Altering Auto Reverser (AD 520) trip current

[esfeld]

Is there a way to lower the trip current (currently 2 Amps) of the MRC AD 520 AR?

[skagitrailbird]

The very short one page "owners Manual" says nothing about being able to adjust the trip current. In an article on Tony's Train Exchange site comparing various AR's there is no mention of adjustable trip current for this unit. It seems likely that it is not adjustable.

[jjdamnit]

Hello All,

I have the same Auto Reverse unit on my pike and it does not have a way to vary the trip current to a lower level.

The Bachmann E-Z Command DCC Automatic Reverse Loop Module (44912) does have the ability to vary the trip curent from 1A to 2A to 10A. These settings are preset and selected by a dial on the unit.

Hope this helps.

[Stevert]

Wow, that Bachmann unit is pretty expensive for having only three pre-set, non-adjustable settings.

For less than 1/3 the price, I'd suggest the Digitrax AR1 instead.  It uses a trimmer pot, and is therefore nearly infinitely adjustable within it's range (6 amp continuous, 8 amp peak).

I use two AR1's on my layout, and once adjusted, have found them to work well.

[mfm37]

Actually, you don't want to be able to adjust "trip Current" on an auto reverser. It needs to trip faster than any other short circuit protection and it needs to trip on any short. So trip speed is what counts. as long as the reverser trips before the booster's circuit breaker, it is fast enough. If it is not tripping fast enough, see if trip speed on the booster can be set longer or more importantly make sure your wiring is robust enough.

Martin Myers

[rrinker]

 That's mostly true. Even if it trips faster, if the autoreverser doesn't even consider it a short until 2 amps flows, it might not trip at all. For seamless operation on the reverse loop, the autoreverser needs to trip on the slightest hint of a short, but not be so senitive that normal motor spikes of a train running fully within the loop cause it to trip. If it waits until there is a 'solid' short, by then you have half the loco across the gap with weight on the wheels and the action will be jerky if it even works. Adjusted properly, even a lightly weighted wheel bridging the gap should cause the autoreverser to trip. That's a rather high resistance short, akin to the quarter test (you do NOT press the quarter down) so not a lot of current flows, but it still needs to be detected as a short for the AR to work.

You need both - the AR must operate faster than the booster or upstream protection (which is why an AR-1 won;t work downstream of a PSX, the trip time on the PSX is not adjustable) AND it needs to treat a lesser current flow as a short relative to the upstream device.

                    --Randy