Steph, thank you for providing info on wiring for DCC - you just knew that there would be more questions, did not you!
Yep!
Please try to make the answer understandable to a silly old bear(e).
No problem - it's only a resistor and capacitor after all. Actually, you'll probably find chapter and verse in the Heyside thread...
Got that... arrange for the snub stubs to be at the outer ends of each power bus. What happens if we then need to test just (say) the middle of three boards and for which there are no snub stubs?
Don't worry about it. The need for the snubbers increases with size and complexity of the layout. It's related to the ability of the layout wiring to either reflect the DCC signal around so it gets jumbled or act as an aerial.
My intention was to use 1mm diameter copper stripped from twin and earth. What current can that carry? What diameter copper cable is needed for 10A plus contingency?
Pass. I buy my cable from either motor factors or RS. In either case it's a breeze to rock up and say "can I please have a reel each of black and red insulated flexible cable that's rated around 5Amps?"
I know what you are talking about here... just do not understand what you mean about "having them switched from the track supply (also switched)", a diagram might help here.
Sorry, lack of clarity: Get two f**king big switches (technical term, but see comments about current ratings). Wire one into the track feed bus, the other into a separate bus that's connected to the accessory/point decoders. Normal position for both is 'ON', under fault conditions flick the track feed one to 'OFF', set the point(s) through your handset and then reset the track switch to 'ON'
My immediate reaction was balan/unbalan... and then thought, silly old bear(e), this is an AC circuit. Twisted pair is a sure recipe for a short if I use bare copper wires!!!! If I use 15A rated twin, multistrand, cable then I can strip the insulation and wind the two insulated wires to create a twisted pair (others might think that this discussion could only be between a twisted pair of modellers). A power bus created as a twisted pair is going to be a pain in the proverbial with droppers every 21cms (30' prototype rail length) - removing the insulation from a twisted pair, keeping the un-insulated wires apart and then making the feed joints looks like a mind-numbing activity.
Actually, not a bad analogy to compare with balanced/unbalanced cable architectures. Twisted pair speaker cable works because it stops the cable acting as an aerial and picking up external interference.
So, a thought in terms of architecture; run a pair of twisted-pair buses down the boards. Each is switched at the booster, one for 'track' the other for 'points'. Both may have a snubber at the end furthest from the booster, if it's needed. Each bus has one connection on each board. From that connection a series of spurs can be taken to each track section or point/accessory decoder.
Your track is wired normally - with a bare copper wire roughly following each rail, under the boards. each of these wires is connected by a spur to the track bus. I'd suggest using tinned copper at a high enough rating to take the 5A or so suggested, where they cross I'd suggest putting heat shrink insulation on both wires.
Take care with the selection of whatever means you use to switch the polarity of the crossing vees on your points (sorry, I only just thought of this). These too need to be able to carry sensible current - a couple of Amps might be enough here, depending upon how many locos you could have in each track section.
Steph
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