DCC On/Off Switch

[JohnieP]

I’m thinking of separating my layout into different power zones to help with fault detection. I’ve spoken to Gaugemaster and they suggested that I use a GM507 switch. I’ve never done any soldering before, but I wondered if a Hornby R047 On/Off lever switch could do the same. I will be using Hornby Isolated fishplates (R920). If the Hornby lever switch is ideal would I just require one power clip to put the wires from the lever switch into in order to operate the isolating section?

[96RAF]

If you are into the need for power zones then it would be preferable to have a proper zoned power bus rather than rely upon power clips, although they will do the job to a certain level of reliability.

 

Learn to solder - it is not difficult, just needs some basic procedural skills and cleanliness of the parts to be soldered, then lots of practice on old bits of rails.

[JohnieP]

Thank you for the advise RAF.

[Chrissaf]

The Hornby R047 is technically equivalent but a far more expensive version of the GM507 switch. But they are both Single Pole Single Throw (SPST on/off) switches.

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This means that they will only be able to isolate one rail only of a power zone, which is not very helpful if you intend to use them to help with diagnostics. To completely isolate a power zone you need a DPST (Double Pole Single Throw) switch that can then isolate both rails of a power zone.

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Hornby do not make any switches with Double Poles.

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GM probably suggested the GM507, because they can be used when you design a DC Analogue layout with switched zones, and you only need to isolate one rail. But you have stated that you want to isolate a power zone for fault diagnostics, thus that would need both rails to be isolated (but I cannot quite see what methodology you would use to undertake such a diagnostic task). Not only that, but you have indicated your layout is DCC not DC, so that makes your switching methodology even more of a strange requirement.

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The Guagemaster switches are very common electrical switches that are just re-badged with a GM part number at inflated prices. Their switch types can be purchased from loads of different suppliers at much cheaper prices.

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A selection of switches at cheaper prices.

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Here is a link to my 'How to Solder' tutorial.

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Rather than asking GM who have a vested interest in selling you their products, why don't you outline what it is you want to achieve** and let us offer some unbiased suggestions and recommendations.

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Note**

What is the issue you want to resolve?

Why do think adding switches will facilitate the issue resolution?

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Excessive use of Hornby Power Clips can be a 'fault liability' in their own right, as they are not that reliable. It is much better, much more reliable and much more aesthetic to use 'directly soldered to rails' wiring.

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[JohnieP]

Thank you chrissaf for your reply. The layout I'm going to be creating is 14ft x 8ft. I was considering using power zones on the layout for help regarding fault detection. However, after doing a few Google searches some comments have said this isn't required for a layout of this size. Is this correct?/media/tinymce_upload/e3b2bc1d5bb039b030521a79cab00c7a.jpg

[Chrissaf]

I believe you may have been reading comments & articles with an originating American bias relating to the use of 'DCC circuit breakers' to separate a larger layout into multiple power domain zones. The theory being, that a 'short circuit' in a zone will only trip the associated 'DCC circuit breaker' thereby identifying that the short is in that defined area of the layout. The other reason for a 'DCC circuit breaker' is on large exhibition layouts, the zones that do not have the short continue to operate, thereby giving the public something to continue watching whilst the fault is rectified. The shorts in question not being faults par say, i.e not permanent shorts due to wiring and track faults. But more brief transient shorts of the type generated by rolling stock bridging opposing power rails on say points for example. Thus easy to rectify in an exhibition environment allowing the 'DCC Circuit Breaker' to be quickly reset to bring the whole layout back on line without the public hardly noticing.

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DCC Circuit Breakers are commonly used on layouts in the USA where they tend to have a DCC Controller (that they call a throttle) connected to a number of high current boosters (each 5 amps or more). The UK layouts tend to use single DCC controllers that integrate the 'throttle' function with a 'booster' function. Thus, although 'DCC Circuit Breakers' are available to purchase in the UK, they are not commonly used for 'home based' UK layouts.

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Yes, your layout is quite large if looked at from the point of view of the amount of track metres rather than overall physical floor space size. If you do separate the layout into 2 or 3 isolated power zones, then I would suggest using 'Boosters' not DCC Circuit Breakers to power them. If a short occurs on a section of the layout powered by a 'booster' then I believe only that one section will lose power.

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However that all said. Using mechanical (electrical) isolating switches to aid diagnostics may be complete overkill on your layout. Unless your wiring installation skills are absolutely dire, the chances of getting a permanent wiring type 'short circuit' fault is in my view quite low. Most shorts on a layout are transient in nature i.e rolling stock wheels bridging opposite power rails on point frogs. It then becomes obvious where the short has occurred. You just look for which train has stopped when crossing a point. Or go round the layout manually moving each train in turn to see which one clears the fault.

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It is true to say that permanent shorts are far more onerous to trace than 'open circuits'. Shorts have to be identified by breaking down the layout into ever decreasing smaller electrical sections and the inclusion of electrical isolation switches could potentially hasten that process. But as said before, if the wiring is originally installed with care.....wiring 'short circuit' faults are rare.

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Hornby points (for example) do have a habit of generating a short due to poor quality control at the factory, where the insulation under the frog area has become dislodged or broken through. But these faulty point shorts are usually present on the point 'out of the box' at the time of installation. I can't recall seeing any post on this forum where this type of point fault has developed later, on an established working layout. I have noted that in your case, your points are PECO ones, so I mention Hornby point issues more so for others reading.

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[96RAF]

I had a turntable on my old layout which was fed as yours is from a second radius track. It was unavoidable in the space I had but was nothing but trouble.

 

If you can try to modify the lead in track so that you have a minimum half straight (R600) entering the TT, say by pulling the feed in point more to the right  and changing it to an ST240 (opposite hand).

[ColinB]

Having been soldering for years with my job as an Electronics Engineer, I did find that when soldering rails it is a good idea to use separate flux as well as solder with flux in it. The solder seems to take quicker, which means the plastic sleepers don't melt. I also find normal commercial miniture switches are a bit more reliable than those designed for model railway use.

[ColinB]

Actually thinking about it, if you don't want to solder you can buy fishplates already soldered. It is an expensive way to do it, but better than those power clips, Peco do them. I think you will find someone one a certain auction site does a DPDT switch with a screwed connector ( we used call them chocolate box connector), on it. Again a bit more expensive but "do able". You will be amazed at what small PCB boards you get get from China for very little cost.

[96RAF]

You can buy most small electrical items these days with screw connectors in lieu of solder tags. Very handy if you are restricted in what you are able to do.

A power track with screw connectors would be more reliable than slide in clips or push button clamps.

[JohnieP]

Thank you all for your advise. I've got some of the Peco Power Feed Joiners already. Regarding the bus wire I've read some people only use the one pair of bus wires to power the whole layout. I've looked on Brian Lambert's website and it shows how a sub bus can be used. Am I right in thinking that the sub bus would need to join the main bus wire so that power goes to the sub bus. If this is correct does the wire connecting the main bus wire to the sub bus wire need to be the same size wire as the main bus? The wire which I will be using for the main bus wire is 32/0.2 and the wire for the droppers is 16/0.2.  

Some people have said they have had dropper wires 12 inches in length that join the main bus wire without any issues but is it more sensible to have sub bus wires so that the dropper wires don't have to be so long in length.

The baseboards are arriving within the next couple of days. I may to start with just use my Gaugemaster prodigy controller and see how I get on. If I think I need a booster I will upgrade at a later stage. Following the advise on here I think I will keep this as one rather than having districts as like posters have already said the likely cause of the short circuit would be derailments over points.

Many thanks once again for all your help and advise regarding this.

Best wishes,

Jon

[Chrissaf]

Your droppers are a bit of overkill. They can be 7/0.2mm rather than 16/0.2mm. The smaller size is perfectly adequate as long as the length is restricted to 300mm (12") max. They will be easier to install on the rails too and won't be too obtrusive i.e easy to hide with ballast.

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Brian's use of a 'sub-bus' has somewhat special use. Most domestic home layouts don't use them. I think that perhaps you are taking your research a bit too far and over egging your wiring solution. Not everything you read may be applicable to your layout unless it is a massive one of exhibition design standards and contains hundreds of metres of track.

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Your previous posts indicated that you were future proofing by splitting your layout into two or three power zones and I see now where you got the idea for the bulbs from mentioned in a previous post of yours (Brian's site). By all means future proof, by creating two or three power zones. Each power zone you create would then have its own Bus made of 32/0.2mm wires with 7/0.2mm (7/0.2mm IMO) droppers. Initially, the multiple Buses would be connected together in parallel for connection to your controller in a 'radiating star' configuration. But could later be separated if the need arose in the future, probably via Boosters.

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This is where opinion becomes like 'Marmite' some do and some don't, but my opinion is that the Bus wires should be twisted to reduce susceptibility to external electrical interference and improve DCC signal reliability.

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The theory of Twisted BUS Wiring for DCC by Mark Gurrie (member of the NMRA).

[JohnieP]

Thank you once again for the advise Chrissaf. :)

[Flashbang]

From my web sites DCC page re dropper wires.... "Having installed the DCC bus around the layout in suitable sized cable, there is now a need to connect the bus to the rails.  These wires are called 'Droppers'. This I recommend being carried out using 16/0.2mm or 7/0.2mm flexible wire in the same two insulation colours as the bus itself e.g. red/black or brown/blue etc. Note; I recommend if using the smaller 7/0.2mm wire then to try and keep each dropper wires total length to around no more than 300mm."

  If you're planning to later on, to section the layout into power zones (Also called 'Districts'), then I personally would plan ahead and fit Insulated Rail Joiners (IRJs) at the track laying stage and install the IRJs in all rails leading into and if necessary out of the proposed zone. Fitting them later on may well be very much more difficult!  Once they are all fitted connect the dropper wires from the rails inside the zone to the main DCC bus pair of wires. This will ensure the whole layout works from the one consoles output.  Later on if and when the zones are to become operational, simply remove the dropper wires from the main bus that feed the rails of the isolated zones rails and connect them to a pair of sub bus wires which are fed from either a Boosters output (for additional power [Amperage] needs) or to the output of an all Electronic circuit breaker to proved totally independent overload/short circuit protection from the rest of the layout.  Note: A Booster will also provide independent overload/short circuit protection too. An example might be to zone all the sidings that feed around on the right to the top of the plan. Starting the separate zone where each track leaves the point on the main line loops.   Finally, I would highly recommend not to rely on Plug-in power clips or metal rail joiners with dropper wires attached. As both can lead to loss of electrical connection and with DCC possible data loss too.  The very best connection is a correctly soldered one, made to ideally the rails underside or its outer web area!   Anything that relies on a push fit or slide on connection is prone to fail with a high resistance connection.