Coach Lighting in DCC - Advice sought.

[JST]

I am getting to the point of wanting to put lighting in my coaches or to be more specific, in three sets of ten coaches. I want each set to be switchable through DCC and am hoping to use just one decoder for each set.

 

I will of course need to fit pick ups to the coach. My idea is to put one decoder at the end of each set and connect the coaches with mini plugs. I could just thread the wire through as the sets do not get broken up but plugs seem a more flexible idea.

 

I am thinking of putting three LEDs in each coach and am aware that the lighting output of a loco decoder will not cope with that sort of load. I am therefore thinking of putting some sort of latching relay in the coach which would be switched by the decoder. A stay alive is also an option.

 

My questions are:-

1 Is this feasible or am I completely out to lunch thinking I could do this?

 

2 What sort of mini plugs would I need and where could I source them?

 

3 As per question 2 for the relay.

 

4 Anyone got any alternative ideas if the above is not going to work.

 

Many thanks

 

John

[RAF96]

Even a basic decoder will provide 100 mA function output for lighting so you can easily run 10 leds if you trim back their current to 10mA apiece. I use old flaky decoders for coach lighting, so plenty of capacity if you use one decoder per coach. Stick them all on the same rake address and hide them in the toilet compartment if installed.

[Suzie]

If you are running your LEDs from track voltage you can put a few in series, and if using white LEDs you will not have to run them at full power.

 

I suspect the 0.5A you can get out of a Zimo decoder should be enough to light a whole rake.

 

You might like to think about getting a roll of 12V LED light strip...

[JST]

Thanks. Yes I will use LED light strips.

 

I don't have any spare Zimo decoders but a mix of flaky Hornby, Digitrax and Gaugemaster ones (or more to the point, blown motor output ones - don't ask!). I have no idea how much each of them give for the lighting function. If by "trimming back their current" you mean fitting a resister in the circuit, would a 1k resister do it for a 10 led strip?

[Suzie]

You will need to experiment. I suggested the Zimo decoder in that £20 per rake is probably not too big a price to pay to just have a single decoder in the rake.

[Phil S]

The problems with wiring between coaches - even with commercial models using custom designed multipole micro connectors - is how fiddly they can be to connect and the problem with corners - such as a simple crossover betweenn adjacent tracks, and double-that with a modern network rail single lead exit to a single track branchline from 2 running tracks  - S-shape snake.  That excludes potential major disasters if a rake ever derails!   Individual coaches offer much  more flexibility at the expense of more pickups in total.  Also easier to test!

1 trip to a concrete floor encourages further thought on the advantages of separation 8-(.  'Power Couplings' between coaches cost more than a decoder!!

 

Analogue / Digital compatibility is another question:  If ever to be used on analogue - if following the better method of eg 'posher' LGB coaches over the basic track-voltage bulbs [now leds]... a 5V regulated constant lighting level once 5v is achieved... or constantly changing with speed  (in analogue use) ..... but simple regulation from full dcc track voltage COULD be wasting a lot of power BUT NEED NOT BE..   If stock is only ever to be used on digital, design is easier.

 

Also - is it worth the effort of remote switching the coach lights on and off?

I have some [H0] that are dcc controlled (including opening doors etc), and some which use a latching relay to be switched by an external magnet, and others which are on-always. As has been mentioned - part-dead decoders are a function-based option, and are in yet more coaches.

 

A simple circuit can be made like this:

'Full wave rectification' of the ac digital waveform with 4x 1N4148 diodes as a bridge, followed by a smoothing capacitor to eliminate flicker - HOWEVER a capacitor initially appears as a short circuit when power is applied ... therefore it is best (essential) to precede the rectifier (diodes) with a small series resistor to limit the surge.  (33-47R may be suitable) ..after this lighting can be connected...

 

12.00Vdc lighting strips are designed for just that!! ... if the applied voltage is increased to 14V, then the current through them (and heat given off through a plastic roof) is doubled.  At 12Vdc, each 50mm (3 leds and 1 resistor) takes 20mA .. at 14V > 40mA   ( Conversely, at 8-10V for a dimmer effect, the current is lower)

A 300mm long coach might have 5 x 50mm @ 20mA over compartments.

 

Using LEDs in series uses available current efficiently - which is why the 12Vdc strips use typically 3 LEDs in series, with the 1built-in resistor per 50mm length,

BUT at the 'expense' of a higher voltage to turn on the lights... not so analogue compatible. Okay for dogital-only lighting due to constant voltage (F or Track)

 

Unless you use a special current-source IC ( readily available 2-pin devices for 5mA, 10mA or most commonly 20mA ) you will need a resistor to limit the current through the LEDs [ although some of this will be from the in-rush/surge limiting resistor.  The best way of choosing this is by testing but ensuring <20mA/led.  Buy a range of values on Ebay 8-)    eg 470 -1k -  2k2 for a start.

 

However, as with Train-Tech coach lighting strips, by using LEDs in parallel, a lower voltage can be used ... and this is desirable if running on analogue track, or off a single battery as with the train-tech lighting strips.

[A 12v lighting strip of say 250mm is a combination of 5 parallel sets of 3 LEDs]

 

As well as simple voltage regulators - like the 7805 or 78L05 which give out 5V from any voltage above say 7V... and waste heat ... there are efficient non-linear  versions and voltage changing modules which are like miniature switched mode power supplies ... about 1 x 2cm each which can be adjusted to produce any higher OR lower voltage (sometimes both ... but they tend to be larger) to allow you to set the brightness easily.

 

'Flashing LEDs'  are also available - for modern style end of train lights - and as these include additional circuitry inside the 'led' - need their instructions to be followed ... today i have just used some 'supplied for 12V' at 3V without problems. [blue flashing emergency lights]

 

Making your own can work well with stripboard and 'larger' surface mount leds- allowing custom positioning for each coach/compartment.  Especially for sleeper coaches.

 

A tip from Train-Tech to transport their coach lighting to shows etc without flattening the battery ( they deect movement, and stay on for 4 minutes more)

is to use a magnet extenally to anchor/attract the ball bearing switch  ... I originally used the latching relays for this, but their solution requires no modifications to their board.   Tiny manual swiches can also be bought and fitted to coach undersides for manual on/off.

 

 

[Junctionmad]

Its worth pointing out that most modern leds, will happily illuminate at 2mA in my experience, white obviously tends to be a bit higher , but I have 3mm leds white that are very happy on 5mA

 

Dave 

[RobjUK]

I've got a batch of white LEDs from RS Components, their part number 175-1962 ["Duris E 2835"].

 

They are an ultra-bright surface mount type, so high output that when I was experimenting with resistor values for loco illumination I ended up with a 10K series resistor for a headlight and 100K for internal cab lighting. That's roughly 1mA for very! bright and 0.1mA for moderate brightness.

 

They were about £7 for a pack of 100.

 

The LEDs are about 4mm square and quite easy to solder thin flying leads to.

 

Using those you could easily run a hundred from a basic decoder, without even getting in to series connections.

 

 

[JST]

Thanks for all the knowledgeable input. Food for thought. I have a single auto coach which I think I will use for experimental purposes first.

[lennie]

As you can see things can get complicated, and maybe expensive.

From my point of view who doesn't have the knowledge electronic wise I went this way.

using Train-Tech projects. 

As a previous comment, Fully Automatic.

Rather than go into how, have a look at their website, look under Tips.

Find the one that features. Lights & Tail Light using an Inspection coach.

 

[NoelG]

I've seen some folks use a bridge rectifier chip, resistor and capacitor connected to led strip lights powered by pick bogie pick ups to give always on flicker free lighting. In one case I saw them use a rotory pot under the coach body to allow the lighting level to be varied. Train Tech battery powered coach lighting strips work really well but are somewhat expensive compared to DIY sets, but no need for power pick ups on each coach, flicker free and works particularly well on coach where the roof pops off or access is easy, or you remotely mount the battery under the coach body. Word of caution 'Light Bleed', some coaches may need significant work to avoid light bleed through cracks in coach bodies or even glowing through thin plastic roofs, glazing recesses, etc. You may need to paint a few coats of dark paint on the inside of some coach roofs, and even seal gaps where light can bleed with tape or silicone painted black, which sometimes interferes with the way a coach is snap fit assembled.

[WIMorrison]

on the subject of picking up from the wheels to get the power how do you do it for bogies that done have it installed?

 

I have wondered about these items from DCC Concepts https://www.dccconcepts.com/product/pickup-springs-1-5mm-axles-48-pack/ but I am not clear how they work , especially as most of the axles on my trucks are insulated on both wheels from the axle. They also do wipers but only for 00/H0 which doesn't work for 9mm track

[Andymsa]

I use various methods for coach pickups.

 

A. Double axled bogies, I use two strips of phosphor bronze that have an angle on them and go under each adjacent axle being careful to have the insulated side on bot axles on one side. Adjustments are made to get the slightest touch so not to retard the wheels. I put a small dab of electolube on the axle.

 

B I have used the dcc concepts wipers on single axled coaches.

 

the hardest part is finding a way to mount to the coach and each coach is unique in this aspect.

 

stangely enough I have had issues with the rakes that have throughout connections as opposed to individual coaches, but one thing I found that helps on the whole rake beng connected is to remove the weight from each coach and they seem to run better, well for me they do.

[RAF96]

You can use Hornby Pullman wheels X9096 which have one wheel live to the axle so by fitting them opposed you pickup from one rail and return to the other. A simple wiper on each axle completes the pickup.

 

You can also use ESU (50707) or DCC Concepts coach lighting pickups 

 

 

[WIMorrison]

1 hour ago, RAF96 said:

You can use Hornby Pullman wheels X9096 which have one wheel live to the axle so by fitting them opposed you pickup from one rail and return to the other. A simple wiper on each axle completes the pickup.

 

You can also use ESU (50707) or DCC Concepts coach lighting pickups 

 

 

 

 

14 hours ago, Andymsa said:

I use various methods for coach pickups.

 

A. Double axled bogies, I use two strips of phosphor bronze that have an angle on them and go under each adjacent axle being careful to have the insulated side on bot axles on one side. Adjustments are made to get the slightest touch so not to retard the wheels. I put a small dab of electolube on the axle.

 

B I have used the dcc concepts wipers on single axled coaches.

 

the hardest part is finding a way to mount to the coach and each coach is unique in this aspect.

 

stangely enough I have had issues with the rakes that have throughout connections as opposed to individual coaches, but one thing I found that helps on the whole rake beng connected is to remove the weight from each coach and they seem to run better, well for me they do.

 

Thank chaps,

 

I have looked at these but unfortunately they only make them for 00/H0 which doesn't work for H0e using 9mm track

 

The only think I have seen that fits 9mm are the springs I refer to earlier but when the axle is insulated at both ends they wont work

 

Any other ideas?

 

 

[Crosland]

On 03/04/2019 at 23:29, Phil S said:

A simple circuit can be made like this:

'Full wave rectification' of the ac digital waveform with 4x 1N4148 diodes as a bridge, followed by a smoothing capacitor to eliminate flicker - HOWEVER a capacitor initially appears as a short circuit when power is applied ... therefore it is best (essential) to precede the rectifier (diodes) with a small series resistor to limit the surge.  (33-47R may be suitable) ..after this lighting can be connected...

 

Since DCC is a square wave you can use much smaller smoothing capacitors than you would with, say, a sine wave from a mains transformer. Certainly much smaller than you would use for a stay-alive that can cause problems at power up.

 

On 03/04/2019 at 23:29, Phil S said:

Unless you use a special current-source IC ( readily available 2-pin devices for 5mA, 10mA or most commonly 20mA ) you will need a resistor to limit the current through the LEDs [ although some of this will be from the in-rush/surge limiting resistor.  The best way of choosing this is by testing but ensuring <20mA/led.  Buy a range of values on Ebay 8-)    eg 470 -1k -  2k2 for a start.

 

You can use an LM317 voltage regulator with a single resistor to make a current regulator for any current you wish (see the data sheet). It effectively becomes a 2-pin device.

 

Just remember that with any current regulator, any excess voltage appears across the regulator. For example you want to drive a 2V LED at 20mA from a 12V supply. The current regulator regulates the current to 20mA and the LED drops 2V. The remaining 10V in the circuit appear across the regulator and, with 20mA flowing, cause a power dissipation of 0.2W. In most cases, for our application, things will be fine but do check.

[Phil S]

Adding to the additional points from Andrew about my earlier post;  I was advocating the use of the 2-pin devices for space-economy reasons - keeping the bulk down as small as possible -  and ease of assembly. to give a constant lighting level for one or 2 leds  (or more) - whereas a single resistor would not suffice.    Using multiple components, I think it is better to 'preassemble' and pretest with a modular approach using a small piece of strip board - even with 'just 2' components ...

 

For more spacious applications, then the switched-mode versions of the regulators are more efficient, as are Buck converters .. the linear calculation given does not then apply .. and over 80% efficiency is practical.....   and good analogue compatibility with a 5V minimum needed.

Example Module 17mm x 11mm x 4mm @ <60p from Ebay...converts any DCC-range voltage* ( 4.75Vmin - 23Vmax) to a user-set value

Super mini 3A DC-DC Converter Step Down buck Power 3/5/16V MP2307 Chip V1B3   *preceded by a bridge rectifier to provide dc input

Non-isolated step-down module (BUCK)    Rectification: Synchronous rectification    SOFT START BUILT IN to MP2307
Input voltage: DC 4.75V-23V     Output voltage: DC 1.0V-17V (Adjustable, Output Less than Input)
Output current: Rated current 1.8A (3A MAX, can not be prolonged)
Conversion efficiency:96%(highest)     Switching Frequency: 340kHz.

    
INRUSH PROBLEMS in the Past:  The original Hornby Illuminated Pullmans - a rake of 5-6 tripped my dcc ..... and I have many more illuminated coaches nowadays  .... but that may have been before (or one reason why) I added PSX intelligent breakers to ALL my 00/H0 layouts ... and no problems since (?) 

 

So what I am experimenting with, for an improved set of lighting in my existing coaches, is  <33R followed by 4 x 1N4148 full wave rectification and a token 10uF (35V) electrolytic which is still quite small physically ... followed by the Super Small Buck Regulator described above..

8x6 holes on Strip board and 17mm x 11mm of user-variable voltage conversion.

From V=IR,  The INITIAL surge COULD be    I = V/R   or (12  to 22)V / 33  =  1/3  to 2/3 Amp per coach momentarilly (0 volts across capacitor)

6 to 10 rakes of 5-6 coaches in the 'fiddle yard'...   can take it over the 3A of that power district ( for a fraction of a second ... but that's all a fast cut-out takes .... which is where the PSX's come in.   (Bulb-based coach lighting was probably worse )

A larger resistor would reduce the in-rush current, but waste more power the rest of the time - and make it less analogue compatible !

With 120mA of coach lighting at 12V, from 16Vdcc input gives 33R  dropping 4V [linear calculation] .. okay for dcc, but high for analogue 8-(

A smaller capacitor would provide less energy storage which might cause the lights to drop out over junctions or dirty track.

 

Edited April 5, 2019 by Phil S
Soft start of mp2307 added to info summary

[Phil S]

For N gauge coach lighting - and hence pickup methods - look at Dapol, Fleischmann ( and Roco ) N gauge stock > spare parts diagrams ???

[JimFin]

6 hours ago, WIMorrison said:

 

 

Thank chaps,

 

I have looked at these but unfortunately they only make them for 00/H0 which doesn't work for H0e using 9mm track

 

The only think I have seen that fits 9mm are the springs I refer to earlier but when the axle is insulated at both ends they wont work

 

Any other ideas?

 

 

 

https://www.dccsupplies.com/item-p-102421/n-pickups-10-pack-dr-60010.htm

 

[Art Dent]

Hi JST

 

I have fitted coach lighting to several coaches and I have these detaied on another forum < link here >.

 

I either use the pickups that RAF96 showed in his post < link > or sinple phosphor bronze contacts (like this ebay item < link > £3.33 for 5 pairs including 40-inch of decoder wire) and a 12V self-adhesive lighting strip.

 

I'm not sure why you want the lighting to be decoder-conrolled.  Most coaches have their interior lights on even in broad daylight - at least that's how I remember it.  If you want the be able to turn the coach lighting off - for example for coaching stock in a siding - there is a cheaper alternative.

 

What would be cheaper (and you can switch individual coaches on or off at will) would be to include a latching magnetic reed switch in the roof of the coach.  Thus the lighting can be turned on or off with the aid of a magnet on a stick (in the same way that the lighting in the Rails Dynamometer Car can be).  If the reed switch is placed in the centre of the coach, you don't need to remember (or mark in some way) which end the reed swich is.

 

Rather than spending £20 a pop on a cheap decoder, the magnetic reed switches can be bought fairly cheaply.  Problem is the latching type are difficult to source - possibly RS Components, Farnell or Rapid (Rapidonline) may stock them.

Layouts4u have them at £3.25 each < link > but they mak do a discount if you order a quantity.

 

Hope this helps,

 

Art

[Art Dent]

Additionally ....

 

You may find that a small stay alive/anti-flicker circuit is helpful.  The following pictures show the small curcuit that I use in OO-gauge stock (you haven't said as far as I know which gauge you are working in)

 

 

Circuit Diagram

 

 

Components

 

 

Finished unit (approx 25mm long and 13mm in diameter)  Red & Black leads are the 12V DC feed to the lighting strip, the two yellow leads are the DCC feed to the bridge rectifier.

 

 

Showing the unit being tested on a 3-LED strip.

 

Hope this helps,

 

Art

[WIMorrison]

I do like your idea of the latching reed switch. you could place magnet in the entrance to the sidings and switch them off when you are parking them up, I agree that whilst running they would be on all day - I see them at the carriage sheds all dark until they are pulled out for the roster, that's when the lights go on and with 20 odd coaches £70 (or less) is a lot cheaper than £400!

[Art Dent]

5 minutes ago, WIMorrison said:

I do like your idea of the latching reed switch. you could place magnet in the entrance to the sidings and switch them off when you are parking them up, I agree that whilst running they would be on all day - I see them at the carriage sheds all dark until they are pulled out for the roster, that's when the lights go on and with 20 odd coaches £70 (or less) is a lot cheaper than £400!

 

The only problem with this idea is the proximity required between reed switch and magnet (a few mm at most).

 

The reed switch would have to be in the roof of the coach and a magnet in a roofed carriage shed and as close to the roof of the coaches passing underneath to work.

 

I don't think it would work for a magnet in the trackbed and the reed switch in the coach underframe.

 

May be worth trying though.

 

Art

Edited April 5, 2019 by Art Dent

[WIMorrison]

I might try it with just one switch then  

[Art Dent]

11 minutes ago, WIMorrison said:

I might try it with just one switch then  

 

I have modified several Lima and Bachmann BSKs and BCKs and have a swtchable tail lamp so that it could be turned off if the coach was running behind the loco trather than at the end of the train.

 

In one coach (can't remember which) the switch was under the coach floor between the frames and hardly visible.

 

In the Lima BSK, there was an on-off push switch mounted behind the 'porthole' in the corridor connector such that a pen or small screwdriver could turn the tail lamp on or off.

 

If I can find the pictures (or the thread where I posted the fabrication) I'll post in this thread.

 

Art

Edited April 5, 2019 by Art Dent