Dcc Bus resister

[bulleidboy]

I use DCC filters/Snubbers on my DCC Bus. My Bus cables supply power to the track and to my twenty five Cobalt Digital point motors. I do not have a separate bus for the points. I also have a DCC Concepts Power Boost - so a 5amp supply (this is a recent addition). I have not found any problems in just using one pair of bus wires - I am not changing points every other second, so no extremes of power being used while loco's are running. In some ways my layout is set-up as DCC was originally reported "Just two wires to the track", and all loco's and points can be operated via my Hornby Elite controller - I also use HM7000 with my iPhone. Also my layout is an end-to-end, so I do not have loco's running continuously around a layout. The choice is yours.

[RAF96]

The case for a split bus was 2 fold: first if a derail say by a wrongly set point occurred the point could be reset, the track restored and away you go; second there have been reports of track bus spikes damaging some acc decoders.
A decent workaround for a single command station is to run the track bus thro' a circuit breaker in parallel with the acc bus, both connected to the one controller.

[Too Tall]

Just to add a couple of questions to this thread, for my clarification.

1. If I prefer to do a loop for my bus, can I still use a filter/snubber split from the feed with a T junction, or am I better splitting the loop and having 2 feeds with a filter /snubber each end ?

2. I plan on powering my points with the Hornby HM6010 accessory controller, Can I just take power from the main Bus for these ?

[Brian]

Hi
A DCC Bus pair of wires can be a Ring - continuous two loops of wire, Radial - end to end or Star - pairs of wires running out in all directions.

If the correct size of wire is used for the bus IMO a ring is just wasteful on wire. Radial or Star will work as well and saves on bus wire.

On a ring only one Bus Filter would be fitted, Radial has two filters one at each end and Star can have two or more filters though usually two are ample.

The HM 6010 can operate from either a mains adaptor of the DCC track power. However, here I would be inclined to use a separate power supply and leave the DCC power to run the trains!

[Too Tall]

I am currently wiring my track as I lay it.
I have 14AWG which runs around the baseboards approx 52 ft (16m) total length, (as I have a hollow middle L shape) connected at various points to 12 way distribution blocks, from which 20AWG feeds are taken for track droppers of generally under 40cm lengths, although there are 4 or 5 of up to 1 meter.

In my particular instance, it makes no odds to the length of wire required if its a loop or 2 equal-ish lengths.

I did intend to make it a loop and feed the controller in with a T junction.
is it best to do this, and connect one filter via a T junction (as the filters are not pass through).
or should I feed 2 similar lengths with a filter on the end of each ?

I just assumed that a loop was better as it would mean less voltage drop at the farthest point ?

For reference its a 5 amp controller and the filters I have are the DCC concepts ones.

[Brian]

Hi
14AWG (approx. equal to 2.0mm2 metric) will carry around 12 to 15 Amps and should be fine, while droppers of 20AWG (approx. 0.5mm2 metric) is a good choice. I doubt 14AWG over the distance mentioned would produce much volt drop, if any! Dont forget that the rails also carry current too.

I can see no benefit in making the main bus pair a ring! Though that choice is up to yourself. IMO a radial (end to end) bus will work just as well with the 14AWG wire. Try to feed a radial bus pair as near as practical in the middle of the wire run, but a slightly off central feed location is acceptable, so don't get too hung up on getting the exact middle position. Then add two Bus Filters - one at each end of the main bus pair. On a ring use one filter. If using a ring I would position the filter around the furthest from the place where the feed connects onto the ring from the DCC system.

[darkscot]

This is a very interesting topic that I am glad I stumbled upon at this time as I am currently rewiring my baseboards. I am definitely going to fit snubbers as I have had issues in the past with my locos that I now strongly suspect were caused by voltage spikes. For example when going over points the loco sound would sometimes stutter and the driving lights flash and/or change direction. This was not due to a bad track connection as they have keep alive capacitors in them.

I am not sure about the separate bus for the points though. I currently only have three sets of points with Cobalt IP motors, this will probably increase to a maximum of five or six in the near future. I don't have the space or budget for more.

My DCC bus is end to end format which for me seems the best option.

[Too Tall]

Indeed Brian, I have read that a Ring isn't the best way as it can itself cause issues.
So I will do as you suggest and have 2 end to end runs with filters at the ends