We have a rather large layout, equipped with a Digitrax Super Chief operating system. A recent addition of about 800' of track has two reversing loops, long enough to accomodate 100 car trains. These loops experience intermittent shut downs, which have has us puzzled. Calls to Digitrax have not resolved the problem. Trains run through the loops for a period without incident, then after a while, trip the PM42 circuit breaker protecting the loop trips every time thereafter. The booster is not shutting down, as in high temperature, the breaker just trips and won't reset without pulling the locomotives through the track gaps. Obviously if this was caused by a wiring error, it would occur from the start, which it does not. Anyone have a thought about this?
What are you using as the auto-reverse for the reverse loops? If you are using one of the PM42 circuits what are the other PM42 circuits being used for?
Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum
Eight hundred feet of track? That sound like hundreds of feet of track bus lines, in any case. How big are your bus wires? (And the answer had better be #12 or even better, #10 wire.)
I'm guessing that the lines are too long, and you may actually have a short somewhere along the line. Have you tried the "quarter test?" Power up the loop, no trains, and put a quarter across the rails. The breaker should trip immediately. Try this every 10 feet or so all the way around the loop. When bus lines get too long, or if the bus wire is too small, the round-trip resistance of the wires is high enough to keep a circuit breaker from tripping, even on a dead short. In a marginal case, the breaker might trip intermittently like yours.
Alternately, have you tried swapping the problem district to a different PM42? Or adjusting its sensitivity?
It takes an iron man to play with a toy iron horse.
Victor We have a rather large layout, equipped with a Digitrax Super Chief operating system. A recent addition of about 800' of track has two reversing loops, long enough to accomodate 100 car trains.
We have a rather large layout, equipped with a Digitrax Super Chief operating system. A recent addition of about 800' of track has two reversing loops, long enough to accomodate 100 car trains.
I'd sure like to see photos of that layout.
Check the voltage at the distal ends of the bus as well as doing the quarter test. You might need to add a booster. Perhaps a large bus that just connects major portions of the layout with each section powered by a lighter sub bus.
Dave
Lackawanna Route of the Phoebe Snow
Another thing you can do is re-locate the PM42 or reverser to the middle of the loop to reduce resistance. Also put a small fan behind the command station and the boosters. Digitrax units trip at a pretty low temperature. If you are running at half or more capacity they tend to heat up some and not handle shorts. Mine did the same and a fan corrected it. I picked up the fan at a Target store. It's about 3 or 4 inches in diameter and cost about 6 bucks. It's very quiet to boot.
Springfield PA
Thanks to all those who responded so quickly. I appreciate the time and thoughts. The layout is powered by a Digitrax 20 amp supply, through a DCS200 command station, and two DB200+ boosters. Several PM42's are used for districts, and several AR1's for various reverse loops. The AR1's are connected through PM42 breakers. Bus wire is 12 gauge, track jumpers every few feet are 18 gauge, and rail joiners are soldered. Using Peco code 83 track and Insulfrog switches throughout. Have tried the "quarter trick" and PM42's shut down, but have not tried moving throughout the length of the loops while doing this, so I'll give that a try. Also tried swapping PM42 and AR1 units, with same results. Have adjusted both throughout the ranges, with no improvement. Track voltage is about 14.6, amps with the heavy trains about 2-3, with several trains operating amps have reached 5.0.
It seems odd that the train runs for a few "laps", then shuts down crossing track gaps every time thereafter. Found that setting PM42 trip current above 7.5 amps makes them ineffective, as the DB200 rated at 8 amps then shuts down before the PM42. With the current load of the single train at 2 amps, I wouldn't think the PM42 needs to be much greater anyway. Will try the quarter trick throughout and see what happens.
I was going to paste a schematic of this area of track, but cannot figure out how to attach a jpeg here.
If the wirign order is booster to PM42 to AR1 to track, if the PM42 trips out then the AR1 isn't sensing the short as the train crosses the gaps, or it's not set quit right so that it trips and reverses before the PM42 can drop. Besides current, PM42's also have a setting for response speed. You may need to reduce the response time on that PM42 section so the AR1 has time to act first. It follows up the chain, with the booster set on the slowest response, the PM42 next, and then the downstream reverser for fastest (althouhg AR1's don;t have a speed adjustment, so you end up setting the PM42 to accomodate them).
Is it ANY train, after a time of running, or only the larger ones? One single reversed feeder out of all of them could cause problme slike this, where there's not enough current flow in the single feeder to be seen as a short all the time, but add enough powered locos or lighted cars and the valid current draw plus the leakage ends up exceeding the trip point for the breaker.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Why use AR1's at all? You can set-up the PM-42's as reversers. I would also caution setting to 7.5 amps or anthing even close. That much current can easily fry electronics during a short
Randy,
Good suggestion. You described the order they're wired in, booster to PM 42 to AR1. We'll try setting PM42 to slowest reaction. The problem occurs with any train, short or long, and even just "light" locomotive. Just seems to be related to the amount of time the track is powered.
We're using AR1's at the suggestion of Digitrax. They said if using the PM42 as the reverser, then use an adjacent PM42 relay for circuit breaker protection. I agree, 7.5 amps is too much, we just tried it to see if anything changed, which it did not.
AR1 is fine here. It used to be in the PM4/PM42 manual about using the same PM42 for both a breaker and auto reverse, just jumpring two sections together, but they removed that and no longer recommend doign that because people have had problems. The AR1, being a single unit, can be placed where the reverse loo is, whereas for 2 loops not near one another you'd end up using 2 PM42s to avoid extremely long bus runs, and use one section of each, wasting 3 sections on each one. A rather expensive proposition when the AR1 is just as effective and cheaper. And easier to set up since it's just a potentiometer adjustment, no CVs.
Victor We're using AR1's at the suggestion of Digitrax. They said if using the PM42 as the reverser, then use an adjacent PM42 relay for circuit breaker protection. I agree, 7.5 amps is too much, we just tried it to see if anything changed, which it did not.
Are you using a separate PS14 or equal power source for each PM42 and AR1. If not you should be as they may be under powered.
Ken G Price My N-Scale Layout
Digitrax Super Empire Builder Radio System. South Valley Texas Railroad. SVTRR
N-Scale out west. 1996-1998 or so! UP, SP, Missouri Pacific, C&NW.
You can do a couple of PM42's with a single PS14. According to the manual the PM42 requires 125ma. The PS14 is rated at 300ma.
While you want to make sure those PM42's are powered by at least 12 VDC so they trip when shorted, low or no power wouldn't cause them to trip by mistake.
PM42's are normally closed by default. The auxiliary power is what energizes the relays to trip when a short is detected. AR1's use track power.
Martin Myers
What are you using to power your DB200s? The standard Digitrax power supply will not allow them to get to the rated peak power. Digitrax and others make higher rated power supplies and you may wnat to research that.
Ricky