Hi all:
I would like to thank everybody for their help in the past and hope you will be as kind with this question.
I am in the process of installing a turntable on my layout. I operate with a Digitrax 8amp Super Chief.
The problem is I can only move trains onto and off of the turtable from one end. I cannot turn a train around and drive it off going the other direction. Is there an easy fix to this problem?
All help gratefully accepted!
It's a polarity issue as you mention in the subject, when you turn the table 180 degrees, the + track is now connected to the - track and vice versa. When the engine tries to leave the turntable, it causes a short.
You'll need to either rig up a DPDT toggle switch to reverse polarity (like you would in doing a reverse loop), or (preferably) get a Digitrax AR1 auto-reverser unit and hook that up to the turntable's track. It will automatically sense the mismatch and reverse polarity of the bridge tracks. A nice thing about the AR1 compared to other auto-reversers is you can adjust the sensitivity so it's "just right" and works great.
http://www.digitrax.com/prd_powerman_ar1.php
Thanks you saved me a lot of time and trouble
Thanks for the help.
Who made the turntable?
Some of them, like the Atlas, automatically reverse polarity for you. If you have a turntable with automatic reversing, you need to follow certain rules about wiring the stalls and approach tracks, but other than that you will not need an auto-reverser.
Other turntables do need auto-reversers, though. I have a couple of the Tony's Trains units, and I've been very happy with them.
It takes an iron man to play with a toy iron horse.
I wired DPDT switch (with a center off) and LED direction lights to the turntable track and it works fine. I put it on my turntable & stall tracks panel next to a the turntable push button for power and the tuntable movement direction switch. It works fine and I kind of like it as part of the turntable operations procedure. Cheap solution, I'm saving the auto-reverser for when I get to my loops.
Have fun modeling, Hal
MisterBeasley, you mentioned rules when using an Atlas turntable. I plan to use an HO Atlas turntable on my 'to-be-built' layout. I want to wire it for DCC. What additional rules are you talking about? Or where could I read about it? Thanks.
If you look around the base of the Atlas turntable, you'll notice that about half of the slots for tracks are labelled A, and the rest are labelled B. The A tracks all get wired one way (say, + or red-wire on the clockwise-most rail) and the B tracks the other way (- or black-wire on the clockwise-most rail.) The turntable rail itself is wired through a pair of screw terminals on the rim. As the turntable rotates, it picks up power from a split ring beneath it. At one point (where it goes between the A and B track groups) there is a short dead spot, and then the power comes back with the opposite polarity. It's all done for you.
This is my HO Atlas turntable. I buried the mechanism and used a raised bridge to turn it into a pit turntable:
People often apologize for using the Atlas turntable, but it has the advantage of being very inexpensive, along with its matching roundhouse. Although it is smaller than most units, and won't handle a decent-sized steam engine, it's size lets you put a facility like this into a space where no other commercial turntable would fit. And, you can have a lot of fun doing things like this with it:
http://www.trains.com/TRC/CS/forums/1162765/ShowPost.aspx
Thanks. I did see the A & B, now I understand the wiring. I can see how you lowered your turntable. Great idea! Looks good! Thanks for your help.