Correct cable choice?

[teaky]

Nice, tidy wiring there.

[meil]

On 23/06/2019 at 20:43, teaky said:

Does the 16/0.2 qualify as "meaty" in this context?

 

 

No I would use 24/0.2 or 0.75sqmm

[Poor Old Bruce]

One point I think has not been mentioned so far in this topic is the use of fluxed solder. When you have tinned the wire and the rail and want to join them together, you only need to add extra flux. You should not need to add extra solder as well, you could easily end up with a huge blob of solder at the joint. Get some separate flux for sweating the joints neatly, spread it on the parts to be joined, place the cable onto the rail the apply the iron (and wait for the smoke from the flux to head straight for your nose - Why does it do that?).

[DCB]

2 hours ago, hobbyhorse said:

I'm a bit belt and braces when it come to wiring. For my ON30 layout which is quite large I've used 16/0.2 for the droppers with short runs to the connector blocks, each section of rail has 2 droppers,  from these the baseboard internal wiring is 24/0.2. Then the main bus is 32/0.2. The rail code is 83 so quite a small size with the droppers soldered to the bottom which becomes invisible once ballasted. The layout is designed for operations with upto 8 people required, and lots of locos on the layout requiring quite a lot of power. Hope this helps.

 

 

OMG. Super neat but it reminds me of the nightmare of rewiring our Village Hall main circuit board back in the early 2000s.  All the wires the same colour and then the little tags fall off.   My experience is the choc block connectors are the no 1 source of "voltage drop" after point blades and closely followed by fish plates. I try to avoid them preferring soldered joints or proper multipin connectors where wires need to come apart. Fish plate failure is directly proportional to the power unit's rating and the current consumption of the trains, a long double/ triple headed freight with around 2 amps being drawn will absolutely hammer the fishplates, This is probably why US modellers are pretty paranoid about droppers and bus wires. A fully lit double headed 12 coach Pullman will also be up there in the consumption stakes and probably wont actually run far without tripping 90% of DC cut outs, but will be fine on most DCC set ups.  I run 2 X 1 amp DC power units sometimes to power my freights and have seen fishplates glow red hot.

In this day and age wiring a new DC layout for DCC conversion has to be plain common sense, so I use old van wiring rated at 5 amps and colour coded, the bit along the roof to the tail lights, 10 or more feet long. I get big chunks from the local scrap yard.  Previously I used phone wire, single core one piece right back to the section switches, and have not suffered any  noticeable voltage drop despite one section being around 30 feet from the controller,  However the next section fed through several connectors and a mix of wires over the lifting section has noticeable voltage drop/ trains slowing.

What you will find invaluable is section switches to isolate various sections of track, ideally both feed and return to aid fault finding. That way you can switch everything off and re apply power progressively to locate faults.  Without them it can be almost impossible to fault find and even with them can take ages when the fault is intermittent, as in metal wheels bridging an isolated rail gap.

[sharris]

11 hours ago, meil said:

No I would use 24/0.2 or 0.75sqmm

 

I'm assuming that as it's a roundy roundy that the bus will be a loop too (a bit like a ring main).

 

 The most distant part will be ~12m from the controller and fed through both sides of the loop so 16/0.2 would be approaching the current capacity/voltage drop characteristics of having 32/0.2 on a linear layout. 

 

[RobjUK]

9 hours ago, DavidCBroad said:

My experience is the choc block connectors are the no 1 source of "voltage drop"

 

There are two grades of choc blocs with very different clamping characteristics.

 

The cheap ones just have a bare screw protruding in to the body, and only really work well if the cables in use are a fairly snug fit before clamping; with smaller wires, a lot of the strands can end up beside the screw and hardly any actually clamped.

 

The better type have a "wire protection leaf", a flat plate under the screw to trap the wires and stop them bypassing the screw - or getting twisted off as it tightens.

 

If you are using them with fine wires, it's well worth getting the better grade - though they can be harder to find.

Example: https://uk.rs-online.com/web/p/non-fused-terminal-blocks/4649744/

 

 

[Junctionmad]

As a young engineer, I joined a “ blue skies “ R&D facility of a major multi national ,” only two things will get you fired” my boss said , “ insulation tape or chocolate blocks “  

[RobjUK]

8 hours ago, Junctionmad said:

only two things will get you fired” my boss said , “ insulation tape or chocolate blocks “

 

I detest the things as a "general use" connector, we often come across them in bodged repairs in industrial gear. However for this specific application, I can't think of anything more suitable at a sensible price. 

That's why I suggested at least the higher quality ones that have a chance of giving a decent long term connection.

 

If I was doing an under board wiring setup I'd probably use miniature DIN rail terminals (for 15mm rail), but it's something we stock so I'm familiar with them. However, in small quantities they are almost £1 per terminal, which is far more expensive that standard 35mm rail terminals..

 

The full size ones (for 35mm rail) we use in large quantities are too big, about double the size,  and overkill for this type of application..

 

Photo of a few miniature ones fitted to a rail plus some individual parts, for people who are not familiar with them; the big one is a fuseholder terminal:

 

Edited June 30, 2019 by RobjUK
typo

[teaky]

Just to round this thread off.

 

I'm going to go with solid core stripped out of 1mm twin & earth for the main bus wiring and 7/0.2, kept short, for the droppers.

 

Thank you for your help everyone. 

[AndyID]

On 06/07/2019 at 07:34, teaky said:

Just to round this thread off.

 

I'm going to go with solid core stripped out of 1mm twin & earth for the main bus wiring and 7/0.2, kept short, for the droppers.

 

Thank you for your help everyone. 

 

Don't bother trying to keep the droppers very short. 7/0.2 has little resistance - less than 0.1 ohms per meter. (A meter length will drop less than 0.1 volts at 1 amp.)

[john new]

Squires offer the 560-736 Lead Scart Plug to Scart Plug Universal 2.5m..... (Other makes available, and I have several in store from TV/video use*)

 

There is no note about current capacity or wire sizes.

 

The intention =  13.5v DC for a DCC controller input and 2 x 16v AC for points and a second controller's input (DC walk around). Amps around 1.5A up to 2A max IIRC the various notes correctly. 

 

Mechanically it looks my best option with extra pins available for future expansion, electrically I have no idea if the gauge of wire is suitable as it isn't stated. The one power box will be used for feeding more than one layout (not simultaneously) hence looking for commonly available connectors.

 

Has anyone any experience of using SCART cables to link the after transformer layout supply feeds to a floor located mains power-box? Reason for asking - need to know before ordering/fitting the associated chassis mount fittings etc.

 

The alternative option - probably XLR fittings/known cable type.

 

* NB I know some of these may not use all the pins.

Edited July 13, 2019 by john new
Added a footnote re pin use.

[RobjUK]

4 hours ago, john new said:

Has anyone any experience of using SCART cables to link the after transformer layout supply feeds to a floor located mains power-box? Reason for asking - need to know before ordering/fitting the associated chassis mount fittings etc.

 

SCART cables are definitely not suitable for any kind of power connection.

 

They consist of many fine cores, mostly tiny coaxial cables & a multicore screened group in the top quality stuff.

 

The photo below is the makeup of a good quality SCART cable; I just happen to have some bulk stuff kicking about.  A bit blurry, getting a good focus was not easy but clear enough to make out the individual cores, I think.

The "large" red/green/blue/yellow/white/black cores are each a tiny coaxial cable with a few strands of screen wrap and an extremely small centre core - it's most obvious in the green one.

The overall cable is almost all insulation, due to the quantity of cores and their types.

 

The connectors themselves could be used at up to a couple of amps per contact, possibly - but "D" connectors are smaller, cheaper and generally better quality.

eg. The D15 type would be suitable, you can use several contacts in parallel for higher currents as needed and all the shells, latches or screwlocks etc. are readily available.

eg.

https://uk.rs-online.com/web/p/solder-d-sub-connectors/6740748/

https://uk.rs-online.com/web/p/solder-d-sub-connectors/6740767/

 

 

 

Edited July 13, 2019 by RobjUK
Photo replaced; first attempt too blurred.

[john new]

17 minutes ago, RobjUK said:

 

SCART cables are definitely not suitable for any kind of power connection.

 

They consist of many fine cores, mostly tiny coaxial cables & a multicore screened group in the top quality stuff.

 

The photo below is the makeup of a good quality SCART cable; I just happen to have some bulk stuff kicking about.  A bit blurry, getting a good focus was not easy but clear enough to make out the individual cores, I think.

The "large" red/green/blue/yellow/white/black cores are each a tiny coaxial cable with a few strands of screen wrap and an extremely small centre core - it's most obvious in the green one.

The overall cable is almost all insulation, due to the quantity of cores and their types.

 

The connectors themselves could be used at up to a couple of amps per contact, possibly - but "D" connectors are smaller, cheaper and generally better quality.

eg. The D15 type would be suitable, you can use several contacts in parallel for higher currents as needed and all the shells, latches or screwlocks etc. are readily available.

eg.

https://uk.rs-online.com/web/p/solder-d-sub-connectors/6740748/

https://uk.rs-online.com/web/p/solder-d-sub-connectors/6740767/

 

 

 

Thanks for that. Had a feeling the wires would be too thin as the flat version cables didn't look very sturdy.

 

I have some D connector pairs in hand recycled from earlier layouts, but if I use them they will need de-soldering/rewiring - the advantage of switching to SCARTS looked like the ability to buy off-the shelf, ready made, sealed, leads.

Edited July 13, 2019 by john new

[melmerby]

If using D plugs/sockets, look out for the quality ones with PTFE insulation and solid & gold plated connectors.

Cheaper ones use fabricated pins and receptacles which are much poorer quality and more easily damaged.

 

[Gordon H]

1 hour ago, john new said:

Thanks for that. Had a feeling the wires would be too thin as the flat version cables didn't look very sturdy.

 

I have some D connector pairs in hand recycled from earlier layouts, but if I use them they will need de-soldering/rewiring - the advantage of switching to SCARTS looked like the ability to buy off-the shelf, ready made, sealed, leads.

 

The only advantage of SCART leads is that they are available off the shelf.

Otherwise they are pretty hopeless for our use.

As has been pointed out their wire cores are typically only suitable for low current audio/video signals (not unreasonable as that is what they are intended for).

They have no latching mechanism, so are quite easily dislodged.

The panel sockets for them are usually intended for PCB use only, which makes them awkward to terminate with actual wires.

I certainly wouldn't use them on a layout.

Edited July 13, 2019 by Gordon H

[melmerby]

1 minute ago, Gordon H said:

 

 

The panel sockets for them are usually intended for PCB use only, which makes them awkward to terminate with actual wires.

 

I was going to say rubbish to that as I have used panel mounted solder terminal scarts*, but when I just tried to find one online I couldn't!

Times have obviously changed.

*N.B Only for TV use, not for model railway use I might add. They are just not good enough. (Mind you they are rubbish for TV as well!) Blame the French.

[john new]

1 minute ago, melmerby said:

I was going to say rubbish to that as I have used panel mounted solder terminal scarts*, but when I just tried to find one online I couldn't!

Times have obviously changed.

*N.B Only for TV use, not for model railway use I might add. They are just not good enough. (Mind you they are rubbish for TV as well!) Blame the French.

"SCART SOCKET RIGHT ANGLE a 21 way black plastic scart socket with right angle solder type connection. PCB or chassis mounting. CODE TYPE PRICE 560-497 Scart Socket Right Angle."

 

Squires have them in the catalogue; part No. 560-497 as above* It was seeing those whilst looking for something else that   started the chain of thought of using SCARTs in the first place. (NB Whether in stock = ? and I won't now be checking).

 

* Link http://www.squirestools.com/files/e06a.pdf Page 13/18 of the pdf. 

[melmerby]

1 hour ago, john new said:

"SCART SOCKET RIGHT ANGLE a 21 way black plastic scart socket with right angle solder type connection. PCB or chassis mounting. CODE TYPE PRICE 560-497 Scart Socket Right Angle."

 

Squires have them in the catalogue; part No. 560-497 as above* It was seeing those whilst looking for something else that   started the chain of thought of using SCARTs in the first place. (NB Whether in stock = ? and I won't now be checking).

 

* Link http://www.squirestools.com/files/e06a.pdf Page 13/18 of the pdf. 

Not what I was looking for, that is really a PCB mounted version and readily available from component suppliers.

The ones I have used in the past had proper solder receptacles, similar to the line plug. As in this line socket but chassis mountable:

https://www.ebay.co.uk/itm/21-Way-Scart-Line-Socket-Plastic-Cover-and-Solder-Terminals-/264140614095

(Squires also have them, item above in your link)

Edited July 13, 2019 by melmerby

[Guest]

I work as an automation electrician and knows how you can use cables and the wires.

Since we are writing about small train layouts and the power feeder is not high, you need just only weak wires, depends transformer and power supply.

This topic is about non-DCC/MM so i present this for you:

TRANSFORMER 14-16 VAC   2,5-3,0 amps

I suggest 0,14-0,25 mm thick wire

 

POWER SUPPLY 12-24 VDC   max.2,5 amps

I suggest 0,25-0,5 mm thick wire

 

When you use train layouts all accessories they don´t need so much power because of the small details.

Most lighting are LED and those doesn´t draw so much in the power.

If you use digital to the tracks i recommended you use 0,5-1,5 mm (depends size of the power feeder).

 

[Dave John]

Hmm, I went for ready made d type for all the control stuff  and Click 4 pole lighting connectors wired with 1.5 4 core flex for the 2 dc power busses 

 

https://www.ebay.com/p/Famous-Original-Male-to-Female-25-Pin-Parallel-Db25-Printer-Cable-2-7m-M5g4/1070134147?iid=252471965711&rt=nc

 

 

[RobjUK]

2 hours ago, Anders63 said:

This topic is about non-DCC/MM so i present this for you:

TRANSFORMER 14-16 VAC   2,5-3,0 amps

I suggest 0,14-0,25 mm thick wire

 

POWER SUPPLY 12-24 VDC   max.2,5 amps

I suggest 0,25-0,5 mm thick wire

 

The critical part with low voltage systems such as model railways is not the _current_ capability of interconnecting cables, it's the resistance per length and the voltage drops that resistance will cause when under load.

 

A few volts drop on a mains power circuit is pretty meaningless - a few volts when you are starting with 12V or thereabouts is catastrophic!

 

Also, voltage drops are far more critical with non-DCC systems as the control voltage regulation for speed has to run through the entire wiring and track system to get to the motor.

 

With DCC, the regulation and speed control are performed within each locomotive - as long as the track voltage does not dip so low that the required motor voltage cannot be achieved, it can stand quite a variation with no ill effects.

 

 

[Guest]

3 hours ago, RobjUK said:

 

The critical part with low voltage systems such as model railways is not the _current_ capability of interconnecting cables, it's the resistance per length and the voltage drops that resistance will cause when under load.

 

A few volts drop on a mains power circuit is pretty meaningless - a few volts when you are starting with 12V or thereabouts is catastrophic!

 

Also, voltage drops are far more critical with non-DCC systems as the control voltage regulation for speed has to run through the entire wiring and track system to get to the motor.

 

With DCC, the regulation and speed control are performed within each locomotive - as long as the track voltage does not dip so low that the required motor voltage cannot be achieved, it can stand quite a variation with no ill effects.

 

 

What the hell are you writing about???

We are not writing about 100 metres layout or what.

When i feed 12 VDC for the LED lighting house it´s shining excellent.

There is a lot of variation by use power feeder depends what you want to connect.

There is hundreds of relay (example) with difference power source to feed it.

What ever with the wires.

You can even use digital layout with the trains and control turnouts motor or switch motor analog.

What ever!

Use copper wires, because they works perfect with the ac/dc power.

[sharris]

11 hours ago, Anders63 said:

 

TRANSFORMER 14-16 VAC   2,5-3,0 amps

I suggest 0,14-0,25 mm thick wire

 

POWER SUPPLY 12-24 VDC   max.2,5 amps

I suggest 0,25-0,5 mm thick wire.

 

 

I'm sorry, but the diameters of the wires you are suggesting are in the realm of wire-wrap wires - fine for small signals across a circuit board, but I wouldn't use wire-wrap wire for supplying power to a device 10cm across a circuit board taking, say, 100mA, let alone a model train that may be taking over an amp 12 metres away.

[AndyID]

6 hours ago, Anders63 said:

What the hell are you writing about???

 

 

I think he's writing about Ohm's Law. You might want to take a look at the chart here.

 

 

[RobjUK]

6 hours ago, Anders63 said:

What the hell are you writing about???

 

Cable resistance and voltage drops - the wires you suggest are far too thin for practical use to power a layout.

 

Quote

TRANSFORMER 14-16 VAC   2,5-3,0 amps - I suggest 0,14-0,25 mm thick wire

POWER SUPPLY 12-24 VDC   max.2,5 amps - I suggest 0,25-0,5 mm thick wire.

 

And sorry, but to be blunt, if you think it's OK to use thinner wire at a higher current  because the voltage is different or it's AC rather than DC, your understanding of basic electricity and electronics is somewhat lacking.

 

Please read up on Ohms Law, as AndyID suggests.