My custom solution for lighting KATO DCC trains

[paolo]

So, here's my take on how to light the interior of a model train.

In particular, I'll talk about N-scale KATO trains (I haven't tried this on Tomix) in a DCC system.

Since I have DCC, if I wanted to use the KATO lighting kits, I'd need to put a decoder for each car.

I have around 80 cars, so the cost would be very high. Besides the KATO light decoders (FR11) are very hard to find, even in Japan.

So I decided to just forget about decoders, and have the lights always on. Passenger trains usually have the interior lights always on anyways, and I don't have a yard where they should be off.

Without a decoder, I couldn't use the KATO light kits, as the LED's would burn out after a few minutes. DCC system outputs around 18V, but those LED's are usually designed for max 14V, according to their manual (I wouldn't push them higher than 12V though).

 

So I've designed a custom board, with the LED's and a few elements needed to make this work.

I have no experience of soldering, so I looked for someone who could do it for me.

A friend told me about JLCPCB.com, a Chinese PCB prototype company, that can manufacture a small batch of PCB's.

They have a very user-friendly design tool, needed to produce the files that are necessary to get the PCB into production.

 

Each board has:

 

• 4/6/8 LED's, depending on the type of car. Shinkansen have eight, some Shinkansen cab cars have six or four (for the Komachi). Other trains have six or eight. The LED's are arranged in two groups in parallel, with each group having the LED's arranged in serial
• a diode bridge, that converts the AC coming from the tracks to the DC that the LED's need (BR1)
• a low-dropout regulator, that lowers the voltage from what is coming form the tracks (around 18V) to 12V needed by the LED's (U1)
• a capacitor, to temporarily store some electric energy in order to avoid the LED flickering effect (C1)
• a resistor for each group of LED's (so in my case, two total, R1 and R2)

 

This is the electrical drawing of the version with 8 LED's:

 

 

 

Here's the list of all the components, with the link to the LCSC Electronics website, used by JLCPCB:

 

• - cold white LED, package 0402, link
• - 40V 1A 550mV @ 1A MBF Bridge Rectifier, link
• Fixed 35V 12V 2V @ 1A TO-252-2(DPAK) Dropout Regulator(LDO), link
• - 22uF ±10% 25V 1.2 Ω @ 100kHz -55℃ ~ +125℃ CASE-C_6032 Tantalum Capacitor, link
• - 402Ω ±1% 0.25W 1206 Chip Resistor - Surface Mount, link

 

This is the PCB view taken from the online editor (easyEDA😞

 

 

Each PCB costs around 1.9 euro, in detail:

 

• EUR 0.3 for the PCB prototype
• EUR 1.6 for the components and the assembly

 

Then of course you need to add the shipping. I got them in three separate orders, each time I refined the design.

The last order was for a total of 50 pieces, EUR 80 for the components and 30 for the shipping.

 

 

 

The minimum size for a PCB if you ask for the components assembly is 2 cm, but that's too wide to fit it inside a car.

So once I received them, I had to cut them one by one so they could fit. I cut them to around 1.3 cm using a Dremel.

The lengths vary from 13 cm to 6 cm.

 

The next problem was how to connect the PCB's to the copper pick up of the car.

The KATO lighting kits come with a set of copper strips that fits in each car, these:

 

 

After a lengthy search, I was able to find them on Rakuten Japan,sold in a package of 20 strips at 480 yen:

 

 

This is the link to the Rakuten page.

If you need to look for them, this is the title of the item: オリジナル　K集電金具　集電板(集電シュー)　カトー(kato)にも使えます　20個セット

 

Using a short piece of wire, I soldered these strips to the PCB (I bent them downward so they make a better contact with the wheels):

 

 

On JLCPCB, they only have cold white LED's, while most of the trains have more like warm white lights.

So I had to find a way to make them yellowish.

I tried putting a drop of orange paint on each LED, but the result wasn't consistent, you had some really orange ones and some white ones.

After watching a video on Luke Towan's YouTube channel, I decided to use his method and apply some Tamiya tape, usually used for masking before painting, on each LED:

 

 

 

To fit the PCB inside the cars, most of the time you need to trim the plastic supports, that I think are designed to hold the transparent acrylic strip used in the KATO lighting kits.

Without trimming those, you won't be able to close them properly.

 

This is the final result (sorry but getting the right color temperature it's a bit hard, in the pics they all look much more blue than they actually are):

 

 

 

 

 

I used them on Shinkansen (N700A, E2, E3, E5, E6, E7), E233, E235, E657, E353. They all fit perfectly.

I'd prefer them to be a bit warmer, but they're good enough.

 

I think that's it 😄

 

Paolo

[Yavianice]

Pretty cool! Could this be the first step to JNS branded lights? 😉 

 

I'm guessing that for TOMIX trains it would be a bit harder because the boards have to be even narrower. But, for WIDE lights and Green Max it would be a bit easier since neither of those have any mounts. I usually end up taping the "standard" lightboards to the roof anyway.

 

The "springs" that come with TOMIX are also available for purchase from Hobbysearch.

 

https://1999.co.jp/eng/10660255

 

and KATO collectors

 

https://1999.co.jp/eng/10660256

Edited August 18, 2020 by Yavianice

[Martijn Meerts]

Wouldn't call it a first step, since there's also 

 

 

Of course, combining the best of the 2 options should make a really nice custom light board, and not just for Japanese trains either.

 

 

 

[Yavianice]

Ah yes, indeed. Still, nice!

[paolo]

1 hour ago, Yavianice said:

Pretty cool! Could this be the first step to JNS branded lights? 😉 

 

I'm guessing that for TOMIX trains it would be a bit harder because the boards have to be even narrower. But, for WIDE lights and Green Max it would be a bit easier since neither of those have any mounts. I usually end up taping the "standard" lightboards to the roof anyway.

 

The "springs" that come with TOMIX are also available for purchase from Hobbysearch.

 

https://1999.co.jp/eng/10660255

 

and KATO collectors

 

https://1999.co.jp/eng/10660256

 

Ah, I didn't know HS had those available; it's not easy to find them cause they have weird names. I don't understand why KATO doesn't make their own. At least the ones I bought seem better cause they're made of copper.

 

You could still shave a couple of millimetres and make the PCB narrower, I don't think that would be a problem..

 

1 hour ago, Martijn Meerts said:

Wouldn't call it a first step, since there's also 

 

 

Of course, combining the best of the 2 options should make a really nice custom light board, and not just for Japanese trains either.

 

 

 

 

I saw this post only after I finished my little project. I think the components are pretty much the same, you need those to make it work.

As I understand it, he's doing the soldering himself, which I could never be able to do. I think that since it's done with a machine, you can use smaller packages, saving space.

 

[SuperAzusa]

53 minutes ago, paolo said:

As I understand it, he's doing the soldering himself, which I could never be able to do.

 

Same here. If I had to pick a project to spend money on, it would have to be this one due to my own lack of soldering ability.

 

If the PCB manufacturer could print on the other project's boards, however, I think there would be a real case for JNS to commission a good run of these for everyone to buy.

[Madsing]

Very interesting!

I often order PCBs from JLCPCB, but I have never used their assembly/soldering service.

Question: I see that C1 is “only” 22uF. Is it enough to ensure stable lighting? Can you evaluate how long the LEDs stay on after a power cut?

[Martijn Meerts]

Yeah, for prototyping or if you have the tools for it, you can do your own soldering which would make things cheaper, but if there's a lot of interest from people to buy these, having pre-soldered versions made would be quite a bit more affordable.

 

Either way, more people working on something like this generally means all the best ideas can be combined into a single board, or maybe a couple of different boards (white, warm white, incandescent, maybe different lengths), and do a larger run of those. I think there would be enough interest on the forum alone to get a large run done at least.

 

Personally, I'm still waiting for a board with a simple dcc decoder built in so I can control the lights 😄

 

[paolo]

1 hour ago, SuperAzusa said:

 

Same here. If I had to pick a project to spend money on, it would have to be this one due to my own lack of soldering ability.

 

If the PCB manufacturer could print on the other project's boards, however, I think there would be a real case for JNS to commission a good run of these for everyone to buy.

 

I don't think they can do all those strange shapes, I believe they only do rectangular ones, but I didn't investigate much. I know for certain that if you want to use their assembly service, the PCB cannot be narrower than 2cm.

 

1 hour ago, Madsing said:

Very interesting!

I often order PCBs from JLCPCB, but I have never used their assembly/soldering service.

Question: I see that C1 is “only” 22uF. Is it enough to ensure stable lighting? Can you evaluate how long the LEDs stay on after a power cut?

 

I think that if you go with a bigger capacitor, you'll start having issues of fitting it inside the car. It's good enough to avoid any flickering. There are some sections where the light goes off sometimes, but it's more due to some bad connection. Sure, putting a bigger one, if you can fit it, would be better. The lights turns off almost immediately after cutting power.

[chadbag]

2 hours ago, Martijn Meerts said:

 

Personally, I'm still waiting for a board with a simple dcc decoder built in so I can control the lights 😄

 

 

It's on my list :). I bought the components last year for that simple DCC decoder project you mentioned but real life (new house planning) has overtaken me.   I'll get to it eventually if someone else doesn't do it first.  I too am ultimately wanting that version.

 

[chadbag]

3 hours ago, paolo said:

 

I saw this post only after I finished my little project. I think the components are pretty much the same, you need those to make it work.

As I understand it, he's doing the soldering himself, which I could never be able to do. I think that since it's done with a machine, you can use smaller packages, saving space.

 

 

The board I use uses the same surface mount components and they are close together -- a lot packed into the space.  While soldering "by hand" I am using solder paste and a hot plate so it is quick and a poor man's "wave solder".   Just FYI.

 

My board was designed to fit all sorts of trains -- Japanese, European etc from all the manufacturers.  As such it is dense, narrow, and you can clip the ends off to make custom lengths of board.  It was made to be very customizable.

 

This seems to be a nice simple board and has the advantage that you can have them assemble it if you want.  Nice job.

[chadbag]

47 minutes ago, paolo said:

 

I don't think they can do all those strange shapes, I believe they only do rectangular ones, but I didn't investigate much. I know for certain that if you want to use their assembly service, the PCB cannot be narrower than 2cm.

 

One thing they can do is to print the board with "cut outs" inside a larger square board.  So the assembler can place the components on the larger board and then you get them and just break the out bits off yourself to get the narrower board.   The funny shape was made to make it easier to cut length off the board but it could be done as one long thin board without all the undulations.

 

[Martijn Meerts]

1 hour ago, chadbag said:

 

It's on my list :). I bought the components last year for that simple DCC decoder project you mentioned but real life (new house planning) has overtaken me.   I'll get to it eventually if someone else doesn't do it first.  I too am ultimately wanting that version.

 

 

I know, I'm not in a hurry anyway, not like I have a layout to run my nicely lit trains on 😄

 

[paolo]

2 hours ago, chadbag said:

My board was designed to fit all sorts of trains -- Japanese, European etc from all the manufacturers.  As such it is dense, narrow, and you can clip the ends off to make custom lengths of board.  It was made to be very customizable.

 

This seems to be a nice simple board and has the advantage that you can have them assemble it if you want.  Nice job.

 

Thanks. Yeah, my design is very simple and it fits well with my trains. I never thought to adapt it to others, like you did.

Yours is a pro solution, mine is like the one done in a garage 😁

 

[chadbag]

3 hours ago, paolo said:

 

Thanks. Yeah, my design is very simple and it fits well with my trains. I never thought to adapt it to others, like you did.

Yours is a pro solution, mine is like the one done in a garage 😁

 

 

Mine is the over engineered, probably done the wrong way by Electrical Engineering standards way.  I am sure there are a ton of optimizations that could be done.  But I understand it (or at least understood it when I did it).  It is the kind of thing a logically thinking software engineer would design who is not a EE and only has a basic understanding 🙂   .  I have a large assortment of trains, both Japanese and European ,with anything from Shinkansen, to Japanese EMU/DMU, to long Euro carriages and I wanted something that would be universal.

 

I am interested on how your 22mF capacitor could be enough to do anything at all though with the number of LEDs you have.  My sample boards use an order of magnitude higher capacitance (though you get a second or three or more of light after removing power).  Maybe my track was just dirty but when I used a smaller capacitor capability and pushed a car around the track I did not notice any significant reduction in flickering.   I made the board flexible so that you can use multiple capacitors in parallel to get the level that works for you.

 

I do need to take pics from my sample boards so I can give approximate values to things to those who got a few boards from me for testing.   I've tried various size and color of LEDs and various capacitance values and wanted to share what I have done with those experimenting.

[SuperAzusa]

Do you think a MK2 of the design in the OP is possible? With the "cutout" feature suggested above, and the circuitry such that you can trim unneeded LEDs ala Popondetta/chadbag's design? 

[chadbag]

1 hour ago, SuperAzusa said:

Do you think a MK2 of the design in the OP is possible? With the "cutout" feature suggested above, and the circuitry such that you can trim unneeded LEDs ala Popondetta/chadbag's design? 

 

 

The LEDs are two sets of LEDs in series according to the diagram, so you can't just lop off LEDs from the circuit.  You'd have to bridge where you lopped off.

 

The one I did uses parallel LEDs so you can lop as many off as needed.   

 

One way is not better than the other -- just different goals and ways of setting up the circuit.

[chadbag]

This one uses a dropout regulator instead of a linear voltage regulator that I used.  Not being a EE type I need to read up and experiment with the dropout regulator.

 

This circuit, except for the LEDs being in parallel, is very similar to my V2 circuit.  I adsded a Zener diode to limit input voltage into the cap and some small resistors and caps to smooth out the voltage into the chips etc.  But basically very similar.

 

[paolo]

I took a video of all the trains running at the same time, I didn't notice any flickering:

 

 

Sometimes you can see some flickering (but also the motor car stutters) in places where I did a poor job with the Unitrack (especially on turnouts), but in 99% of the layout you don't see any problem, which is good enough for me. Is the package of the capacitor you're using much bigger than the one I used? Cause if not, then it's better yours for sure.

[chadbag]

6 hours ago, paolo said:

I took a video of all the trains running at the same time, I didn't notice any flickering:

 

TEST VIDEO

 

Sometimes you can see some flickering (but also the motor car stutters) in places where I did a poor job with the Unitrack (especially on turnouts), but in 99% of the layout you don't see any problem, which is good enough for me. Is the package of the capacitor you're using much bigger than the one I used? Cause if not, then it's better yours for sure.

 

Mine is made to use multiple capacitors in parallel which act as one large capacitor.  I use the same regular surface mount capacitors in the normal size similar to what you use.   You can get larger capacity ones in about the same size (that fit the pads) though the ones I have are 16V and not 25V ones in large capacity.  (Which is why I have a Zener diode in my circuit -- to tamp down the input voltage just in case).  I need to go through my component stash to see what all capacitor sizes I have.

 

My components are laid out a lot more densely if you look at my finished boards in the other thread.

[chadbag]

10 hours ago, paolo said:

I took a video of all the trains running at the same time, I didn't notice any flickering:

 

TEST VIDEO

 

Sometimes you can see some flickering (but also the motor car stutters) in places where I did a poor job with the Unitrack (especially on turnouts), but in 99% of the layout you don't see any problem, which is good enough for me. Is the package of the capacitor you're using much bigger than the one I used? Cause if not, then it's better yours for sure.

 

 

So my boards use ceramic surface mount capacitors.  The really small square ones you can see in the thread on my board.  The V1 board does have space for one larger tantalum surface mount capacitor but the V2 board only has lots of spaces for the smaller ceramic ones.   Being in parallel they are additive.

 

I am looking for the V2 boards I put together last year.   I thought they were in my Rai Star 700 but those are all V1 boards (same idea -- slightly different circuit).