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Shinkansen DCC Interior lighting with Flicker-Free feature


Costas

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Here is a semi-detailed thread outlining a realtively cheap method of illuminating the interior of your trains and while at the same time incorporating a flicker free feature which utilises a minimum of components.

 

I touched on the method over on another thread over here and this covered off some basics. This particular thread will go into more detail by highlighting some of the installation steps of installing the components in a Kato 700 series Shinkansen.

 

In the past I have utilised Kato's purpose made lighting kits. While these work very well they are not relatively cheap and with the advent of very cheap LED strip lighting I decided to use this technique to illuminate the interior of the cars.

 

LED strip lighting is quite common place these days and is available in a variety of colours and sizes. The LED strips I am mainly interested in are fitted with either cool or warm white LEDs and are designed to operate off 12v and these usually have 3 LEDs spaced in their own group every 50mm. So a 100mm length of strip will have 6 LEDs and a 150mm length will have 9 LEDs etc etc. A typical Shinkansen car will require a strip length of 150mm therefore each car will house 9 LEDs across its interior roofline. The end cars have less space [shorter] so I normally cut the strips in groups of 6 LEDs for the end cars.

 

LED strips are normally supplied in multiples of metre lengths and users can cut these with scissors providing they cut them at the correct points which basically means that users can cut them at every third LED ie in multiples of the group(s) of 3 LEDs.

 

Each group of 3 LEDs are wired in series. 3 White LEDs in series will usually drop approximately 3.7v per LED or around 11.1v for a group of 3 LEDs wired in series. As these strips are designed to operate on 12v they are fitted with a current limiting resistor to suit [one resistor for every group of 3 LEDs]. On the strip pictured, the resistor fitted from factory is a 180 Ohm surface mount 1206 package style. Since the LED strips are designed for general lighting applications and not N scale interiors, you will find that the LEDs will be way too bright if you use them as is. We need to replace the original resistors with a higher value to reduce the current and thereby reduce the brightness of the LEDs.

 

Depending on the LED strip [you may have to experiment with the resistor values to suit your own personal preference. For the strip shown, I found that a value of 2.2K Ohms resulted in a suitable brightness. I also have another brand of LED strip which has a white background instead of brown as pictured. I found that the other brand required a higher value resistor [4.7K Ohm] as the white strip caused a higher reflectivity inside the cars which meant that the LEDs looked brighter when lit - so I needed to reduce the brightness even further with that particular brand of LED strip. The resistors are cheap so having a few common values around 2.2K and 4.7K etc is not an issue.

 

Here is a pic of the LED strip I have used for this build with a couple of 2.2K Ohm surface mount resistors [1206 Size package] in the foreground. It is not too hard to remove and replace the resistors on the strip if you have a decent soldering iron. Remember that you will need to change all the resistors ie. 1 resistor feeds 3 LEDs.

 

 

7tn2.jpg

 

I found that a length of 9 LEDs resulted in a current draw of 45mA before I replaced the resistors to dim the LEDs. Once I replaced the 3 resistors on this strip with 2.2K Ohm types, the current dropped down to 5mA for the whole strip ie it will mean that each car will draw 5mA when on the track.

 

Here is a quick photo highlighting the difference in brightness. LEDs on left have had the resistors changed while those on the right are unmodified. The colour balance is not quite accurate as I did not set my camera correctly but note that there is a slight colour shift when we reduce the brightness of the LEDs. Also note that this particular LED strip is a cool white LED type.

 

 

GX5g6j.jpg

 

 

 

This particular conversion is designed for DCC and in this case a bridge rectifier is required to convert the DCC square wave AC type signal to a DC signal so that we can power the LEDs correctly. A standard 1A DIP package bridge rectifier is all that is required. I chose a standard leaded component here as the long legs will come in handy a while later.

 

To achieve our flicker free feature, a tantalum surface mount capacitor is soldered to the DC out put of the bridge rectifier. Do not use a standard electrolytic type capacitor as they are inferior in performance when it comes to the flicker free feature. I use a single 100uF 16v tantalum capacitor for this role. A 100uF tantalum capacitor will allow a decay of a few 100 milliseconds or so and I find that is usually all that is required to stop flicker from dirty track. If you have excessively dirty track you can actually use a larger value or simply solder two or more capacitors in parallel across each other as this will increase the capacitance and therefore the decay time. If you use three 100 uF capacitors soldered together [in parallel], then the capacitance value becomes 300uF ie 3x as much and the decay will increase three-fold as well.

 

Like I said - 100uF tantalum works extremely well for me - but you can go larger depending on how much room you have or how dirty your track is.... 🙂

 

 

Standard 1A bridge rectifier and 100uF 16v tantalum capacitor:

 

f8ns.jpg

 

 

 

I then cut the DC output legs on the bridge rectifier so that I can neatly solder the tantalum capacitor directly onto the DC legs of the rectifier:

 

6pdi.jpg

 

 

I then solder the capacitor to the bridge to effectively make one single module - Make sure that you solder the capacitor around the correct way as it is polarised. The capacitor's stripe must be connected to the POSITIVE output terminal of the bridge rectifier. Triple check this, as if you get it wrong, the capacitor can catch on fire and it will more than likely damage your car.

 

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Completed module ready to install...!

 

mQrRB0.jpg

 

 

 

 

I'll pause the build for now and add to it later this afternoon... Need to pop out for some 'other duties' but will be back soon...!

Edited by Costas
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Costas,

 

Thanks very much for the details. Very similar to what I have been fiddling with with basically the same parts except the led strip (been using individual smd LEDs).

 

The big surprise is that the led strips look to be 5ma LEDs, I always assumed they were 20ma smd LEDs!

 

Jeff

Edited by cteno4
  • Like 1
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The lower the current drawn the better the anti flicker works in that we can get away with a much smaller capacitor etc.

 

This is why I can get away with a single 100uF tantalum capacitor with my modded/dimmed LED strips.

 

When using the Kato lighting kits and a single high brightness LED drawing around 30mA I needed a capacitor value that was approx. 5 to 10x larger to achieve the same result.

Edited by Costas
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Had to post this as a new post as the forum would not allow me too many photos per post.

 

 

 

Next step is to remove the shell and then the bogies and floor pan off your model. This will expose the copper pickup strips and centre weight.

 

iptu.jpg

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By removing the centre weight it allows us to install our small rectifier and flicker free 'module' using some double sided tape into the very bottom of the car. Mount it in one of the centre sections closest to the centre of the model rather than at one of the far ends. Reason for this is that we need to solder the AC terminals of the bridge rectifier to the copper strips and you do not want to do this at the far ends as this will restrict the up/down movement of the copper strips to some degree which we do not want.

 

Use a permanent marker etc to temporarily mark the upper side of the copper strips to indicate approximately where the rectifier's two AC input pins/legs sit.

 

 

gld7.jpg

 

 

 

Now remove the two copper pickup strips and carefully bend the two rectifier's AC input legs outwards as shown. It is imperative that the legs are positioned slightly BELOW the copper strip's height but not by too much...!

 

A note on the copper pickup strips.... AVOID touching these with your bare fingers/hands if you can. Try to always use tweezers. If you touch them with bare hands/fingers, your skin oils will start to tarnish the copper fairly quickly. Once they start to tarnish/corrode, the corrosion can move along the strips and then cause all sorts of pickup issues if it works its way to the truck/bogey pickup area.

 

It is also a good idea to clean the end contact areas with a soft eraser etc since we have removed them from the model.

 

Before re-assembling the model, I also add a small drop of CRC 2-26 to the contact areas when reassembly the copper strips as this helps immensely in keeping tarnishing to a minimum and also improving electrical contact at any copper to copper contact points.

 

 

q5fz.jpg

 

 

 

 


Now simply 'tin' the two rectifier legs with solder and also tin the UNDERSIDE of the copper pickup strips in the area where you marked in the previous step. Note that remember to tin the underside and not the top side of the strip. Reason is that we will be soldering the two rectifier legs directly to the underside of the copper pickup strips while the items are positioned in the car itself.

 

 

VeL3iM.jpg

 

 

 

Before we solder the rectifier to the copper pickups, solder two wires to the positive and negative terminals of the capacitor/rectifier and run these as shown in the photo. I use a small dab of CA [super glue etc] to hold the wires temporarily in position where they run in small channel just above the bogey. Its a handy tip which makes assembly a lot easier.

 

I use a 30 AWG wire size which is thin and easy to position etc. If you use a wire size that is too thick , it may not let the upper floor/seating section to sit correctly when we clip it back in place.

 

Make a note of which wire is connected to the positive and negative terminals as we will need to connect to the correct pads on the LED strip.

 

 

93vv.jpg

 

 

 

We can now re-install the copper strips and this is the point where we would solder the UNDERSIDE of the copper strips to the bridge rectifier's two input legs. I position the copper strip correctly in the car and then simply [and quickly] heat the rectifier's leg and copper strip together and at the same time adding some solder to form a bridge of solder between the two. Make sure you work fairly quickly here as if not careful you can actually start melting some of the adjacent plastic that the copper strip is resting on if you take far too long.

 

 

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Once both strips are soldered to the two rectifier input legs you can re-install the centre weight.

 

ajrt.jpg

 

 

 

 

Now carefully feed in our two wires through the two small gaps in the floor/seating section. I utilise the two small rectangular cutouts which the Kato lighting kit pickups would normally sit in. Clip the floor back into place and ensure that our wiring is not fouling anywhere. Now carefully check the area underside where the coupler assembly swings and ensure that our two wires sit flat against the floor section - This ensures that the coupler assembly will not 'catch' anywhere on our wires.

 

 

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Edited by Costas
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Now trial fit a section of LED strip into the car and cut to length - Remember to cut in multiples of 3 LEDs. Usually it is fairly clear where you can cut these strips if you look carefully at the strip soldering terminals. You should see a set of solder terminals for every group of three LEDs as you move along the strip.

 

Once happy - cut it to length and also cut your wires from the car to a suitable length [cut them a tad longer than required as it is usually easy to hide them from view in the majority of cars]

 

Now solder the wires to the correct pads on your LED strip - You did remember to take note of which wire was which... :)

 

Once the wires are soldered to the LED strip - Peel the protective backing paper off and carefully stick the LED strip into the car's roof. I usually start at the far end and work back towards the wiring with a pair of tweezers pushing the LED strip onto the inside of the roof. 

 

I find that the adhesive they use is not permanent, in that you can peel the LED strip off at any time and reposition it etc without any problems. So if you make a mistake, carefully peel it back up and start again.

 

 

9a3i.jpg

 

 

 

Once happy - place the shell back on and tuck the wires in as you close the shell. Try and position the wires so that they are not visible if you can, in most cases this is easy to achieve especially if there are no adjacent windows right at the end of the car.

 

Shot of the finished product.....

 

skt4.jpg

 

 

 

 

Hope everyone finds the above of some benefit...!

 

All in all it works out as a much cheaper alternative [while also providing superior performance] as compared to the KATO lighting kits. While not suited to everyone [you do need to posses some soldering skills etc], I would not consider it a difficult modification to carry out.

  • Like 4
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It's a really good idea and quite simple too.

 

 all we need is a DC version now and I'll be really happy

For the DC version, leave out the rectifier brige, use an AC capacitor (for example a foil type) and modifiy a single led strip, where each led has it's own resistor. Or alternatively, cut the middle traces on the strip into 3 parts and add a resistor to each led manually. (with 1 resistor/led the leds will be connected parallely and the lights turn on above 3.2V track voltage) Everything else can stay the same in the DCC version.

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Many thanks for this useful topic!

Usually in my headlight LEDs i put 1uF capacitor to avoid flicker on the reverse... but your system it's a great job!

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Outstanding description Costas! Very detailed step by step methodology! Definitely useful in lighting 16-17 cars shinkansens!

 

However, my limited skills can't allow me to perform this operation without burning out something....

 

My cheaper alternative to interior lighting has always been illumi by FModels, but they're only compatible with Tomix and MicroAce models not Kato.. They cost around 500yen per piece versus the Tomix's 830yen per piece... Also hassle free, just drop in and run~  

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Well with dc the bridge rectifier will need to stay in there or the lights will only work in one direction, it will drop some voltage though. I guess you could double up and have half the LEDs for one direction and the other for the other direction.

 

Costas, excellent design and wonderful write up! Great gift to the group!

 

Matteo, does a 1uf cap really work on tail/headlight flicker? Would think it would need a higher one.

 

Jr500, this is very simple and pretty hard to ruin things and if you do burn some strips learning they are ultra cheer, strip of 300 usually les than $10! Once your collection grows 500yen per car gets very to a pretty big total! I would be looking at a few thousand dollars to light my current collection. With this its like less than a dollar a car and only a minute or two to install.

 

Jeff

Edited by cteno4
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Well with dc the bridge rectifier will need to stay in there or the lights will only work in one direction, it will drop some voltage though. I guess you could double up and have half the LEDs for one direction and the other for the other direction.

True, but if you solder two leds back to back next to each other (with reversed polarity and a common resistor), then you get the same footprint and the 1.4V voltage drop from the diode brige won't be a problem. (imho 1.4+3.2=4.6V is a bit too high for minimal turn on voltage in analog mode)

 

Anyway, if someone is using a PWM based CL controller (for example from tomix), then the diode bridge can stay and the DCC version will work flawlessly without any modification. I have to add that using this lighting strip in trains is a great idea!

 

ps: If only one resistor is added in series to the whole circuit between the cap and the strip, but with a higher watt rating, then maybe modifying the whole strip one by one could be avoided. The main resistor should limit the current while the original resistors should distribute it evenly. (i have to test this on a scrap 12V strip i have at home from the kitchen upgrade)

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ps: If only one resistor is added in series to the whole circuit between the cap and the strip, but with a higher watt rating, then maybe modifying the whole strip one by one could be avoided. The main resistor should limit the current while the original resistors should distribute it evenly. (i have to test this on a scrap 12V strip i have at home from the kitchen upgrade)

 

This look an interesting option, you could hide the big resistor on the undercarriage, my only worry is about the car with the motor if there is enough space to do the job

 

Costas how have you solved the space issue in the car with the motor?

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yeah i keep going back and forth of doubling up with leds or going the rectifier route. i was looking at my fiddlings and realizing while i could do things that would work and be pretty cheap on components it was getting harder to come up with a nice system for the strip with led and resistors to mount them to. i have some nice flex pc tape with two leads on it but splitting those and mounting etc were getting daunting. was starting to think about having a pcboard strip made (one larger pcb and just cut it up).

 

using these strip lights would be nice solution though and just rewire them. ive not yet tried to scrape or burn off the lacquer on the traces on the strip leds yet to rewire them, if easy heavily moding them might not be too bad a choice. not doing dcc right now and dont have tomix controllers. 

 

thanks again costas for putting this out there, gotten me back to fiddling with my lighting ideas for the cars!

 

btw anyone seen a CL power supply circuit for build your own? or as an add on to a regular dc power supply?

 

funny i am just about to install the strips as well for under counter lights in the kitchen. just using aluminum U channel to pop them in and hide as the granite counter top refects light pointed straight towards it so have to focus them back towards the backsplash for reflection down and out. not as efficient, but dont get the little sun points all along the counter top! amazing its so cheap to do with the strip lights compared to the commercial under the counter led systems, plus in the time i first researched and bought some samples to try out and then buy the whole set the parts had changed on all three systems i was looking at! plus they all did not fit perfectly under our set of cabinets. with the strips and U channel i can make it custom!

 

jeff

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Martijn Meerts

Hmm.. I'm gonna have to source me those components and try this. I do like the Kato and Tomix kits, but it is rather annoying that the light isn't even throughout the length of the car. Only thing I don't really like is pasting the LED strips to the ceilings, I'm bound to forget that while opening up a car and rip the entire thing apart ;)

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It's a really good idea and quite simple too.

 

For the DC version, leave out the rectifier brige, use an AC capacitor (for example a foil type) and modifiy a single led strip, where each led has it's own resistor. Or alternatively, cut the middle traces on the strip into 3 parts and add a resistor to each led manually. (with 1 resistor/led the leds will be connected parallely and the lights turn on above 3.2V track voltage) Everything else can stay the same in the DCC version.

Why use an AC capacitor on a DC system??  I don't understand this

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btw anyone seen a CL power supply circuit for build your own? 

Any pulse with modulation (pwm) system with a mosfet driver would work. For example i usually make them out of a pic microcontroller, a pot and an L293/L293D driver chip. If the pwm steps are smooh enough (so you can set a low %), then low speed values would be too small to move the train but large enough to turn on most led based lighting. This is what rokuhan uses for Z scale. Frequency is not that important, but high frequencies work better for lighting, but can damage some dcc decoders that are accidentally put onto the tracks. For low frequency, 50/60 Hz works (and it's dcc safe), but going higher is usually better. Older AC based CL is not good, since it can't handle directional lights and could damage some motors. The added benefit of pwm is that with it it's very easy to make the trains start and stop slowly and most rtr trains with led based lights would work without any modifications.

 

I could add my 2 chip circuit here, but the logic is in the software and i should clean up the code before posting it here. (and you will need the microchip software development enviroment and a pic microcontroller programmer to make it work) The good side of using tiny microcontrollers is that you don't have to solder much or think of complex circuits. The bad side is that you have to write a lot of carefully timed assembly code. Imho, it's easier and sometimes cheaper to buy a tomix, rokuhan or similar controller.

 

Why use an AC capacitor on a DC system?? I don't understand this

If you leave out the diode bridge for a lower turn on voltage, then reversing the train will reverse the polarity on the rails and that means the capacitor will get both polarities. (just with a very low frequency) DC caps won't tolerate reverse polarity well. Using extra low voltage drop signal diodes for the bridge with DC caps is also an option, but it's very hard to get strong enough ones that could handle the current.

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ps: If only one resistor is added in series to the whole circuit between the cap and the strip,

 

This is not recommended as you would need to rewire each group of 3 LEDs in parallel with each other [messy] and then the current draw will triple which impacts on the flicker free performance ie. the capacitor value would need to be increased three-fold as well.

 

 

Costas how have you solved the space issue in the car with the motor?

Yeh - I hear you. I just took a photo of my motor car this morning for you guys.

 

As there is no room underneath - the rectifier and capacitor are simply mounted at one end of car. I will also be installing a small decoder at the other end.

 

Note that in this case I have mounted the capacitor directly on top of the rectifier and arranged the leads to suit. The DCC power leads are simply soldered directly onto the copper strips carefully... :)

 

 

g5qi.jpg

 

 

 

 

 

Closeup to highlight wire routing and soldering to the copper pickup strips.......

 

q7d9.jpg

Edited by Costas
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"ps: If only one resistor is added in series to the whole circuit between the cap and the strip,"

This is not recommended as you would need to rewire each group of 3 LEDs in parallel with each other [messy] and then the current draw will triple which impacts on the flicker free performance ie. the capacitor value would need to be increased three-fold as well.

 

I meant that you leave the factory resistors in place, so they can balance the current for each group of 3 leds, but you can add a single resistor between the whole strip and the capacitor. This way the current limit will be the sum of the two resistors, but you only have to add a single resistor and don't have to replace the rest. The current draw should be the same, since a single resistor can be replaced with two resistors in series and many resistors in parallel can be replaced with a single one. It's a nonlinear equation, but solvable.

 

The resulting circuit would look like this:

post-1969-0-78854200-1391473455_thumb.png

 

To get the right value for you resistor, then first you have to calculate the sum of the resistance in the strip (length dependent), then take the supply voltage, substract the leds and the bridge and then choose a value that limits the current to the desired value together with the factory installed resistors. This resistor will have to tolerate the total current used by the leds, so a higher wattage version is needed, but you only need one.

 

Closeup to highlight wire routing and soldering to the copper pickup strips.......

 

Nice clean wiring and easy to reproduce and needs very little disassembly. Thanks for sharing the photos with us!

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"ps: If only one resistor is added in series to the whole circuit between the cap and the strip,"

This is not recommended as you would need to rewire each group of 3 LEDs in parallel with each other [messy] and then the current draw will triple which impacts on the flicker free performance ie. the capacitor value would need to be increased three-fold as well.

 

From what I see, the led strips are already wired in parallel, with one resistor every 3 leds, you don't need to rewire anything

 

with a quick math, If I want 0,006A (6mA) current on the leds with 12V I need to do 12V/0.006A=2000 ohm resistor

I'm not sure about the wattage I need, I think that usually a 1/4 watt resistor should be enough with 12V

 

Please review my maths it was 20 years ago the last time I used these skills

Edited by Melandir
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no the three led sets are wired in series you can see the zig zag trace doing them head to tail in series with the resistor at one end of the chain.

 

the odd thing i noticed on another thread of the led strips in the station someone posted they were shining quite bright when they were running them at 4.5v. i thought with 3 leds in series they would not turn on at that low of a voltage, tried on a couple laying around here and couldnt get them to glow till about 7v, so not sure how they were able to get things that bright at 4.5v.

 

jeff

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I meant that you leave the factory resistors in place, so they can balance the current for each group of 3 leds, but you can add a single resistor between the whole strip and the capacitor.

 

 

Ah - OK, yes that will work almost the same as changing out the resistors on the strip. A value around the 2.2K to 4.7K Ohm should get you in the ball park in regards to the appropriate brightness level. The main reason I prefer to change the actual resistors on the LED strip is simply that no extra space is required in the car to house an additional component - in most cases though it may not present a problem.

 

BTW - the wattage of the resistor can be very small since the current is extremely low... A 1/4W resistor will be more than enough - you could even go down to 1/8W resistor if there are readily available locally in your region.

Edited by Costas
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lurkingknight

for those of us in north america, digikey.com or digikey.ca is a great place to look for these parts outside of the led strips... I might actually try doing this, however, I don't have any dcc hardware so I'd be a ways off from trying this.

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