Nimbus
I'm about to get stuck into wiring a layout extension.  Currently I have a largish TMD that has fairly simple wiring in that the track and Cobalts all share the same bus, which is controlled via an ECoS.  Moving forward I would like to seperate the track power feed and the bus providing the Cobalt control signals, mainly to stop  point control shutting down if a point is incorrectly set and a short is generated.  It will also (hopefully) ensure that Cobalt's don't lose their addresses when a short occurs.

I have found the advice on the website regarding how to wire up a simple "stand-alone" point when utilising a separate Accessory bus.  Looking at the wiring diagrams provided for slips, I believe the same principles can be carried across (using the S2 switch to provide correct frog polarity).

There is one scenario that has me unsure how to proceed, namely a double junction and how to switch the frog polarity on the crossover.  Here is a copy of the wiring example from the DCC Concepts website   https://www.dccconcepts.com/manual/cobalt-ip-digital-and-double-junction/

As you can see, both the normal frog switch and the S2-C switch are being utilised by point motor #1.  However by using an accessory bus, the normal frog switch is no longer useable.  Is there any other way to enable correct frog switching of the crossover?  Perhaps Ahjay's wonderfully versatile REX can come to the rescue?

I do have a few more questions, but will pause to get this one cleared out of the way.


Steve
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john whiteside
Hi Steve.
You would have to use a AD decoder, with a Anolog motor, so you get the extra contacts, or you could use the contacts on the Digital motor to control a Rex.
Any problems please give us a call.
Regards. 
John.
  
John Whiteside
DCC Concepts
Technical / Customer support 
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AHJAY
Hi Steve

to add to Tech services response...

There was only ever one short batch with short-related address issues. No other production has ever had it and no future one will either... and if you have any of those with the issue we do have a fix for it anyway... so do not worry about that.

* You might benefit too from looking at the newsletter in which we reviewed our tiny track sensor so you cannot over run a point anyway!
* Slips - Yes - principals are the same. Slips are simply two points on top of each other. Left hand motor switches right hand frog
* Double Junction.... You COULD use REX for that double junction (ask if you need help doing it).

An accessory power bus does not need to be an issue with frogs of course.
Separating power bus between track and main can work quite seamlessly as long as the source of power for both busses is identical and the "electronic separation" is just via circuit breakers.... Just set the accessory bus breaker at a higher level than the main track breaker. That way there are NO frog wiring related issues, and shorting the main track will not stop the accessory power bus so you can change the points to correct the problem.

Think about it though - to be honest it is my opinion that a separate accessory bus is not necessarily that great an idea for most layouts as long as layout use is disciplined ...and track can easily be wired to prevent over-run issues... Its up to you whether you do it though of course.

regards, Ahjay
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Nimbus
Hi John,

Thanks for the feedback.  I actually have two "spare" Analog IP motors as well as an ADfx8.  Am I correct in assuming that S2-C and S3-C can both be utilised for frog switching?


Steve
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john whiteside
HI Steve.
Yes both can be used as the volt free contacts.
Any help you need please give us a call.
Regards.
John. 
John Whiteside
DCC Concepts
Technical / Customer support 
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Nimbus
Hi Ahjay

I appreciate your input, it did get me thinking!  I totally understand your comments about breakers and differential trip currents, something I hadn't considered previously.  So it doesn't matter if the frog power is coming from the "accessory" bus, as long as one of the two conflicting power sources are removed i.e. the track power.  All this being based on having the same ultimate source, which in my case would be the ECoS.

That nicely takes me on to my next question.  As I'm using an ECos, it's a common problem that most (all?) breakers do not trip quickly enough and the ECoS beats them to the shutdown.   Can you recommend a breaker that would work properly with the ECoS?


Thanks,
Steve
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AHJAY
Yes, ESU are a little off the money with their protection timing. It needs to be a few milliseconds slower in its reaction time - this is common with most "Operating system" type controllers as the engineering is more computer than model railway.

The answer is actually really simple. If you have this issue (and you may not) just add an appropriate incandescent light bulb in series with one wire from the ECOS. it will have no negative effect normally and will not light unless its specifically shorted... But because its an inductive load it will buffer any trip current to the ECOS, effectively adding a time delay of a few milliseconds and giving the other items time to react.

Generally the PSX breakers will be a good choice.

regards, Ahjay
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Nimbus
Great, I'll go and do some reading on the PSX breakers.  So a single incandescent bulb in series (i.e. one wire) BETWEEN the ECoS output and PSX units?  A quick bit of reading elsewhere seem to indicate that something like a 12V 21W brake light will do.  Does that sound right?

I forgot to say earlier that I always read your newsletters 😉
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Iain Morrison wimorrison
If the reason you are creating the accessory bus is to allow you to switch points if there is a short this removing the short and letting the layout start operating again then you CANNOT power th frogs from the accessory bus, they must only be powered from the track bus. if you power th frog from the accessory bus then you will short that out also and be unable to change the points 0 in fact if you do wire the fogs from the accessory bus then there is no point in having an accessory bus.
Iain Morrison
Modelling h0e using Z21 with iTrain automation and Railcom
There are also unknown unknowns – the ones we don't know we don't know
http://www.wimorrison.co.uk
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Paullampit Paull

I’ve been following this post with interest and as someone who has little or no electronics knowledge I rely heavily on advise from others - when I started my original dc layout 12 years ago I was told quite specifically to make sure I had a separate accessory bus and yes the frogs are effectively powered from that and Iain’s comments now resonate with me as I have never understood when I had a short why I couldn’t change the point

it seems therefore that current advise would be that there is no need or reason for a separate bus at all - am I right in that assumption?



Ahjay I have a box of 6 ip digital that I have installed and when I have a short induced by running against one of those points all 6 lose their address - all the ip analog ones through an adfx8 are ok as are the 40 odd classics run through ls150s

I note you say you have a simple fix for this and I would be grateful if you could share that with me

regards

Paull
n gauge British transition gwr
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Iain Morrison wimorrison
there are real advantage to a separate accessory bus because as you have found you can switch the points when there is a track short circuit. Almost all the time track short circuit is due to running against a point set the wrong way.

the real advantage comes on a larger layout as you can power the track through a booster leaving all the power available for accessories rarther than sharing the power between the two.

The fix is to put a 'snubber' or 'filter' across the track and accessory bus that will absorb the power spikes - somewhere around 100 ohm 2w resistor  with a 0.1 microfarad 50v capacitor in series. I think that DCC Concepts sell them as complete units
Iain Morrison
Modelling h0e using Z21 with iTrain automation and Railcom
There are also unknown unknowns – the ones we don't know we don't know
http://www.wimorrison.co.uk
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AHJAY
It is a personal choice.

It is not necessary, and advantages are sometimes offset by other complications and costs. You can easily create a layout with only one bus and NO problems if you set out to do so and use the switching on Cobalt motors to eliminate the possibility of conflict. The slight disadvantage

If you want to use an Accessory power bus then do so however. Accepting that you may create route conflicts that cause shorts is a valid reason for doing it. Wiring so that a short kills only the track power bus and leaves points changeable is the core advantage.

Personally I prefer to wire things so that the opportunity to make an over-run of a wrongly set turnout is removed so only one bus is needed.

Its all about choices.

regards, Ahjay

.
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AHJAY
Paul

Ring and ask for John or Mick. Ask them for 6 of the inductive loads we supply to fix this issue. 01729 821 080, (10~5)

regards, Ahjay
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