Automatic Reversing & Reversing Sections

DCC Automatic Reversing SectionsVirtually all automatic reversing will fall into 3 categories with the wiring principles for all being the same:1. Reverse Loops2. Wyes3. TurntablesDCC has the ability to automatically reverse sections of track we call Reversing Sections while our trains are running and not affect the direction or speed of the trains. This is because we put a constant square wave AC current on the track and control the trains (locos) by sending messages to them (actually to receivers we call decoders) to tell them what to do such as start, stop, change directions, etc. . We are thus ...

To make the DB200+ an Auto Reversing Booster follow the following steps: 1. Remove input power from the DB200+ by turning off the Input Power Supply. 2. Move the Mode Switch to the center P/R or OP position 3. Restore power to the DB200+ by turning on the Input Power Supply. Use the below diagram as a guide to configuring the DB200+ for Reverse Loops. Please note that for Auto Reverse applications the DB200+'s Mode Switch is set to the center P/R or OP position. Also note the DB200+ connections to the track- the DB200+ track connections are NOT directly ...

The tuneable trip current (TTC) adjustment allows you to set the current at which the reversing section reverses when the train crosses the gap into the section. This allows you to improve the operation of your reversing sections.The tuneable trip current is adjustable from .25 amps to 8 amps. Turning the TTC screw clockwise increases the current trip point and turning the TTC screw counterclockwise decreases the current trip point. The total adjustment is approximately one half revolution of the TTC adjustment screw. The TTC adjustment is made using a full load on the reversing track--the total number of locomotives/cars ...

The AR1 is usually located close to the point where the gaps are cut for the reversing loop. The length of the reversing loop is determined by the maximum length of the train that will use the loop.1. Turn off track power. (Note: Failure to turn off power before connecting your AR1 may damage your AR1.)2. Connect Track Power from Rail A and Rail B mainline to the AR1. Rail A connects to terminal 5 and Rail B connects to terminal 4.3. Connect the wires from the reversing section to terminals 1 & 2 on the AR1. (Note: terminal 3 ...

This H0-scale railroad track plan first appeared in the Atlas Model Railroad Company's book "Six Railroads You Can Build", written by John Armstrong and illustrated by Tad Stepek. This book was first published in 1958 and has been reprinted several times. A classic bowl of spaghetti, the Transbay Interwoven has two reversing loops and a turntable. DC Control For DC operation, Atlas specified three Atlas Controllers (for the reverse loops and the turntable), two Atlas Selectors (to control eight track segments) and ten controllers for the railroad's turnouts. DCC Makes Things Simple With DCC, the wiring of this railroad is ...

This Atlas Snap-Track layout appears in the Atlas Model Railroad Company's book "Beginner's Guide to HO Model Railroading". It includes a reversing section which can be controlled with a Digitrax AR1. DC Control For DC operation, Atlas specified an Atlas Controller (for the reverse loop), two Atlas Selectors (to control eight track segments) and seven controllers for the railroad's turnouts. DCC Makes Things Simple With DCC, the wiring of this railroad is considerably simpler. Because each locomotive has a unique address, the section insulated gaps and the two Selectors are not necessary. Likewise, the Controller is replaced with the AR1 ...

When using the your PM42 with an AR1 Auto Reversing controller do not use the "fastest setting" in the Short Circuit Sensitivity Settings section:

Problems occurring on most auto reversing sections are a result of improper wiring or gapping. Digitrax auto reversing units such as the PM42 or AR1 require a "hard" short which means there must be good current flow to both sides of the gaps, on the reversing section side and on the "normal" side. Our experience has been that over 90% of reversing section problems are a result of improper wiring or improper gaps. Another 5% is a result of improperly wired or configured auto reversing units. It is poor practice to put the gaps immediately behind a switch (turnout in ...

  One major consideration is that the reverse section controlled by the AR1 must be longer than the longest train. It is a common misconception that the AR1 will work with an analog controlled ("DC") locomotive; it will not. The AR1 is meant to be used only in a DCC enviroment. The AR1 coordinates the phasing of the reversing section with that of the mainline (non-reversing) section of the layout.  Because a Digitrax layout can be a complex enviroment with detection and transponding, etc. consult the approriate Digitrax user manuals and the Digitrax Tech Support Depot knowledge base.  

How do you wire an AR1 with a BD4 so that you get block detection within the reverse loop and without the BD4 permanently detecting the AR1? It should be wired with the AR1 between the power source and the BD4. All four detection sections of the BD4 will have to be inside the reverse loop.

Q: I want to use the AR1 for a reverse loop between two different power districts (i.e. different booster for each connected track). Is this possible or do I need to make a special wiring set-up to do this? SThis diagram shows how to do this The usual rules apply, the AR1 track section must be longer than the longest train you will run.

If Engine "B" is operating on the main line when Engine "A" enters the main line from the auto reverse loop, will Engine "B" change direction or will Engine "B" continue its journey?With DCC, the reversing of locomotive direction takes place within the locomotive, and only when it is commanded to do so.  If you grew up in a DC model railroad world, it's easy to forget this feature of DCC.  When Engine "A" transits the reversing section and returns to the mainline, any "change" will have been to coordinate the track polarity of the DCC track current present on ...

The BDL168 can be used as an autoreversing unit for return loops. One of the BDL168 Detection Sections is connected to the non-reversing area, with the balance of the detection connections being made within the reversing area. Here is a wiring example: Note that an auto-reverse section can only use detection sections that are contained in a BDL168 zone that is correctly set up for auto-reversing.

I have multiple reversing districts, do I have to buy a separate booster for each one?You can run more than one reversing district off a single booster, but there is the potential problem that might arise is if you have more than one set of wheels crossing more than one set of gaps at the same time. In this case, the booster will detect a short and shut down (unless the polarities just happen to be matched up in which case you won't see a problem). We recommend that you use the AR1 Auto-Reversing unit or the auto-reversing capability of the ...

My layout is the Apex & Hypotenuse design, from the Atlas design. I was wondering where would you suggest I wire the AR1. We remember this layout design, if for no other reason than its ingenious complexity. This railroad initially appeared in the Custom Line King Size Plan Book - H0 Railroads You Can Build, originally published by Atlas Tool in 1966. This book was yet another collaboration between the late John Armstrong and illustrator Thaddeus (Tad) Stepek. This railroad must have required a certain level of dexterity by the operator since the reversing segment is actually two different return ...

What is it and how do I find a DPDT?It's an electrical switch; double pole - double throw (DPDT). Here is a schematic of a DPDT: More typically, they look like this: The DPDT is very common to model railroading and found at just about any store that sells electronics.  It comes in a variety of arrangements, with the most common being a DPDT Center-Off switch.  Analog OperationsIn the early days of Direct Current model railroading, reverse loops had to be controlled by hand, and the DPDT was perfect for the job.  The DPDT was wired in such a way ...

Can I combine the power input requirements for PM42's with other units for economy?Digitrax recommends each PM42 module to have its own seperate power source. The criteria for choosing a power supply for the PM42 is any power source that can deliver 12-15V AC or 13.8-15V DC with a minimum of 125 ma. The Digitrax PS14 meets the minimum power requirement of a PM42.It is possible to power more than one PM42 from a single power source. When powering multiple PM42's special care must be taken to insure identically phasing of all PM42's and ample current availability to power all ...

The Texas & Southwestern has a reversing loop, and DCC insures reliable and simple operation of trains in the reverse loop. This reverse loop is handled with a Digitrax AR1 Auto Reversing Controller. The automated features of the AR-1 make for seamless train movements, but an issue quickly arose. Because a reverse loop in a traditional DC-powered model railroad environment required manual operation, the track insulating gaps for the loop were usually located for the convenience of the operators. So the track gaps of the original track plan were situated to keep this inconvenience to a minimum. Note also all ...

My PM42s seem to correctly trip on track shorts and auto-reverse reliably, but the power briefly drops out during these events, and when the PM42s attempt a fault recovery into a persistent short circuit, why is this?No power on earth can stop the track voltage of the booster from collapsing to a low value when a true short circuit is present. This is simply Ohm’s law in action!Actual track voltage seen depends on: the loop resistance of the short circuit, the current capacity of the booster and power supply and whether the Booster employs "smart" fault detection and recovery along ...

Use a throttle to change the PM42's Option Switches 01, 02 and 09 as detailed in the PM42 instruction manual. The PM42's trip current threshold can be set at a value from 1.5amps to 12 amps. Always use the lowest possible setting, consistent with good operation and reliable short circuit detection and recovery. Higher current settings are not "better." We ship the PM42 with a moderate current trip threshold of 3amps so it will work on most DCC boosters and layouts with no changes.This is because some boosters cannot supply enough current with the track feeder resistance to reliably allow ...

Q: How do I use the AR1 and automatically control the turnout? I'm confused here. It is good that the AR1 controls the switching of the track power for a reverse loop automatically but it seems the turn out direction also needs auto control. Am I missing something here? Need help understanding...Please explain. A: The AR1 is handles correcting the track polarity mismatch when a reversing section is encountered by a locomotive. When the polarity inside the reverse section does not match the polarity outside the reverse section, the AR1 detects the short circuit and flips the polarity so that ...

Q: I am building a new DCC layout that will include a logging spur that is simply a single long piece of track with no loop. I want to have a train go back and forth on this track which automatically reverses when it gets to each end. While the AR1 was designed for reversing loops, can it be wired to simply reverse a train on a straight piece of track? A:  Not in the way that you intend. One of the interesting problems with DCC is that we often still think in terms of DC, where the track polarity ...

Since many Zephyr and Zephyr Xtra Starter Sets are used on smaller railroads, a natural choice for setting up an automatic reversing section would be an AR1. If you have more than one reverse loop, then the PM42 is a better choice. These automatic reversing strategies will work equally well for any Digitrax system using any Digitrax Starter Set.  Alternately for larger railroads, an auto reversing booster such as the DB150 can be used for automatic reversing if the section is large.

  Q:  Can I use a PM42 with a non-Digitrax DCC Command system? A:  The PM42 was specifically designed to work with Digitrax Direct Home wired layouts. Any system that is configured this way will probably work with the PM42 with no interoperability issues. Digitrax has no control over or knowledge of each specific non-Digitrax system and how it may interact with the PM42. The PM42 can be used as a stand-alone auto-reversing unit and short circuit manager with many third party DCC systems, but for systems without LocoNet capability a number of the networked management features will not be available. ...

Q:  What is the preferred way of protecting a reverse loop with circuit breaker management and still having automatic reversing? A:  There are two ways of protecting a reversing section with a circuit breaker and reversing section controller. 1.  Use one PM42 (circuit breaker manager) and one AR1 (automatic reversing section controller). 2.  Use two PM42s (one as a circuit breaker manager and one as a reverse section control). The following diagram displays both methods: a) The first method (left), is where one section of a PM42 configured for circuit breaker operation feeds one or more AR1s (automatic reversing section controller), or b) The second method ...

Q:  Can two sections of a single PM42 be configured to perform both the task of a circuit breaker and also automatic reverse section control for a single reverse loop? The PM42 can be configured so that one section of the PM42 is used for circuit breaker operation, feeding into another section of the same PM42 which is configured for automatic reverse section control. In the field, this configuration has been found to be unreliable in some layout configurations.  If you are having problems getting this to work in your setting, we recommend using an AR1 to handle the automatic reversing secion.  The ...

  Q:  What is the basic configuration and Option Switch (OpSw) settings for each of the four sections of the PM42 when configured for automatic reverse section control? A:  The PM42 is a 4 section multi-purpose device where each of the four sections can be individually configured to act as either a circuit breaker, or auto-reverse section controller or DPDT relay. When configured as an auto-reverse section controller, the PM42 adjusts the rail phasing of the reversing section it controls whenever a locomotive, or car with metal wheels, bridges the gaps between the rails of that reverse section and an adjacent non-reversing section ...

Connecting a turntable to a DCC model railroad is easy.  Each of the tracks approaching the rotating turntable bridge should be wired with the same orientation.  The power feeds through a pair of conductive rings to a pair of electrically conductive brushes that are wired to the rails of the turntable bridge.  DCC power is fed to the turntable bridge through an AR1 Autoreverser; when a locomotive enters or leaves the turntable bridge, the AR1 properly orients the DCC signal.  Some turntable designs have a "split-ring" electrical pickup, where the two electrical contacts that power the two rails on the ...

I am building a layout that will have two completely separated track plans; not connected with each other by any track. I am running one layout with a Super Chief that has one AR1 reversing controller.  I would like to run the second layout with the same throttle. It will have a reversing loop, as well as a turntable.  I have thought that I could run the second layout with a booster and a couple of AR1s or PM42.My questions is, will I have any problems with the reversing loops, especially if one on each layout is triggered at nearly ...

  Digitrax AR1 is a DCC Automatic Reversing Controller.  We have become aware of another product of a similar name that may cause our customers some confusion. Circuitron makes an automatic reversing unit called the AR-1 that is used for automatic reversing of analog powered trains. The Digitrax AR1 is not the same device and does not work in the same way.

In earlier generations of model railroading, the reverse loop (reversing section) was the bane of many model railroaders. As the rails of a track come back upon themselves, an electrical short circuit is created. In the analog control world, the solution is to use toggle switches and special wiring to allow the locomotive to move on to the next block. Electromechanical solutions relying on relays and track detectors can also be used to automate reversing on an analog layout. The wye is another example of a reversing section on a layout. One of the advantages of digital command control is ...