Re: DCC

Bob Pombrio <bob_pombrio@...>
 

At what length does the wire have to be twisted?  5 feet 20 feet?  I am working with a 4x8 layout and my main bus/power feed is Reese vehicle trailer wire.

http://www.summitracing.com/parts/reh-85205?seid=srese1&gclid=CI6GuYmU8rwCFTQOOgod6FsAGg

So it's not twisted.  I went with this stuff because my table is actually 3 32" sections and I wanted a quick way to bridge the sections.  The idea is to be able to easily move the layout form room to room.


From: "len.jask@..." To: WiringForDCC@...
Sent: Saturday, March 1, 2014 12:05 PM
Subject: Re: [WiringForDCC] DCC

 
Hello all,
Interested discussions and opinions here. In my planning stage I'm also pondering the best as not to have to do it over. I'll be laying out in large scale with lots of feet of wire! Every layout/scale is unique as well.
Based on working in the power conversion industry:
 The command bus is small signal and tightly twisting is best. Yes it greatly reduces capacitance but most important it contributes to noise immunity.
As to the power bus I'm still pondering on twisted vs separated. For the actual DC power feed to the booster it is irrevalent as it's pure DC.
From the booster to the track is where it gets tricky. Any conductor of given length generates a magnetic field based on direction and the right hand rule. Two conductors side by side where the currents are opposite the magnetic field cancels but there is capacitance. If spread apart enough, the capacitance is nullified and magnetic field is disregarded, just like the track spread.
For most of my projected layout I plan on using scale telephone poles for most wiring to keep it above ground. The command buss will be Cat5 twisted and the power will have 3 inch spread, just as in the rails so capacitance is null. I'll twist the feeds and for any power bus thats not spread I'll twist the leads as well.
Measure thrice, cut once!
Len Jaskiewicz


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