Author Topic: Auto reverse loops.  (Read 890 times)

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wtfritzler

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Auto reverse loops.
« on: June 18, 2014, 05:13:59 PM »
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I have an N layout that has 2 reverse loops. I reverse loops were originally controlled by 2 (two) Loys Toys reversers that had 8 wires each. Before I bought the layout the owner switched the Loys Toys reversers to Digitrax AR1. The Digitrax reverser only have 4 wires so several of the original 8 wires were jumpered out at the reversers. I assume they were jumpered and wired correctly as they work fine when the trains are running fast but when run slower at more realistic speeds the engine hesitates sometimes,(at the reverser tracks) or at one point it MAY stop completely at a reverser track. I've been adjusting the pots up and down for weeks and just when I think I got it the engine may stumble, hesitate, or even stop. Run it faster without making any adjustments and it runs fine.
Any opinions on this or are there better Auto Reverser circuit boards available?  Also, will pay for expert help in getting these reverse loops working right.
Bill
#480-305-0405, Chandler AZ

mmagliaro

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Re: Auto reverse loops.
« Reply #1 on: June 18, 2014, 06:18:55 PM »
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Well, as a disclaimer, I admit I don't own one of these AR1 thingies.  But I looked it up, and the wiring instructions are here:
http://www.digitrax.com/static/apps/products/autoreversing/ar1/documents/AR1.pdf

All it does is trip when the current draw is over a preset limit.  The theory is that when your engine crosses the gap out of the reversing section, it will create a short that will draw a lot of current.  If the detector can detect that fast enough and switch the polarity before
your booster overload trips, it can prevent the shut-down and allow the train to seamlessly go in and out of the loop.

The current trip is settable from 0.25 to 8A, which seems reasonable. 

Two things:
1.  Have you actually traced the 4 wires from that AR-1 to the trackwork in the reversing loop to make sure they are correct?
I wouldn't automatically trust jumpers and some previous layout owner's tinkering.  Be sure.

2. How slow are you running the train when this thing fails to trip?  *VERY SLOW* ???  I say that because I know that
at least on my DC layout, if I have the throttle very very low and the engine is just barely creeping, I can put a dead short across the rails
that will not cause even 1 amp of current to draw.  In fact, just the other day, I was diagnosing a short in a switch frog, and
I was reminded that it was very easy to turn up the throttle just a little with a dead short in there and not even draw 1/4 amp.

So it's possible that you have a very efficient engine and you are running it so slow that the short cannot trip a .25 A detector.




mark dance

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Re: Auto reverse loops.
« Reply #2 on: June 18, 2014, 06:41:16 PM »
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I have had to 5 of my 7 AR-1's - which use mechanical relays I believe - as they did not trip reliably in my applications where I run a variety of power with a variety of power draws...anything from a single Kato or Atlas unit to 4-5 Lifelike units.  After messing with current threshold settings on the boosters and PM42s for the power districts where the A/Rs were being used, I just replaced them with solid state units from Tony's Trains.  Sicne then I have had no problems.  I believe these reversers are now being sold as PowerShield X by DCC Specialties but I could be incorrect.

YMMV

md
Youtube Videos of the N Scale Columbia & Western at: markdance63
Photos and track plan of of the N Scale Columbia & Western at:
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mmagliaro

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Re: Auto reverse loops.
« Reply #3 on: June 18, 2014, 07:33:44 PM »
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I have had to 5 of my 7 AR-1's - which use mechanical relays I believe - as they did not trip reliably in my applications where I run a variety of power with a variety of power draws...anything from a single Kato or Atlas unit to 4-5 Lifelike units.  After messing with current threshold settings on the boosters and PM42s for the power districts where the A/Rs were being used, I just replaced them with solid state units from Tony's Trains.  Sicne then I have had no problems.  I believe these reversers are now being sold as PowerShield X by DCC Specialties but I could be incorrect.

YMMV

md


 5 engines could draw, maybe 1-1/2 amps.  They would also draw as little as 0.3 amp.   And one engine that is really
efficient might only draw 60 mA.   The more I think about it, the more I think it would be almost impossible to find a current draw
that will work for all engine combinations.

Bill, when you get that thing set so it works with one particular engine at any speed, is it still true that you can come back the next
day with that exact same engine and string of cars, and find that it no longer works?   I would expect that to be reliable
once you get it set.  But getting it to work for your whole fleet, I think, is going to be frustrating.


jagged ben

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Re: Auto reverse loops.
« Reply #4 on: June 18, 2014, 08:38:01 PM »
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When metal wheels bridge the gap between reversed-polarity rails, the short is directly though the wheels, so the current draw through the motor is essentially irrelevant to the question.   The trip setting should simply be a bit above the maximum draw you'd ever expect to see from a consist.  For N scale, 2.5A is probably fine.

What WILL cause a problem is inadequately sized wiring, loose terminations, or bad splices or solder joints.  At 12V you only need 5 ohms of resistance to drop the current draw for a short below 2.5A.   5 ohms is nearly nothing; you wouldn't likely notice it slowing down your trains.   But it will affect the reverser.

This is just speculation, but with the jumpered wiring mentioned above, I would wonder if there might also be a parallel or incorrect path for short circuit current.  If not all of the short circuit current is traveling to the correct terminals on the reverser then that would be a problem.

eric220

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Re: Auto reverse loops.
« Reply #5 on: June 18, 2014, 09:05:33 PM »
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I initially used AR-1s on my layout. The one in the brewery turnaround never worked right, and I thought about investigating other options for a long time. The final straw for me was when the solenoid in the AR-1 at the upper staging yard stuck and shorted out the whole layout. The kind people here put me on to DCC Specialties, and I wound up trying their On Guard AR auto-reverser. It's a solid state version the AR-1, same wiring hookups and everything. I've only had one or two hiccups with them. In general, they operate with no problems.
-Eric

Modeling a transcontinental PRR
http://www.pennsylvania-railroad.com

mmagliaro

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Re: Auto reverse loops.
« Reply #6 on: June 18, 2014, 10:15:47 PM »
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When metal wheels bridge the gap between reversed-polarity rails, the short is directly though the wheels, so the current draw through the motor is essentially irrelevant to the question.   The trip setting should simply be a bit above the maximum draw you'd ever expect to see from a consist.  For N scale, 2.5A is probably fine.

What WILL cause a problem is inadequately sized wiring, loose terminations, or bad splices or solder joints.  At 12V you only need 5 ohms of resistance to drop the current draw for a short below 2.5A.   5 ohms is nearly nothing; you wouldn't likely notice it slowing down your trains.   But it will affect the reverser.

This is just speculation, but with the jumpered wiring mentioned above, I would wonder if there might also be a parallel or incorrect path for short circuit current.  If not all of the short circuit current is traveling to the correct terminals on the reverser then that would be a problem.

How silly of me.  Of course, you are right.  When the engine bridges that gap, it should be a dead short.
Yes, could be faulty wiring.