# Wiring questions



## Fire21 (Mar 9, 2014)

This is my N-scale track plan. It's not finished, but you can see where I am adding a reversing track to the inner loop (it's a folded loop). There are turnouts at the top center (just above the underpass) that connect the inner loop to the outer. I have electrically isolated the two loops at these turnouts. I will isolate the reversing track also. Here's my questions:

1) I know I need a polarity reversing switch for the reversing track. I'm pretty sure I also need a reversing switch for the inner loop, correct?

2) Since I will be able to run trains from the outer to the inner loop both before and after they reverse direction, do I also need a reversing switch for the outer loop?

I tried so hard to learn something about electronics, but just do not understand things!!

Sorry the pic isn't any clearer.....


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## jesteck (Apr 15, 2014)

I'll try to keep it as basic as possible, and I'm talking about DC only, not DCC. Guys smarter than I am have written whole books about this. When your train enters a reversing loop, the polarity in the loop has to match that of the rails it is leaving. While in the loop, it is being powered independently because of the insulators. When it tries to reenter the main (or other) track in the opposite direction, if you don't change the polarity before it gets there, you get a short; so yes, anytime and anywhere your train can change direction, you need to isolate, insulate, provide a power feed for the insulated section, and provide a polarity switch for the re-entry. For what it's worth, I used to use DPDT toggles on the track plan on my control panels to indicate clockwise or counterclockwise direction; a glance at the panel as the train approached a turnout would show any potential polarity conflict, and I could flip a toggle for the control block affected and those that followed and the train would continue rolling merrily along. Not so easy with polarity toggles not mounted on a "track plan" oriented control panel, or no panel at all.


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## Northern Route (May 12, 2014)

I you plan to use DCC on your layout, the simplest and easiest way to wire the reverse loop would be to install a DCC reverse loop control. When you run a train through the reverse loop the system will change the polarity for you and you won't notice any difference in the operation of the train. To wire for DCC just wire the command station to the track and forget about block switches.


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## Ray Haddad (Feb 19, 2014)

Something you need to consider whenever you add a reversing loop is that you can, if you plan it right, allow reversal in both direction. By that I mean you need to be able to reverse and then go back to the original direction or the reverse is kind of pointless. To travel in both directions from the mainline through the loop in either direction is the holy grail of design. So, most folks design into their layout two loops or a fit a double slip or crossover within the loop. You need an entry into the loop from either direction for that to work. Naturally, this will complicate your wiring in DCC but as has been pointed out, there are ways to automate this.

Puzzle it out for a while. If you plan on adding a turntable you can sometimes get away with a single reversing loop but remember when you run in one direction and then reverse, that becomes endless unless you can reverse back again.


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## DonR (Oct 18, 2012)

In my opinion, if you have a DC layout, it would
be best to have a DPDT reversing switch for 
the reverse loop section, and both the inner
and outer loops and all connected by insulated
joiners. 

That will make it possible to have, for example
a train running on the outer loop when another
runs through the inner reverse loop. The polarity
reversing required would then not affect the
train running on the outer loop.

Keep in mind that polarity change reverses the
locos. So at some point you are going to
have to stop a loco so as the be able to
change polarity to the same as the track
where the loco is. This would have to be
done before the loco crosses an insulated joiner, 
for example from inner to outer loop.

As as Ray noted, these complications are 
completely eliminated if you go DCC and
use a reverse loop controller to power
that one isolated section of track. 

Don


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## Northern Route (May 12, 2014)

On DC with a reverse loop you have to stop the train in the reverse loop, throw the DPDT switch to change the polarity of the reverse loop and now your train is running backwards so you have to change the direction switch on your cab. Now to stop a train and run another train or run 2 trains at the same time, you need to create electrical blocks on the layout with a bunch of DPDT switches on a control panel to control which cab you are using to run one of the trains. Even on a small layout it is a lot of work to make the control panel, you need to buy a bunch of switches and use a lot of wire to go from the track to each switch. on top of that you are still limited as to the way you can run your trains. DCC eliminates all of that mess.

Curtis


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## Northern Route (May 12, 2014)

If you are just going to change directions of the engines, just make the reverse loop a spur siding with a wye to run the engine into the spur throw the turnouts and leave the spur through the wye. In the real world they usually don't turn the whole train and on diesel engines they run engines around the train on a siding and couple up on the other end. On passenger trains they made the wye long enough to accommodate the whole train to save using a lot of real estate for a reverse loop.

Curtis


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## Fire21 (Mar 9, 2014)

I apologize for not mentioning that my layout is DCC, but I did post it under the DCC forum. Thanks so much for the replies, you've given me some food for thought. :stroke:


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## DonR (Oct 18, 2012)

DCC, Good for you.

All you need is to isolate the one reverse connecting
track and power it through a DCC reverse controller of
the same make as your DCC controller.


Don


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## Northern Route (May 12, 2014)

I just read it off new post. I didn't look to see which forum it was from and the first reply mentioned DC. DCC is the way to go, I used NCE Power Pro since 2003 and I am pleased with the way it works and NCE support. My reverse loops are controlled with Bachman reverse loop controls and the layout is broke up into power districts with four boosters and 4 SBC 3 circuit breakers set at 3 amps. Which DCC system are you using for your layout.

Curtis


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## Fire21 (Mar 9, 2014)

Northern Route, I'm using the Digitrax Zephyr extra. This my first real layout build, and I figured since the Zephyr is expandable, I'd stay inexpensive at the beginning, since it's just a 4x8 layout.

DonR says I'd need to use a Digitrax reverse controller. Would other brands also work? I see Northern Route has NCE power but Bachman controls.

Ray Haddad suggested I add a second reversing section...is it as simple as adding a second reverse controller for that section? Listen to me...I sound like I know how to wire a reverse controller!!! LOL.

Sorry for my confusion, but as I've said, this is my first foray into DCC, and I'm an old dog who has trouble learning new tricks!! Thanks again for everyone's help!


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## Northern Route (May 12, 2014)

If you add another reverse loop you will need a second reverse loop controller. When I bought my Bachman controllers NCE did not make one and they recommended a separate booster for each reverse loop, which I thought was pretty expensive. The reverse loop controller doesn't talk to the system it just senses a short and changes polarity. As far as brand, staying with same brand may have some benefits. On the other hand most brands will work with any system, but you will have to research which one is best for your needs. My suggestion is not to have any reverse loops on a layout of that size and change the reverse loop into a wye and you will need a reverse loop controller for the wye. The wye will let you turn the engines from either direction and you can add industrial sidings to the tail of the wye. That also depends how you want to run your layout and equipment you plan to run. I am just making suggestions on that issue and remember the two rules of model railroading: Rule 1 Its my railroad and I will do what I want.
Rule 2 Refer to Rule 1.

Curtis


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## Magic (Jan 28, 2014)

Fire21 said:


> Northern Route, I'm using the Digitrax Zephyr extra. This my first real layout build, and I figured since the Zephyr is expandable, I'd stay inexpensive at the beginning, since it's just a 4x8 layout.
> 
> DonR says I'd need to use a Digitrax reverse controller. Would other brands also work? I see Northern Route has NCE power but Bachman controls.
> 
> ...



Check with Tony at 

http://www.tonystrains.com/index.html
He has reversing controllers that might be cheaper than Digitrax. 

Magic


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## Fire21 (Mar 9, 2014)

OK, I'm still struggling with how to wire my reversing track. A couple more questions: 

1) If I use the auto-reversing modules mentioned in several replies, that changes just the reversing section of track, correct? When my train enters back onto the inner loop going the opposite direction, does it just continue going forward as if nothing happened? Or do I need some sort of "polarity" reverser for the loop track?

2) I've read that the reversing section must be as long as your longest train. Why would this be needed, since it's just my engines that are taking power from the tracks? If I had lighted passenger cars, would this still apply, or do they care what polarity it is?

I am working on getting a second reversing section so I can run both directions. I'm just scared of these reversing sections since I know I can fry my decoders, the auto-reversers, and even the power supply if I do things wrong!!


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## Northern Route (May 12, 2014)

question 1. The module takes care of the polarity no mater which direction you are going. If the polarity is the same when entering the reverse loop, it will change when leaving on the other end of the loop also the opposite is true the module will change the polarity when going into the loop and stay the same when leaving the loop. If decide to back out instead of going through the loop the polarity is already correct and the module will not detect a short. As far as your locomotive goes, it doesn't care, all it knows which direction it wants to travel since the decoder has the bridge rectifier to change the AC current to DC current, it chooses the polarity of the DC current for the motor.

question 2. Metal wheels! The module doesn't read current, it only reads a short in the track. Each time a metal wheel crosses the gap, it allows current to bridge the gap, so when the metal wheels bridge the gap on both ends of the reverse loop at the same time it creates a dead short which will stop the train and could damage the reverse module if you have more amperage going the track than the module can handle.


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## DonR (Oct 18, 2012)

You need not worry about frying anything with an automatic
reverse loop controller. As mentioned, it has a very fast
sensor when your metal loco wheels span the main/reverse loop
insulator joint. It 'see's the short circuit and quickly changes the
phase (polarity) of the isolated reverse loop track.

You connect the 'input' of the controller to the track adjacent
to the isolated section or to your layout track buss.
You connect it's 'output' to
the isolated track. That's how simple it is.

If you do install a 2nd reverse loop you'll need a 2nd reverse
loop controller.

The recommendation of a track long enough to accomodate
your longest train is valid if you are using metal wheels
on your train cars. They also short across the joiners at
the other end. However, you can 'get around' this
problem by putting a tiny drop of clear finger nail polish
on the rails on either side of the insulated joiner. That
keeps the wheels from touching both tracks at the same
time, thus no short. If all of your car wheels are plastic the length of
the isolated section doesn't matter.

Don


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## Fire21 (Mar 9, 2014)

Wow, thank you guys! That makes things much clearer for me and makes my heart rate settle back down. I reckon I'll order me a couple reverse controllers and see where I can take this layout. Again, thank you!! :smilie_daumenpos:


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## DonR (Oct 18, 2012)

Read the instructions that come with your reverse controller. They'll
describe how to set the sensitivity of the sensor. It's a simple
screwdriver procedure on mine.

You'll be pleased with the way your trains run through a reverse loop
with no stopping, stuttering or slowing. The controller does all of
the work. You don't have to do a thing, except of course,
see that your turnouts are set for a clear route.

The DC guys don't have it so easy, pshaw.

Don


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