

[Chrissaf]

I should add that if your points all have R8232 DCC clips fitted, then there shouldn't be any need to supplement the layout power with the R8201.

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It may be still be a good idea however to include the R8201 as there have been recent reports on the forum of R8232 clips overheating and even glowing red due to poor conductivity, only usually an issue where a large proportion of the track power distribution is reliant on getting its power via one particular set of point clips.

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Supplementary questions:

There are two cross-overs between loops. One at 4 o'clock position and one at 8 o'clock. Do both cross-overs exhibit this short circuit issue or only one and if so which one.

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Also, is it the act of switching the points that creates the short OR is it only when a loco (train) starts to cross over them.

[2e0dtoeric]

Just a thought - perhaps the short is triggered by the turntable. If you have not totally rewired it for DCC operation, with the 'table in one position, there will be no short, but rotate it 180', and you now have a short, because the polarity of the 'table is not reversed as it rotates.

[Chrissaf]

Excellent observation Eric......completely passed me by.

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To prove Eric's theory, disconnect the one track input into the TT at its 1pm position and test to see if the short circuit fault goes away. If it does post back here for further advice from the TT experts on here. Me not being one of them.

[RDS]

Hi menacesco and welcome to the forum.

I agree with Chris, that is an excellent first post and in this case, essential to have your picture.

 

You do not need insulated fishplates with your style of layout on DCC.  The turntable could be the problem but why would this only happen when crossing from one oval to the other.  Surely, if the turntable was a problem the short would exist as soon as power is applied.  However, I also suggest you disconnect the turntable until you get the layout working.  As Chris says, you do not need a Reverse Loop Module on that layout.

 

I have now added droppers and a BUS to my layout but I used to operate a layout that was at least as complicated as this layout with only one power connection to the track on my outer loop.  I would start off by removing all but the one power connection and then checking all the point clips are in the correct place on the points (I assume you are using point clips and that is why you say the points are live all the time).

 

Just make one change at a time and recheck, otherwise you may fix the problem without actually being able to determine exactly what caused it in the first place.

 

Incidentally and on a completely separate subject, how do you get to the far side of your layout when the inevitable derailment on that side occurs?

[96RAF]

I have read the above and wondered why my 3 loop with cross-over twixt outer to mid and mid to inner works at all, even faultlessly as it does, as I have no IRJ's fittted anywhere, Hornby points clips in all the usual locations and bus droppers connecting loop to loop to loop in 4 places around my present 6 x 4 ft layout.

 

I also have a branch off the inner loop to a turntable (DIY) and its associated half dozen off roads, although my TT has my unique LED indicators to show DCC 'polarity' of the bed and a manually operated DPDT to switch said polarity to match the in/out road in use.

 

[Chrissaf]

Incidentally and on a completely separate subject, how do you get to the far side of your layout when the inevitable derailment on that side occurs?

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Not only that, but how do you reach that far over the layout during the construction phase. Hang from the ceiling perhaps, like Tom Cruise in Mission Impossible.  😆

[96RAF]

Mine is similar but on castors so that when I want to get round it I just wheel it across the room. Mind you I have a bit of side slack as well as back and forth unlike the picture.

[Howbi]

What if an Electrofrog point had been installed inadvertantly with Point Clips fitted as well?   HB.

[Flashbang]

Hi

Assuming all the points are Hornby and are not Electrofrog from any other manufacturer, then as IRJs have been fitted in all points linking loop to loop, I would suggest one loops track feed had been reversed to the other loop.  Hence the short appearing when a loco bridges the IRJs.

All rails should have the same polarity. Double check your rail connections that one isn't crossed.  e.g. All inner rails need to be from the same supply connection.

[RDS]

What if an Electrofrog point had been installed inadvertantly with Point Clips fitted as well?   HB.

 

Would it matter - as long as the Point Clip has been fitted in the correct position.

 

[Chrissaf]

The one thing to note with electrofrogs, the output V of the frog needs Insulated Rail Joiners to prevent shorts. Looking at the photo however, I don't think my eyes can detect any electrofrogs, it all looks like standard Hornby track products to me as far as I can tell based on the fairly distant view that the photo gives of the layout.

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Plus if there were electrofrog points installed with insulated Vs, then there would be a need for far more power connections to eliminate track dead spots.

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@FB  I would suggest one loops track feed had been reversed to the other loop.

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Hence my comment in my first reply regarding the R8201 Link Wire Kit at the 7 o'clock track position.

[menacesco]

I should add that if your points all have R8232 DCC clips fitted, then there shouldn't be any need to supplement the layout power with the R8201.

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It may be still be a good idea however to include the R8201 as there have been recent reports on the forum of R8232 clips overheating and even glowing red due to poor conductivity, only usually an issue where a large proportion of the track power distribution is reliant on getting its power via one particular set of point clips.

 

 

 

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Supplementary questions:

There are two cross-overs between loops. One at 4 o'clock position and one at 8 o'clock. Do both cross-overs exhibit this short circuit issue or only one and if so which one.

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Also, is it the act of switching the points that creates the short OR is it only when a loco (train) starts to cross over them.

Hi Chrissaf,

Thanks to you, and the other contributors, for the useful guidance. In reply to your question above:-

Originally I wired the whole layout with one power source on the outside oval and with all points live using point clips. This caused the controller to "flash" indicating a short circuit. I followed a process of elimination, together with reading lots of forum posts about wiring, and that is how I have ended up with fitting insulated fishplates between the crossover points and thinking that I needed a reverse loop module (not fitted or tried yet). After fitting the link wire this week, to power the inner oval and sidings, I had a layout that seemed to work except when the crossover point at 8 o'clock from the outer oval was switched. None of the other 3 points affecting the crossover between ovals seem to affect the power supply! I am therefore wondering, based upon the comments in this thread, if I have a problem with that particular point?

I am going to go back to basics today and remove the insulated fishplates and link wire and swap the suspect point from its present position with the one at 4 o'clock and see what difference this makes.

If the problem is the point then what should I do to fix it. It was supplied brand new by Hornby a few months ago.

Thanks again.

[Chrissaf]

Look very closely at the frog. The V where the two opposing rails come together. They are are extremely close together with a micro gap between them. The two rails might be bridged here due to a manufacturing defect. It may not be even visible to the naked eye and will need a multi-meter tester to prove it.

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Shorts are really hard to find without the aid of a multi-meter with a resistance measuring or continuity checking capability. They can be bought on Amazon / e-bay very cheaply indeed for about £5 for the really cheap ones (good enough for just basic model railway testing - plus the AC voltage range can be used for testing for the presence of DCC voltages @ about 14 to 15 volts).

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Fix or replace, it depends upon exactly what the fault is.

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In general,  apart from a reversely wired R8201 or possibly the TT, there is nothing in your layout design that in itself can produce a track short other than a faulty point. Rather than masking the fault with IRJs (insulated rail joiners) it is definitely best to track down the source of the short and eliminate it. As your layout is still under construction it could be a loose track pin or piece of metallic debris bridging the track somewhere, you could try going over your track with a vacuum cleaner (small nozzle attachment for lots of suck).

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Note just as an aside, many on here report that these curved Hornby points are more trouble than they're worth. Constant derailments and poor running on them.

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PS - Best if you don't click the 'Blue Quote Button' embedded in the posted text box when trying to reply. This just replicates all the previous text unnecessarily in a yellow box. It is best practice to scroll to the bottom of the page and write your reply in the great big empty reply text box and click the Green Reply button (as this reply has done).

 

[Flashbang]

Hi

If you're starting to remove the IRJs I personally would go one step further and remove all the track power feeds for all rails and the Turntable too..

Then start off by just connecting the outer loops power feed, power up the DCC system to see if all is good. If ok then power down and then reconnect the inner loop and retest on DCC power again to prove all is OK or not.  If it is OK then reconnect the next power supply item in the same fashion as before, by powering down, reconnect and test.   This way you will eventually find the problem, hopefully!

 

Chris, Yes sorry you did mention power clips at 7 o clock, but I really thought it worth well while re stating the obvious! 

[poliss]

Wasn't there an issue a while back about certain points being defective and causing short circuits? Something about them being wired wrong?

[Chrissaf]

No harm in re-iterating possible issues FB, the more they are mentioned the more the significance of what is being advised might sink in.

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Menacesco,

Just a bit more detail about RLM and shorts. There are two types of 'shorts' you will come across in a model railway layout. One type is normal and comes about by having a particular feature designed into your layout topology. It is this type of designed in 'short' for which the RLM is designed for. The 'Reverse Loop' track topology - needs a diagram to explain effectively - try this link.

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Then there is the second type of 'short' that comes about as a result of a fault or manufacturing defect. It is very unlikely indeed that these second type of 'shorts' can be overcome by fitting a RLM. If the RLM protected track section has a 'short' then that half of the RLM circuit will still have the 'short' whether the RLM is there or not. All that will happen is that the RLM will fail to work at all.

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Unfortunately, your short falls into the second category. The source of it needs to be found and remedied.

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If you isolate a small section of your layout that contains that 'short' by using IRJs, then all that you are doing is creating a dead section of track, because as soon as you connect that section to the DCC power to run a loco on it, the 'short' will become back in circuit and trip the controller. Trying to fix it with IRJs is chasing rainbows, it can't be done.

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Another thing to check on the suspected faulty point. After removal, turn it over and look at the underside. In the frog area there is likely to be two bare wires that provide the power path to bridge over the plastic frog. These two wires are bare conductors and not insulated. They must not be touching. If they are, that is the source of your 'short'. It is possible one of the wires has broken away, and touching the other wire.

[menacesco]

Thanks Chrissaf, and others, for the guidance. I have now fixed the issue, the problem being a faulty curved point - now replaced and the layout works perfectly. I have also managed to convert my turntable although I had to find a fix for loose bridge rails once the connectors were removed. I am now starting the process of converting the points to DCC operation. 

One thing I am concerned about is the quality of Hornby locomotives. I have a "Duke of Gloucester" loco that derails when the front non-driven wheels start bouncing (is the assembly too light?), and a R3342 Shunter where the coupling rod fixings keep coming away from the wheels. 

[Chrissaf]

Firstly, for the benefit of all and others reading this thread. Can you be specific about what was wrong with the curved point.

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Its a bit like reading a crime novel and you get to the last chapter and "the killer is..........." and you find the next page has been torn out. We are are all on tenter hooks eager to know exactly what caused the short. It adds to our knowledge base to help others reporting similar issues.

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Secondly, may I suggest that as these loco running issues are a completely different subject that you post a new topic with an appropriate title. There might be owners of these locos that are not reading this particular thread because the topic title refers to 'DCC Track Wiring' and not these specific locos.

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EDIT: I see you have already started a new topic for the R3342 Shunter.

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Glad however, that you have now got the track problem sorted, even if you haven't told us exactly the nature of the curved points fault.

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PS - Had you searched the forum for solutions regarding the conversion of the Hornby R070 TT for DCC working, you would have found many references to alternative modifications that do not adopt the Hornby rip out all the contacts solution. These alternative modifications may have suited your purpose better and not resulted in loose bridge rails.