Accessory Bus - how do you wire to NCE Power Cab

[Jonnya]

Dear all,

 

In the spirit of " the only stupid question is the one you don't ask" how do I connect an accessory bus wire to my NCE Powercab?  I have laid the bus wire around my layout already.  I have a separate track feed and whilst I am still in the very early stages of building the layout I have tested it with the Powercab and my loco is working.  I assume I don't just connect the accessory bus to the two feeds into the PowerCab.  I intend to run point motors, signals and a turntable.

 

Thanks in advance.

 

Jon

[Nigelcliffe]

Yes, you just connect the wires together. 

 

As to what this achieves depends on what your aims may be.....

 

If you want easier fault finding, that's it done as you can disconnect different bus wires to isolate sections of wiring from each other. 

 

If you want a derailment (and short) on the track to not affect accessory operation, then you need more hardware:  specifically a Power District Cutout Device.   Minimum of one, which is fitted to the track-feed bus, and set so it trips at a lower current than the PowerCab.   So, the Cutout will trip on a short circuit, leaving the PowerCab working and thus accessories working.

 

NB, if you've used some of DCC Concepts Accessory devices which have a direct single wire "frog" output, then that output provides a back-door route from Accessory to Track bus  (bad idea if you've gone to the effort of separating the buses!), and your cutouts probably won't work reliably in all circumstances for derailments at the turnouts in question.   

[Brian]

You can connect all accessory decoders to the track bus pair as well of course the rails. The down side is if you run a loco into an unset point the system trips out and all stops until you physically move the loco back away from the point.

By running a second pair of bus wires from the Track output terminals you then feed all the accessories from this bus pair.

The Track bus also comes from the same Track terminal feeds but goes to an all electronic circuit breakers input which has its trip current set to below that of the main console. The output of the CB feeds the track bus pair of wires.

Now if a loco runs into an unset point the CB trips but the console remains operational allowing the point to be moved over by the DCC system.  The short is then removed and the CB self resets and the loco continues on.

 

Basic idea shown here...

Dual Bus by Brian Lambert, on Flickr

[Jonnya]

Thank you both. Really helpful.