A few Z21/DCC questions

[01276]

Hi Guys,

 

I am in the process of planning my next loft layout, and would really appreciate some assistance for the couple of questions I have been unable to find answers to. I have highlighted my questions in bold for those who want a quick read.

 

A little background on the layout I plan: My loft space is 4x5mtrs. Basically I plan to have 3 loops round, over two levels with the lower level mainly containing a storage yard for my stock).  I’m not going overboard here and my plan is very restrained and priced for what I can realistically afford. The top level will have around 15 Cobalt IP digitals, block detection (more on that later), while the lower level will be for storage where I plan to reuse old Hornby points and motors which I already have to save ££s. The points will be set up in a local non-DCC arrangement, track will still be powered via the main controller though.

 

I’ve been very busy researching DCC systems and I have decided that Roco Z21 is the system for me (right price, like the interface, enough options for expansion). As I already mentioned I am planning to use Cobalt Digital IP. I have read that these can be prone to digital interference so I was planning to run separate Cobalt power bus to them. My first question is on the Z21 how do I run a separate track power bus and a Cobalt bus to avoid any interference? If I run two busses but connect them to the same DCC output on the Z21 is that going to defeat the point? Is there something I can buy to do this?

 

Edit: this next question I answered myself while typing, though if anyone can confirm my assumption is correct that would be great..

Secondly block detection: I plan to use Digikeijs DR4088RB for this with Rocorail to do some automation. As I understand it, if you have a piece of track/yard which is not under block detection a train basically goes off the map. If I bring a train out of the yard (non block) onto the main track which is under block detection it will recognise a train is in that section and what it is by the decoder address(?). Eg. If I brought out my class 31 to the main line, then clicked class 31 automatically run to block B, it would know the Cl31 is in block A and run it to block B.

 

Thirdly, there seems to be little documentation of people using Z21s with British signals and so it is currently my area of least knowledge. There are some videos on youtube by “digitalcareline” using Uhlenbrock modules. First question, I’m pretty sure I need a separate switch module and can’t programme signals into the same DR4088RB I am using for block detection. No mention in manual so presume it’s not possible. If that is the case then the DigiKeijs DR4018 is what I would go for. Has one one tried one of these with Z21 and train tech signals?

 

Thanks for any help 

 

[Dungrange]

Edit: this next question I answered myself while typing, though if anyone can confirm my assumption is correct that would be great..

Secondly block detection: I plan to use Digikeijs DR4088RB for this with Rocorail to do some automation. As I understand it, if you have a piece of track/yard which is not under block detection a train basically goes off the map. If I bring a train out of the yard (non block) onto the main track which is under block detection it will recognise a train is in that section and what it is by the decoder address(?). Eg. If I brought out my class 31 to the main line, then clicked class 31 automatically run to block B, it would know the Cl31 is in block A and run it to block B.

 

I've been looking at the Dijikeijs DR4088LN-CS for my own purposes and the DR4088RB seems to be similar, except that the Loconet bus is replaced by R-Bus.  My understanding is that if you bring a train from the yard onto the main track (which you have effectively track circuited), it will recognise that a train is in your mainline section, but I don't think it will know what train is in that section. As far as I ca tell, all the DR4088RB is doing is detecting that current is flowing through the track by monitoring one of your dropper wires for that section.  It would therefore detect a locomotive, a coach with lighting or a wagon with resistor wheel sets.   As far as a I can tell, all it will register would be 0 - unoccupied or 1 - occupied for each of 16 different block sections.  These would effectively be like on/off switches for signalling or whatever.  If you need to know what locomotive is there, then you will need to use some form of Railcom detector, which of course would only work if all of your locomotive decoders support Railcom.   I think some of the more expensive block occupancy detectors have Railcom for some of the sections that the monitor, but not usually all.

 

Unfortunately, I can't help with the other queries, as I'm still just looking at a switch to DCC.

Edited August 30, 2017 by Dungrange

[Ron Ron Ron]

Hi
I can't help you with the block detection questions, but it might help if you could be a little clearer here....
 

.......The top level will have around 15 Cobalt IP digitals, block detection (more on that later),   while the lower level will be for storage where I plan to reuse old Hornby points and motors which I already have to save ££s.
The points will be set up in a local non-DCC arrangement, track will still be powered via the main controller though.

You mention Cobalt iP on the top level and re-using old Hornby solenoids on the lower level; however which points are you referring to when you say "The points will be set up in a local non-DCC arrangement" ?
Do you mean all of the points, or just the old Hornby or just the Cobalts?
 
By "main controller", do you mean the DCC system (i.e. the Z21 you've decided on)?
 
 
 

..... I was planning to run separate Cobalt power bus to them.
My first question is on the Z21 how do I run a separate track power bus and a Cobalt bus to avoid any interference?
If I run two busses but connect them to the same DCC output on the Z21 is that going to defeat the point? Is there something I can buy to do this?

What you refer to as a "Cobalt Power Bus" is commonly known as an "Accessory Bus".

This is a separate Power Bus from the Track Bus, used exclusively for powering and operating accessories such as points, signals and anything else that might be switched or controlled by DCC.

 

The Power Bus output of your DCC system can be used to supply both the Track (Power) Bus and the Accessory (Power) Bus.

Simply feeding both from the same output effectively makes them a single Power Bus and they will form one Power District.

 

One way of separating them, is to use DCC circuit breakers, so that a short on the track, which shuts down the Track Bus, will not cause the Accessory Bus to shut down as well.

Using this method, you still have a single Power District, but divided into two sub-districts.

There is a reasonable degree of isolation as far as any interference is concerned.

 

Another option is to completely separate the Accessory Bus from the Track Bus, by powering it from its own Booster, rather than the inbuilt Booster that powers the main track output of the Z21.

You will have to purchase an additional Booster for this.

This Booster is connected to the Z21's "B Bus" (i.e. Booster Bus) output.

The Booster will need its own mains power supply, which may come packaged with the Booster, depending on which make it is.

The Booster has its own track power output, to which you connect the Accessory Bus.

Using this method, you will have created two separate Power Districts.

For a sizeable layout with a good number of DCC powered and controlled accessories, this is by far the best option, but it does come with the additional cost of the extra Booster.

 

 

An alternative approach would be to look at DCC Concepts Cobalt Alpha range of products to provide the separate Accessory Bus.

Alpha can be integrated to work with the Z21, or set up as a completely independent points and signal control system.

It will allow you to operate points and signals via a mimic panel, using switches or buttons, via a frame using mini point levers, or even a stud and probe set-up.

.

Edited August 30, 2017 by Ron Ron Ron

[01276]

Thanks both for your excellent and speedy replies  .  

I was watching a video on youtube about using DigiKeijs with RR&Co http://www.youtube.com/watch?v=ZksqVYMvz4A. It shows locos in each sections and as far as I know the chap isn't using any other form of detector so maybe it's just a RR&Co feature?

 

Regarding the points, the Cobalts will be controlled by the Z21 via the handset/Rocrail, these will be on the main lines. The 4 road storage yard under the layout will be controlled by Hornby Solenoids and will be operated by their own non dcc local control (Hornby R044 switches) - much like a separate small ground frame in the real world! And yes, main controller = Z21. 

 

Thanks for the explanation, a lot of things fell into place after reading that in my mind. A Roco 10765 or LDT DB-4 booster seems to be the easiest way to separate and will be useful  to have when I want to power signals. 

[Dungrange]

I was watching a video on youtube about using DigiKeijs with RR&Co http://www.youtube.com/watch?v=ZksqVYMvz4A. It shows locos in each sections and as far as I know the chap isn't using any other form of detector so maybe it's just a RR&Co feature? 

 

Okay - if you go to 7:40 in that video you will see him drive a Class 128 from the depot (no block detection) into Platform 2 at his station called 'Woodford Wells' (which has block detection).  You should notice that Traincontroller detects the presence of the Class 128 making the track circuit pink, but it doesn't detect what type of train it is.  The guy in the video has to manually tell Traincontroller what the mystery unit is and he does this by dragging an icon into the block to tell Traincontroller that the newly detected unit is a class 128.

 

As far as the other trains are concerned, these will simply have been entered into Traincontroller at the start of the operating session and therefore the software knows that if train A starts off in block B (because that is what the operator has told it) and the software drives that train to block C then it can update the screen to show train A in block C.  That is Traincontroller knows what it is doing, but isn't actually detecting what is in the blocks.  It's detecting that the blocks are occupied, but the other details are coming from the scheduling and the manual inputs at set-up.

 

I don't know much about Traincontroller or Rocorail, but I'm assuming you could do something similar with Rocorail.  The key point is that you'd need to tell your system what you were driving onto the mainline after it has been detected by the Digikeijs block occupancy detector.  That is, you tell it, it is a class 31, and it takes the rest from there.

Edited August 30, 2017 by Dungrange

[PaulRhB]

With the cobalts being prone to upset with shorts you can add these to the accessory bus to prevent the spike,

https://www.dccconcepts.com/product/bus-suppressorsterminators-2-pack/

 

I had that issue and protected the bus with these as random Cobalts were losing their address, source identified by email with Mick at DCC Concepts and sorted fast.

[01276]

Okay - if you go to 7:40 in that video you will see him drive a Class 128 from the depot (no block detection) into Platform 2 at his station called 'Woodford Wells' (which has block detection).  You should notice that Traincontroller detects the presence of the Class 128 making the track circuit pink, but it doesn't detect what type of train it is.  The guy in the video has to manually tell Traincontroller what the mystery unit is and he does this by dragging an icon into the block to tell Traincontroller that the newly detected unit is a class 128.

 

Thanks, I must have lost concentration and missed that part but it makes sense now. 

 

Regarding automation,  I need to have a good think about this. With multiple throttles possible via Rocrail/ipads I am wondering if I could achieve nearly the same thing by setting a loco to a sensible speed and just letting it go in a circle around the loft while I control other trains manually around it. It would save a lot of time, effort and wiring. But you don't know until you investigate these things and the above is all definitely food for thought. If I decide against automation I will still install isolating fishplates for blocks as per my block plan when track laying to cover a future switch to automation later. 

 

Finally thanks Paul for the tip. Did a bit more research via Brian Lambert's site and will fit some of these. Did you fit them to both your accessory and track power bus? 

[melmerby]

I have Tortoises controlled by NCE Switch-Its & Switch-8s

They are on a separate accessory bus but they do not have "Bus Terminators" (that in itself is a rubbish term as you can't terminate a line of indeterminate impedance!)

I do not get any problem with the points being upset if a short occurs.

 

AFAIK most people don't have problems with "Unterminated busses"

 

Keith

[RFS]

If you're using full automation, absolute reliability of your point motors is criticial.  If a motor doesn't switch for any reason, the software won't know and can send a train at speed along the wrong route with possibly serious consequences. 

 

Therefore you need to have absolute confidence in the motors you choose.  Tortoises, with NCE Switch8s (the MK2 version) give me no problems at all.  Have Cobalts reached that level of reliability yet? If you say they are prone to "upsets" (even the latest incarnation) then I would think carefully before using them in that environment.  Or in any location where you cannot tell for sure the motor has switched, automation or not.

 

As far as bus terminators are concerned I've tried them and they make no difference at all.

 

Having your turnouts on a separate bus is to be able to still change them if there's a short on the track bus, a fault that most commonly occurs when you manually drive a train to a point set against it (ie operator error). 

[PaulRhB]

The cobalts decoders are what gets confused by a short so you could use an analogue cobalt with another decoder. The issue is caused by humans driving into points so in theory the automation would also remove most of the shorts.

Edited August 31, 2017 by PaulRhB