I’m trying to wire a loop that goes around my railyard. I’m using a Digitrax AR1 for this reverse loop but I’m having problems. My train can enter the loop but it will short out when it exits the loop. I’ve watched a handful of videos and other online resources but nothing seems to work. I’m hoping someone here can help me or walk me through what I need to do as I’m still relatively new to the hobby.
Tough to tell just what you have going on with the details you provided. A couple basic questions. Is your train shorter than the stretch of track you have wired up to the AR1? You did isolate it with 4 insulated rail joiners, correct?
Give us some more details. A sketch would be great - be sure to follow the instructions for how to post one. Hang in there through your initial moderation period.
Can the train enter either end of the reverse loop, or just one way? If just one way, it could be you’ve got a connection to the reverse loop that is hooked up to the main track wiring. Check to be sure all the track connections in the reverse loop are only connected to the AR1 output.
You indicated that you have fully isolated the reverse loop.
It is possible that the reverse loop or the adjacent track is miswired. You need to to determine if any feeders are crossed or connected improperly. Any feeder inside the reverse loop needs to be connected to the output side of the AR. Any feeder outside the reverse loop needs to be connected to the main bus that feeds power to the input side of the AR.
The usual cause of a train entering a reverse loop without shorting but then shorting upon exit is that the polarities match when entering, but the polarities are mismatched when exiting, indicating a wiring fault. If the wiring checks out, then you need to check the settings on the AR1. It could be a timing issue.
Absolutely true, but when you view things from underneath that layout, as you wire, it’s easier to get L & R confused.
One of the worst moments for an anesthisiologist is to look over the “ether screen” and see the surgeon is operating on the wrong side. Even worse when it happens to be an appendectory. (yes ththe later really happend, but fortunately not to me)
That’s why most wiring mishaps occur…“Dyslexics ‘Untie’!”
If you are running the test car in a previously undetected reverse polarity section, and you see that the “Red” “+” side of the car is over a “Black” “-” track feeder, that might be an indication of a problem.
The shielding colors of wires typically don’t change, no matter what angle you view them from.
If all your wireing is correct, you can adjust the trip current on the AR1 useing the set screw. It might be set too high. What DCC system are you usuing? Joe
I’ve never been fond of the “test car” method. Too easy to get confused while running the test car around the layout unless the rails are also color coded in some manner. Better to get a blank sheet of paper and draw the track as two separately colored rails, for example red and blue. Now, you have a permanent visual record of where red meets blue and blue meets red, the point of reverse polarity.
But, in this case, that is not even the issue. If you take the OP’s word for it, he already knows where that point of reverse polarity is located, and he has fully isolated the reverse loop. From the OP’s description, it sounds like a balloon track running around the yard. So, his issue is likely either a miswired feeder or a faulty setting on the AR1.
Of course, there is always the possibility that everthing is operating properly, feeders and AR settings, but the entire train is longer than the reversing loop. So, is it? Try just running the locomotive through the reverse loop.
The fact that the locomotive does not short upon entering the reverse loop but does short upon exiting the reverse loop is typical of a malfunctioning reverse loop. One end of a reverse loop will always be in phase with the adjacent track, while the other end of the reverse loop will be out of phase with the adjacent track. Why? Because the reversing section itself will have its polarity flipped by the AR unless there is a miswired feeder or a faulty setting on the AR.
If the entrance to the reverse loop is in phase with the adjacent track from which the locomotive is entering the reverse loop, the AR won’t even be triggered. The AR will only be trigged upon the locomotive’s exit from the reverse loop, so that the polarity inside the reverse loop matches the polarity of the adjacent track to which the locomotive is exiting. Now, the original entry point to the reverse loop will have the mismatched polarity with the adjacent track from which the locomotive is entering the reverse lo
It would seem so. If a pair of feeders are crossed in a non-reversing section of track, a dead short would occur. But the wiring of a reverse loop can present other issues.
Lucky me, I have never miswired a reversing section (loop) of track. I am always careful to fully isolate the reversing section, keep the feeders in phase, and connect all feeders inside the reversing section to the output side of the AR. But, what happens if a pair of feeders inside the reversing section are inadvertently connected to the main bus feeding power to the input side of the AR? I don’t have an answer for that form of miswiring.
Anyhow, I would just urge the OP to confirm that his wiring is correct.
In any reversing section (loop), the polarity inside the reversing section is always going to match the polarity of the adjacent track on one end of the reversing section and be mismatched with the polarity of the adjacent track on the other end of the reversing section. Those matches and mismatches change each time the AR is triggered.
It can’t matter which way round the feeders are connected within the reverse loop. The polarity (phase) will always be “wrong” at one end of the loop. That’s why the reversing device is used. Inside a reversing loop one can use two feeder wires of the same colour to remind you it doesn’t matter. DCC or DC will be the same.
what if, as you suggested, there’s a reverse section feeder wired to the mainline bus? there would be a permanent short whenever the AR attempted to reverse the polarity at one end but works fine at the other end
Exactly. Imagine a reverse loop with one set of feeders. That pair of feeders is wired to the main bus. A loco enters the reverse loop on the side where the polarity inside the loop matches the polarity of the adjacent track from which the loco enters the loop. No short, the AR is not triggered. When the loco attempts to exit the loop, the AR is not triggered and a dead short occurs. That is the scenario that the OP describes. So, it could be a wiring issue.
DC or DCC any reversing section cannot be wired directly to the powerpack feeds. You need some sort of separate polarity (phase) control to which thecreversing section power leads are attached. MRR had a good general article on this at pages 46-47 April 2021 issue.
My takeaway from this article was the benefit to wiring the reversing section with a NSDR (non short detecting reverser) which includes using just a DPDT switch manually thrown, same as for DC. The difference is which track section experiences the polarity or phase change. For DC you reverse the “main” to match the reversing section. For DCC it works better if you reverse the phase within the reversing section when using a DPDT.
If you first wire the reversing section correctly for use with a manual DPDT then you just slip the auto reverser in place of the DPDT and it should work. Way easier to build a reversing section using the DPDT first and test it for correct operation before inserting the auto reverser in its place.
If a reversing section is correctly gapped and wired, the auto reverser will work just fine IF the user takes into account the protocols associated with a particular auto reverser, including the settings for timing and current trip setting and the concern for mixing mechanical relays (e.g., the OP’s Digitrax AR1) and solid state circuitry like a circuit breaker upstream. A DPDT takes none of that into account.