Turnout wiring for DCC operation

[ben mason]

I am currently working on the track for my layout using a Powercab and Cobalt point motors. In order to avoid short circuits do I still need to reverse the polarity of the point frogs? The Cobalt digital IP motors have switches built in which would make this easy to achieve, however there is nothing shown in the instructions telling me to do this.

[nigelcliffe]

I am currently working on the track for my layout using a Powercab and Cobalt point motors. In order to avoid short circuits do I still need to reverse the polarity of the point frogs? The Cobalt digital IP motors have switches built in which would make this easy to achieve, however there is nothing shown in the instructions telling me to do this.

DCC wiring of turnouts is the same as DC. You need to swap which of the left/right rails connects to the frog depending on blade position.


Now, a little wrinkle which can bite:
In some Cobalt Digital turnout motors, they have a single "frog" output. Internally, that connects to the two wires going in from the track which powers the motor and carries the DCC instructions. This works if wired to the track, ***BUT***... The standard recommendations for DCC wiring is to have two DCC "buses" arranged around a layout, one for track and one for accessories (turnout motors, etc..). The Cobalt's single wire breaks that recommendation, by connecting the track to the accessory bus. This causes all sorts of problems, their exact consequence depends on exactly what wiring and other devices are deployed on the layout. (Some of the consequences are dire).
So, with Cobalt motors, I recommend they are wired as any other motor with internal switches. If you have one of the versions with the single output, instead use the other supplied switch with three contacts, one to each of the rails and one to the frog. Then, you can have separate track and accessory bus wiring if you ever need it.


- Nigel