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SHORT CIRCUIT PROBLEM

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SHORT CIRCUIT PROBLEM
Posted by tnhllblly06 on Sunday, October 21, 2012 12:07 PM

     I am at my wit's end with a short circuit problem on my layout.  Any help will be appreciated.  I have a fairly large layout that I am wiring for DCC.  My bus wire is 14 gauge.  20 gauge feeder wires are soldered to the rails every 3 feet or so, and connected to the bus with "suitcase connectors".  Everything is color-coded. The wiring was going along smoothly, until I hit one particular section of track....short!  The loco stops the minute it hits there.  The track piece was actually hot to the touch.  I replaced the track section, but the minute I connect the rails, short!  I can see the inside rails sparking when they touch.  I've double-checked the wiring, and it all looks good.  Any ideas as to what else could be causing the short circuits? I've disconnected all the wires on the other side of the layout from the short.  Thanks!

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Posted by twcenterprises on Sunday, October 21, 2012 1:04 PM

It would be helpful if we had a track diagram or photo(s).  I am assuming the track is electrically isolated at the joint in question, which leads me to think one of two possibilities.  Either you have a reversed wire/switch somewhere, or you might have a reversing section or loop.

Brad

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Posted by gandydancer19 on Sunday, October 21, 2012 1:13 PM

I agree with Brad.

Elmer.

The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.

(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.

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Posted by rrebell on Sunday, October 21, 2012 3:09 PM

Just was through this. Check an insulator that has gone bad and see if one of your drops is the wrong color, I found both!!!!!!!  Best way I have found to check for shorts while you are under the table is to put a couple of alligator leads to the track and run anything they will power (motor or light, etc), on mine I run a train at slow speed and if I connect a wire wrong, it stops instantly).

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Posted by richhotrain on Sunday, October 21, 2012 3:10 PM

Is this a new layout that you are wiring or an existing layout that you are converting from DC to DCC?

The symptoms that you describe very definitely suggest a reverse polarity problem, either caused by a reverse loop or wires crossed and out of phase.

Rich

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Posted by tnhllblly06 on Sunday, October 21, 2012 9:42 PM

Thanks for the help.  This is a new layout that I am wiring, and the section in question is not part of a reversing loop.  It shorts out as soon as  I connect the inside rail to the bus, or to another piece of track.  The outside rail connects just fine.  I have kept a loco on the track powered up as I went attaching my feeder wires, with no problems until I hit this one spot.  Some other posters have mentioned insulators???  What are they referring to? 

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Posted by richhotrain on Monday, October 22, 2012 4:55 AM

Without a track plan, we are left to speculate what your layout looks like and how you are approaching the wiring process.

It sounds as though you have completed the track work and are now wiring it to the bus. If that is the case, and if you are certain that there is no reverse loop or reversing section, then the short is occuring because of mismatched wires.

So far, the feeder wires that you have connected from the rails to the bus have provided electrical current and you are able to run a loco on the powered track. Now you install a set of feeders on the next section of track and a short occurs.  That tells me that you have reversed the feeder wires.  What happens if you reverse those two feeder wires?

Rich

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Posted by zstripe on Monday, October 22, 2012 6:18 AM

I'll have to agree with Rich on this one.  If the feeders were crossed, the moment the power is on, it will short out... A diagram would certainly be helpful...

Cheers,

Frank

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Posted by MisterBeasley on Monday, October 22, 2012 6:25 AM

What kind of turnouts are you using?  You may have a problem with certain power-routing turnouts if they are not isolated past the frog.

It takes an iron man to play with a toy iron horse. 

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Posted by richhotrain on Monday, October 22, 2012 6:41 AM

MisterBeasley

What kind of turnouts are you using?  You may have a problem with certain power-routing turnouts if they are not isolated past the frog.

That raises another good question.

Is the OP wiring sequentially, section by section, as he moves around the layout?  Or, are different parts of the layout already wired as the OP adds feeder wires in between previously wired sections of the layout?

In his initial post, he mentioned he "disconnected all the wires on the other side of the layout from the short". 

Rich

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Posted by tnhllblly06 on Monday, October 22, 2012 6:55 AM

     All the turnouts on the layout are made by Atlas.  I don't believe that I need to do anything special with them, but I'm not sure.  My feeder wires are red (outside rail) and black (inside rail). Red wire to the outside rail, no problem.  Either wire touched to the inside rail causes a short.  Black wire to outside rail....short.  I am going to go out there today and look at everything again.  I'll also try and figure out how to put a diagram of the layout up here.  I know that would be more of a help than my attempts at explaining what it looks like.  Thanks for the thoughts.

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Posted by richhotrain on Monday, October 22, 2012 6:58 AM

Atlas turnouts are not power routing.

You mentioned that you replaced the section of track where the short occurred and the same thing happened all over again.

Just out of curiosity, what section of track caused the short?  Turnout?  Flex track?

Are you simply wiring as you move down the layout or are you wiring different sections on the layout in no particular order?

Rich

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Posted by tnhllblly06 on Monday, October 22, 2012 7:07 AM


One last thing, Rich.  I do have other parts of the layout wired, without running into any problems.  The section that I am having trouble with splits off of the main line and reconnects with it further down the line. I was able to wire approximately one half of it before I ran into this problem.  I do have a few feeder wires soldered past the point where it reconnects, but I don't understand how I was able to solder 4-5 sets of feeders on this particular section without a problem,  before I hit this spot.  Like I said, I'll go out there today and recheck everything, and hopefully I'll still have these last few remaining hairs on my head when I come in!  Thanks to all for the thoughts so far.

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Posted by richhotrain on Monday, October 22, 2012 7:08 AM

Do you have a track plan that can be emailed so that we can post it?

Rich

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Posted by richhotrain on Monday, October 22, 2012 7:11 AM

tnhllblly06


One last thing, Rich.  I do have other parts of the layout wired, without running into any problems.  The section that I am having trouble with splits off of the main line and reconnects with it further down the line. I was able to wire approximately one half of it before I ran into this problem.  I do have a few feeder wires soldered past the point where it reconnects, but I don't understand how I was able to solder 4-5 sets of feeders on this particular section without a problem,  before I hit this spot.  Like I said, I'll go out there today and recheck everything, and hopefully I'll still have these last few remaining hairs on my head when I come in!  Thanks to all for the thoughts so far.

I think that we are right back to our original suspicions, either a reversing section that is not obvious to you or feeder wires inadvertently crossed over to the wrong rails.

Rich

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Posted by richhotrain on Monday, October 22, 2012 7:20 AM

Another thing that I will mention is that even on very large layouts, where the common recommendation is to drop tons of feeder wires and even solder the connections, it has been my experience that just a few sets of feeder wires will carry power throughout large parts of the layout.  The electrical connectivity is usually interrupted only by turnouts and other such specialty track pieces like wyes and slips.

So, when you suddenly encounter a short, it is the result of reverse polarity for whatever the reason.

Rich

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Posted by MisterBeasley on Monday, October 22, 2012 8:22 AM

I had an intermittent short that was driving me crazy.  I eventually traced the problem to an Atlas 30-degree crossing.  It was shorted internally, and would short the layout when an engine passed over it a certain way.

It's not a likely scenario, but it's a possibility.

It takes an iron man to play with a toy iron horse. 

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Posted by richhotrain on Monday, October 22, 2012 9:20 AM

MisterBeasley

I had an intermittent short that was driving me crazy.  I eventually traced the problem to an Atlas 30-degree crossing.  It was shorted internally, and would short the layout when an engine passed over it a certain way.

It's not a likely scenario, but it's a possibility.

I think that, at this point, anything is a possibility.

That's why a track plan would be helpful as well as knowing which track the OP is connecting the feeder wires to that is causing a short - - - a turnout, a specialty track such as a wye or slip, or simply a section of flex track.

Rich

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Posted by Texas Zepher on Monday, October 22, 2012 10:51 AM

I was going to ask if a loco would run on the section before the rails were connected, but then I saw the post where the OP said it also shorts when the feeder is connected not the rails.  That is the thing that confuses me. Usually the feeders won't short unless the rails are already connected.   

Also the later note that says this is not the first feeder in the section but about the 5th, that really makes me think something obvious is being assumed, overlooked, or at least not being stated in the messages.

My guess is that there was/is an unknown/forgotten insulated rail joiner or a gap that has been crossed at that particular point in the layout.

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Posted by richhotrain on Monday, October 22, 2012 11:23 AM

An interesting question would be what happens if you disconnect the rail joiners at the opposite end of the track that is shorting after you place feeders on the other end of that track.

I suspect the answer is that there is no longer a short.

Rich

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Posted by tnhllblly06 on Tuesday, October 23, 2012 9:42 AM

Rich,

     You are right on the money!  When I disconnected the rail joiners fron the other end of this section (from a turnout), no short.  This morning I scraped up all the track, reconnecting and resoldering as I went.  The minute I connected to the other end, a short ensued.  Does that mean this is some sort of reversing section?  Like I stated previously, it's a long section of track (approx. 20 feet) between two turnouts.

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Posted by richhotrain on Tuesday, October 23, 2012 9:54 AM

tnhllblly06

Rich,

     You are right on the money!  When I disconnected the rail joiners fron the other end of this section (from a turnout), no short.  This morning I scraped up all the track, reconnecting and resoldering as I went.  The minute I connected to the other end, a short ensued.  Does that mean this is some sort of reversing section?  Like I stated previously, it's a long section of track (approx. 20 feet) between two turnouts.

That would be my guess.  It is probably a reversing section. 

Any chance that you could email a track diagram that I could post?

Rich

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Posted by maxman on Tuesday, October 23, 2012 10:02 AM

tnhllblly06

Rich,

     You are right on the money!  When I disconnected the rail joiners fron the other end of this section (from a turnout), no short.  This morning I scraped up all the track, reconnecting and resoldering as I went.  The minute I connected to the other end, a short ensued.  Does that mean this is some sort of reversing section?  Like I stated previously, it's a long section of track (approx. 20 feet) between two turnouts.

Not necessarily a reversing section, although that could be a possibility.  Is this a simple passing siding?  What type/brand of turnouts are you using?

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Posted by richhotrain on Tuesday, October 23, 2012 10:09 AM

maxman

Not necessarily a reversing section, although that could be a possibility.  Is this a simple passing siding?  What type/brand of turnouts are you using?

The OP mentioned earlier that he uses Atlas turnouts on the layout and they are not power routing.

Rich

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Posted by floridaflyer on Tuesday, October 23, 2012 10:43 AM

Could the OP follow the inside rail, the one that shows the short, around the layout and see if, after going around the layout, that the rail he follows ends up on the inside at the point he started. I would also follow any divergent tracks coming off the inside rail and see where that leads. If everything ends up at the inside rail no reversing section exists, if not then a reversing section exists. this may be a little time consuming but without a picture of the track plan we really don't know what may be happening.

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Posted by richhotrain on Tuesday, October 23, 2012 11:08 AM

Like most shorts and reverse polarity problems, they could be quickly identified and resolved if a track diagram would be provided.

Rich

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Posted by tnhllblly06 on Tuesday, October 23, 2012 6:10 PM

I just finished a rough (very rough) freehand sketch of the layout.  Now that I put it down on paper, I think I can see a big problem, but I'm not sure about the solution.  How do I go about emailing it to someone who can post it for me?

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Posted by rrinker on Tuesday, October 23, 2012 6:23 PM

 If you can get it in the computer to email, just go to Photobucket and sign up for a free account and upload it there. Or send it to me, I can put it in my account.

            --Randy

 


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Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by richhotrain on Tuesday, October 23, 2012 6:45 PM

tnhllblly06

I just finished a rough (very rough) freehand sketch of the layout.  Now that I put it down on paper, I think I can see a big problem, but I'm not sure about the solution.  How do I go about emailing it to someone who can post it for me?

Check your Messages, I just sent you my email address.

Rich

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Posted by richhotrain on Tuesday, October 23, 2012 11:23 PM

Here is the OP's track diagram.

This is a classic reverse loop where the track folds back onto itself.  That divergent leg of the right hand turnout is the trouble spot where there is a reverse polarity issue.
 
The solution is to isolate that "short circuit section" by placing gaps in the rails in two spots.  The divergent leg of that right hand turnout needs to be gapped.  Then, the other end of the short circuit section needs to be gapped.  I would recommend that the resulting "reversing section" be long enough to accommodate your longest train.  The easiest way to do this is to gap the rails of the straight section of the left hand turnout at the other end of the "short circuit section".  That way, the entire section of track between the two turnouts becomes the reversing section.
 
There are a couple of ways to power the reversing section. 
 
Since the section is isolated from the rest of the layout due to the rail gaps, you could install an auto-reverser which is powered on the input side from the main bus, with power provided to the reversing section of track from the output side of the auto-reverser.  I use a Digitrax AR-1 for this purpose, and it costs around $25 for the unit.  The auto-reverser corrects the reverse polarity issue automatically as the loco crosses into the reversing section and again as it exits the reversing section.
 
The other way to do it is to install a double pole double throw (DPDT) toggle switch which works somewhat like an auto-reverser except that you reverse the polarity manually by throwing the switch just before the loco enters the reversing section.  Once the entire train is inside the reversing section, you throw the DPDT switch once again.  The DPDT switch only costs around $5.
 
Rich

Alton Junction

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