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Bus Wiring – DCC Main Bus
John models OO and writes:
“Greetings from the UK everyone. I have a garden room that is purpose built at 17’ x 11’ and building my dream layout. My question related to main bus wiring. I’ve connected my controller to the track at the nearest point and then daisy chained clockwise around the room. I’m running four tracks all the way around so have simply ‘linked’ wire every 5’ or so to the adjacent tracks to provide power to them. I’ve done this all the way around right back to with 3’ of the first connection by the controller. I’ve used 32/02 cables as the main bus and 7/02 as the short link soldered to the track discreetly. Locomotives run fine one on each track even one on each track at the same time. However, the end of the main bus wire returning, should l connect it back into the controller or just leave it hanging underneath with insulated terminals crimped on. Thanks for reading.”
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The general recommendation for DCC is to leave the end open. Ideally, the controller connection should be as close to the middle of the power bus as possible. Signals on the wire attenuate over distance so connecting at one end may reduce the signal reaching the other end, For a layout of the size you’re talking, you might want to look into DCC boosters. All the major DCC manufacturers have ones for their systems.
Thanks Dale. Thank you for you advice and I have been thinking about a booster as when accessories are factored in like point motor operation it could be a drain on the system in terms of current. I also just watched a video from Charlie Bishop of Chadwick Model Railway and it was exactly this topic. He strongly recommended not returning the bus wiring into a ring main configuration. This is more to do with signal from the DCC controller. Dependent on where the locomotive or an accessory is in terms of position on the bus wiring ring (if returned to the controller) the signal could arrive twice to the decoder. Once the short way and then a second hit coming from the long way.
In consideration then the recommendation is to not return the Bus Wire to the DCC controller output or create a Ring Bus Wire..
Yes, don’t make a continuous circuit.
Google tells me that 32/02 wire is the equivalent of 17 AWG, which I would have thought is a bit thin for the main bus wire, especially for a run of 50 feet. The recommendation (in North America) would be for 14 AWG wire, although when looking up the gauge of 32/02 wire I see that one website says it can be used for “longer runs of DCC bus cables”. I think you will need some boosters. Do you have a volt meter, and if so what does it say is the voltage on the track at the end of the bus?
One thing I would suggest at this point is connecting the end back to the power supply and then cutting the wire at the mid-point of the circuit, so you have two shorter runs. This would put the controller at the md-point of the bus which, as Dale says above, is the ideal situation.
And when considering boosters, as well as point motors and other accessories, if your points have live frogs and you are using an automatic polarity switch (as opposed to a mechanical one connected to the motor) these also have a current draw. (I found this out the hard way and had to upgrade my power supply!)