Hi all,
I've just completed the only real "tricky" section of the lowest staging level of my new layout build, and have started testing the track. It's not really tricky at all, just an area that won't be the easiest to access once the next pieces of benchwork go in (it's not completely obscured or anything, it'll just have fairly low overhead space making it harder to work on later. Not ideal, but I lost 2 ft of width from my original planned layout space, and needs must and all that.) Schematically, the layout is effectively a very long dogbone, with all track between the ends laid out as a double mainline with crossovers as needed. Electrically, everything between the two balloon loops is wired linearly, as in "black to back, red to front" for both mainlines. This necessitates a reversing section on the mainline at each end, such that southbound trains on one mainline can be looped back to become northbound trains on the other mainline (and vice versa at the other end). This lowest level consists of the turnouts from the double mainline and the start of the staging yard throat, and of course the balloon track reversing loop. This is a DCC layout in N scale, with testing currently being done with a BLI F3 with Paragon 3 sound being run by an older Digitrax Zephyr (DCS51) because I inadvertantly left the Digitrax EVO (DCS210, not the 210+) destined for this layout in our storage unit last week. No circuit breakers, but eventually I'll split the layout into power districts with a PM74, just haven't gotten that far into the build yet to need more than 1 district.
Anyhow, had a slight issue with the AR-1 I picked up for the reversing loop. The relay would click, but the Zephyr circuit protection would trip and power cut to the layout. Per the AR-1's instructions in such a situation, I attempted to dial down the trip current, and ended up taking it all the way to the minimum of 0.25 amps, but the Zephyr still tripped. Double checked wiring and gaps, no obvious issue observed. Gaps are maybe about 1/16th inch wide and even with each other on straight sections of track, although one gap is probably closer to about 1/32nd inch. Disconnected the reverse loop feeders from the AR-1 and attempted to run into the loop, thinking if I accidentally wired a loop feeder to the main bus or there was a bridged gap I couldn't see, my test loco would continue into the loop. But as expected, this test stopped the loco cold at the gaps. So I knew it most likely was someting with the AR-1 or the Zephyr. (If a gap was bridged on just one rail, the loco still would have stopped at the gap. But I really doubted this was the case.) 45 minutes searching the interwebs, and I found the solution: op switch 18 to closed to change the Zephyr's trip time from 1/8th second to 1/2 second, otherwise the Zephyr is just too fast for the AR-1. Worked like a champ (well, mostly... still dialing in the trip current limit on the AR-1, and sometimes I still get a very brief Zephyr short stoppage. No big deal, it still needs more testing running the locos in all possible orientations and directions and notes taken to see if it's random or a regular, predictable event, but I'll hammer out the dents over the next few days.)
But the whole experience got me thinking. So, I'm testing with a single sound loco at the moment, right? But my typical lash-ups once the layout is slightly more operational will be 3 or 4 locos, some with sound and some without. Obviously, there's going to be a bit of a difference in current draw depending on which mainline freight happens to be passing through the reversing loop. I haven't measured but going by some generalizations I've seen online for N scale locos, if I have a train pulled by a non-sound ABBA set of cab units pulling 0.25 amps each that'll be about 1 amp in the reversing loop, but if a train has an ABBA sound set pulling 0.5 amp each, that'll be about 2 amp in the reversing section. And if I run a local turn pulled by two non-sound RS units that would be closer to about 0.5 amp combined. (Give or take, of course.)
What would be the best practice for setting the AR-1's trip current? Maximum anticipated amp draw or minimal? If I dial in the AR-1 for the maximum expected draw, how might that affect the occassional low-amp trains that might pass through the reversing section, such as that local peddler which would nominally only have 2 lead units?
Once I transition over to the EVO, will I have the initial issue of the command station tripping before the AR-1, like I had with the Zephyr? Sad to say, I got the EVO about 3 years ago, but only had it out of the box for maybe an hour... Not really familiar with it yet. Life got in the way and this new layout was delayed.
Would I ultimately be better off using one of the four Detection Sections of the PM74 for auto-reversing versus using an AR-1? I assume the PM74 is solid state, versus the relay of the AR-1, so that should be a quicker phase switch for auto-reversing, right? I haven't heard any feedback from folks using a PM74 for auto-reversing (but haven't really looked specifically for that, either, so I might have stumbled over someone mentioning using one as such but it didn't stick in the ol' noggin), can anyone offer a quick review of your experience using it in that role?
Thanks for reading!
-Jason
jkovacs5What would be the best practice for setting the AR-1's trip current?
the AR trip current needs to be higher than the expected current drawn by any train(s) in the reverse loop.
the AR trip current needs to be lower than than max supplied current (3A?) of the booster (i.e. Zephyr).
when the metal wheels bridge the rail gaps the short circuit current should be equal to the max current supplied by the booster
the AR should trip faster than the booster.
greg - Philadelphia & Reading / Reading
Might want to try another brand for reversing like frog juicers.
I am going to take this off topic for a couple of minutes but I had a low clearance yard and reverse loop on a previous layout. you can not put in enough atlas rerailers in the loops and after every turnout. Rerailing derailed cars can be a nightmare. Trust me on this.
I long ago replaced the Digitrax AR1 with a solid state auto reverser. In my case, I use the PSX-AR. The AR1 simply reacts too slowly.
Rich
Alton Junction
I think the only way to do it is "real world" testing - just run each engine or combination of engines you plan on using through the reverse loop, and adjust the AR-1 up or down until they all go through OK.
I had trouble with one of my reverse loops where everything worked fine say going around clockwise, but the other way the reverser wouldn't trip, or would keep tripping back and forth. Eventually found one of the wires connected to one rail of the reverse loop was also connected to a rail of the mainline. It wasn't enough to trip the DCC system's short circuit shutdown, or even to stop the engine, but threw off the AR-1.
I've also had a couple of sound equipped engines that balked going into a reverse loop no matter what. Adding a capacitor or one of the "keep alive" type devices to the engine seems to solve the problem.
ndbprr I am going to take this off topic for a couple of minutes but I had a low clearance yard and reverse loop on a previous layout. you can not put in enough atlas rerailers in the loops and after every turnout. Rerailing derailed cars can be a nightmare. Trust me on this.
And while we're off the topic...
You mentioned that you plan on subdividing your layout into power districts, but not immediately. Mine is divided, but only after a long time. I realized too late that I didn't separate my track and bus structure to provide for power districts until it was too late. So, my separation was far from optimum. Given that you are building a second level on top of the lower one, it might be a good idea to divide things into power districts now before it gets to be impossible.
For my reverse loops, I went with solid-state devices immediately. They've always worked perfectly.
It takes an iron man to play with a toy iron horse.
Oh, I know that frustration all too well. I'm upgrading to a little less than a 1-car garage sized layout from 8 years of stuffing too much stuff into a small apartment bedroom.
On this one, the low clearance is like 5" vertically on a shelf only 7" deep for about 3 ft, and one side is fully exposed and accessible right from the main aisle. The yard itself has about a foot of overhead clearance, and the reversing loop is primarily behind a backdrop within a very accessible helix. Only the start of the yard throat and the start/end of the reversing loop are in the lower clearance area. But there's more than enough clearance to rerail anything that goes to ground, or clean track or other simple maintenance. Cutting in a new turnout or wholesale redoing the track work, that's when the low clearance would be a real challenge.
MisterBeasley And while we're off the topic... You mentioned that you plan on subdividing your layout into power districts, but not immediately. Mine is divided, but only after a long time. I realized too late that I didn't separate my track and bus structure to provide for power districts until it was too late.
You mentioned that you plan on subdividing your layout into power districts, but not immediately. Mine is divided, but only after a long time. I realized too late that I didn't separate my track and bus structure to provide for power districts until it was too late.
Hi Mr Beasley,
Yes, I misspoke a bit there. When I said I'm not immediately putting in power districts, I meant just that I'm not that far into the build to where the first district division would even be yet. I've already planned where those division breaks will be and will gap the track and run busses accordingly when I get that far.
I'm seriously considering upgrading to solid state reversers right away. Minimize any issues down the line. The solid states, or at least the PSXX-AR I've mostly researched, seem a lot more customizable for trip current AND timing than the AR-1, which only allows a rather low-precision trip current adjustment. I may try a Frog Juicer as an immediate alternative to test, as I have them laying around, but that PSXX-AR has really caught my eye.
richhotrain I long ago replaced the Digitrax AR1 with a solid state auto reverser. In my case, I use the PSX-AR. The AR1 simply reacts too slowly. Rich
Thanks Rich. I am very strongly considering doing exactly the same.
gregc jkovacs5 What would be the best practice for setting the AR-1's trip current? the AR trip current needs to be higher than the expected current drawn by any train(s) in the reverse loop.
jkovacs5 What would be the best practice for setting the AR-1's trip current?
Thanks Greg, that makes sense. Set it for the maximum load from any and all expected trains in the section at a time (just 1 possible in my case) but less than the trip current of the booster.
To make sure I'm following the logic right, the trip current setting in the reverser basically sets a lower amp limit at which to flip the phase, right? So set it to the highest expected draw, and the reverser won't see those amps drawn by trains as a short no matter how limited the draw is (for single-unit trains, say, versus the 4-unit jobs) until the train bridges the gap. Then the reverser senses the full amps from the booster (3 for the DCS51, 5 for the DCS210), trips before even reaching the full booster amperage, and flips the phase. Timing is everything though, as the reverser needs to be quicker than the booster. I think that about covers it?
Thanks for the help everyone. I guess this means I should be breaking out that sound ABBA set for my testing/dialing in of the reversing loop. Oh darn, shucks, what a bummer! Seriously though, I need to test performance on a grade anyway, so seems like a perfect time to unpack those and a string of cars, get this reversing section hammered out before some hardboard goes up and limits the easy access.
And I think I'll pick myself up a solid state reverser too, see how that compares to the AR-1 myself. I'm pretty confident I want to go that route now anyway, save myself some potential headaches down the line. I have a (much smaller) side project where I could use those AR1s in a much less critical situation, so it's no real loss spending some more on a couple solid states now for the "real" project.
Thanks again!
jkovacs5 richhotrain I long ago replaced the Digitrax AR1 with a solid state auto reverser. In my case, I use the PSX-AR. The AR1 simply reacts too slowly. Rich Thanks Rich. I am very strongly considering doing exactly the same. -Jason
jkovacs5To make sure I'm following the logic right, the trip current setting in the reverser basically sets a lower amp limit at which to flip the phase, right? So set it to the highest expected draw, and the reverser won't see those amps drawn by trains as a short no matter how limited the draw is (for single-unit trains, say, versus the 4-unit jobs) until the train bridges the gap. Then the reverser senses the full amps from the booster (3 for the DCS51, 5 for the DCS210), trips before even reaching the full booster amperage, and flips the phase. Timing is everything though, as the reverser needs to be quicker than the booster. I think that about covers it?
good summary