Hi again
Please don't misunderstand - I don't doubt that you've made a tidy job of it: All I can do is suggest things I know really do work - I never propose random theories.
acceptance is up to you.
tidyness isn't always the issue though, its configuration sometimes... and...yes, it can sometimes be the control system - but more often its a power supply thats only just big enough - sometimes replacing that will fix what looks like control logic problems too.
Some of the layouts I fix by troublehooting also have very tidy wiring but they make a couple of small fundamental errors: A more simple example of how tidy isn't always the issue:
A good example was one that had used heavy copper tape for the bus:
OK in its own right but he'd done exactly the wrong thing and run the copper neatly in two parallel runs along a bit of 1-1/2" timber to keep it tidy - and in the process, he inadvertently created a nice long capacitor with his tape.
In this case, breaking it into two sub busses and adding the suppression cap + resistor cured over a year of runaways (I might add that his DCC supplier was advcating more boosters and bigger power supplies and all sorts of costs - this fixed it for less than 50p.
Accepting that you made it tidy... why not just try something that may help and cannot hurt.
Try this as a simple change that'll cost almost no time or labour.
Firstly, while I accept that your layout is small enough for it to not be much of an issue, having the power bus in a ring is not recommended by any Mfr.
(1) Cut the ring at the point farthest from the controller, making a "tee" with two equal length arms.
(2) Add a filter as I described to each end - it really is only a few pence.
Two benefits come from the filter.
Cleaner waveform
suppression of voltage spikes that may be caused by the odd momentary short....worth protecting against anyway even if no other benefit results!!
Re wire: 16x0.2 is pretty small wire for a power bus. 32 x0.2 (equivalent to 10 amp mains cable) is about as small as I'd ever go.... 40+ x 0.2 is better still. Yes it seems large, but its only slightly dearer to buy and will serve your layout better.
the issue is NOT current carrying ability - it is preventing voltage drop under load - and wire that is too light becomes resistive under load, and with an AC signal in light-ish twin wire that then translates to inductance and that makes it worse.....exactly the sort of thing that causes a bad waveform and resultant mis-information on the power bus.
The termination/filter will help that a wee bit too.
Richard
DCCconcepts
QUOTE (Howzatt @ 8 Aug 2007, 08:18)
<{POST_SNAPBACK}>
Many thanks Richard for his constructive comments re my loco runaway problem. For the record, I believe my track wiring to be first rate, using ring main cable for a power bus with each separate piece of track of connected to this with 16/0.2mm multistrand wire. My layout at the moment is basically a simple 2 ovals on a 8'x4' board. I've read about adding a terminator network elsewhere to cure this problem and I will certainly give this a try, but I really don't see why I should need to go down this track (sorry!). The fact remains that with my system, and with certain loco's, capacitors need to be left in place to prevent uncontrollability. This doesn't seem to cause any adverse effect as slow running can be perfectly controlled to a crawl. I'm starting to think that there could be an odd fault with my DCC controller. A scope connected across the track may shed more light on this when I can borrow one.
Best regards
![](http://www.modelrailforum.com/forums/style_emoticons/<#EMO_DIR#>/dry.gif" style="vertical-align:middle" emoid="<_<)
