Hello one, Hello all! I am still in the process of planning my layout, It is (thus far…) going to be a freelanced SP, UP, & BNSF layout (This is subject to change without warning…) using Digitrax DCC, and based in the modern era. This will not stop me from running the Oh-so-glorious steam locomotives. But, where there is a steam engine there must be (in my little world at least…) a roundhouse & turntable. And, since I like to know how to do as much of something as possible before I start (though in some cases experience cannot be substituted) I would like to know how to wire a Digitrax AR1 to use auto-reversing with a turntable. I know how to wire it to a wye or generic reverse loop fine. But the AR1 manual off of the Digitrax site gives no insight (to me at least…) on how to use it with a turntable, except for adjusting the trip amperage. I honestly have no idea on how to do this. So any help would be appreciated! (And a diagram would be even more appreciated as I am a visual learner, but I’ll manage if you cannot make one) 
You have a choice, and it depends to an extent on what the turntable is designed to do in the way of auto-reversing…if at all. Many have split power ring design so that the wipers make contact with rings of opposite polarities depending on the position in swing of the bridge. Is your turntable of this type? If not, you would probably be advised to wire the AR-1 into the leads that are meant to power the rails on the bridge. If it is of this type, you do not need the AR-1.
So, your bridge rails need DCC signal, and would get their power/signal from a connection into the main bus. You would interpose the AR-1 between the feeders to the bus and the bus itself by making the bus feed the inputs on the AR-1 and the feeders to the TT would go to the outputs on the AR-1. Matters not which wire to which rail, the AR-1 will figure it all out for you upon first incursion of a loco onto the bridge.
Thank you for the quick reply, selector! I am not sure on which type of turntable the CMR kits are, but looking at pictures, they look to be the kind you have described in you diagram (Thank you!!!) but I have e-mailed CMR just to be sure. Again, many thanks!!
My pleasure, Jake.
One more important thing; when you wire the bay tracks into the house, be sure that the wires to all “right” and the wires to all “left” rails correspond with those incoming to the other side of the turntable. That is to say, the approach track must have precisely the same power orientation, feeder-wise, as those leading into each bay. That way, the split ring design will automatically reverse the power leads internally when the loco is swapped end for end. When you drive it into the bay in the opposite direction from the way it was facing when it entered the bridge, the split rail will have effectively switched feeders to each rail, and that will logically be in conformity with the wiring to those same bay rails.
-Crandell
I just recieved an e-mailed CMR, and it turns out that power is supplied through the pit rail, and that there is a 2-inch “dead-zone” on each side to keep a short from occurring. To wire the AR1, which they recommend if I will be using sound decoders, which I will, and have a goal of having every loco sound-chipped. (I dream big…) I must connect one lead on the output to each dead zone, and on on each input to my track bus. Okay, easy enough. Way easy enough! [:D]
Im curious about this myself. I posted here to move this thread to my forums so I can follow it better in the morning with a pot of coffee.
I will be ordering AR1’s in the future and most interested in the TT function. Specifically the Walthers 130 RTR one.
Same-same, Safety Valve. Split ring design, no AR-1 needed…the table reverses itself as it rotates through about 90 deg of either end, the approach or the house. The way it works is that there are two sets of ring arcs, not complete rings, that run around the inside of the pivot. Metal wipers swipe those arcs. Wires run from the wipers up to the rails for power. Wires run from your controller bus to the metal arcs. As the bridge pivots, the wipers eventually pass over the gaps between each ring arc, at which point the bridge rails go dead. As the bridge continues its path, the wipers once again pass over to the adjacent ring arcs, but this time the wires going to the arcs have been wired in reverse to how the arcs just left are wired. That effects the polarity reversal. So, no need for the AR-1.
Jake, did the response you received actually state that the design is one of split ring with auto reverse? This is important!!! If the rings are split, but don’t provide reversing, it would be a very strange design. I would wonder that they bothered to split the ring at all since the effect will only be to cause your decoder to loose power during the bridge rotation and to then power up when the wipers next regain contact with the rings. That would be unnecessary…*unless…*the rings were actually wired in reverse on each half. In that case, I think the AR-1 is obviated.
Here is what CMR’s website says:
HO and N scale turntables feature:
Laser cut acrylic parts
Sealed wheel bearings
Bronze oil impregnated axle bushing
Auto reverse track polarity
Bridge track power via a split rail system
Lift off removable bridge
Drop in construction for easy installation
Split ring system?
Someone needs to throw down slabs from the mountain somewhere saying YES the AR1 is needed or… NO the AR1 is NOT needed.
While it is true that I dont NEED an AR-1, I will be using sound decoders, which will momentarily power off when crossing the dead section on the pit rail. They said that to avoid this, I must wire one output of the AR-1 to each dead zone, and one input to each track bus wire.
Okay, three things to deal with from my point of view.
Let’s deal with the two built-ups in HO from Walthers first. Categorically,…no other mechanism is needed for the avoidance of shorts when reversing locomotives. Period. They each have the split ring design which obviates the necessity for short control. Just hook up wires, programme your indexed stopping points, and run trains.
Secondly, the built-ups have no provision for a device to maintain power to the decoders while the wipers are crossing the necessary gaps in the rings…no terminals to hook anything up. So, with the two Walthers units, the decoder goes silent momentarily and then repowers audibly when contact is re-established across the gaps.
Thirdly, I am unaware that the AR-1 stores electricity and meters it out to the rails via some hitherto unbeknownst-to-me mechanism while the wipers are slipping through space awaiting their crossing to the other ring arcs. It certainly is not, as I just stated, anything that Walthers saw fit to provide in their construction. So how CMV manages to keep power to the rails during this process of reversal is beyond me to describe or to account for. Maybe they have yet a third mini-arc in the “gaps” where the AR-1 can provide power during the transition…but that would mean more terminals on the bottom of the CMV pit. Are they there? (Edited- took out the capacitor in the AR-1 bit…not needed since it is always powered)
Edit - add - About the CMV kit, the claim is that it has a “two inch” gap? If so, it is nearly three times as large as the ones in the Walthers built-up. Why the gap at all? For what purpose? If the AR-1 is needed, then the rings don’t need a gap at all since paying for the AR-1 and what it is meant to do is part of the design in the first place! Bottom