Lighting Trains

[gavino200]

1 minute ago, chadbag said:

Any of your existing lit trains are probably running without a rectifier right now so you have an example already.

 

 

TORMs have a little rectifier bridge. I don't know what's in a Kato light circuit but I wouldn't be surprised if there was one.

 

As it's been explained to me, the downside of having no rectifier might be shorter LED lifespan. So it's hard to judge without a case/control study.

[gavino200]

The rectifiers are very small btw, so there's not much downside using them.

[chadbag]

This guy claims there is no or only very little shorter LED lifespan based on what his suppliers said:   http://www.sbs4dcc.com/tutorialstipstricks/nem651connectorhalfwaverectification.html

 

You can go directly to a rail to complete the circuit but you get only "1/2" power and it is turning the LEDs off/on a zillion times a second.

[gavino200]

16 minutes ago, chadbag said:

This guy claims there is no or only very little shorter LED lifespan based on what his suppliers said:   http://www.sbs4dcc.com/tutorialstipstricks/nem651connectorhalfwaverectification.html

 

You can go directly to a rail to complete the circuit but you get only "1/2" power and it is turning the LEDs off/on a zillion times a second.

 

It's a matter of opinion. People disagree. kvp, I believe had a strong opinion about it. But IIRC he said the problem wasn't related to the LED "being turned on and off quickly" but to a current being applied in the "wrong direction" for half of the time. Apparently LEDs do not enjoy this. 

 

But who knows, I certainly don't. I may wire up a train with half the cars rectified and half unrectified. That way it should be easy to keep track of any difference over time. 

 

My gut tells me that the rectifier is probably unnecessary. But I'm also a little intrigued with using these little things too. Perhaps @Kiha66 might have an opinion. This is far beyond my knowledge level. I'm basically just a copy monkey.

 

I wonder if using a capacitor ads anything to the question of whether rectification is necessary or not? 

Edited February 21, 2019 by gavino200

[Sheffie]

An LED is first and foremost a diode. It wants to conduct in one direction and not in the other. As to whether the latter shortens its lifespan... perhaps, if the voltage is high enough. I think that operating temperature is going to have a much bigger effect than reverse voltage (+10 C => half lifespan, as I understand it). But I don't think reverse voltage will actually generate heat, because the diode isn't usually conducting. Now, will putting it in an enclosed space with other electronic components (that are generating their own heat) affect its lifespan? Again, possibly. There could be quite a few factors affecting this equation.

 

I'm following this thread because I'm considering lighting some carriages, btw. I don't think I could ever handle DCC work, but lighted carriages would be nice

Edited February 21, 2019 by Sheffie

[Kiha66]

The link you posted Gavin sounds about right.  As an LED is a passive component it is generally much more reliable but will still wear out in time.  Cycling will still affect the lifespan but much less than other bulbs, and the timespan is so long that you'll probably have quite a few other issues before the LEDs ever go bad.  I've used the technique of attaching a lighting function to the rail rather than the common wire in a few steam locomotive decoder installations where space was tight.  IIRC my C62 is wired as such and I've had no problems from it.  I have not used PWM dimming in any of those locomotives so I couldn't say if you'd get a visible flicker.

[gavino200]

4 minutes ago, Kiha66 said:

The link you posted Gavin sounds about right. 

 

The link is Chad's. I can't take credit for that.

 

Regarding the capacitor though. Will the cap be affected by rectified vs. unrectified current?

[Kiha66]

Oops!  Guess I need to work on my reading comprehension.  I'd be wary about attaching a capacitor to raw DCC trackpower as it very much is affected by cycling.  Even worse on an AC system (or square wave in the case of DCC) the capacitor acts as a short with very low resistance, drawing a huge load and possibly tripping your DCC booster.  At the very least it will muddle the DCC signals and could lead to poor running.  I would recommend that if a capacitor is to be use it be after the voltage is rectified to DC.

[Sheffie]

6 minutes ago, gavino200 said:

Regarding the capacitor though. Will the cap be affected by rectified vs. unrectified current?

 

I think capacitors really only work to buffer a DC voltage. Basically, when the power comes on, current flows briefly through the capacitor while it charges. If the voltage drops, current flows back out (through your LED) until the capacitor has discharged.

But if you try to pass AC (unrectified current) through a capacitor, it will charge and discharge continuously, draining some power and generating some heat, and it won't provide the sort of reservoir of charge that you want.

 

This is based on my school physics lessons, not experience with trains, so I may be wrong.

Edited February 21, 2019 by Sheffie

[cteno4]

Sheffie is spot on, caps won’t do you anything on ac for flicker and is going to cause the issues kiha points out for dcc as well. If you want to use a cap to prevent flickers from missed contact with the rail, then you want a bridge rectifier and put the cap on the dc side to smooth out any dips.

 

bridge rectifiers usually take out a volt or so.

 

Jeff

[gavino200]

I did my first round of testing using the @Dani method with caps. I lit one car. Overall it's a proof of concept. The car goes around the track without even the slightest hint of flicker. The light is completely solid. 

 

A few points.

 

1. I soldered the components together without a board. It's not terribly hard but it's a bit time consuming. Having a printed board would make this very simple and fast.

2. The capacitor is a little large. I could see it being a problem fitting it into some cars. Also, it may be visible in some cars. I'm going to look for a smaller one.

3. The spacing of the LEDs is relatively large. This makes the lighting a bit uneven in the car. This may be improved with a different strip with more LEDs. Or using a layer of paper to act as a diffuser. But that would add a PITA factor.

4. I used a Kato copper strip pair. to connect the wires to track power. This works well but a source for these copper strips would be needed. (Relatively easy I'd bet)

 

Dani's 2.2K Ohm resistor was spot on. Perfect brightness. 

 

The circuit.

 

 

 

Soldered to copper strips

 

 

 

Installed in an Orient Express car. Zero flicker.

 

 

 

 

 

[Sheffie]

Nice! What is the capacitor's capacity for capacitance?

[gavino200]

1 minute ago, Sheffie said:

Nice! What is the capacitor's capacity for capacitance?

 

These are 220uF 40 V Tantulum SMD caps

[Sheffie]

Aww man, I was gonna guess 220uF. I totally should've put that in the post.

 

So now the question is, can you put a slightly smaller rated capacitor in there and still get reasonable protection. Say, 180 or 150 (assuming they are significantly smaller in size)

Edited February 23, 2019 by Sheffie

[gavino200]

I think I'll keep using these caps until they run out. But the search is on for the smallest 25V 100-250uF cap available. I'm going to place my results in this thread as I go.

 

 

Below is a size chart for SMD capacitors - the 7343 of my cap seems to refer to the EIA metric size code

http://abiliocaetano.com/smd-capacitor-sizes/

 

 

 

Size given here - 2.5 x 0.6 x 0.7cm/1" x 0.24" x 0.27"(L*W*T) - considerably smaller than the 7343 smd caps

Even though not SMD they'd still be more suitable.

 

https://www.ebay.com/itm/20PCS-100uF-25V-2-Pin-Yellow-Radial-Dipped-Tantalum-Bead-Capacitors/311061736564?epid=1339188035&hash=item486cb96c74:rk:4:pf:1&checksum=311061736564186c96b99066427c97efc94c981cd9cf&enc=AQADAAADAFjVrDbVsZ8oH%2F8PNHtt9VX4%2Fw7FZcmMuqsX8uaFEduVwJIhJ4IJdA5PQPSUliyTbqhj11gMAWAhaxNzxpHk2xKULx9hpYrOmVKYr9DDb%2B4Q5IRyG2ZoQGVb%2FIKrUYZtNR0cZZZywGqpvQeV42QFIwOq4l2FWQeIA2HnDvYAySCSgQrlwBe2l%2BjfTlUaRrrA5c65viKOYBzSWvGPT3HkEXlLocPzc65rZNZXnrDaV2j4rX2CfNAMnzC27c0YsPoyhbRYRoewP%2BQrFO1Ld3v4Lg%2BnbIoom8IAm%2FhS%2BfnLuVZfJSQGv%2Bvc4wrLo5lnMXtMdBJw2gm%2F0nNXuws2vSmtWqfhs2nHoXDrAvsX60UcMrpdVRUxb%2BwSJKS1X4HQqYZLryNgg4ehDXAkcAB5P%2FtJU%2BaGQhjcoXlxIQL0XJ0Lv7o%2Flcq4VuI04RjxhnU8LdZA%2B9RwQN%2BocK9xD1VYk97bKBt1nLQTXCYW4AzKZnMIwTJp8VxSSJHCvJBVQurVVcYEys9dWjOnNugpCJVEAUsmgR7N1kSw%2FmT0jOSpaaV8XXnzzLUme7wY4QSqk886%2B5uZjSLwrnAHtr3cTIc%2FCgwIZkdhFo%2FmP9R6lky%2Fc8hMtVkfUHp%2F2Fa8e7dP%2BmgB25RtoUw3N3AcwNfO1elXbGFDu8wYRpz5A5k2iUMU5VNFNz%2FGnE5hQ2HlAgDe4jzMXZLZAVY5DsJ%2Bxrys9CLVQ3RZquI5o7SVMxjhoGliKqXD4qPXUp5IEWbXcWLaSGokOTYiQcXJn8uCcSOymwS7MdAd9uTnFENhu3KQoKDOiC5gEN0z0Xj5u6RntO9qNZc%2BD5UqryrKz5%2FJceXGRv83xXH30ypR8%2Fkvk6fZ8jfSCqaZbGAKyDUJB%2BYumQHO8yXUP0Z%2BgzFvvf22bUk7MJDY05dYxMGSNpTawLttlt34tUoe2MdsocSp4wKvSSJfio3KqW5E9%2Bqvwl%2FMYz%2Fk1GQCroYyTqDS29p27K3dZbc1OKR3hwJC5819i69G0yO7q5rS1%2B9eoQ%3D%3D

 

 

 

These are EIA code 2917 (7.3x4.3x2.9 mm)

https://www.ebay.com/itm/6-3V-35V-Various-Types-SMD-Tantalum-Capacitors-2-2uF-10uF-22uF-100uF-to-470uF/254079988045?hash=item3b2858f14d:m:mxwhpbyWfMquLJ1TVIGKyKA:rk:57:pf:0

 

 

These are 6032 size - just 1mm smaller than what I used.

https://www.ebay.com/itm/AVX-6032C-SMD-Tantalum-Capacitor-6-3V-10V-16V-25V-20V-35V-4-7uF-330uF-TS/152719020992?var=452356676418&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20131231084308%26meid%3De76f3334c2404d1a836385e3e2f81ee9%26pid%3D100010%26rk%3D1%26rkt%3D4%26sd%3D152719020992%26itm%3D452356676418&_trksid=p2047675.c100010.m2109

Edited February 23, 2019 by gavino200

[gavino200]

2 minutes ago, Sheffie said:

Aww man, I was gonna guess 220uF. I totally should've put that in the post.

 

So now the question is, can you put a slightly smaller rated capacitor in there and still get reasonable protection. Say, 180 or 150 (assuming they are significantly smaller in size)

 

Yes, I think so. KenS  mentions in his 'Sumida Crossing' website that he had success using 100uF. I bought these a couple of years ago to replace the cylinder type 220uF capacitor that came with a SoundTrax decoder.

[chadbag]

I'm still waiting for my parts but I've thought of using a popsicle type stick to attach things to and using a paper diffuser.  I have  both 100mF and 220mF on order.  We'll see when the parts come 

[gavino200]

34 minutes ago, chadbag said:

I'm still waiting for my parts but I've thought of using a popsicle type stick to attach things to and using a paper diffuser.  I have  both 100mF and 220mF on order.  We'll see when the parts come 

 

What (physical) size are the caps you ordered?

[chadbag]

20 minutes ago, gavino200 said:

 

What (physical) size are the caps you ordered?

 

The 220 are like your I expect.   I don't have specs on hand.  We'll see. 

 

I expect each light will be custom designed (in terms of layout etc) for each wagon.  Those that have ends without windows may stack the pieces there.  

[gavino200]

7 minutes ago, chadbag said:

 

The 220 are like your I expect.   I don't have specs on hand.  We'll see. 

 

I expect each light will be custom designed (in terms of layout etc) for each wagon.  Those that have ends without windows may stack the pieces there.  

 

It's not possible to get much smaller. But a "D" saves a mm over what I have for the 100's. Also, DIPs, which are available also for a 100mF are quite a bit smaller. I expect that will be the best choice overall. 

 

The whole circuit doesn't take up much space. With a slightly smaller (height) cap it should be easy enough to make a setup that would fit into any carriage.

[Kiha66]

Nice work Gavin!  How long to the lights stay on once power is lost?  That should be a good indicator of how much smaller (in terms of uF) you can go.

[gavino200]

14 minutes ago, Kiha66 said:

Nice work Gavin!  How long to the lights stay on once power is lost?  That should be a good indicator of how much smaller (in terms of uF) you can go.

 

Not long. The lights go off gently over about a second. The only reason to go smaller than 220 might be a slight decrease in size. 25V/220uF seems to be an impossible combination with smaller sized caps. You can get one parameter or the other but not both.

 

I did open up the Orient Express car again to add a light diffusor. I feared that adding paper would darken it too much, so that I'd have to experiment to find a new suitable resistor. But my wife suggested using paper from an old notebook instead of printer paper. It's a lot thinner and slightly oxidized so it doesn't ruin the nice warm white color. The car has nice even lighting. 

 

I used double sided sticky tape to secure the LED strip to the roof of the car. 

[Kiha66]

Sounds like you could drop to 25v 100uf then since it would still cancel out the flickers but shouldn't need to provide power for that long.  1/2 a second seems more than enough for flicker reduction.

[gavino200]

A second carriage - another experiment. On the plus side the circuit works. It's a problem positioning the capacitor so it's neither blocking closure nor visible through the window. At the moment it's still a "technique for those who don't value their time". But I might be able to streamline it somewhat.

 

I've hit a problem with the LED strips. It's only possible to cut the LED strip at the solder/break points. The circuitry is quite complex - not a simple ladder. If you cut between LEDs within a segment of three the LEDs after the previous cut point don't work.

 

This means you have to light the cars in units of three LEDs. I think 6 is a bit short. 9 is too much. 7 would probably work best. But it's not possible. 

 

I tried: 

removing the LED --> nothing lights

replacing the removed LED with a conductor ---> then only the final LEDs light. The LEDs before the cut point don't work.

I attempted to replace the LED with an SMD resistor. This should work, but it's very tricky and I haven't succeeded.

 

I wonder if it's possible to buy LED strips that can be cut at any point without losing function. If they exist they'd be more suited to this application.

Edited February 23, 2019 by gavino200

[gavino200]

Actually, it doesn't look bad with a paper filter added. But I do still think it needs one more LED. I'm deliberately being nit-picky here. It's not just about getting this train lit. Rather I want to evolve a lighting method that's simple, versatile, and relatively quick. After using up these LED strips I'll try to find a different brand that's better suited. 

 

 

LED with paper strip.

 

 

Installed in wagon shell.

 

 

I'm not sure if this "special car" is supposed to be lit, or if the table lighting is all that's needed. I'm going to leave it for now.

 

Edited February 24, 2019 by gavino200