I've been thinking about getting an "auto-reversing" unit for my layout. I've had a reversing section of isolated track on my layout ever since it's creation 13 years ago, but occaisionally I still "forget?" to manually switch polarity in time to avoid tripping the breaker on my DCC unit. I have read somewhere that tripping the breaker in these things is not always a good thing, so I have recently installed an inline fuse that trips before the unit does. Anyway, sometimes I run some old STRAIGHT DC locos on my tracks. What would I do with the "Auto-reverser" in this case? Would I have to elecronically ISOLATE it in DC, and go back to manual switching?
Mike C.
The only reverser I know of for DC is the DPDT switch.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
So, you're running a DC locomotive on your DCC layout, right? And you want to use an auto-reverser instead of a toggle?
It won't work. An auto-reverser works by flipping the polarity of the reversing section. A DCC engine will keep right on going when you do that, but a DC engine running as "Engine Zero" on your DCC system will reverse direction. If you just let it run, either the engine will "ping-pong" between the ends of the reversing section, or it will get stuck at one end and short out.
It takes an iron man to play with a toy iron horse.
MisterBeasleySo, you're running a DC locomotive on your DCC layout, right? And you want to use an auto-reverser instead of a toggle?
I don't think this is what he is asking. I believe that he is saying "I want to run a DC loco with a DC power supply. Do I have to electrically isolate the DCC auto-reverser?"
maxman MisterBeasley So, you're running a DC locomotive on your DCC layout, right? And you want to use an auto-reverser instead of a toggle? I don't think this is what he is asking. I believe that he is saying "I want to run a DC loco with a DC power supply. Do I have to electrically isolate the DCC auto-reverser?"
MisterBeasley So, you're running a DC locomotive on your DCC layout, right? And you want to use an auto-reverser instead of a toggle?
I cannot answer his question except to say that since the AR unit will not work, he is creating an unresolved short and may be damaging the AR unit. On the other hand, if the AR unit doesn't work on a DC powered track, it may not be damaged if it is inoperative to begin with.
Let's see if someone can answer this question.
Alton Junction
There are two problems. It's not necessarily that the autoreverse won;t work in DC, it's more like it won;t have the expected results. The all-electronic type may not work at all on DC. The relay type, all teh really are is a DPDT switch that is automatically operated.
Problem is - it reverses the wrong section of track. With DC, when you enter a reverse loop off the main, you then change the polairty of the MAIN to match the exit side of the loop so the train can continue on. With DCC, you are changing the polarity of the loop track since the polarity (really phase since it's a bipolar square wave) has no bearing ont he direction of travel of the loco.
So even if the autoreverser would detect the short and operate, what would happen is you train would instantly reverse direction. Until it tried to back over the gaps at the entrance of the loop, in qhich case it would instantly change direction again - poor man's back and forth shuttle.
If the track is a simple balloon loop, it is entirely possible to make it 'automatic' in a way that would work with DC and DCC. It requires that you always traverse the loop in the same direction though. Track polarity would eb controlled by switch machine contacts (or for more current carrying capcity, a relay triggered by the switch machine contacts). Instead of the typical DCC method of feeding the loop itself through thise revesing 'switch', you would feed the main. Thus the polarity will match for the train entering the loop. Once within the loop, the turnout needs to be thrown, and the main line polarity will flip to match the exit side fo the loop.
This can also be made to work with a wye.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The AR unit will be "locked" into one position - the DC supply / engine won't make it work, but it won't hurt it either. The simple solution would be to add a DPDT reversing switch between the AR and the track. Use the DPDT switch when operating DC, on DCC, the AR will work normally as it should and just feed through whatever position the DPDT switch was left in.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
My layout operates DCC and DC via a selector switch. I run mostly DCC, but I occaisionally want to run "the old stuff". From what I'm reading, I probably need to install some switches so's I can isolate it during DC operation. I kinda figured that.......thanks fot the input!
If I understand correctly what Mark recently replied, you won't need to "isolate" it. Just install it as you would for a strictly DCC powered layout.