# Digitrax AR1 - train hesitates



## JeffHurl (Apr 22, 2021)

Hi everyone. 

I'm having a small issue with my DCC N scale layout. When my locomotive either enters or leaves the isolated section, it will hesitate (actually stop) for a second or 2 before continuing.

It only appears to happen when the AR1 module needs to switch phase.

Below is my layout. Please disregard the blue colored track. It is an elevated section, completely separate from the green track, and isn't even laid yet.

The red dots are main feeders, with the "B" being common, and the "R" being hot. The blue dots are feeders coming from the single Digitrax AR1 module.

I'm not getting any indication of a short other than the one caused by the loco either entering or exiting the isolated section which the AR1 should be handling.

All turnouts are Peco Insufrogs, and I have gapped the frog rails in certain sections to prevent shorts. The loco seems to be fine once it "recovers" from the stall.










I'm not sure if it's the decoder in the locomotive having issues, or if it's teh AR1 not doing its thing quickly enough, or if the NCE Powercab trying to shut down for teh brief instant it senses a short...

Any help is appreciated.

Tagging @DonR our resident wiring expert!


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## mesenteria (Oct 29, 2015)

The device needs to be set to trip faster. Decoders are notorious for not liking even the briefest of power interruptions unless they had capacitors in them to help them to run over short sections where they can't pick up power.


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## DonR (Oct 18, 2012)

Jeff

The AR 1 has a 'trip' adjustment...which can be read as 'sensitivity selector'.
Here is the AR1 manual section that describes it.



https://www.digitrax.com/media/apps/products/autoreversing/ar1/documents/AR1.pdf



You should be able to overcome your problem with this.

Don


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## JeffHurl (Apr 22, 2021)

Ok, I'll try decreasing the trip value and see if it improves. I had read that, but I thought that adjustment was only to get it to trip versus not trip at all.

Perhaps the lower the trip setting, the sooner it will trip also.


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## mesenteria (Oct 29, 2015)

Read the instructions. As you describe what you think is the case just above, it sounds like you might be decreasing sensitivity, which would be going the wrong way. You want to decrease sensitivity, but you do that by decreasing the reaction time. What this does is to reduce the _decoder's_ sensitivity, effectively, not the AR's sensitivity.


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## JeffHurl (Apr 22, 2021)

It trips based on the amount of the current. So wouldn't decreasing the threshold also decrease the time it takes?


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## DonR (Oct 18, 2012)

Jeff

I agree the instructions are really not all that clear. However, just
keep fiddling. I suspect the factory setting was for one of the
larger scales. You want to reset it to be more sensitive to
your N locos. Just experiment and you'll find the right setting.
The AR1 is highly regarded by the Hobby so you have a
quality product.

Don


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## JeffHurl (Apr 22, 2021)

Thank you all! I turned the adjustment counter clockwise about 1/3 of action, and it's running smoothly.


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## mesenteria (Oct 29, 2015)

Glad it worked. There are times in the hobby when the operator could really use some confidence and some reliability, and this is one such occasion.


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## JeffHurl (Apr 22, 2021)

I am still getting an occasional pause. It only occurs occasionally, but always in the same spot. It right where the isolated reversing stretch starts from one direction.

I guess I'll adjust the setting a little more.

Just running the loco... No freight cats yet.

Still putting everything through a lengthy test run before I commit to building the elevated areas and forming the tunnels. I figure give it a good stress test. Maybe later this coming week I'll be sure a nice long consist can keep from having any issues.

I had to replace 2 PL10s. The posts on the back sides of the toggles I have are small and close to each other, and I fried 2 of the PL10s because the leads were bent into each other causing a short.

Easy enough to swap them out.

Everything is running great except an occasional pause going into the reversing section.


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## DonR (Oct 18, 2012)

You really should not have even the slightest pause at your
isolated section joints. 
The headlight should never flicker there. Do continue 'fiddling' with the
'sensitivity' control of the AR1.

Don


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## JeffHurl (Apr 22, 2021)

I should have mounted the AR module on the top side of my control panel, lol!


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## DonR (Oct 18, 2012)

They usually are not that much of a problem...guess it was
set way wrong for N scale at the factory. I didn't have to do
a thing when I installed mine...worked perfectly from the start,
but then, it was HO.

Don


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## JeffHurl (Apr 22, 2021)

Well, it's possible that my gap is bit too long, and it's just losing power briefly enough to have a pause. I need to stand at the spot and probe the tracks with my volt meter to see if it registers a short in the tracks.


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## mesenteria (Oct 29, 2015)

The gap can only be 'too long' if the two gaps are staggered by about as long as, or longer then, the most affected loco's pickup wheel base. Is that the case? If you do have the gaps staggered, but only by 4 mm, then there should be no effect on even the teensiest scale locomotive.

One thing we haven't looked at is the matter of rail height difference near or at the gap....either places. Wobbly trackage tends to yaw and pitch the frames of locomotives, and this in turn lifts one or more metal tires clear of the electrified rail. A slightly depressed rai lend across a gap will mean that gap is as long as it takes to re-establish contact with the rail. That could be more than a cm.


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## JeffHurl (Apr 22, 2021)

The gaps I have to isolate the section controlled by the AR1 are simply plastic rail joiners that connect to the turnout. I just checked, and the loco I'm using is a SD70ACe with all wheels picking up electricity. So I doubt it's a gap issue now that I think of it.

I'll spend some more time watching it and see if there's anything physical that catches my eye as the train rolls through that section. I'll also monitor my track with a volt meter to see if it any hiccups are noted.


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## DonR (Oct 18, 2012)

I doubt that your gap, even if long, would cause your problem.
The loco wheel would simply sink into the gap. Most have
more than one wheel per side that is in contact with the rail
before the gap so that should provide power to the loco.

I continue to think AR1 'sensitivity' adjustment is the answer.
There absolutely should not be even the blink of the headlight
going over the gap. I can't recall any other N operator having
your problem.
If you find that you can't get smooth operation, I would suggest
contacting Digitrax...be sure to tell them you are N scale and the
model loco you are using as well as your DCC control model. They
have an excellent warranty policy.

Don


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