Digitrax AR1 and reverse loop question

[Spaceman Spiff]

Hi everyone, I am about to start adding DCC to my project. I have attached a drawing -please forgive the quality a paint shop pro I am not lol.

Anyways the black line represents the mainline with a reverse loop . I will add a AR1 to the red boxed area. Off the main line I have a spur line line that connects to the reverse loop (green line). My question is can I add another AR1 to the green line section? There could be a chance there would trains running on the green section and the reverse loop at the same time.

Any suggestions on how to make this work?

Thanks

Spiff

[KenS]

A DCC auto-reverse control is actually something you add to a section of track, not a switch.  It acts to keep the controlled track "in phase" with adjacent track by sensing short circuits. Since it acts by reversing the phase of the controlled track, the most important rule is that a train can be crossing only one end of the controlled track at a time (e.g., if the green track is shorter than your longest train, you can have a problem as wheels at one end will be shorting across the tracks when the other end is at correct phase).  This means you can't just add it to a switch, because that's shorter than a train.

You could add one to the long black track between the red and lower purple boxes as long as it also included the lower part of the loop to the upper end of the green track, provided you'll only have one train in the section at a time (technically you can have more, as long as two don't both cross an end at the same time). You need to gap and insulate both rails at both ends of the controlled track.

The AR1 is connected between the two rails of the controlled track and two "normal" rails.  Other systems, like the PM42, are normally wired to the power bus as the reference (input). You can wire the AR1 the same way (bus to track).  To wire an AR1 to the green track, the AR1 gets wired to one adjacent track, and the other adjacent track has to be "in phase" (i.e., never reversed) with that reference.

It's often simpler just to wire reversing controllers between the power bus and the track to be reversed. You still need to ensure you don't wire adjacent track backwards or have two reversing sections adjacent to each other.

If you can't fit just one reverser (or don't want to wire the track that way), then what you'd need, assuming the track is long enough, is one AR1 on the green track, and another on a section of the track leading from the red box on the main (not on the loop).  An issue with the approach is that the track between the ends of the green track and either end of the other reversing track must also be longer than the longest car or train with all-wheel pickup (for cars with individual lights and motors it doesn't matter if the two ends of the train are triggering different reversers, but an all-wheel-pickup train (like some Tomix trains) can't bridge the two.

So the correct answer, if there is one, will depend on the length of track and the length (and internal wiring) of the trains you'll run.

[The_Ghan]

Hi Spiff,

It looks like that spur wraps around to form another loop.  Consider your sketch and break up the sections differently, for wiring purposes, for a second.  If you consider the spur as the main line and the reversing part of the loop separately, the picture becomes clearer.  Your drawing is basically a simple oval of track, with a reversing branch at the top and a separate branch to the main line below.  Have a look at the plan I've included and note the following:

1. I've divided the track into three sub-districts: red for the reversing loop, the simple oval (black, blue, pink and green) and the return to the main loop (dark blue at the bottom);

2. The simple oval of track will be divided into a number of sections, I've shown four: black, blue, pink and green (you're spur).  Each of these needs to be isolated across one rail (the same rail).  Decide whether you go for the inside or outside rail and stick with it.  You can break it down into more sections if you need to, and you should if you are planning to have places where the train might frequently stop, but I have another thread on that;

2. Note that the switches all belong to sections on the simple oval of track.  Two of them are on the same section, which is fine unless you want a train stopped on black while another enters red from the right;

3. The reversing loop (shown in red) needs to be double isolated at each end, ie: at each switch.  This is because we are going to use a power management device to alter the phase as the train either enters, or exits the track;

4. If you've already purchased an AR1 then you would wire that to the red section, following the instructions in the manual;

5. If you haven't yet bought an AR1 then I would go for a PM42.  You can program any of the four channels to do the job of an AR1 and save a bit of money;

6. There is no need to wire an AR1 to the green track as it is part of the simple oval and will remain in the same phase as the black and pink sections.  Ie: the inside rail is ALWAYS the inside rail;

7. The track back to the rest of your layout, at the bottom, only needs to be isolated on one rail unless you want to make it a separate power sub-district, which I would do if what's shown on screen is only a small portion of your layout.

I hope this helps.  If you need more info on how the AR1 works please don't hesitate to ask.  Also, I strongly recommend reading up on the "Texas and Southwestern" Case Study from the Digitrax site ... http://tsd.digitrax.com/index.php?c=335

Cheers

The_Ghan

[Spaceman Spiff]

Thanks for the replies guys. I will be working on this hopefully on Thursday.

Spiff

[Spaceman Spiff]

Just a quick update. I hottie reverse loops working correctly using 3 AR1's.

Thanks for the help

spiff