# Seeking DCC Reverse Loop Clarification



## Deane Johnson (Sep 19, 2016)

As my layout construction progresses, I'm trying to get my mind around the proper setup for the single reverse loop the plan has.

It could probably be considered sort of a Wye feeding an engine terminal. All of the track stays in phase on the entire layout, except for the space between the two red marks on the enclosed sketch.

It needs to handle engines arriving from either direction, but the only one in question would be from the right side of the wye.

Does a single "reverser" handle both ends of the isolated section?

Would this be a good auto reverser to choose:

http://www.modelrectifier.com/product-p/ad520.htm

Is there something better or more cost effective?

In Googling for diagrams, similar examples all showed a "booster" being involved. Why would I need a booster? That would seem to be more dependent on the load one was placing on the controller and have nothing to do with "reversers".

BTW, my controller is the MRC Prodigy Advanced 2.

Thanks for your help once again.

Deane


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## rickbz28 (Jan 10, 2016)

Digitrax makes AR1 auto reversing unit MSRP is only 29.99.http://www.digitrax.com/products/autoreversing/ar1/


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## Guest (Jun 1, 2018)

As my layout construction progresses, I'm trying to get my mind around the proper setup for the single reverse loop the plan has.

It could probably be considered sort of a Wye feeding an engine terminal. All of the track stays in phase on the entire layout, except for the space between the two red marks on the enclosed sketch.

It needs to handle engines arriving from either direction, but the only one in question would be from the right side of the wye.

Does a single "reverser" handle both ends of the isolated section?

Yes, you wire the auto reverser to the two rails in the block and it automatically reverses the polarity to the same as the rails outside the block.

Would this be a good auto reverser to choose:

http://www.modelrectifier.com/product-p/ad520.htm

I'm sure that would work fine but they don't give any information about the unit on the page.

Is there something better or more cost effective?

You could look at Tony's Train Exchange or Lichfield Station or even big online retailers like MB Klein and check out their prices.

In Googling for diagrams, similar examples all showed a "booster" being involved. Why would I need a booster? That would seem to be more dependent on the load one was placing on the controller and have nothing to do with "reversers".

You don't need a booster. You would only need a booster if your layout's power requirements exceeded your power supply.

BTW, my controller is the MRC Prodigy Advanced 2.

Thanks for your help once again.

Deane


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## Deane Johnson (Sep 19, 2016)

Thank you both. It all makes sense. That Dixitrax unit looks like a good way to go.

I hate to move ahead on these things without a clear understanding of where I'm headed.


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## DonR (Oct 18, 2012)

Deane

Total agreement with the others. The MRC lacks information
so I also agree that the Digitrax AR1 reverse
loop controller is the way to go.

It may help you to understand how the reverse loop
controller works:

When a loco wheels span the first insulated joint there
is a short circuit because the isolated section
is out of phase (polarity) with the main track. The reverse controller quickly senses this, flips the phase of the track and the loco continues on without so much as a blink of it's headlight.

Then when those same loco wheels reach the other end of
the isolated section, they again short and again the 
reverse controller flips the phase of the isolated section.
The train chugs smoothly along. The controller doesn't
care which end is first spanned by the loco. It works with
a loco going in either direction. However, it can't handle
a loco entering the isolated section from one end and another
loco entering from the other end. This situation always
results in a solid short circuit. One loco must be removed
by hand to resolve it.

Your isolated section must be longer than the longest
lighted passenger train...or train with a lighted caboose...
for the same reason as above. Metal wheels can sometimes
also 'trick' the reverse controller and result in a short.

Knowing these limitations and how to avoid the
problems goes a long way to enjoying your ability
to turn a train around to go the other way on your layout.

It is especially fun when you have a single track main with
passing sidings. You can have one train going clockwise
and another counter clockwise...but you must be a very
alert engineer to avoid crashes.

The size of a layout and length of track has nothing to do
with whether you need a booster. The number of locos and
lighted cars that you run at the SAME TIME determines
the current draw. Most of today's DCC controllers can
handle 3, 4 or more non sound locos running at the
same time.

Don


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## Deane Johnson (Sep 19, 2016)

DonR, as usual, clear and useful detail.

Everything turns out to be pretty much as I had anticipated it might be, but I've learned with electronics to make absolutely certain before proceeding. I hate those puffs of smoke.

Thanks.

Deane


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## furnmkr (Apr 21, 2018)

*PSX-AR*

I am planning on using PSX-AR auto reverses on my layout. They also include a circuit breaker.


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