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Author Topic: Carriage lighting?  (Read 365 times)

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Offline jamespetts

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Carriage lighting?
« on: November 26, 2019, 02:17:17 AM »
Does anyone here have experience of DCC switchable carriage lighting? I am interested in having this for my layout, but there are a number of constraints and problems that make it hard to decide on an efficient system.

One of my main interests is realistic operations, so one thing that I am very keen for carriage lighting to do is to be on when the carriages are running in service and off when in a yard or running ECS. This should not be a major problem for carriages which, on my layout, only run in service (e.g. HSTs, for which I can use Dapol lighting bars if/when they ever become available again), and should be relatively straightforward for one or two car DMUs which have decoders already in every carriage.

The complexity comes with rakes of locomotive hauled carriages which sometimes run as ECS and are sometimes stored in yards on my layout, and also the one three car DMU that I have so far. There are essentially two ways of doing this, both of them unsatisfactory:

(1) use a separate function decoder in each carriage; or
(2) put an electrical connexion between each carriage in the rake.

Function decoder per carriage

Using a separate function decoder in each carriage seems excessively expensive. I had a look at N gauge carriage lighting solutions at Warley, and bought for testing purposes a Digikeijs DR800 light strip. This cost £24 and has a built-in function decoder. This seems quite an advanced system with many different CV options. This package includes pickups, stay alive capacitors and passengers.

However, this seems to be about as cost effective as a one function decoder per carriage solution can get, as the cheapest function decoder on its own that I can find is circa £14 (the Digitrax one function decoder), and this excludes pickps or the actual LED strip, let alone stay alives or passengers.

For six my six rakes of mk1/mk2 carriages consisting of between 8-10 carriages, this would cost circa £1,300 for the whole set, not including the centre trailer of the class 101 DMU or any other locomotive hauled set that I may wish to run as ECS from time to time.

This method is at least relatively straightforward and avoids the problems of attempting electrical connexions between vehicles.

The unit is very long (far longer than any N gauge carriage), and it is probably possible to connect these together between multiple carriages with wires so as to be able to use this for more than one carriage (see below).

Electrical connexions between vehicles

In principle, this is much more satisfactory: a single accessory decoder could then be used in a rake and each vehicle in the rake powered from that decoder, greatly reducing cost. However, getting a good electrical connexion between carriages is difficult in N gauge (this may be easier in 00). I have posted about this previously on the forum, and my carriage lighting purchase has prompted me to look into this again.

I have tried a number of solutions, none of them entirely satisfactory.

Individual plugs and sockets

These gave a workable electrical connexion, but were too bulky, looked unsightly and caused problems on cornering.

Peho magnetic couplers

These are mechanically and electrically sound and much less obtrusive than the individual plugs and sockets, but the coupling distance is too large compared to the otehrwise very satisfactory Dapol NEMCoup knuckle couplers.

I attempted to shorten this using a knife and glue (only the special two part cyanoacrylate designed for plastic worked, but that worked well), and whilst in some ways this was successful, the unit was then unable to traverse tight corners of the sort that I have in my fiddle yard (minimum ~305mm). On a layout with only gentle curves, this might be a good option

Self-designed magnetic couplers

I produced my own design of magnetic couplers, much smaller than the Peho couplers, and had a small batch 3d printed. They have a much better coupling distance than the Peho, and, being narrower, do not cause cornering problems, but attaching the wires is very fiddly and the quality of the electrical connexion is dubious. Also, although unobtrusive when new, once I have soldered the wires onto the steel sheets that attach to the magnets, these look unsightly.

I have yet to test these fully, however, although initial testing shows that they are strong enough to allow a significant load: I was able to drag the remainder of two two car 101s (including two motorised units not under power) through a 305mm curve without this disconnecting. Adding a further motorised 101 was too much for it, but this should be enough for any purpose.

Given the amount of work involved in setting these up, however, this will not be viable for 6 8-10 coach trains.

Plug and socket connectors

I bought some of these from a lighting specialist stand at Warley. They are akin to pin headers used in electronics.

These are much easier to set up than my own design, allow closer coupling than the Peho type and are less obtrusive than the original electrical connectors that I use. These seem to allow for cornering at a reasonable coupling distance, although so far I have only tried attaching these to a class 101 with Black Tack (which is surprisingly effective, but I am not sure how durable), and this is likely to be a very large task to set up.

Number of poles

All of the above types of electrical interconnect use only 2 poles. A better system (electrically) would use 4 poles, allowing all carriages to pick up track power and (separately) transmit lighting power to all of the strips. However, this would be impossibly bulky in N gauge.

One of the functions of carriage lighting (and a reason that I am considering this fairly early in the layout project) is the ability to do away with resistance wheelsets necessary for computer controlled DCC operation. This will not work if there is only one function decoder per train, as, with two pole connexions, there would only be one pickup vehicle.

How to solve this latter issue is tricky and may require multiple function decoders per rake.

***

I should thus be very interested in how others who have considered this issue have addressed it in light of the above.

Offline Nigel Cliffe

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Re: Carriage lighting?
« Reply #1 on: November 26, 2019, 09:33:52 AM »
Cheaper decoder options:
a - use the cheapest loco decoder you can find, such as the Lais units badged by various people for about £10.

b - if needing 60 decoders, then talk to the decoder maker's directly about a bulk order.  Some may drop the price a lot.   

c - build your own function decoder, eg. Paul Harman's design.  Should be well under £3 per decoder, and being DIY, if you understand what's happening, a stay-alive should be simple to add to the design.    But, even if one goes away from strip-board, it still ends up somewhat bulkier than a surface mount mass produced decoder - probably easy to hide in OO, more difficult in N. 
dccdiy.org.uk/

Coupled carriage options. 
Could be "1 pin" as all you need is the lighting function from the decoder to turn lights on/off, and the pickup on one side of the carriage is the power source.   If you fit two diodes in the carriage (rectifying the DCC signal to form a decoder positive), then the pickup can be from both sides of the carriage, which may have advantages for current detectors which are usually only fitted to a single rail.   Experiment needed to confirm it all works - particularly over any booster boundaries.
There are variants on the "1 pin" approach, with more electronics in the coach, so the 1 pin is only transmitting a data signal, not carrying the lighting current for the entire train. 


« Last Edit: November 26, 2019, 10:43:25 AM by Nigel Cliffe »

Online njee20

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Re: Carriage lighting?
« Reply #2 on: November 26, 2019, 09:36:20 AM »
I was going to suggest LaisDCC decoders, and definitely contact them, for an order of 50+ I'd expect them to offer a good discount. I negotiated a price some years ago on a smaller order.

Offline jamespetts

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Re: Carriage lighting?
« Reply #3 on: November 26, 2019, 11:46:50 AM »
Thank you for your replies; that is most helpful. The LaisDCC website suggests only one dedicated function only decoder, which is bulkier and intended for H0/00 scale; but presumably one could use a smaller motor decoder and put a 10k ohm resistor accross the motor wires?

Online njee20

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Re: Carriage lighting?
« Reply #4 on: November 26, 2019, 11:57:55 AM »
Are you just thinking about programming them? You can either do that, or you can program them in something with a motor. I'd be inclined to do that. If you have the ability to do so putting the entire train on the program track with one decoder in a loco should program the entire train in one  go - ultimately it's presumably just address you'd be changing.

You don't need any load across the motor pins once they're programmed.

Alternatively what about reed switches with magnets at a point on the layout to switch them on/off? Would mean the lights came on or went off coach by coach as they crossed the magnet, but far cheaper.

I'll be honest I'd consider if you really want to go down that route anyway. Most interior lighting isn't that bright from the outside. I personally think Dapol's light bars are far, far too bright. Given the expense of converting a whole fleet I certainly wouldn't do it. Are you planning to operate regularly in the dark?

Online RailGooner

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Re: Carriage lighting?
« Reply #5 on: November 26, 2019, 12:14:26 PM »
For my EWS Hospitality Train build I fitted each coach with a six-pin socket and blank.


Images © Mark Adedeji, on Flickr

I'm currently working on a Network Rail NMT build. Here I'm opting for a LaisDCC 860010 Super Small Size 2 function decoder in each coach. Though I'm still pondering whether to use a 4 function decoder for a couple of the coaches that have external lights/effects in addition to internal lights.
« Last Edit: November 26, 2019, 12:27:27 PM by RailGooner »
“We are indebted to those soldiers who served with courage and distinction to bring peace to Northern Ireland,” UK Defence Secretary Gavin Williamson said. “The welfare of our former service personnel is of the utmost importance.”

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Online njee20

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Re: Carriage lighting?
« Reply #6 on: November 26, 2019, 01:19:04 PM »
I'd also thought about that on my NMT - having the roof lights on the pantograph well etc.

Online RailGooner

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Re: Carriage lighting?
« Reply #7 on: November 26, 2019, 01:55:41 PM »
977993 the Pantograph coach, yes me too. I got a neat circuit board with all the necessary LEDs for 977994 the Track Recording coach, from ebay. I'm also toying with having lit VDU screens and server racks.
« Last Edit: November 26, 2019, 02:07:56 PM by RailGooner, Reason: added link »
“We are indebted to those soldiers who served with courage and distinction to bring peace to Northern Ireland,” UK Defence Secretary Gavin Williamson said. “The welfare of our former service personnel is of the utmost importance.”

Per Ardua ad Astra | Mens Agitat Molem | Victoria Concordia Crescit | Utrinque Paratus | Caveat lector

Online njee20

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Re: Carriage lighting?
« Reply #8 on: November 26, 2019, 02:25:14 PM »
Oh no that is awesome - duly ordered!

Online crewearpley40

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Re: Carriage lighting?
« Reply #9 on: November 26, 2019, 02:32:08 PM »
We will all be looking forward to photos upon completion.

Online DCCDave

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Re: Carriage lighting?
« Reply #10 on: November 26, 2019, 03:06:53 PM »
Back to more mundane coaches, Gresleys,

I've ordered a couple of LaisDCC decoders (860010 Super Small Size 2 Function) to experiment.

I have several light bar ready Gresleys but don't want to fork out for Dapol light bars so plan to make my own light strips.

I'm clear on how to wire the decoders to the track pickups, and assume blue along with white AND yellow wires will give me lights in either direction (or should I use another function). I'd appreciate some suggestions on an appropriate SMD LED warm white strips (are these appropriate: warm white, 12VDC)? Do I need to put anything between the decoder and the LED strip (resisters, capacitors) ?

Cheers
Dave

Offline Nigel Cliffe

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Re: Carriage lighting?
« Reply #11 on: November 26, 2019, 04:02:11 PM »
Back to more mundane coaches, Gresleys,

I've ordered a couple of LaisDCC decoders (860010 Super Small Size 2 Function) to experiment.

I have several light bar ready Gresleys but don't want to fork out for Dapol light bars so plan to make my own light strips.

I'm clear on how to wire the decoders to the track pickups, and assume blue along with white AND yellow wires will give me lights in either direction (or should I use another function). I'd appreciate some suggestions on an appropriate SMD LED warm white strips (are these appropriate: warm white, 12VDC)? Do I need to put anything between the decoder and the LED strip (resisters, capacitors) ?


Decoder wiring -  only need to use one function output (eg. white wire) and then change the function mapping to do what you want (eg. lights in both directions, and which function key operates the lights).   But all that assumes the function outputs are rated high enough for the current in the strips you indicate.  Unfortunately I think you risk blue-smoking decoders: see some estimates below.



LED strip.  Well, depends on how marginal you want to be....   The function output voltage on a DCC decoder depends on the track voltage, so for a range of common DCC systems, it could be anywhere from 10v to 18v.   Those strips are designed to be run from a 12v power supply (and put out a lot of light at 12v).  So the question is how to regulate the input voltage to be 12v or less. 

You could "wing it" and hope they're OK.  They might be,  or might not.

Or you need to either fit a voltage regulator (which may get warm), or work out/measure the current drawn by the strip in your coach at 12v, then calculate a sensible resistor value to cope with likely track voltages. 


Very rough calculations (which I wouldn't trust beyond ballpark without actual measurements of the strips)

Seller says max 12W / metre, at, presumably, 12volts.  So that's 1A per metre.   
Assume 150mm in a coach, so that's  0.15A.   So, for 150mm of strip, you need a decoder with 150mA function outputs.   That's OK on some brands/models, but its "blue smoking dead decoder" on the Lais you mentioned which is rated to 100mA.  (One can get round this limit by using the decoder to switch a transistor, which in turn switches the strip of LEDs).
 
Now resistor values (which doesn't alter the current requirement):  to drop 18v to 12v is a difference of 6v. With 0.15A, 6V, V=IR, gives R=40ohm, but also Watts=VI = 0.9W.  So, needs a 1W resistor, which is big, and may have heating issues. 


Conclusion:   personally, I'd not use such lighting strips in a N gauge coach.  Too bright, too much current, too much heat when trying to regulate them.    I would string up suitable LEDs (I'd use surface mount ones), with appropriate resistors.  The calculations for resistors are simpler, there won't be big heat issues to deal with, and things would be a lot more controllable.   



- Nigel


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Re: Carriage lighting?
« Reply #12 on: November 26, 2019, 10:21:25 PM »
Conclusion:   personally, I'd not use such lighting strips in a N gauge coach.  Too bright, too much current, too much heat when trying to regulate them.    I would string up suitable LEDs (I'd use surface mount ones), with appropriate resistors.  The calculations for resistors are simpler, there won't be big heat issues to deal with, and things would be a lot more controllable.   
- Nigel

 As ever a comprehensive reply Nigel. If I were to build my own strips on PCB using SMD LEDS and resisters do you have any recommendations for parts?

Many thanks
Dave

Offline Nigel Cliffe

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Re: Carriage lighting?
« Reply #13 on: November 27, 2019, 08:48:50 AM »
Conclusion:   personally, I'd not use such lighting strips in a N gauge coach.  Too bright, too much current, too much heat when trying to regulate them.    I would string up suitable LEDs (I'd use surface mount ones), with appropriate resistors.  The calculations for resistors are simpler, there won't be big heat issues to deal with, and things would be a lot more controllable.   
- Nigel

 As ever a comprehensive reply Nigel. If I were to build my own strips on PCB using SMD LEDS and resisters do you have any recommendations for parts?

Many thanks
Dave

Not directly, because I've not had cause to light a carriage.   I'd be looking at electronics suppliers (RS, Farnell, Rapid) for white LEDs, surface mount, and not too small to be difficult to handle.  Check sizes before you order, some get extremely small for hand-soldering.    To an extent, one can bias the colour of a cooler white LED towards warm with thin yellow-ish paint over the LED.   

If a small order, check postage and minimum order sizes.  Often Farnell and RS don't have minimum order values, whereas Rapid have a minimum order value.

https://uk.farnell.com/cree/clm3c-mkw-cwaxb233/led-warm-white-1-56cd/dp/1855550
https://www.rapidonline.com/0603-1608-metric?Attributes={"Colour":["White"]}
https://www.rapidonline.com/0805-2012-metric?Attributes={"Colour":["White"]}

Suitable resistors need quick sums, but typical LEDs have a max forward current of 20mA and a forward voltage of about 3v.  Assume 18v track voltage, so need to drop 15v.  V=IR 15=0.02*R,  so R=750ohm. 

That's the minimum value, which will have a screaming bright LED, so at least double, if not more, and end up with 1500ohm to 2kohm to begin experiments, and might need higher still.  One resistor per LED, and as the LEDs are surface mount, surface mount resistors are no more difficult to handle.  603's are reasonably large as surface mount goes, so (Rapid being random choice, equivalent will be available at RS or Farnell):

https://www.rapidonline.com/0603-smd-resistors?FromPrice=0.3109999895095825&ToPrice=1.31099998950958&SortAsc=FromPrice&Attributes={"Resistance":["1.5k%26amp%3BOmega%3B","1.6k%26amp%3BOmega%3B","1.8k%26amp%3BOmega%3B","2k%26amp%3BOmega%3B","2.2k%26amp%3BOmega%3B","2.4k%26amp%3BOmega%3B","2.7k%26amp%3BOmega%3B","3.3k%26amp%3BOmega%3B"]}

( That's ~ £0.56 for 100 resistors ). 


I'd make a thin PCB, say 0.3 to 0.4mm thick, cuts fairly easily with a Stanley knife enough to then snap along the line, though will blunt the blade (so use an old-ish blade).  Available from numerous sources in small pieces, including Eileen's Emporium. The material is usually double-sided, so can use the back as well as front - for example run the main power feeds along the back and bridge round to the front with a scrap of wire when needed.   
Scratch insulating lines in the copper using blade or corner of a file, check its isolated the two halves with a multimeter before fitting any components. Put the surface mount component in place, hold with a cocktail stick whilst bringing iron and soldering to each side - the solder will flash around the contacts onto the PCB.



Nigel


Offline jozasa

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Re: Carriage lighting?
« Reply #14 on: December 03, 2019, 12:58:48 AM »
Back to more mundane coaches, Gresleys,

I've ordered a couple of LaisDCC decoders (860010 Super Small Size 2 Function) to experiment.

I have several light bar ready Gresleys but don't want to fork out for Dapol light bars so plan to make my own light strips.

I'm clear on how to wire the decoders to the track pickups, and assume blue along with white AND yellow wires will give me lights in either direction (or should I use another function). I'd appreciate some suggestions on an appropriate SMD LED warm white strips (are these appropriate: warm white, 12VDC)? Do I need to put anything between the decoder and the LED strip (resisters, capacitors) ?

Cheers
Dave


I have done it with a standard LED strip of 5050 warm-white leds (you can cut it every 3 leds) in my 4 Dapol lightbar-ready coaches. Train is driven by a Dapol class 50 loco

My Ecos central power supply is set to give 15 volts to the tracks for N gauge as per ESU recommendations. But to be safe, I first measured my rectified track voltage, and turned out to be roughly 12-13 volts, a little depending on track load.
I found that a full strip of 24 leds (6 leds for each of the 4 carriages) takes 270 mA in current at 12 volts directly. That would be some 44 ohms of resistance of such strip

But it is indeed too bright, so you have to add a resistor in series anyway. I used 1Kohm, and the total current obviously dropped to some 12 mA for the whole train. The needed wattage of such resistor is 0,1 Watts as per Ohm's law, negligible then (I used a small 1/4 watt resistor). Any decoder can handle 12 mA in function outputs, so I used a cheapo Laisdcc in the first car and wired the cars all together. I used the yellow wire (default for rear-lights), and then remapped the function in the decoder, so I could light the train with F4, independent of direction. I gave the decoder the same address as the loco, so in the ECOS I can have "coach lighting" as an additional "loco function". I also added a stay-alive tantalum capacitor of 100uF/25v in the decoder.

It worked beautifully electronically speaking, but the train was derailing every now and then because of the wires between coaches (the yellow and the blue all along the train, in decoder-wiring size).

No matter how I adjusted the bloody wirings (more or less "loose"), I still had occasional derailments, so I got fed up in the end, and wired each carriage individually.

I think the "risks" of commercial LED strips have been somewhat exaggerated here. Once you add limiting resistors, currents and wattages are perfectly manageable. And they are indeed a cheap and fast way to light coaches.

PS. The Led strip you link is waterproof and RGB. You don't need any of those. Use warm-white or cool-white, and NON waterproof


« Last Edit: December 03, 2019, 01:16:29 AM by jozasa »

 

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