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How to connect "districts" if you have one controller?


Wizardtrains
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Hi all,

 

I recently received some excellent help in wiring up a reverse loop I have on my layout from several RMWeb members. Having successfully isolated the loop I now wish to isolate a couple of other sections, namely the station area and the loco depot.

 

If I wire the isolated sections back to my Z21 controller it would obviously result in me reconnecting them all so I understand I need to seperate them in some way. Please can someone explain how this is done? I have come across the PSX circuit breakers but firstly they don't appear on DCC concepts web site any more? And, I am not entirely sure how they function apart from protecting the circuit against shorts - under normal use would I not be connecting all my isolated sections back together again?

 

So to clarify I understand that this diagram would not work but what are the options?

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It appears that you are talking about a DCC layout.

 

There is no need to retain the isolating sections that would commonly be found on an analogue (dc) layout so taking your diagram literally, there's no need to split the layout like you have. A single pair of wires from controller to track is all that is needed - except for the reversing loop you have already dealt with.

 

A short circuit in one DCC section will affect all other sections connected directly to the controller so there is no benefit in splitting the layout into sections unless you add a switch between each section and the controller. This would enable you isolate each section individually until the short circuit disappeared as it would be on the section most recently isolated.

 

The way you have shown the wiring above is correct if you plan to add circuit breakers between the Z21 and the track feeds shown - one breaker for one track section.

 

Can we ask why you want to split the layout like you've shown?

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Hi Ray

 

Sorry but the diagram was only meant to be an example to show districts, my actual plan is far more complex. I have the return loop mentioned, a double track main line, a loco depot and a station with several sidings, as below.

You mention the circuit breakers, which one's should I use and do these keep the districts isolated during normal use?

 

Thank you for your reply, I know this must be obvious to most on this site.

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The normal reason for splitting a DCC layout into sections is to add a District Cut Out (DCO) to the feed for each section. This will check for a short circuit (due to derailment or over-running a point not set properly) and will cut power to that section while the rest of the layout can still operate.

 

More importantly, if you have your point motors, etc, powered and controlled by a separate Accessory Control Bus (this can be DCC or other alternatives) it will be possible to operate mis-set points to remove the short circuit. If everything is connected directly to the DCC source, the short circuit will also inhibit point operation.

 

So, in simple terms, a DCC Accessory Bus can be connected direct to your Z21 output (accessories are unlikely to short out the DCC signal), and you add a DCO into each feed to each District.

 

 

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Thanks Ian, so I add a "DCO" or circuit breaker to each district feed. I've looked at the PSX1 POWER SHIELD at about £40, it looks good but the cost soon mounts up. Are there any decent cheaper alternatives?

 

Also in the case of the reverse loop, will connecting all the bus wires (via a PSX or other) at the controller not cause problems?

 

Cheers

Clive

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25 minutes ago, Wizardtrains said:

Thanks Ian, so I add a "DCO" or circuit breaker to each district feed. I've looked at the PSX1 POWER SHIELD at about £40, it looks good but the cost soon mounts up. Are there any decent cheaper alternatives?

 

Also in the case of the reverse loop, will connecting all the bus wires (via a PSX or other) at the controller not cause problems?

 

Cheers

Clive

The PSX was developed from the original Power Shield and is well-liked because it has the ability to discern a true short, in which case it shuts down, from the similar current-inrush that occurs when a section is powered up with multiple sound-equipped locos in it, when it doesn't shut down. As a benefit to the safe operation of a layout, the PSX is an investment. Other breakers are available. Some use relays, which may prove slower to operate than the solid-state PSX.

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You should also consider whether it is actually a cutout that you require or a booster.

 

The Z21 has 3 amps available to power the layout and this will be used up quite quickly on a large layout, especially when you have locos with lighting and sound. You may be better considering a 10805/10806/18087 as a booster to provide power for separate power districts which will enable you to have shorts, but more importantly will provide sufficient power for the layout to operate.

 

You need to plan this carefully as each power district is electrically isolated from the other ones . A good way to go given you have a larger layout would be to power the accessorises directly from the Z21 and the track through one of the boosters above. You could also split the booster outputs into districts using a PSX, NCE EB1 (cheaper) or MERG DCO (cheapest option)

 

A rule of thumb is to assume 250 mA per loco with lights, 400 mA per loco with sound, and only plan to use 60% of the controllers output to allow for other items like point motors, coach lighting, etc. This would mean you could run about 8 locos without sound before you start to hit power issues - your plan will have a lot more than that in use.

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Hi Iain, thanks for the information.

 

I have a Lenz TR100 (Transformer 15V, 45VA) which will power all the point motors via a couple of LS150's (6 OUTPUT ACCESSORY DECODER), these are left over from a planned continental layout that work never allowed the time to build. Now retired I'm hoping to put some of these things to use.

 

The above should reduce the load on the Z21, I also have a couple of old transformers (Gaugemaster) that I will use for layout lighting and motorised accessories in 16V.

 

The plan is to leave the Z21 to run two trains on the mainlines and have the ability to control a third in the sidings (I mainly watch the trains go by!). The layout is planned to be very scenic and will also include moving vehicles using the magnorail system (again from the continental layout that was planned), the 3A from the Z21 should be able to cope with running the three locomotives I hope. Coach lightingfor me uses the battery Coach Lighting Kit with Latching Reed Switch from "layouts for you" so no drain there. Should I upgrade to DCC lighting throughout then maybe a power booster is a future option. Right now I'm just trying to get up and running but am finding no sooner than I get one issue sorted that I'm coming cross another. My fear is blowing a DCC fitted locomotive with an expensive sound chip.

 

Any other thoughts on the reverse loop wiring?

 

 

 

 

 

 

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4 hours ago, Ray H said:

...Can we ask why you want to split the layout like you've shown?

This is the most pertinent question asked so far.

1 hour ago, Wizardtrains said:

...My fear is blowing a DCC fitted locomotive with an expensive sound chip...

Is this the main motivation for wanting the isolated sections?

 

Apart from the reversing loop - which a suitable reverse loop module will look after, not a PSX as drawn above - the layout is very simple. If you build the two loops and sidings as one section, and test as you go by shorting out the newly added track (often called the coin test) to see that the short circuit protection on your DCC system is always triggered, then that is 'job done' as far as protecting the locos on track, whatever decoders they are equipped with.

 

The most significant job in protecting decoders is having a progamme track connected to your DCC system, on which any newly installed decoder (or revised installation) can be tested for correct installation under limited current conditions. That's a far more essential item than adding PSX's in track feeds to isolated sections.

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Ah, I do have a reverse loop module (Gaugemaster) that will be wired into the loop, had some help with that on another post and feel confident that is correct. Now the bus wires under the loop and the bus wires under the remaining tracks both go back to the Z21 then? I was worried that when the reverse loop activates it would affect the main line bus in some way.

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I can think of several reasons I would want to split a layout into several sections, none of which are to prevent damage to a decoder:

 

Split it into power districts which can each be supplied by their own booster, to provide more current.

Split it into power sub-districts with each one protected, so if 1 shorts out, it is the only one which stops. This makes makes troubleshooting easier. The only difference between power districts & sub-districts is that the latter are all powered from 1 booster.

Wire it in sections as if it was DC, just in case DC is required at some point in the future (ie. if the layout gets sold to somebody who may want to use DC, it can be converted without having to lift track to add isolating rail joiners).

Provide the facility to add block detection, so each block can be wired through an induction detector.

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The advice above about power shields v extra boosters is good but  if you do decide you want ‘circuit breakers’ the PSX is available in multi units which work out slightly cheaper than buying individual units.

 

The advice about a separate programming to protect newly installed decoders is definitely best practice  but is a different issue to reasons for splitting the layout into districts.

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8 hours ago, Ray H said:

.....Can we ask why you want to split the layout like you've shown?

 

3 hours ago, 34theletterbetweenB&D said:

This is the most pertinent question asked so far.......

 

 

Also (from the OP, Wizardtrains)...

 

8 hours ago, Wizardtrains said:

......Having successfully isolated the loop I now wish to isolate a couple of other sections, namely the station area and the loco depot.

 

If I wire the isolated sections back to my Z21 controller it would obviously result in me reconnecting them all so I understand I need to seperate them in some way

7 hours ago, Wizardtrains said:

....You mention the circuit breakers, which one's should I use and do these keep the districts isolated during normal use?

 

After following this thread up to this point, I'm still not sure what the OP is asking exactly, or why?

Wizardtrains, would it be possible to say what your thinking is and why you wish to "isolate" sections of the layout?

Also, what do you mean by "isolation"?

 

Ron

 

 

.

Edited by Ron Ron Ron
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Sorry chaps, I appreciate so much you trying to help but I'm obviously not giving enough information to get the guidance I need. I think my problem is not having the knowledge to understand fully the replies. many of the terms are not familiar to me. I think I would be correct in assuming that there are many more ways than one of wiring up DCC.  I'll try to draw a better diagram over the next few days and come back to this.

 

Thanks again.

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There are as many ways to wire up DCC as their are people with opinions on how to do it and they will mostly all consider that the way they have done it is the best way ;)

 

Most of the good advice is already here in the thread, but in summary;

 

- consider how much power is needed

- consider fault finding and making it easier - you may want isolation switches to reduce fault finding to specific areas

- run at least 2 busses (you are doing this with an accessory bus from Lenz and track from Z21, though this way can cause issues also due to separation of command systems)

- consider operation of layout

- make sure bus wires are heavy enough

- consider how many droppers are needed and double that estimate (you can never have too many droppers)

- consider component locations for faultfinding and operation (can you get to them, can you see them when operating)

- consider wire routing to minimise runs

- remember that DCC locos and stock still draw power when sat 'idle' - especially lights and sound

 

and most important - Apply the KISS principle as far as you possibly can, complexity may impress some people but it makes it hard to fault find (and unfortunately you will get faults :( )

 

Good luck

 

Iain

Edited by WIMorrison
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11 minutes ago, WIMorrison said:

..... run at least 2 busses (you are doing this with an accessory bus from Lenz and track from Z21, though this way can cause issues also due to separation of command systems)...

 

 

Iain, re-read what he said. 

There's no mention of 2 systems.

Just a mention of a Lenz power supply and Lenz accessory decoders.

 

 

 

.

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20 minutes ago, Ron Ron Ron said:

 

Iain, re-read what he said. 

There's no mention of 2 systems.

Just a mention of a Lenz power supply and Lenz accessory decoders.

 

 

 

.

Point taken Ron - in that case the point needs to ignore the Lenz Bus problem reference but there still needs to be an accessory bus and a track bus with the track bus through cut-outs (low tech car headlight bulbs or higher tech PSX/EB1/DCO) :)

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