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Auto Reversing Problem still, a year later

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  • Member since
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  • From: Millarville, Alberta. Canada
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Posted by CPbuff on Friday, October 16, 2020 12:12 PM

Another update! To isolate the problem, I have removed all feeds from the layout (as I use terminal blocks under the layout for trouble shooting) except for one located on the top track where the "A" is on the diagram, I reversed polarity too and the problem continues, I moved the feed to where the "B" is on the top of the diagram and tried both polarities and the problem continues, so I am going back to thinking somethings wrong with the AR, although all AR's bench tested fine... ( using a process that MRC supplied to me a while back)...

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Posted by rrinker on Friday, October 16, 2020 1:21 PM

 Easy to test. Bypass the AR. Connect the loop tracks with the feeders matching one of the two tracks, for example, on the top loop, if you have the rail to the top of the digram as A, and the rail towars the bottom as B like where the A abd B are in the top left, then wire the loop the same way so that on the loops ide of the upper right gap, the top rail is A and the bottom rail B.

 Now a train should smoothly run into the loop at the top right, crossing those gaps with no problem. Main to loop, loop to main. There WILL be a short if you attempt to cross the gaps at the bottom of the upper loop though, because now the polarity is backwards across the gaps.

If this works, and there's no reason it shouldn;t, put the AR back in place. If the train will no longer enter/leave the loop at the upper gaps, there is something wrong with the AR. If it goes in, but shorts coming out, reverse the feeds to the AR with the train in the loop. If it now comes out of the loop fine, that points to the AR not reversing. If the AR is not working, then the train should now cause a short at the upper gap, because the loop polarity no longer matches the track on the other side of that gap.

ANd if you get a short as soon as you turn on the power - that means you don't have both rails gapped at each end of the loop. Or a feeder from outside the gap connects to a rail inside the gap, or vice-versa.

                              --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by Lastspikemike on Friday, October 16, 2020 2:23 PM

An object lesson here is to wire the reversing loop for fully manual operation and get it to work. Only then fit the auto reverser.  The loop has to work in one direction with no polarity change. Only when leaving the loop is it necessary to have changed the polarity (phase for DCC). 

For DC it is easiest to reverse the main line polarity while the train is entirely within the reversing loop. 

For DCC it is easiest to reverse the loop polarity, but also while the train is entirely within the reversing loop. 

Plastic wheels on the last few cars of a train will allow longer than loop trains to work.  

Also, in this particular case, the length of both of the connecting tracks between the facing reversing loops also needs to be longer than the longest train of metal wheeled cars. 

Alyth Yard

Canada

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Posted by richhotrain on Friday, October 16, 2020 4:50 PM

Lastspikemike

An object lesson here is to wire the reversing loop for fully manual operation and get it to work. Only then fit the auto reverser.  

I have never felt the need to do that. If the reversing section is longer than the longest train and fully gapped, then install the auto-reverser and make sure that all feeders powering the reversing section are wired to the output side of the auto reverser. That's all there is to it.

Rich

Alton Junction

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Posted by richhotrain on Friday, October 16, 2020 4:55 PM

rrinker

 Easy to test. Bypass the AR. Connect the loop tracks with the feeders matching one of the two tracks, for example, on the top loop, if you have the rail to the top of the digram as A, and the rail towars the bottom as B like where the A abd B are in the top left, then wire the loop the same way so that on the loops ide of the upper right gap, the top rail is A and the bottom rail B.

 Now a train should smoothly run into the loop at the top right, crossing those gaps with no problem. Main to loop, loop to main. There WILL be a short if you attempt to cross the gaps at the bottom of the upper loop though, because now the polarity is backwards across the gaps.

If this works, and there's no reason it shouldn;t, put the AR back in place. If the train will no longer enter/leave the loop at the upper gaps, there is something wrong with the AR. If it goes in, but shorts coming out, reverse the feeds to the AR with the train in the loop. If it now comes out of the loop fine, that points to the AR not reversing. If the AR is not working, then the train should now cause a short at the upper gap, because the loop polarity no longer matches the track on the other side of that gap.

ANd if you get a short as soon as you turn on the power - that means you don't have both rails gapped at each end of the loop. Or a feeder from outside the gap connects to a rail inside the gap, or vice-versa.

                              --Randy 

My guess is that a feeder is miswired.

Rich

Alton Junction

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Posted by richhotrain on Friday, October 16, 2020 5:16 PM

CPbuff

Another update! To isolate the problem, I have removed all feeds from the layout (as I use terminal blocks under the layout for trouble shooting) except for one located on the top track where the "A" is on the diagram 

That is quite confusing. If you removed all feeds from the layout except for one, you would lose power as the loco crossed over from the non-reversing section to the reversing section. You would need at least two pairs of feeders, one powering the non-reversing section and one powering the reversing section.

Rich

Alton Junction

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Posted by BigDaddy on Friday, October 16, 2020 7:02 PM

richhotrain
That is quite confusing. If you removed all feeds from the layout except for one, you would lose power as the loco crossed over from the non-reversing section to the reversing section. You would need at least two pairs of feeders, one powering the non-reversing section and one powering the reversing section.

I assume he still had the reverser in the circuit.

But I still don't understand.  It is unlikely that 3 AR's are bad.  I remember a previous thread about a short and it turned out to be part of a DC bus, still wired to a DCC system that the OP forgot about.

There is still something missing that neither the we nor the OP realize.

Henry

COB Potomac & Northern

By the Chesapeake Bay

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Posted by CPbuff on Sunday, October 18, 2020 10:23 AM

Just some clarification for some of you! This is a brand new layout of which is only DCC and I have never owned DC anything.  The MRC Auto reverser takes power from the track only ( not the bus) and supplies power to the inside of the loop allowing the loco to continue around, when the loco leaves the loop the AR should? automatically change the polarity to match the track feed leaving the loop. Thats why only one track feed is required , When coming into the AR before the AR gap, the feed is the same as the feed and polarity after it exits the gap leaving the loop! I am working through Ricks suggestions and I will let you all know later!

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Posted by rrinker on Sunday, October 18, 2020 10:54 AM

 Do you have the AR hooked up the right way? Input and output are not interchangeable. Red goes to the main bus, yellow feeds the loop. You should probably have a short bus under the loop and more than one feeder to the rails, with that loop bus powered by the yellow wires from the autoreverse. 

 Inadequate feeders can cause the autoreverser to not flip, if it does not sense a current that exceeds the trip point. The MRC unit has no adjustment, so it either works or it doesn't. You should get a click out of it if you short the rails, before the system shuts down, if it is working. 

Another possibility is that the trip time of the MRC AR is too slow to work with your DCC system - what system are you using? If the main breaker trips faster than the AR, you will have the problem you are experiencing.

                                         --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by richhotrain on Sunday, October 18, 2020 10:58 AM

OK, that clarification definitely helps. So, that explains the feeder protocol with the MRC Auto Reverse Module (see the diagram below in the next reply). With no feeders connected to the bus, the MRC AR Module receives power from the non-reversing section of track (red wires) and carries that polarity into the reversing section of track. Have you connected the two yellow wires the same way as the two red wires (inner to inner and outer to outer)?

Rich 

Edit Note: Randy types faster than I do. Laugh

Alton Junction

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Posted by richhotrain on Sunday, October 18, 2020 11:05 AM

MRC-AR.jpg

Alton Junction

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Posted by rrinker on Sunday, October 18, 2020 1:49 PM

 It shouldn't matter which way the yellow wires are conencted, as these are the ones that change phase when the reverser flips. One way, it will match the top but not the bottom initially, the other way it will match across the bottom gaps but not the top ones initially. When the gaps are crossed, it should flip the yellow wires so it matches the phase across the gaps.

 Even if the AR doesn't work, or if it fails to trip before the main booster, a train should be able to cross one set of gaps, since the phase has to match on one end no matter what. It will fail on the other end if the AR isn't working, but crossing one set of gaps should always work - it would work that much even if the AR was not in the circuit.

                                   --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by CPbuff on Sunday, October 18, 2020 3:01 PM

Thanks again Randy! I did your diagnostics and have figured out that the brand new AR is failing! 2 AR failures in the last 2 years... I took the last AR I had from the lower loop placed earlier and moved it to the upper loop and everything seems to be working for that loop(upper), so now I have to purchase another AR... but with the luck I've been having with MRC, would a Digitrax AR work on the lower loop even though we have a MRC AR on the upper loop?

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Posted by richhotrain on Sunday, October 18, 2020 3:29 PM

OK, so you have a "good" AR that works on the upper loop with no issues entering or exiting the upper loop. Does that "good" AR also work on the lower loop with no issues entering or exiting the lower loop?

Rich

Alton Junction

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Posted by rrinker on Sunday, October 18, 2020 4:21 PM

Just get a PSX-AR and be done - more expensive, but they work with nearly anything, and have options for some remote indicators to tell you what's going on.

 Digitrax is more or less replacing the AR-1 with the BXPA1, which is a solid state  auto reverser, breaker, and block detector all in one, but unless you use Loconet, the block detection feature is pretty much useless. The PSX-AR is an AR and breaker in one as well - if flipping the loop doesn;t fix the short, the unit will completely disconnect power to the loop track. The MRC AR and the AR-1 don't do this.

                              --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
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Posted by richhotrain on Monday, October 19, 2020 7:22 AM

CPbuff

I did your diagnostics and have figured out that the brand new AR is failing! 2 AR failures in the last 2 years.

I doubt that the AR is failing. I suspect the problem is that the MRC AR operates on a mechanical relay and reacts slower than your DCC booster. So, a short is recognized by your booster faster than the MRC AR can react.

I had a similar problem when I was using Digitrax AR1s for my reversing sections on my old layout. The Digitrax AR1s worked just fine until I decided to break my old layout into power districts controlled by PSX circuit breakers. The PSX with its solid state relay would trip faster than the AR1. So, I replaced the Digitrax AR1s with PSX-ARs and everthing worked fine once again.

But before running out and purchasing a couple of expensive PSX-ARs, I would install a temporary DPDT switch on that lower reversing section and manually operate the lower loop to make sure that it is wired and gapped correctly.

Rich

Alton Junction

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Posted by Lastspikemike on Monday, October 19, 2020 11:17 AM

MRR book DCC Projects and Applications, Vol 3 page  28-29 and Vol 4 page 26-27 probably describes your problem. They point out that not all boosters work with all ARM even if the ARM triggering time is adjustable.

The issue is speed. The ARM must reverse the polarity faster than and at lower amperage than the short circuit protector in the booster.  If you experience a main power cut when your ARM seems not to work then likely that is the issue. It will appear to work in one direction because there's no polarity problem entering from one of the two directions. 

The ARM is just a pretty sensitive short circuit protector that reverses polarity instead of shutting down the power. By installing an ARM you put two "circuit breakers" in series. The one shuts off the power only for a nano second while it reverses the power connection to the reversing loop. That way the decoder never "sees" a power cut. More importantly, the booster never sees the short because the ARM works faster. But if the ARM is just a tiny bit too slow it will trip too late and the booster circuit breaker operates instead. Solid state ARM are faster than relay types, and cost more.

If the main booster "sees" the short "first" then it will cut power to its entire power section.  The ARM will see the short and not have time to reverse polarity before the booster shuts it down.

On one of my reversing loops, running DC, I use an old fashioned Atlas Snap Relay wired to a turnout switch as if to a frog but wired into the power to the reversing loop instead. I could and probably will wire it to the turnout frog as well. 

When the points for the turnout are thrown the polarity inside the loop reverses. This is the same way you wire a reversing loop for DCC. Normally, you wire opposite to that for DC, throwing the turnout points would reverse the main line but that wouldn't work for me because other locomotives might be affected while running in other blocks. Plus, I want to hook up my MRC Tech 6 to run DCC on occasion and I wanted the layout to accommodate that with no fuss.

The trick there is to allow for enough line between the turnout and the isolating gaps setting the limits to the reversing loop to allow the operator to throw the points. The locomotive(s) must be out of the loop, and the last car with steel wheels inside the loop before the points are thrown. Now, if you fully automate a reversing loop using DCC you need a similar lead time for the ARM to reverse polarity and throw the points plus you need to wire it so the trailing car(s) are inside the loop before the points are thrown.

As suggested by others, try wiring your reversing loop with a manually operated DPDT switch (or snap relay if you have one lying around, which is a solenoid actuated DPDT switch which will possibly work quickly enough to avoid a power drop out) and check that your wiring is correct and the polarity reversing works correctly. When all is well the ARM should slip right in place of your DPDT in  the wiring you will then have.

Alyth Yard

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Posted by wjstix on Wednesday, October 21, 2020 1:33 PM

It wouldn't be a bad idea as suggested to wire the section up to a toggle to work the reversing section manually. If that works fine, then the problem is with the auto-reverser. However, that may not mean the reverser is defective!

IIRC, the MRC auto-reverser doesn't have a sensitivity adjuster; Digitrax does. It may be you've wired everything OK, but the sensitivity of the AR isn't quite right. On my Digitrax AR it took a couple of test runs to get it set just right so it worked properly every time.

 

Stix
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Posted by gregc on Wednesday, October 21, 2020 1:50 PM

wjstix
It wouldn't be a bad idea as suggested to wire the section up to a toggle to work the reversing section manually. If that works fine, then the problem is with the auto-reverser. However, that may not mean the reverser is defective!

+1

greg - Philadelphia & Reading / Reading

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