Date
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Reverse loop headache
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Nick Ostrosky
Please reference this photo. https://groups.io/g/w4dccqa/photo/268225/3492538?p=Name%2C%2C%2C20%2C1%2C0%2C0
I've been testing my reverse loop (red) wiring with a loco. The loop is wired to a PSX-AR. It has gaps on either end, staggered 3/4" apart as per the AR instructions. When entering or exiting from the "East" side, no problem. When entering or leaving from the "North" side I get a short (both the AR and the PSX circuit breaker for the adjoining section). Tracks on either side of the loop are in the same power district, same PSX circuit breaker. I've tested with two locos (one Stewart F7A and the other an Overland centercab) to eliminate the loco as a potential issue; same issue with both. Both locos operate just fine on the tracks adjacent to the loop. I have a second reversing section gapped and wired exactly the same way without any issues at all. I had this exact same configuration on the previous iteration of this layout with no issues. I've checked the wiring to make sure I didn't inadvertently mix up left rail/right rail (in my case color coded red and black). Is there something obvious I'm overlooking? Is the staggering of the gaps potentially an issue, or should it not matter which wheel of a loco crosses a gap first? Not sure what other questions I should be asking to resolve this problem. Thanks! |
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John Bishop
Try using a lighted caboose to check. That eliminates any engine as a factor, but also you can see exactly where the wheels are, the exact point at which you get a short. John Bishop
On Sunday, September 25, 2022 at 10:44:12 AM PDT, Nick Ostrosky <nick79ostr@...> wrote:
Please reference this photo. https://groups.io/g/w4dccqa/photo/268225/3492538?p=Name%2C%2C%2C20%2C1%2C0%2C0 I've been testing my reverse loop (red) wiring with a loco. The loop is wired to a PSX-AR. It has gaps on either end, staggered 3/4" apart as per the AR instructions. When entering or exiting from the "East" side, no problem. When entering or leaving from the "North" side I get a short (both the AR and the PSX circuit breaker for the adjoining section). Tracks on either side of the loop are in the same power district, same PSX circuit breaker. I've tested with two locos (one Stewart F7A and the other an Overland centercab) to eliminate the loco as a potential issue; same issue with both. Both locos operate just fine on the tracks adjacent to the loop. I have a second reversing section gapped and wired exactly the same way without any issues at all. I had this exact same configuration on the previous iteration of this layout with no issues. I've checked the wiring to make sure I didn't inadvertently mix up left rail/right rail (in my case color coded red and black). Is there something obvious I'm overlooking? Is the staggering of the gaps potentially an issue, or should it not matter which wheel of a loco crosses a gap first? Not sure what other questions I should be asking to resolve this problem. Thanks! |
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Allan AE2V
Hi Nick,
Other readers that have had the problem of the loco entering just fine from one side, but not the other, have had their main track bus wired to their reversing section in addition to the automatic reverse section controller. Make sure you ONLY have the two output wires of your PSX-AR wired to your reverse section and nothing else. Since you mentioned a previous iteration of your layout also makes me wonder if you missed removing a wire or two. There is also the possibility that your PSX(s) are tripping faster than the PSX-AR. I still think you have a connection to your main track bus erroneously going to your reversing section. Allan Gartner Wiring for DCC |
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Don Weigt
Nick, Try disconnecting the wiring from the reverse loop, and check if either rail is connected to a rail in the rest of the yard. I suspect you have a short. -- Don Weigt Connecticut |
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Nick Ostrosky
I don't have any lighted rolling stock. Could I accomplish the same thing with a test light in some way? This issue appears to occur as soon as a wheel bridges the gap.
Nick
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Don Vollrath
Nick, it sounds like the PSX and PSX-AR are fighting each other for tripping sensitivity. Make sure both units are
powered directly from the booster AND that all other entrances to the AR section are unoccupied AND that the AR unit flips the polarity first. ( a trip amplitude and time sensitivity adjustment on both units) The AR unit should work with or without staggered isolating rail joiners. If all else fails… verify the wiring and isolation of the AR section. DonV |
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Don Vollrath
To verify the isolation of the AR track… disconnect both wires for that section from the output side of the AR unit, then with other track power ON use an AC volt meter to verify that there is near zero voltage from either/both AR rails to other powered rails on the other side of the isolation gaps. ie- an open circuit.
You can use a similar technique by using an ohmmeter with track power off and look for infinite ohms from each of the AR rails to other tracks. DonV |
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Nick Ostrosky
So far:
Verified that the only power to the reverse section is from the AR, both by verifying wiring and volt meter after disconnecting AR as suggested. Zero volts to the track section with the AR disconnected, no ohms to indicate a possible short between the AR and non-AR sections. Verified AR is fed directly from the booster (alternatively I did try daisy-chaining it from the neighboring PSX, no change in results). My second AR (the one that is functioning correctly) is fed from the track bus to my yard power district and not directly from the booster, which I was thinking may have affected the area of the yard adjacent to the problem AR (i.e., two ARs adjoining the same power district, I was thinking they may have been somehow fighting each other). Disconnected that until I can run a direct line from the booster, but it had no impact on my problem AR in subsequent testing. I started playing around with CVs 55 and 65, setting the problem AR as secondary and tweaking CV 65 up to 8 to see what difference it would make. Still have the same result. I have zero familiarity with how much I should change CV 65; should I have seen any change by changing it from default to 8? Appreciate all the suggestions, pretty sure I'm going to have a "duh" moment when I finally figure this out. |
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Don Russell
I think I had the same issue I had power to the track within the reverse section. The only power inside the reverse section comes from the AR itself.
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Don Russell On Sep 26, 2022, at 4:41 PM, Nick Ostrosky <nick79ostr@...> wrote:
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Don Weigt
Nick, While testing with reverse loop wires disconnected, did you check for shorts from both reverse loop rails to both non-AR rails? A connection between either reverse loop rail and either non-AR rail will short one phase or the other of the reverse loop track power. Your symptoms still suggest you have an undiscovered non-AR connection to one or both rails of your reverse loop. -- Don Weigt Connecticut |
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Don Vollrath
Try swapping the AR units. It is possible that one of them is malfunctioning.
DonV |
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Nick Ostrosky
Tried a couple more things today:
Changed out the AR to see if the AR was the problem. Same result, so the AR appears functional. Changed out the PSX assigned to the neighboring yard section, also no change in results. Re-verified that all the wiring from the PSX to the yard was correct, same for the AR. Verified that there is no continuity across the gaps with an ohm meter on both ends of the AR, so power coming in from the neighboring power district seems to be eliminated.
Question: is it possible my gaps are too small? When watching a loco cross the gaps the leading right wheel crosses just fine, but the short occurs when the leading left wheel hits the staggered gap (i.e., left wheel crosses second). The gaps on both ends were cut the same way, razor saw.
Nick
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Allan AE2V
Nick,
You said you checked across the gap. Did you check diagonally across the gap? It still sounds like you have a connection between your reversing section and the non-reversed adjacent sections. If you get Model Railroader, see the Sept issue and my DCC Currents column. It's all about gap crossing issues. Allan |
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Nick Ostrosky
Again, many thanks for all the suggestions. Allan, per your September article, I did start to make all those measurements across the gaps – only to realize my trusty old volt meter died on me (and not just the battery)! So I will pick this back up when I can replace it, which may take a few days.
Nick
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For basic continuity checks I use a 9V battery connected to a piezo electric buzzer and a pair of alagator clips. I hook this to the rails when I start wiring a section and it will buzz as soon as I touch a wire to the wrong place.
Tim Rumph Lancaster, SC |
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Nick Ostrosky
Don V has been providing considerable assistance offline in identifying my core issue. With his help, we've identified the Tam Valley booster as the root problem. With just my Powercab, everything works as designed. Once the booster is added to the mix, it trips along with the PSX and AR. In checking with DCC Specialties it appears I have the appropriate trip settings for the PSX and AR (3.81A and 1.27A, respectively), which should prevent the booster from tripping (booster trip is 5.6A per TVD documentation). I added a delay to the PSX per their recommendation but that doesn't appear to have any effect. Does anyone have any experience with a NCE / TVD / PSX combo that could provide some direction on resolving this issue? Thanks!
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I think that the delay needs to be in the booster rather than the breaker. That will give time for the breaker to trip so the booster won't. Also, what are the trip currents for the PS* devices?
Tim Rumph Lancaster, SC |
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