I was just reading a post where in someone said that more than one reversing loop could be connected to a single auto reverser. So my question is "What is the limit on how many reversing loops can be connected to a single auto reverser and are there any "as long as........" parameters that have to be followed?
Thanks
wdcrvr
That is correct.
A single auto-reverser unit may be used to control more than one reversing section (or loop as you call it).
However, only one train at a time may be entering or leaving the multiple reversing sections controlled by a single auto-reverser unit .
In theory, there is no limit to the number of reversing sections that may be controlled by a single auto-reverser unit. But, from a practical point of view, even as few as two reversing sections may be problematic.
Rich
Alton Junction
DCC specialties has the OG-AR for about $40. They work super fast and best of all no adjustments needed. I think there is a 3 amp limit for them. If for some reason your reverse loop buss has a draw of more than 3 amps there could be risk of failure. Another thing that would cause problems with control of more than one reverse loop is if the polarity is already flipped when the other section gets tripped it would sense a short and shut down.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
locoi1sa Another thing that would cause problems with control of more than one reverse loop is if the polarity is already flipped when the other section gets tripped it would sense a short and shut down.
Another thing that would cause problems with control of more than one reverse loop is if the polarity is already flipped when the other section gets tripped it would sense a short and shut down.
Nope, that's the beauty of it. As long as there is only one boundary crossing at a time, it doesn't matter how many time the phase gets flipped. Remember, you can flip the phase under any train that is completely in the reversing section as many times as you want, and it doesn't matter.
Jeff But it's a dry heat!
Odd all these auto-reversing questions are suddenly popping up.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
DigitalGriffin Odd all these auto-reversing questions are suddenly popping up.
DG,
I agree. I suspect that what is happening is that a lot of interest has been generated by a few of the earlier posts, so people start thinking about auto-reversers and begin asking questions about them.
As I review all of the recent posts, many of them are about layouts under construction as opposed to problems with reverse polarity on existing layouts.
Hopefully, everyone is making hard copies of these threads for future reference. A lot of helpful information being exchanged reagrding auto-reversing units and issues with reverse polarity.
Vail and Southwestern RR Nope, that's the beauty of it. As long as there is only one boundary crossing at a time, it doesn't matter how many time the phase gets flipped. Remember, you can flip the phase under any train that is completely in the reversing section as many times as you want, and it doesn't matter.
As long as one boundary is crossed. Yes. What would be the chance of crossing 2 boundary at a time? Without seeing a track plan the chances are good that 2 boundaries could be crossed. If the gaps are directly across from each other then every metal wheel set crossing it will trip it. If you spread the gaps about 3/16 apart then it would take a loco or a lighted car with pickups in each truck to trip it.
locoi1sa Vail and Southwestern RR: Nope, that's the beauty of it. As long as there is only one boundary crossing at a time, it doesn't matter how many time the phase gets flipped. Remember, you can flip the phase under any train that is completely in the reversing section as many times as you want, and it doesn't matter. As long as one boundary is crossed. Yes. What would be the chance of crossing 2 boundary at a time? Without seeing a track plan the chances are good that 2 boundaries could be crossed. If the gaps are directly across from each other then every metal wheel set crossing it will trip it. If you spread the gaps about 3/16 apart then it would take a loco or a lighted car with pickups in each truck to trip it. Pete
Vail and Southwestern RR: Nope, that's the beauty of it. As long as there is only one boundary crossing at a time, it doesn't matter how many time the phase gets flipped. Remember, you can flip the phase under any train that is completely in the reversing section as many times as you want, and it doesn't matter.
Well, if the operator only runs one train at a time, he wouldn't have a problem. I would just have a reverser for each reversing section, but with the caveat that only one boundary can be crossed at a time, it's not necessary.
A single metal wheel bridging the gap on a single rail does cause a short, and will set off the reverser. Staggering the gaps still gives allows a single wheel to cause a short. I imaging that it's pretty rare that even gaps that we think are directly across from each other actually short at the exact same time. Staggering the gaps prevents a autoreverser from potentially seeing two shorts in such quick succession that it thinks it need to flip the phase twice. I expect that this is more important with the relay based reversers than the solid state ones. (Actually, with a very little work in the design of the reverser it should never be an issue anyway, but it seems that don't all account for that possibility.)
I see a lot of questions about how many loops could be controlled by a single auto reverser. Let me answer the the question like the engineer I am. No one ever thought about asking the question of how a 5 amp rated auto reverser trips when only a 3 amp booster is used. Knowing this you can figure out how many loops an auto reverser can control or if the gaps in a track must be stagered. Try this little trick and it sure gives problems. Use a lot of thin wire on the output side of the auto reverse an you find that it doesn't work. If the resistance of the wire is high enough the short only causes a voltage drop and not a power outage that is necessary for the reverser to change states. There is the answer; keep the reverser local where it is needed to eliminate problems and use the standards the NMRA has about wiring.
By the way, staggered gaps is a structured thing not electrical.
DR Chess I see a lot of questions about how many loops could be controlled by a single auto reverser. Let me answer the the question like the engineer I am. No one ever thought about asking the question of how a 5 amp rated auto reverser trips when only a 3 amp booster is used. Knowing this you can figure out how many loops an auto reverser can control or if the gaps in a track must be stagered. Try this little trick and it sure gives problems. Use a lot of thin wire on the output side of the auto reverse an you find that it doesn't work. If the resistance of the wire is high enough the short only causes a voltage drop and not a power outage that is necessary for the reverser to change states. There is the answer; keep the reverser local where it is needed to eliminate problems and use the standards the NMRA has about wiring. By the way, staggered gaps is a structured thing not electrical.
So, what is the conclusion that should be drawn? One auto reversing unit for each reversing section?
As for your example, wouldn't too thin a wire on the output side still result in problems with only one reversing section wired to the auto reverser?
richhotrain ... So, what is the conclusion that should be drawn? One auto reversing unit for each reversing section? ...
...
I depends on the layout and operation style of the users. One auto reverser per reversing section is certainly the most flexible and least likely to give problems, but also definitely not necessary in some situations.
As far as not being able to cross the boundary of two loops running off of one reverser at the same time, that's not entirely true; although it's not a bad rule to have to ensure no problems. Each reversing section has two electrical boundaries(depending on the layout of the track there can be more than two physical boundaries, but still only two electrical boundaries). When one boundary is in phase, the other will be out of phase and vice-versa. Say you have a layout with two reversing sections, section 1 and 2, running off the same reverser. Each section has boundaries A and B, so you have boundaries 1A, 1B, 2A, and 2B. When 1A is in phase, then either 2A or 2B will be in phase, and whichever one is in phase with 1A can be crossed at the same time as 1A. For example, if 1A and 2A are in phase at the same time, 1A and 2A can be crossed at the same time and 1B and 2B can be crossed at the same time. Basicaly what it comes down to is since the two reversing sections are electrcally common, there are only two electrcal boundaries - in the above example, 1A and 2A are the same electrical boundary and 2A and 2B are the same electrical boundary.
It is not the number of loops it can control but the limited is how close the auto revesers is to the detection point to detect a solid short. Not to mention the statistical probability of multiple locos bridging gaps in multiple loops. I don't consider wheel shorts as a big problem because the piriod of the short is less than the momentum that will carry the train.
Since you're looking for a number, if a best buss system could be used, it is alway one more than what you have connected. There is no limit on number. The limit is wiring.
DR Chess It is not the number of loops it can control but the limited is how close the auto revesers is to the detection point to detect a solid short... The limit is not just the distance from the auto reverser to the detection point, but a combination of wire size and distance. With thicker wire you can have the reversing section further from the reverser. The problem is the thinner the wire the higher it's resistance and the longer the wire the higher it's resistance. If the resistance is to high, the reverser will not see the short. For example, if your reverser trips at 3 amps and there is enough rsistance in the wiring that a short will only draw 2.5 amps, the reverser will not see the short.
It is not the number of loops it can control but the limited is how close the auto revesers is to the detection point to detect a solid short...
The limit is not just the distance from the auto reverser to the detection point, but a combination of wire size and distance. With thicker wire you can have the reversing section further from the reverser. The problem is the thinner the wire the higher it's resistance and the longer the wire the higher it's resistance. If the resistance is to high, the reverser will not see the short. For example, if your reverser trips at 3 amps and there is enough rsistance in the wiring that a short will only draw 2.5 amps, the reverser will not see the short.
Your missing the point. As I stated earlier why does a 5 amp rated auto reverser trip when supplied by a 3 amp booster. I would suspect that is is not current that trips the unit, it is the voltage drop. Too high of resistance because of poor wiring will not allow the voltage to drop enough for the tripping of the auto reverser. So the rating of some, not all, on an auto reverser is more than likely related to the relay or FETs used and not the trip point. Adjustments more than likley allow offset to accommodate the resistance.
Of course, auto reversers are not needed if turnouts are connected to DPDT by a tortoise or blue point remote throw. Only going through a turnout that is not selected will cause the short, it might save a derailment. This is DCC and trains only run backwards when commanded.
I am not making any sense out of these recent replies.
Back in October when then this thread started, the OP asked, "So my question is, What is the limit on how many reversing loops can be connected to a single auto reverser".
This recent, rather esoteric, discussion doesn't really seem to have a point related to this question.
DR Chess Your missing the point. As I stated earlier why does a 5 amp rated auto reverser trip when supplied by a 3 amp booster. ...
Your missing the point. As I stated earlier why does a 5 amp rated auto reverser trip when supplied by a 3 amp booster.
Because auto reversers are generally designed to trip faster than the booster circuit breaker. When you have a short, you will have peak currents greater than the rated output of the booster. If those peak currents are high enough and the reverser trips fast enough, you can have a reverser work although it is set for a higher current than the booster is rated for. I suspect it quits working when you use long thin wire on the output of the reverser because you are reducing the peak current of the short to below the reverser's trip point.