The Snapper's DCC Workshop - NEW Heljan Class 25/3

Discussion in 'Techniques' started by TheSnapper, 19 August 2017.

  1. richard carr

    richard carr Western Thunderer


    Yes if you want a 47/4 they are available, any other version and it probably isn't.

    I certainly have mine for 47401, the cab casting is exquisite.

    Dan Randall likes this.
  2. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    If the internal width of the body cavity is at least 55mm then yes it should.

    Overall dimensions of the T1-1828s speaker is 155 x 55 x 24 mm or 135 x 55 x 24 mm if you remove the mounting lugs.
  3. Dan Randall

    Dan Randall Western Thunderer

    Thanks Richard - I think it's a 47/0 I require (a Western Region "namer", in two-tone green, with serck vents & full yellow ends :thumbs:).

    The cab moulding, is indeed, exquisite and I do hope we see a workbench thread on your 47 build. :)



    With apologies for the hijack Tim... :oops:
  4. cbrailways

    cbrailways Western Thunderer

    Sorry if I have somehow missed it above but what exactly is 'Swiss Mapping'?
  5. Cliff Williams

    Cliff Williams Western Thunderer

    The JLTRT 47/4 is available I have one to build too when I get a chance.

    Interesting to read of your aversion to speakers in tenders Tim, having done a couple in my time I would disagree with you there, but then if we were all the same life would be very dull!
  6. richard carr

    richard carr Western Thunderer

    My understanding of Swiss mapping (which of course may be complete bo***cks) is that enables you set up the lights on a loco in the way that Swiss railways do it and it's really complicated and requires numerous CV settings to achieve.
    I'm told it works, but I have never seen the need to apply this to a UK diesel, our lights are nowhere near as complicated as the Swiss are.
    To get independent control of UK headlights and tail lights you only need the two lights functions and 2 further decoder functions.

  7. Cliff Williams

    Cliff Williams Western Thunderer

    Depending on options fitted there can be more decoder aux outputs used than that, I typically use between six and eight Aux outputs. diverting the red tail lights away from headlight aux power.
    The JLTRT 26 to the left of this post uses:
    Headlight Forward
    Headlight reverse
    Aux 1 - No1 Cab interior light
    Aux 2 - No2 Cab interior light
    Aux 3- No1 cab red tail lights
    Aux 4- No2 cab red tail lights
    Aux 5 - No1 cab Lucas headlamps
    Aux 6- No2 cab Lucas headlamps

    Heljan 37s can swallow up seven outputs
    Headlight Forward
    Headlight reverse
    Aux 1 - No1 Cab interior light (customer fit)
    Aux 2 - No2 Cab interior light (customer fit)
    Aux 3- No1 cab red tail lights
    Aux 4- No2 cab red tail lights
    Aux 5 - roof fan

    if using ESU chips as I do these can be mapped to be directional on a function key, makes for much easier control.
    The biggest to date has been wiring up an LMS Twin so each of the marker lights are independent, I did run out of Aux outputs though which is a first.
  8. TheSnapper

    TheSnapper Western Thunderer


    Yes the term "Swiss Mapping" can be a bit off-putting, as it was for me at first.
    I can do no better than point you to Paul Chetter's post at "the other place":

    The ZIMO 'Swiss Mapping' Thread - DCC Sound

    I just find it simpler to use than anything else, to activate Function Outputs with higher F-keys (eg From F21) which normally do not have sounds allocated to them. Each to his own, I suppose........

  9. cbrailways

    cbrailways Western Thunderer

    Hi Tim, Thanks for that. I will have a read of that thread in the other place.....

    My reason for asking was that I have been pondering about motorised loco coupling/uncoupling. I assume it could control that as well? Has anybody else thought about that?
  10. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    DCC controlled uncouplers are around. It has been done using micro motors and/or electromagnets. I don't think for 3 link though - a tad too far I suspect.
  11. cbrailways

    cbrailways Western Thunderer

    I'm using DINGHAMS.
  12. Nigel Cliffe

    Nigel Cliffe Western Thunderer

    Yes, many years ago... ( just looked up and some of my posts on the subject are nine years ago !!!).

    I've made AJ's couplings with DCC control from the loco in 2mm, 4mm, and 7mm scales. Most examples are 4mm, and my 2mm example was a one-off as most of my 2mm stuff uses DG couplings.
    Decoders of choice were Zimo (4mm larger locos and above) and CT (smaller 4mm locos and 2mm scale).
    Read back through my old blog postings on Various and Random

    For larger scales, use of very small servo motors is a possibility, or shape-memory alloy devices (could write more about what you need for this, and a lot of it is "don't go here, its horribly hard work"). But, in the end, electromagnets are the simplest if the mechanism is low friction and requires very little torque/power.

    3-link uncoupling is a doddle (I've did a proof of concept example many years ago of a little slide bar alongside the coupling hook which rises and thus lifts the link off the hook), but 3-link re-coupling isn't something which can be easily done automatically.

    - Nigel
  13. cbrailways

    cbrailways Western Thunderer

    Hi Nigel, Thanks for the above info and link. I'll have a read and a ponder.:drool:
  14. Threadmark: Installing Sound into a Heljan 0 Gauge Railbus

    TheSnapper Western Thunderer

    When a friend asked me to install a sound decoder into his 0 Gauge Heljan Railbus, I thought, OK, this is a quick simple job – a plug-in 21-pin decoder, space already for ESU 23mm speaker, room in the roof for a stay-alive unit (which is really is really essential for this 4-wheeled vehicle).

    I was wrong, of course; it turned out to be a bit more involved and time-consuming.

    Beneath the driver’s cab at one end, there is a removable cover which reveals the chamber ready to accept an ESU 23mm speaker.

    Railbus#01 (Medium).jpg

    The instructions for fitting the speaker indicate that at the same end there is a small hole in the inner roof, leading to a conduit in the driver’s cab down which wires can be fed into the speaker chamber.

    First of all I couldn’t find the conduit; I had to line-up it up with the hole, by tweaking the position of the driver’s compartment. I then found that there was no way through the floor into the speaker chamber. So using the sharp end of a scalpel & a pointed grinding tool in the Dremel I carefully created a small opening. I then used a length of brass rod to poke a way through.

    Railbus#02 (Medium).jpg

    Railbus#03 (Medium).jpg

    The speaker wire needs to be very fine as there ain’t much room for thicker stuff through the conduit. I soldered the 2 ends of a loop of ESU Decoder Wire (part # 51940 - 51949) to the end of the brass rod & pulled it through, like a thread on a needle.

    Railbus#04 (Medium).jpg

    Hopefully the photos will explain better than words.

    After removing the blanking plug, the decoder fits easily. I used a Zimo MX644D from Digitrains, loaded with their AC Railbus sound project, created by Paul Chetter.

    railbus#07 (Medium).jpg

    Next problem is where to attach the speaker wires at the decoder end. Usually there are 2 solder pads or holes on the native PCB, but nothing was obvious.

    Research required – Google-is-your-friend time!

    I discovered that Paul Chetter had written an article on installing sound decoders for both the 00 gauge & 0 Gauge versions of the Heljan Railbus, in Hornby Magazine for October 2015. Not having the magazine, I dug further into the Internet & managed to download a PDF copy from PDF Magazine Download - Catalog popular PDF journals . I chose the free download, which was quite slow; I believe you can subscribe for a quicker service if required.

    This showed me all I wanted to know. There is a micro-socket on the board labelled CN6 which is for the speaker wires. Problem is there is no plug supplied! And if there would have been, it would be nigh impossible to connect wires to it, as it would be too tiny. A plug with a couple of flying leads to connect to would have been ideal (I did once try to source some of Heljan’s plugs & sockets, but they would only sell me 10,000!).

    Railbus#08 (Medium).jpg

    The answer revealed in Paul’s article was to solder directly to the base of the relative pins on the decoder connection. This was very tricky and needed a steady hand and a fine bit on the soldering iron. After a couple of attempts, I managed to do it, making sure there were no bare wires shorting, which would have been disastrous to the decoder.

    Railbus#10 (Medium).jpg

    The holes & openings in the speaker enclosure were sealed and the unit wired-up and installed on the underside of the chassis.

    Railbus#06 (Medium).jpg

    Fitting the stay-alive unit (a compact Zimo SC68 unit) was straightforward – it solders directly to 2 pads on the decoder. Just need to make sure the wires are fitted the correct way around! I insulated the casing with shrink-wrap, and fixed it to the roof with double-sided tape.

    And so to testing. Although the overall sound was really good, I found that with the default decoder settings I couldn’t get the characteristic gear-changes to occur until the Railbus was going too fast. There are 4 changes in all.

    The ever-helpful Mr Chetter replied to an enquiry I posted on “the other place”, to say that it is possible induce a gear change when the engine idle sound or the cruising sound is playing, by reducing the throttle and immediately increasing it again, just like you would when driving a car.. The gear change will occur, followed by acceleration sounds.

    However, I wanted the gear-changes to sound automatically within a reasonable speed range, without having to fiddle with the throttle. I tried lowering the maximum speed (CV5), changing the momentum (CV3 & CV4) and using Decoder Pro to change the speed curve, without too much success.

    The breakthrough came when Paul suggested I adjusted CV57, which according to the Zimo manual, reduces top speed by reducing the voltage to the motor and effectively 'compresses' the gear changes into a lower speed range.

    CV57 changes certainly made the difference - I can now get the full 4 gear changes automatically in about 15ft of test track, without adjusting the throttle.

    These are the settings I ended up with

    CV 57 set low to =30
    CV3 = 50
    CV4 = 60
    CV5 =1 (=255, default)
    CV6 - 120 (default)

    I also used Decoder Pro to set the speed curve to a log curve.


    See here for information on setting speed curves using Decoder Pro:
    Comprehensive Programmer - Speed Control Pane

    Of course these settings may change slightly as time goes by, but it’s a start!

    ….and then we had another problem, or rather 2 problems.

    On the layout, the Railbus kept derailing when negotiating point-work. Initially we thought it was due to the long rigid wheelbase, through admittedly tight check-rails, but when checked against a BR Mk1 Horsebox, it was virtually the same. Also the lights both back & front kept flickering on & off, no matter which direction the model was running.

    Eventually we checked the back-to-back measurement and it was quite a way out on both wheels. In fact one was worse than the other. So we removed the keeper plates, extracted the wheelsets and managed to carefully persuade them outwards to the required 29mm.

    On replacing the wheels, we ensured that the pickups were making really good contact, as we suspected this was the cause of the flickering lights.

    Testing again on the layout point-work, all was well and gone were the flickering lights. My friend is pleased.

    Anyone else had problems with Heljan back-to-back measurement?


    Attached Files:

    Osgood, fenman, cbrailways and 6 others like this.
  15. Cliff Williams

    Cliff Williams Western Thunderer

    Yes ! Back to backs are a bit crap on some Heljan stock - Mk1s, Hymeks, 40s are the worst offenders, with some dubious issues on their modern vans.

    I would also advise fitting a stay alive unit it to it, in my case I gave up and threw it in the central section at the doors. Suffice to say it ran faultlessly at Modelrail Scotland for three days.
    daifly likes this.
  16. SoundsLoco

    SoundsLoco Member


    I asked the head man, Peter Zeigler, about the name of this feature during one of my visits to the factory in Vienna.

    The system was developed to make it easier to assign multiple lighting paterns. to single F keys. This was to cope with full lighting arrays of a high end model of a Swiss loco (I forget which one). During development, it was refered to as Swiss Mapping (or more accurately Schweizer Mapping) and the nick name was transfered to the decoder manual as the 'official' terminology. It was translated to Swiss Mapping in the English language manual.

    I think the name detracts from its wider appeal. The examples in the manual serve more to confuse than to illuminate

    It is a very powerful tool allowing project creators and end users alike to customise projects in many ways.

    In simple terms it allows any Function Output (Aux) to be assigned to any F key. It also allows different dimming values for each FO, the ability to layer multiple functions on one key, some or all of which can be inverted (engage to switch 'off').

    It can be used to allow, say, function A to operate only when function B is active, though that function B may operate alone without triggering function A.

    Confusing? Imagine a loco with markers (function B) and a High Intensity headlamp (function A). You want to be able to illuminate markers only or markers plus HI lamp but not HI lamp on its own. (prototypical).

    This is simple with SM. Markers have their own F key for on/off switching. HI lamp has a separate F key for on/off but 'on' is only allowed when the markers are already illuminated.

    It is also possible to eliminate the separate F key for the HI lamp, by making this automatically illuinate when the loco begins to move (or exceeds a user designated speed step) and switches off automatically when the loco is stationary (or drops below the user designated speed step).

    The MX645 decoder mentioned in this thread has 10 FOs as standard so there are plenty to choose from.

    The PluX version of this decoder was fitted to the Little Loco Company Class 15. Each of the four marker lamps at each end, plus the cab light can be independently controlled, so although on the face of it a fairly simple British lighting scheme it still uses 9 FOs. Fitting a Stay Alive capacitor pack does not require the sacrifice of an FO so all are available all of the time.

    There are 17 groups of 6 CVs available for assigning functions to F keys in SM. That's a lot, as you say, but there's no requirement to use all 17 groups, and typically only 3 CVs within a used group would need to be set.

    The other point is that once completed to your satisfaction, there is no need to address these CVs ever again.

    Kind regards,

  17. TheSnapper

    TheSnapper Western Thunderer

    Just a quickie – Dapol 0 Gauge Jinty

    Jinty (Small).jpg

    For sound installations, I normally I like to keep everything on the chassis – decoder, speaker, stay-alive unit (SAU). It makes for easier testing & troubleshooting . Also, for dismantling & painting, if installing in an unfinished model.

    In the case of the RTR Dapol Jinty, there is no room on the chassis as it is totally enclosed & the body is a really snug over the motor etc.

    JintyUnder (Small).jpg

    Fortunately there is plenty of space for a speaker & SAU in the boiler and/or side-tanks.

    The Decoder
    Fitting is straightforward, provision being made for a plug-in 21-pin decoder. I used a Zimo MX644D loaded with Paul Chetter’s latest Jinty sounds created especially for the Dapol model (of which more later).

    JintyMotor_etc (Small).jpg

    The Speaker
    Speaker connection is made to the on-board PCB, and the solder terminals are clearly marked.
    I used a Zimo LS10X15H11 cube speaker, mounted in the smokebox, under the chimney. To make it easier to manipulate into position, I mounted the speaker on a Plastikard “shelf” with strong double-sided tape (see below). I then slid it in from the motor opening, and bonded the “shelf” to the inside of the boiler/firebox with superglue.

    Later, I found that the smokebox door is removable, which would have made things easier, working from the front! However, if you try this, BE GENTLE - it may be best to carefully push it from the inside with a blunt instrument, rather than prise it from the outside.

    The Stay Alive Unit (SAU)

    Stay-alive connections must be carefully soldered to pads on the decoder. See diagram below:


    I used a home –brewed capacitor “array” in this model, as there was plenty of room.
    Here’s how I make ‘em:

    StayAlive (Small).jpg

    The longer “legs” on the capacitors are the positive connection. It’s important to get them the right way round, connecting + to – as above. Connecting the caps in series like this gives you a total capacitance of about 166,000µF, which is loads!

    The speaker & SAU are connected to the decoder with miniature male/female non-reversible leads, available all over e-bay for peanuts, such as here:
    20 Pairs Micro JST 1.25mm 2-Pin Male Female Connection Extended Plug Cables GW | eBay

    Both speaker & SAU are fixed with a favourite of mine - extra-strong Mammoth double sided tape:

    MannothTape (Small).jpg

    (I even use it to stick down my worktop to 2 drawer units!)

    Be careful though – it doesn’t give you any chance to re-position once in place….

    The Sound Project
    I had contacted Paul Chetter ( some time ago to enquire whether he would be preparing a sound project for the Dapol Jinty, so I knew he was working on it..

    The result is the “3F ‘Jinty’ ActiveDrive Plus V17.10”, especially designed for the Dapol model, with some unique features:. Here’s a quote from the user notes:

    “As supplied, your new decoder will work in a ‘Full Gear’ configuration, but you will be able to switch between the available sounds using your DCC controller by following the straightforward instructions below.

    This project utilises Zimo’s ability to switch between the various exhaust sounds enabling simulation of different valve gear settings.”

    I have attached a full .pdf copy of the user notes.

    Needless to say, the overall performance of the decoder and the sounds are excellent.
    However, the different “cut-off” settings produce noticeable changes in the exhaust “chuff” for a variety of situations, which all adds to the illusion!


    See attached .pdf file for full details.

    Oh, and by the way, the firebox LED glows RED when Coal Shovelling ids activated (F12 & Random), if you like that sort of thing…..

    The decoder & sound project is available directly from Paul at
    (Usual disclaimer – I have no connection except as a satisfied customer).


    Attached Files:

    Last edited: 7 November 2017
    dibateg, Rob Pulham, 3 LINK and 4 others like this.
  18. Steph Dale

    Steph Dale Western Thunderer

    That seems a little perverse, Tim.

    If you wire capacitors in series their overall capacitance is lower than the capacitance of a single capacitor. They sum in parallel.

    So is there some other reason you've done it that way? I've tended to try and get them to as high a capacity as possible in the assumption it makes them more effective. Is there some optimisation required?

    Old, but still relevant page from my website: On-board power for Zimo DCC decoders.

  19. richard carr

    richard carr Western Thunderer


    What capacitors are you using and where can you buy them from ?

  20. TheSnapper

    TheSnapper Western Thunderer