Digitrax AR1 - TTC

Model Railroader Electronics and DCC
1

I have four AR1’s on my layout, and all four have performed flawlessly for several years. Each time that I installed one, I never had to adjust the Tunable Trip Current (TTC). Each AR1 worked just fine without any adjustment.

The TTC allows you to set the current at which the reversing section reverses when the train crosses the gap into the reversing section. The TTC is adjustable from .25 amps to 8 amps. Turning the TTC screw clockwise increases the current trip point and turning the TTC screw counter clockwise decreases the current trip point.

My DCC system is the NCE PH-Pro 5 amp system.

Yesterday, I ran a loco across the gaps into one of the reversing sections. The loco stopped immediately upon crossing the gaps, a short was indicated, and the booster shut down.

Recently, I had re-routed some adjacent track connected to a turnout that leads into the reversing section. I also re-ballasted the track in that area and secured it with a matte medium mix.

After checking my wiring, the rail gaps, and anything else that I could think of, I finally adjusted the TTC one quarter turn. That did it. Everything was back to normal.

Would anyone care to offer any comment or explanation as to why the problem occurred and why I had to adjust the TTC?

Rich

2

Some ballast materials, coupled with the cement used, can cause a change in the resistence across the rails. Sometimes this also shows up if there are large seasonal swings in humidity - what works in the dry winter suddenly fails in the humid summer. It likely will return to normal when the ballast cement completely dries - it can take a week for a matte medium mix to actually dry.

Same thing happens with block detection, especially the more sensitive types. The kind that you can trip by putting a finger across the rails - fresh ballast, or just a humid day can suddenly make the block active with no train present, until you adjust the sensitivity.

–Randy

3

Randy: You are a fountain of knowledge. I would never have thought of that as a source of the “gremlin”.

You are on my "rolodex’ now, amigo!

Joel alias Owen W