DCC in the garden

"Marcus Dawson" wrote

I don't see why it wouldn't affect DCC in the same way, but there are ways around it. You can electrically bond all rail joints and run heavy duty feeder wires to different parts of the layout.

John.

=>I don't see why it wouldn't affect DCC in the same way, but there are ways =>around it. You can electrically bond all rail joints and run heavy duty =>feeder wires to different parts of the layout. =>

=>John.

By "heavy duty" he means the same size as is used for, say, an electric lawnmower extension cord.

HTH

Wolf Kirchmeir ................................. If you didn't want to go to Chicago, why did you get on this train? (Garrison Keillor)

'lectricity is 'lectricity, DCC or otherwise. E = I * R, in this case, the R is the resistance of your power distribution network. I is the current load by all locos (+lighted cars, etc) on the rails. The resulting voltage sag is E. Running a low R power distribution bus is always a good idea with DCC, inside or out. The reason is that DCC controllers detect shorts on the rails and shut down until the short is cleared. If there is too much resistance in the distribution feed, it doesn't look like a short to the controller, therefore, no shutdown, leading to possibly unpleasant consequences. Like a wheel welded to some points, for instance.

It's pretty easy to calculate how large the feeder wires need to be. There are tables of Ohms/foot (Ohms/meter on the East side of the pond, I suppose) by wire size. Use a fat enough wire that the worst-case total R for the power bus distance from supply to rail is "low enough". "Low enough" depends on how sensitive the DCC booster's short detection mechanism is.

-dave

In the US, N-Trak (the modular N scale group) is working on Recommended Practices for REALLY BIG (100+ modules and up) layouts incorporating DCC. As a result of both referencing electrical data and experimentation, we're calling for bus wires to be 12 AWG on new modules, and for existing modules to be upgraded to this standard when refurbished. It's not just the voltage... there's more draw on DCC layouts because you run more trains with more locomotives! (100+ car trains with 5-9 locomotives are NOT unusual... and on a layout with 13+ scale miles of track, it won't be the only train out on the line!)

Higher amperage draw means more voltage drop over a given distance and given wire. DCC is more susceptible to voltage drop... you can't just crank it up higher to keep them running like you could with analog, and if the voltage drops enough the signal is degraded and/or you lose functions (especially noticable with lighting like strobes or headlights).

Our club recently upgraded all our modules to 12 AWG wire for this reason. In Chantilly, Virginia (just outside Washington DC) at the N scale East convention this coming August, the layout is expected to be 500+ modules. It's going to be a major consideration there!

The wire we're using (and is suggested in the RPs I mentioned) is 12 AWG "low voltage" wire, designed for buried outdoor use in landscape lighting. It's stranded, flexible, and looks just like oversized lamp cord or zip cord. You should be able to find it anywhere that sells low-voltage landscape lighting.

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Hi, I think a good rule of thumb would be, as big you is practical, and you can afford.

Rob.

In message , Marcus Dawson writes

I expect so.

However, you should watch out for capacitive effects. See