Separate Accessory BUS wiring

[menacesco]

I am extending my layout and now want to introduce a separate BUS for accessories - points, signals etc. I am using Railmaster and E-Link. Can I just wire both BUS pairs into E-Link or should I use a power manager such as the Digitrax PM42 to protect each circuit? 

[96RAF]

You can wire both track and accessory bus’ into the eLInk Track terminals, but if you incorporate a breaker into either bus branch you introduce protection against both branches falling if say a loco derail due to a wrongly set point shorts the track, then the points bus will remain active, allowing the point to be reset before the track breaker is reset, etc, etc.

 

The split bus system works even better if you have two controllers in play with RM - i.e. Controller A for locos and programming only with Controller B for points and acessories only. In such a case no additional breaker protection is required as the bus are no longer being fed from a common output.

[Chrissaf]

You can do either. But note this. The factory default trip current setting for the Digitrax PM42 is 3 amps. The minimum adjustable trip current for the PM42 is 1.5 amps.

 

The default power supply for the eLink is 1 amp. Therefore for the PM42 to actually work, you would need to upgrade the eLink 1 amp power supply to the Hornby P9300 4 amp power supply as the controller power supply has to be able to supply more current than the configured PM42 trip current.

 

The Digitrax PM42 is basically an American product and in my opinion better suits being used with American controller and booster products. The PM42 for example can also be configured for trip currents up to 10 amps. These ultra high currents are just not readily seen on UK layout products.

 

Since you are using RailMaster, then I feel that a far more superior solution is to source another eLink on the second-hand market [one that is not faulty would be an advantage]. Then configure both the eLinks [your original and the additional one] as RailMaster Controller A and Controller B. Controller A is then used for the track to control trains and perform CV configuration duties. Whilst the Controller B eLink is dedicated for the accessories on the separate 'accessory BUS' you are proposing.

 

The advantages are that short circuit trips on the track 'Controller A' do not affect the output of 'Controller B' and that it is a Hornby technically supported solution, removing any element of doubt about the compatibility of the Digitrax PM42**. Plus the full current output of the eLink controllers are available to power DCC devices, as the current is not artificially throttled to the trigger level set within the PM42. Plus the cost of a second eLink is very likely to be less than the combined cost of a Digitrax PM42 and the Hornby P9300 4 amp PSU upgrade.

 

Note** Although the PM42 has a LocoNet interface capability, the manual states that the unit can function at a basic level without connection to a LocoNet network. It should be appreciated that most of Digitrax's range of products are designed to interconnect using LocoNet [again a technology common in the USA]. The Hornby eLink interface does not support LocoNet protocols.

[menacesco]

Thank you both for your comments. 

I had not considered sourcing another e-link and having two controllers - that's seems like a good solution. I already have the 4amp power supply for my existing e-link, would I need the second one to have 4 amps as well? My layout will only be running a maximum of 4 locos at any one time, and I currently operate c25 points with plans to introduce signals and other powered accessories over time. 

[Chrissaf]

For points and accessories, the original 1 amp supply is more than adequate as you only tend to operate points one or two at a time and signals [if LED] draw such a small amount of current.

[menacesco]

Thanks Chrissaf. I am on the lookout for a secondhand E-Link interface now. 

i read somewhere that changes to the .ini file need to be made for controller B. Is there a post on this I can read?

[Chrissaf]

Using Controller A and Controller B in RailMaster (dual controller mode)

https://www.hornby.com/uk-en/forum/using-e-link-as-a-stand-alone-power-source/?p=1/

 

"railmaster.Ini" file changes for two controllers.

https://www.hornby.com/uk-en/forum/railmaster-operating-2-controllers/?p=1/

 

As the first post above was written for Elite + eLink and you are intending two eLinks. Then I suggest that the optimum .INI file entries are all =1 as documented in the second clickable link.

 

Note also, that Baud rate settings etc need both to be set to those values required for an eLink.

 

[menacesco]

Thank you once again Chrissaf. 

As an aside, with a separate e-link for the turnouts etc, do you recommend using a CDU for additional power bursts? (I've been reading about these in various group pages).

[96RAF]

You cannot use a CDU directly with DCC. you need some form of isolating i terface like a relay system.

[ColinB]

I did read on one of the continental decoder controllers manufacturers website that some people on the continent were thinking of using a CAN bus for controlling the accessories. It is proberbly more suited for this, but perhaps that is one for the future. 

[Chrissaf]

@menacesco

As Rob has stated you cannot connect a DCC Accessory Decoder directly to a CDU. Most (not all) Accessory Decoders already contain a CDU inside them. The Hornby R8247 Accessory Decoder contains an integrated CDU, but I find it fairly weak.

 

In my own case I supplemented my R8247s with an external CDU. This involved building a 'Relay Board' with two relays per decoder port. The output of the R8247 operated the relay coils, then the contacts of the relays operated the external CDU to operate the solenoid point motors. This also meant that I could increase the point operating voltage from the 14 volts DC provided by the R8247 to 19 volts DC to power the CDU [an external CDU needs a separate power supply of its own, it must not use the DCC supply].

 

This is my relay board.

/media/tinymce_upload/bcac5e8b9a0d3cdde321e54d27ab0ece.JPG

[ColinB]

If you want to go the relay option, you can buy ready made relay boards off that popular auction site for not much more than buying the individual components, especially if you don't mind buying it from China (don't worry they make these quite well). You can get them 8 to a board. So this will do 4 points. The issue with the Hornby accessory module is it gets its power off the DCC bus, so if you are driving something like a Peco point motor that requires greater than 2 amps, I suspect you are a bit limited.

[menacesco]

Wow - that looks very impressive Chrissaf. Something for me to consider for when I rewire my layout after completion of the track extension and baseboard modifications. Did you build the relay boards or could I buy these already made up for each decoder?

[Chrissaf]

Model railways is just an excuse for indulging my primary hobby of building electronic projects. Something I have done for more than 50 years. So yes, the relay boards were designed and hand built by me. To be absolutely honest, I really don't have that much interest in model railways, my enjoyment comes from designing and building various electronic circuits that I can use to add scenic interest to the model railway. For example I have designed and built my own signal control boards.

 

When I built my relay board I didn't look to see if there were any 'ready to run' boards available. But recently I have been doing some work with forum ComMod RAF96 [Rob] to evaluate and propose where necessary certain modifications to allow 'ready-made' boards [to be used on his new layout] he purchased from China via eBay.

 

One has to be very careful to select a suitable Chinese made board from the many that are available as only certain relay board models are suitable for use with Hornby Accessory Decoders. These boards are usually listed on eBay as relay boards to be used with Arduino. Note that these Chinese boards usually need their own dedicated 5 volt [sometimes 12 volts] DC power supply.

 

I will ask Rob to add to this thread with his recommendation of Arduino board to use based upon his testing.

[96RAF]

I have written up a summary of my testing of various relay boards for suitability of working with DCC - in particular with R8247 modules.

 

I will post the article on my webpages later under Product Reviews but in essence:

 

1. Solid State Relays (SSR). These are generically for use with an AC load as the control electronics needs to see a passing zero waveform to reset the relays. If you use a DC load the relay latches on until the external circuit is broken. You can get AC-DC load capable boards but they are way more expensive than the AC only boards.

 

2. Mechanical Relays of which there are several types:

A. Those that allow you to have a separate V-In (which powers the module) and/or Vcc (which is the relay control signal circuit power) and which allow you to jumper these voltages as either linked or unlinked. This allows you to have a driver voltage V-In to operate the board and a different or the same (as jumpered) voltage to operate the signal circuit that controls the relays.

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B. Those that have a combined (fixed) V-In and Vcc meaning you have to match the supply voltage to the board. In some cases boards designed for control by Arduino or Ras-Pi have their supply voltage generated by the relay board.

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C. The actual relays on the board can be of various voltages - e.g. 5V to say suit an Arduino, etc or 12V to suit manual switching or an R8247 output, even 24V.

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D. Finally boards can be triggerred by a Hi or Lo control signal potential. This means you either have to give them a positive voltage or a switched negative voltage according to type to operate the relay. Some boards are fixed level and some allow a jumper to be used to switch from Hi to Lo operation.

 

From that you can see that you need to be very careful to pick exactly the right relay module if you want to control them by R8247 or similar pulsed output and also if you want the external contacts to control firing of a CDU.

 

Needless to say I have three varieties of these relay modules and neither is exactly what I need but one of them will do. I have the ability to split V-In from Vcc or not but I have to put up with 5V relays which for the short sharp pulse from a 14V R8247 may shorten their life however I can live with that. My chosen modules are Lo signal control.

[96RAF]

Just to give an indication of the types of module available.

Red 8-way one is an SSR with AC load only and hi level trigger. No use in any respect for our purposes as is. (Chinese)

Large 16-way blue one is 12V relay coils, with fixed DC-In generating 5V power to Arduino and Lo-level triggering input from Arduino. Some adaption required to allow external signalling from R8247 without burning out the Vcc side of the module. (German)

Small 8-way blue one is separable DC-In and Vcc by way of a jumper, Lo-level triggering from external switching (e.g. R8247) but 5V realy coils. (Chinese)

 

/media/tinymce_upload/4bd72dfdd498121583fd9debe9fb0316.jpg

 

I will try to upload the report this afternoon if you want to see the wiring for the test circuits and the summary of test results.

[Chrissaf]

Just to add to Rob's post. Here is an example eBay listing for the lower left version that gives the best operational match to the R8247 of the three shown. The eight relay board [2 relays needed per R8247 port] costs £6.39 delivered from this particular UK based supplier.

 

[96RAF]

Here is the link to my test write up...

http://www.halton96th.org.uk/relay-module.html

[menacesco]

Thank you both so much for the information.

This area of electronics is a little out of my comfort zone, however, I love learning about model railway control electrics and therefore I have ordered some relays and I will use the advice to attempt to set up my own control board. I will read your test write up RAF96 and hope that I will learn about how to wire these relays up?

[Flashbang]

Hi

Damp Squid time! Sorry guys  😮

 

I have to ask WHY spend all the money on Accessory Decoders, Relays a CDU and loads of additional wiring?  When there are extremely good quality Accessory Decoders sold with separate CDUs for each output. Of course if you have the accessory decoders already, then adding the relays and a CDU may well benefit the solenoid point motor operation.  But if starting out from scratch take a good look around!  😮

 

CBUS was mentioned earlier by Colin. That is what I'm using on my new layout along with Servo motors rather than solenoids.  Adjustable servo speed of throw easily carried out once the points over centre spring has been removed.  I'm making CBUS kits up supplied from MERG but there are ready made CBUS modules available too from other suppliers...Google MegaPoints as an example.

 

The other  alternative is of course to use Stall (Slow motion) motors, which come in both Analogue or Digital operation and like Servos provide a more realistic and gentler throw of the points over and back.

 

So, the Solenoid motor or as its sometimes called the "Snap Action motor" has challengers, which IMO are better, and in some cases much simpler to wire and use!  😆

[96RAF]

Agreed Brian, there is better suited to purpose kit out there, but in my case its simply what’s already in the box being reused and supposedly improved upon. I still have my old car relays to fall back on if these new relay modules can’t be made to perform satisfactorily.

[Flashbang]

Oh, I forgot the original topic of a Dual DCC bus... 

Indeed its a good idea and needs one all Electronic overload circuit brealer trip fitted into the rail power Bus (Not the Accessory Bus) So from the "Track" output terminals of the DCC system a pair of wires are taken to the Input of the Overload device. The devices Output feeds all the rails only.

Then a second pair of wires are also taken from the same DCC systems "Track" output terminals and these go straight out to the layout and all Accessory decoders are fed from these.

 

One excellent all electronic overload cut out is the PSX-1 which has adjustable trip current from 1.27 Amp up to a maximum of 17Amps Wow!17 Amps is massive!   Now the down side is that some of Hornby's DCC products are supplied with a meagre 1.0Amp power supply, so they cannot be used in this configuration. But simply replacing the 1.0Amp Power supply with the P9300 etc 4.0Amp power supply will allow dual bus operation and the PSX is set to a lower trip current of say 2.5 or 3.0Amp which will then work well..

 

Example of a simple dual bus system...

/media/tinymce_upload/36462bda857c91decc13820cb1dd6c45.jpg

[Chrissaf]

Of course if you have the accessory decoders already........

 

In my case my R8247s [and my PECO PL-10WE Low Energy motors] had been purchased and stored in their boxes for over a year before I got round to start building my layout. It was only then that I found out that the R8247 didn't have the grunt to pull the skin off my PL-10WE rice puddings. It was now too late to return any of the purchased kit for a refund to get something better, hence I had no alternative except to go with my Plan B relay board.

 

I agree there are other non Hornby decoders that have far more power, features and functionality that are ideal if you are buying everything new from scratch.

[ColinB]

@Flashbang when I mentioned CAN bus I didn't know it already exists in model railway form. I saw a lot of German manufacturers talking about it. The only issue would be interfacing with existing tools. The CAN system is ideal for this because not only can you set solenoids etc, you also have the ability to read back data. Now I know devices exist, I will start digging a little deeper. In my case it would save a ton of wiring. I didn't want to mention this, but I was going to use one of those DigiKeijs units. You get 16 channels, their disadvantage is the output seems to be be switched 5 volts. but if you are going to use a relay board then no issue. They are sustantially cheaper than the Hornby alternative.

[Flashbang]

@ColinB

I would suggest if you want to know more about CAN Bus and model railway controls, then you look at or better join MERG. Who are a UK group of mainly electronic enthusiasts, who's interest are layout control.

There link is http://merg.org.uk/