Wiring problems with Capacitor Discharge Unit

The problem is the wire size!

That willbe the problem.

The length will be contributing to the problem, but the wire size is more important.

Yes definitely.

The shielding could be used as the common return - track and route if you use seperate transformers for traction and turnouts.

No, not to any noticable degree - OTOH the impulse current could affect the traction current.

Current passes more or less only via the surface molecules so diameter is very important.

The type of switch is irrelevant --- I use every possible type without any problem and most of cable runs are between 3 & 5 metres.

Since Maplins gave up selling usable cable I have been buying from Mainly Trains at Watchet and have had consistantly good results.

Regards

Peter A Montarlot

The skin effect is irrelevant for DC control of point motors. It is more pronounced at the sort of frequencies used for DCC.

In the OPs case, thicker cable is the answer and doubling up the conductors using the spares is the first thing to try.

MBQ

Electrical current flows in the outer section s of a solid cable in exactly the reverse form to that of a Newtonian fluid through a smooth tube.

In any case I was justifying the use of heavier cable.

In message , " snipped-for-privacy@hotmail.com" writes

Thanks for the replies. I doubled up the spare wires and there was a huge improvement but not quite enough for reliable operation.

So I think my options are:

1. Find a cable with larger core wires
2. Find a cable with more core wires so I can treble them.
3. Keep the turnout circuits on the baseboard and use some sort of relay system.

I am finding it difficult to compare the wire descriptions on the web - what exactly does 7/0.2, for example, mean?

You could use baseboard mounted SCRs/thyristors between CDU and point motors fired using your lightweight cables to the gate of the SCR. The A-K voltage has to drop to 0.7 volts for the SCR to cease conducting.

In message , Richard writes

It means that each core is made up of seven strands of 0.2 mm. diameter wire twisted together.

I think that your option of baseboard mounted relays is sound . A single pole spring return relay fitted for each operating circuit would enable you to keep the light weight controller as is. The joy of relays being that they are easy to see and repair. However 7/0.2 does me just fine.

Indeed; skin depth is calculated by the formula:

d = square root (2 times resistivity over permeability times angular frequency)

so obviously as frequency tends to zero the skin depth tends to infinity.

For example at 50Hz skin depth is about 10mm whereas at 100kHz it is about

Regards Jeff

In message , Jeff writes

So that's why it's better to use 24/0.2 wire rather than 1 mm. diameter single core wire.

No, unless every strand is individually insulated. This is called Litz wire and is used in high frequency applications where there is a very real benefit from using multiple thinner (insulated) strands.

The advantage of ordinary stranded wire is better flexibilty so it's easier to handle and withstands movement without breaking. As far as current handling goes, it behaves like solid core of an equivalent diameter since the individual cores make regular contact with other cores in the bundle.

Personally, I like solid core for under-baseboard wiring since it is rarely moved and its stays put when you bend it into place.

MBQ

I've just started reading this thread and going back to the original post realised that you using 10 cores for 5 switches. a cdu and a diode matrix.

Are 5 of the cores commoned back at the baseboard?

If so, have a common wire to the switches therefore needing only 6 cores. You could then use 7 core trailer multicore from a car accessory shop.

Andy

In message , Andrew Carr writes

No, I'm using 6 cores for the 5 switches, plus 4 for the controller.

Thanks for trying though :-)

2 AC

= 13 + sheath.