DCC or not DC - that is the question (probably)

[SteveyDee68]

Having spent the afternoon delving into the Power, Control and DCC forums, I have emerged older and none the wiser as to how to go about wiring up a simple micro layout to operate using either DC or DCC. Perhaps some kind RMWebber will explain it in terms I might understand?

 

If this is posted in the wrong forum, hopefully our Moderators will please put it where it should go!

 

I have pottered about with PECO insulfrog points to come up with the following plan for a small micro shunting plank. I know how to wire it up for DC - simple! Three basic feeds, and insulators between facing point toes!

 

 

But to improve power to the track and not rely upon switch blades to provide current, I drew up a second plan with extra feeds augmenting the initial three feeds, as follows:

 

 

At this point, I thought I had worked out a way to ensure power to the tracks including the short bits after an insulated crossing frog, and also thought I could run this under DCC, too. Clever me, pat on the back, improve running over insulfrog points.

 

Then I remembered something about having to isolate point frogs to avoid shorts when using DCC...

 

What was it someone once said about remembering that a pat on the back is only a few inches from a kick up the backside?!

 

Lots of reading, puzzled scratching of chin etc and I drew up the next wiring plan, which I think works under DCC and also with DC power:

 

 

I have only put additional feeds to the side of the track that needs them, either positive or negative (or should that be termed power input and return?) Which leads me to several questions:

 

1) Am I fundamentally right?

 

2) Should I, for simplicity's sake, simply provide feeds to both rails where I have indicated the need for an extra feed?

 

3) My sketch below the plan shows that when rails are joined on one side with an insulated fishplate, a small plastic "insert" means the rail on the opposite side ends up either with an equal physical gap, or puts a kink in the joint. I realise a way around this would be to remove an amount of rail equal to the plastic "filler" from the side with the insulated fishplate. However, that seems an awful lot of fuss with many chances to muck things up! Does it therefore make sense to put insulated fishplates on both sides, and then add an additional power feed to ensure the track continues to receive power?

 

I thought DCC was supposed to be easier!! Any help gratefully received.

 

HOURS OF CONFUSION!

Edited December 29, 2020 by SteveyDee68
Images in right places in text!

[F-UnitMad]

1 hour ago, SteveyDee68 said:

I have pottered about with PECO insulfrog points

 

1 hour ago, SteveyDee68 said:

Then I remembered something about having to isolate point frogs to avoid shorts when using DCC...

If you are using Peco Insulfrog points, then the frogs are not powered, and so don't need isolating.

It's live frog points that need insulation of the frogs, for both DC & DCC.

 

With insulated frog points (usually a plastic frog), then your first diagram with 3 feeds will work just fine with DCC or DC - BUT - what you may want to change for DCC is removing the 'self-isolating' feature of the points, so that all track is 'live' for DCC so loco lights and sounds stay on, if fitted. This can be done either with extra feeds, or by 'bonding' the stock rails with their associated switch rails; this is usually considered good practise anyway for Peco points as you are no longer relying on the switch blades themselves to pass power through to the track beyond the point.

Suggest you have a read of this - https://www.pls-layouts.co.uk/html/frog_types.htm but concentrate on the info about Insulfrogs.

Edit - also, the 'toe' end of the points is the single track end. The diverging tracks end is the 'heel'.

As for gaps caused by insulating rail joiners creating a gap in the join in the other rail, this is a good thing. In hot weather the rails expand, and if you have pushed your rails tight up together so there are no gaps between rails then they end up distorting the sleeper base. This can happen even on a small layout.

Edited December 29, 2020 by F-UnitMad
Further explanation.

[newbryford]

1 hour ago, SteveyDee68 said:

 

Then I remembered something about having to isolate point frogs to avoid shorts when using DCC...

 

 

Regardless of DC or DCC, electrofrogs have to be isolated at the vee as soon as any feed is provided beyond the point frog.

 

What may seem incorrect - but it does work - is that a dead ended fan of sidings with electro or insulfrog points can be powered simply from two rails at the beginning of the fan with metal rail joiners on every joint and no other feed wires or external frog switching

 

You will get the extra reliability of the direct running over the metal frog but now become totally reliant upon blades switching frog power. IMO - a negative trade-off - I would always isolate the frog completely [*] and provide a switch working in tandem with the operating mechanism - be it manual or electric)

 

Looks like I cross-posted with F-UM above!

 

[*] Often described as making points DCC friendly, but is actually making points more electrically friendly - DC or DCC.

 

 

 

 

 

 

Edited December 29, 2020 by newbryford

[Suzie]

It would help really to decide to go for DCC or DC, it will save having to answer the same question twice!

 

Your first diagram is how you would wire it for simple DCC with Insulfrog, for DC you just would not bother with the insulated joiners. If you were doing it properly for DCC with Insulfrog you would add a few more feeds to the dead sections and insulated joiners on the frogs as you have done in the third diagram which is correct for DCC with live frogs.

 

Insulfrog is not like other varieties of dead frog as it needs to be treated the same as live frog when used with DCC, but retains all the disadvantages of dead frog. It will all be quite academic soon as Unifrog will be replacing Insulfrog and the problem will go away.

 

 

[The Johnster]

My view FWIW:-

 

DC pros,

.Cost saving

.Compatibility of older locos

.Small layout with presumably small number of locos means less advantage to DCC

 

DC cons,

.Additional wiring and more switches, with possible consequent reliability issues

.Restriction to operation dependent on isolated sections

 

DCC pros,

.Wiring simplicity

.integration of loco, route setting, signals under one controller

.Control of lights, sound fx, etc.

.12vdc continuous supply to loco improves slow running as pickup is easier

.Stayalives

.Ability to ‘park’ locos anywhere on the layout without isolating sections

 

DCC cons,

.Cost, about double per loco over DC

.Difficulty of fitting chips to older locos

.Pin incompatibility for some locos

.Commitment.  One has to standardise completely or not at all on DCC; it is incompatible with DC on the same layout and switching between systems denies the wiring and switching advantage of DCC, not to mention potential confusion to operators!

 

DCC is most suited to layouts where large numbers of locos operate simultaneously (note operation does not necessarily mean movement, just the number of locos ‘in play’).  On smaller layouts it comes down more to the perceived value of controlling ancillaries like lighting and sound.

 

 

 

Edited December 30, 2020 by The Johnster

[DCB]

You missed the big advantage of typical cab control DC which is fault finding.   Wiring with conventional two wire DCC everything stops with a short circuit, sometimes you cant even reset the points to clear the fault. On anything beyond the simplest layout which can have every piece of stock removed quickly and easily it can take ages to clear a fault which on a sectioned layout would take seconds.  I reckon for UK prototype  it needs a combination of DC sections for fault finding with DCC power.  Then you can either spend hours fitting droppers to every bit of rail or put overload protection in each feed.     Its the Amps that does the damage, 2 amps DC damages fihplates and point blade contacts just like DCC does but if you model overseas railways and need three four or five locos per train you have to up the amps and on DC that means adding all the droppers and point frog feeds associated with DCC.  Take the excess amps out of it and the problem goes away...

[Chris M]

The other big plus for DC is that when you switch the points to a certain track the loco on that track is automatically live. No need to know the code allocated to every loco, no need to select the loco before it will move, just having the points right is all you need. This is the most important thing for me. Train comes into loop and stops, I press one button to switch the points and can just drive the other train straight away. I just couldn't lose this convenience.

 

Another less important feature of DC is that head on crashes are impossible. On my garden railway we hooked up DCC one day and it worked well. Unfortunately within an hour of hooking it up we had our first and only head on smash in 20 years of running.

[Dungrange]

9 hours ago, DavidCBroad said:

You missed the big advantage of typical cab control DC which is fault finding.   Wiring with conventional two wire DCC everything stops with a short circuit, sometimes you cant even reset the points to clear the fault. 

 

But you can do the same on a DCC layout if you use circuit breakers and divide the layout into power districts.  If you design the layout so that there is a separate accessory bus that connects directly to the command station and the track is fed through a circuit breaker then you'll always be able to reset the points (assuming the circuit breaker is set up to trip faster than the command station).  The problem you're describing is where the power to the points has been taken from the track bus.  That wouldn't be 'best practise' for a large layout, but may be considered acceptable for a small one.

 

Anyway, that's not really relevant to this question, which is about the wiring of a small layout where three DC cab sections is not going to make fault finding significantly beneficial, and if required, when operated in DCC the same three switches could still be provided for fault finding (but would normally always be 'on' for operation).

 

The reality, is that wiring for DCC shouldn't be any different to wiring for DC.  Wiring a dropper to each rail would be best practise for both DC and DCC, but with the lower current being used in DC, you can get away with relying on the fishplates, whereas with the higher currents in DCC it is more desirable not to rely on the fishplates to pass high currents.

 

If there is a polarity conflict on DCC then there will be the same polarity conflict on DC.  Drawing out a track diagram with red and black rails shows where these occur and insulated fishplates are required.  The only difference is that DCC is more sensitive to these polarity conflicts as due to the higher currents being used the command station is designed to shut down much quicker than a DC controller would.

 

In terms of DC versus DCC for the particular layout shown I think the main choice is whether the self isolating features of the points is perceived as a benefit as @Chris M does (in which case stick with DC) or whether you'd like all track live to benefit from constant lighting and sounds (in which case, I'd see DCC as preferable).

[john new]

Why not do what I did, i.e. wire it fully for DC with the usual section switches and panel? To make it swappable between either you fit the track power feed and return for BOTH systems up the line from the switch panel with a DPDT acting as a splitter switch so as to select one or the other. My option also uses a plug-in DCC throttle (NCE Powercab) and a plug in Gaugemaster W for DC. This gives an instant visual aid as to which system is in use/was used last time.

 

When running with DCC I just set all the switches to on. With this option DCC is therefore not a worry and can be ignored as regards track wiring, however, you do need to get the DC side sorted which for a dual system you have to do anyway. The best tip coming out of the DCC guidance is make sure there are plenty of droppers for each rail section rather than relying on the fishplates, that in turn will improve reliability under DC. 

 

It is still possible to c**k things up by putting the the wrong locomotives on the track when the DCC is fed in but as it is visually easy to tell which system is plugged in this risk is lowered.  Also make sure your DCC locos have the CV set for DC enabled running, thereby eliminating that as problem if you give the wrong track feed option to your DCC items.

 

I am still a bit of a DCC newbie myself therefore if the DCC experts see that anything above is wrong I would like to know so I can correct my own installation.

 

Edit - addition: initially of course you can connect all the track feeds together underneath - the control panel can be added later to allow more than one loco at a time under DC. I did a quick and dirty cheat, a bit of scrap copper wire stripped from heavy duty cable (Skip bin sourced) mounted between two chocolate blocks with all the wires soldered to that. When I had the panel built the wires were then unsoldered with individual extensions joined on at that location and linked individually to the panel switches. 

 

Edited December 30, 2020 by john new
For clarity and a typo correction.

[SteveyDee68]

Thank you to everybody responding to my queries, nearly all names I recognise from reading threads on the Power, Control and DCC forum.

 

I wanted a simple layout to get to grips with the basics - I am using insulfrog points because I already have them and they are simple to use for DC; I wanted to have the wiring right so that I can then simply plug in a DCC controller to switch it to DCC.

 

Reading various threads, I was picking up the idea that insulated/dead frog points should be treated the same as live frogs in DCC, hence my confusion and asking the questions.

 

A DCC advantage I hope to eventually make use of in particular is 'stay alive' for short wheelbase locos. Correct me if I am wrong, but would that not overcome any disadvantages of using dead frog points?

 

I am going to brew a nice strong cup of coffee and carefully read through all the responses above again. I really would like to be wiring up the track later today and get something running, before my revitalised modelling mojo is, like Chiddi in "The Good Place", totally immobilised by indecision!

 

HOURS OF FUN READING!!

[The Johnster]

I use insulfrogs on a DC BLT for electrical simplicity, and rely on the point blades alone to provide current to the roads they are set to; this is against perceived wisdom and the usual advice but works for me.  I operate my turnouts by hand, again in the interests of electrical simplicity.  With carefully laid track, level and smooth to it’s adjoining piece, running is pretty good and stalls on the frogs don’t happen, though I do have to be aware of carbon deposit and general crud building up and preventing a good connection between blade and stock rail.  My locos are largely small 6-coupled, but there is a Hornby W4 Peckett which has trouble with the long dead frog of a curved turnout in the fiddle yard.  A stayalive would help if one were available for DC.  
 

Stayalives, if I understand their operation correctly, are a bit like electronically simulated flywheels, and operate most effectively at medium to high speeds; unfortunately their effect is diminished at the low speeds when it is most needed, bit even a diminished effect is of great value to smooth slow running.  Having the track current at a consistent 12vdc and controlling the current fed to the motor by a chip aboard the loco is another considerable benefit if DCC.

 

Deciding on DCC is a once and for all commitment which needs to be made before work commences on the wiring of the layout.  A fleet of 15 locos mean that I am committed to not having it; the cost is prohibitive for me and becomes more so with each new loco, bit I am content with DC.  You might not be, but you do need to make the choice soon.  

 

[newbryford]

2 hours ago, SteveyDee68 said:

 

 

A DCC advantage I hope to eventually make use of in particular is 'stay alive' for short wheelbase locos. Correct me if I am wrong, but would that not overcome any disadvantages of using dead frog points?

 

Possibly, but stay alive capacity takes up physical space.

Small locos - that are more likely to need stay alive capability, have limited available space.

 

Catch-22.

 

 

 

[PMP]

20 hours ago, SteveyDee68 said:

Having spent the afternoon delving into the Power, Control and DCC forums, I have emerged older and none the wiser as to how to go about wiring up a simple micro layout to operate using either DC or DCC. Perhaps some kind RMWebber will explain it in terms I might understand?

 

If this is posted in the wrong forum, hopefully our Moderators will please put it where it should go!

 

I have pottered about with PECO insulfrog points to come up with the following plan for a small micro shunting plank. I know how to wire it up for DC - simple! Three basic feeds, and insulators between facing point toes!

 

 

 

This design will work fine with both DC and DCC equipment with dead frogs. It’s almost the exact plan I had on my exhibition layout Albion Yard.

I also had a couple of isolation sections to hold locomotives in on the rare occasions we ran more than one engine in steam. The feeds you’ve shown will work on both types. With DCC and dead frog point when a point is against the locomotive, it will kill the power to it, just as DC does. Unfortunately when you ask dc or dcc you can get a lot of rubbish quoted at you, often from people with no experience of DCC in particular. There’s a prime example above of someone telling you the DCC is 12Vdc and you have to make the commitment before wiring the layout. Those are big red warning flags on their knowledge of DCC.
My layout was built entirely in DC, when I added DCC all I did was to add a separate feed to the tracks for the DCC controller. We had a procedure to remove all engines, disconnect the power, remove the DC controller, plug the DCC (NCE powercab) in and we were ready.

DC/DCc locomotives were never out of storage simultaneously  so incompatible stock never got mixed up. Any isolated sections were switched to ‘on’ for DCC use.

In summary your most basic initial design above will work on both systems. You can start DC and ‘move up’ going the other way needs far more planning

Edited December 30, 2020 by PMP

[Dungrange]

2 hours ago, The Johnster said:

Deciding on DCC is a once and for all commitment which needs to be made before work commences on the wiring of the layout.

 

I don't agree.  It's true that you can't mix DC and DCC track power (ie connect both a DC controller and a DCC Command Station at the same time) so you choose one or the other, but as has been said above, there is nothing to stop the layout being wired for dual use - ie wire it as per DC and then set all the switches to 'on' when a DCC Command Station is plugged in instead of a DC controller.  Most DCC fitted locomotives will operate satisfactorily on a DC layout (unless DC running has been disabled in the decoder), so it's possible to fit decoders in some stock before buying a Command Station if there is a need to spread the cost.

 

1 hour ago, PMP said:

In summary your most basic initial design above will work on both systems. You can start DC and ‘move up’ going the other way needs far more planning

 

I think this is the most important point.  It should be easy to convert any layout wired for DC to DCC (provided wire of adequate cross section has been used in the construction) by simply unplugging the DC controller, plugging in a DCC Command Station and turning all the section switches 'on'.  However, it will rarely be straightforward to take a DCC layout that was designed around being able to park locomotives anywhere and convert to DC, because all of the isolating sections that are necessary for realistic DC operation won't exist. 

[Suzie]

DCC stay-alives work best at low speed when the motor is drawing less average current. The Zimo one in particular is excellent when the train is almost stopped since it uses the stored energy to move the train along to the first bit of live track so as to keep everything powered up.

 

While you might like to think of it as a flywheel it is a lot more capable than a simple flywheel, more like a flywheel with its own gearbox!