Hornby DCC Select wires

[ericr00]

The wires on my Select Controller are Black and Black/white, which ones are the positive and negative, as I wish to replace them with only Red & Black wires ?

[96RAF]

DCC is like AC it goes positive and negative many times a second, so it doesn't matter which may round you connect with DCC unless you are connecting various parts of the layout together when you should match polarity or more correctly phase by connecting red to red, blue to blue, tartan to tartan or any other colour combination you decide to use. Just be consistent, then the waveform will remain in phase.

 

If you cross connect DCC polarity then it will short just like DC.

[Chrissaf]

Just to add to what Rob has said. DCC is a Bi-polar waveform, which means that it has a voltage that swings both positive and negative. Thus DCC does not have any red and black voltage polarity. It does however have 'phase' and as Rob says if you wire in a cross-over in the wiring you get a short. This is probably why the wires are given a white strip to help eliminate wire cross-overs, but using red & black would potentially give someone the wrong impression that measured voltages would have polarity ... which they don't ... hence why red & black are avoided.

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The example Oscilloscope trace below shows a typical DCC track signal Bi-polar waveform. The horizontal line in the middle is the zero volt line.

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