Converting layout from DC to DCC. What have you done?

[dasatcopthorne]

Hi Guys.

 

We are going DCC on a small/medium layout.

 

It currently works fine on DC and we are considering ways to be able to use both.

 

In the main it will be DCC but at times it will need to be connected to a DC layout as a branch.

 

There are a fair number of points and in DC a fair number of sections with common return.

 

We are intending to use NCE equipment.

 

What are your thoughts?

 

Cheers

 

Dave

[Barry Ten]

I wired my American layout for DC cab control with common return, but switched to DCC (Prodigy) without problems. I've since gone over to NCE Powercab and again, no problems. The Prodigy is now running my 4mm layout.

 

The conversion consisted of unplugging the wires from the DC controller and screwing them into the DCC unit instead, so there would be no problem in going back to DC if I felt the need. I don't use any special wiring and other than some additional feeds for frog switching, my Peco points are unmodified.

[Oldddudders]

In fact, as Barry says, the basic needs of DC and DCC are very similar. So much so that DCC could be described as "common output, common return" since a DCC wiring diagram looks exactly like that, with just the famous pair of wires from the command station running under the layout, and attached to as many rails as you see fit, observing polarity at all times, of course. Do as Barry says, and you should have a relative success simply by turning all your section switches to "on".

 

It worked for me in 1997, and I haven't looked back.

[34theletterbetweenB&D]

Same here. Had a three cab DC common return wired and sectioned layout. Took out controllers feeding cabs 2 and 3 and made cab 2 the DCC track feed, cab 3 the DCC programme track feed. So now I can run any or all sections as DC, DCC or DCC programme. If running on both DC and DCC simultaneously it is up to the operator not to drive across a DC/DCC section break; similarly when using the programme track one has to be careful to only make a single section live, with only the loco on it that is to get an address change. I am a lot more careful since the day I re-addressed near twenty locos in one fell swoop. No 'undo' button...

 

 

[PaulT]

I have just converted my nearly 30 year old P4 layout to DCC.

The conversion was finally triggered by old DC controllers getting unreliable.

 

There are over 20 locos, 80+ points and 15 main sections in three groups.

 

I am happily using Roco MultiMaus and have added 3 MERG Block cutouts (BC01) so the three main track groups of sections have individual short circuit protection.

 

Although I don't envisage using DCC control of individual turnouts I have provided an interface to my old CMOS logic route selection so the DCC turnout function actually sets routes; this is based on MERG kits for accessory decoders (ACC3) which are quite versatile for various outputs.

 

Initial reaction from my two friends/operators is favourable provided I disable Momentum settings in locos. They much appreciate no longer needing to faff around with section switches and like the feel of controls.

 

Wiring was an initial concern as it was all light cabling with a track common return. However the many main sections meant that there are multiple feeds to moderately short sections which only require to carry 2 or 3 locos simultaneously. Most locos have Portescap or Mashima can motors so are quite light in current demand. I made careful tests of loop resistance, added a few common return wires where the resistance was a bit high and am now happy with the classic DCC coin tests.

Due to the common return wiring I regard it as unsafe to have combined DC and DCC power so the changeover is total.

 

Wish I had converted years ago!

 

Not only are trains easier to drive but there are some spin off benefits too, particularly the walkabout control of routes.

[Kenton]

Simple. If the layout was correctly wired for DC then it is as simple as throwing all the section switches closed and changing controllers. I wire all layouts with this in mind.

[Edwin_m]

Paul has it right - it is important to use the coin test or check feed resistance and reinforce the feeds if necessary. Not all layouts are wired as Kenton suggests, and a large one using thin wire risks having too much resistance to trip out on a short circuit, just getting very hot instead.

[Kenton]

Not all layouts are wired as Kenton suggests, and a large one using thin wire risks having too much resistance to trip out on a short circuit, just getting very hot instead.

Would agree that not all - probably most are badly wired, taking short cuts from "best practice" to simply get away without comprehensive wiring. It shouldn't be the case but this "short-cut" practice should be discouraged. If only that one day you just might get bitten by the DCC bug.

 

Nothing much has changed between good wiring for DC and for DCC.

 

However a big DC layout will (should) have shown up resistivity issues before making the leap to DCC.

[PaulT]

 

 

However a big DC layout will (should) have shown up resistivity issues before making the leap to DCC.

 

I have to disagree., although "big" is a bit imprecise!

DC layouts are often wired so each section can only handle one loco and thin wires suffice and show no problems.

The DCC possibility of many locos per section can increase current loading hugely and reveal issues that require attention

[Edwin_m]

Not only many locos per section, but the current that flows through a short circuit too. Typically the command station will cut out at 5 amps but it takes only a few ohms in the feeds to keep the short circuit current below that and therefore defeat the cutout.

[PaulT]

Not only many locos per section, but the current that flows through a short circuit too. Typically the command station will cut out at 5 amps but it takes only a few ohms in the feeds to keep the short circuit current below that and therefore defeat the cutout.

 

Absolutely agree.

I get around this by having 3 power zones each protected by Merg cutouts set to 1 Amp....enough for two efficient locos... and safe with old thin wiring. The trip current level can be set to any current level you want.

Many DCC manufacturers offer similar devices but too pricey for my taste and less flexible.

[Kenton]

I have to disagree., although "big" is a bit imprecise!

DC layouts are often wired so each section can only handle one loco and thin wires suffice and show no problems.

The DCC possibility of many locos per section can increase current loading hugely and reveal issues that require attention

So is "large" which I was responding to.

 

All this is back to my point: if the DC layout is wired correctly (and that is not using thin wire) not cutting corners and not omitting feeds (droppers) from track to a sensible bus. Then there is no reason why it should not be an easy change over.

 

The trouble is most people wire their DC layouts without any thought to standards or to future changes. They run the bare minimum of wiring to get the job done, rely on switch blade contacts, and are adept at soldering dry joints on what few track feeds and switches they employ.

[298]

Not only many locos per section, but the current that flows through a short circuit too. Typically the command station will cut out at 5 amps but it takes only a few ohms in the feeds to keep the short circuit current below that and therefore defeat the cutout.

 

If the OP only proposes to use a Powercab then it's 2A output will be less of an issue. The only way to find out is to wire it in and have a go, but be prepared for the obvious issues that might cause a short, such as wheelsets shorting out over pointwork.

[PhilM]

Can anyone clarify what correct DC wiring is please? (to allow a subsequent change to DCC) i.e. what type of wire should I be using rather than the normal bodge!

[Kenton]

By "correct" wiring I refer to the rules of wiring a layout not the type of wire used.

Wiring Rules:

1. Every frog rail has an insulating joiner.

2. Every stock rail has a power dropper. (I bond stock rail to adjacent switch rails - I don't have faith in the switch rail contact)

3. Every frog polarity is switched on the point motor.

4. All isolated sections (including those isolated by the insulated joiner) have a dropper. (In DC the section isolations go back to the control panel switch) - in practice every bit of track will have power if the switches are thrown - no exceptions.

(short cuts can be taken, are often suggested, and sometimes work)

 

But in terms of the type of wire, I have always used standard lighting cable which is single core and capable of taking 5A - It usually comes in 3 core with the 'earth' unsheathed - I simply remove the outer sheath leaving 3 useable leads. For droppers I use a multicore 'bell' wire. It is a bit heavy for soldering to rails - especially if you are disorganised and fail to plan the wiring so that you solder in the wire to the bottom of the rail before laying the track. The wire will happily take 1A. I use the standard "layout" wire for all points and accessories as the current draw is very low.

 

Good track wiring requires confident and competent soldering (no 'dry' joints)

[amdaley]

One thing I would add t Kenton's excellent advice above is to test each connection you make as you make it for continuity. Don't wait until you have all the connections finished. Do each connection as you make it.that way you will know straight away if you have a sound joint or not.