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Discussion Starter #1 (Edited)
Some of you may have seen my other thread on lighting passenger cars cheaply. This has been a fun project and I would like to post the final result in all of it's glory so people who don't want to dig through a massive thread can take advantage

The #1 goal in all of this is to light my cars as cheaply as possible. I have over 20 passenger cars that really need lighting upgrades and all of the commercial options price me out at that point. Many of these cars I got for less than $20 per so I'm not paying another $10 - $20 to upgrade the lighting. Still the flickering and how often the MTH light bulbs on these cars go at a constant 18 volts had me searching for another option.

The goal of this design is to upgrade cars that will be running on a constant 18v system like DCS or TMCC. The result also works well conventionally but that was not the goal. To achieve this as cheaply as possible I came up with the following schematic and board design.

LED_Final.png

From a company called OshPark I can have 3 of these boards built for $2.20 shipped to my house. It takes a little less than 2 weeks for the boards to be delivered. You too can order this board here:

Order from OSH Park

The components are also cheap and can be ordered from Digikey in bulk.


If you dig around on ebay you can get the components cheaper but in the end everything listed above, to light one car, comes to roughly $1.79 for the board, led's, and components. Not too bad. :smilie_daumenpos:

For info on constructing the board from the components check this post out: http://www.modeltrainforum.com/showpost.php?p=1422137&postcount=132

Now on to the upgrade... This is the car I will be swapping the light out. The bulbs have blown several times in this car and finally one of the wires broke on the light socket as I tried to change one. Pretty car but bad lighting.

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In the picture are the tools that I use to do the upgrade. Nothing fancy. Some wire cutters and strippers, a soldering iron, some double stick tape, some wire, the LED's, and the assembled board. It's really tiny :appl:

The first step is to flip the car over and remove 4 screws from the bottom of the car. You will find 2 on each side. One between the wheels and one at the end. Removing these allows you to remove the roof and the seats.

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The top of the car will now pop off. Just wiggle it a bit as you pull up and it should come free. I've not had one yet that I needed to pry up with a screw driver. This will expose the 2 stock bulbs and brackets we will be removing.

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I use a small screw driver to pull the bulb holder up from the mount and then, using the wire cutters, cut the wires at the base of the bulb holders. Once cut you can remove those clear mounts as well.

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Next I pull up the seating area to view the wiring under it. This is where you want to determine the roller power wire and the ground wire. I use my multi-meter to check for continuity between the center rail pickup and each wire. In this case the GRAY wire is the AC positive from the roller pickup.

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I picked one side and removed the stock wires for the bulb holder. Then I added an extension on to the set of wires I decided to keep. Sometimes, if the wiring job is really bad, I'll replace the whole wire. It just depends on what I see when I open it up.

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Now seat the seating area back in the car and you can put the screws for it back in. We are done with the under side of the car. It is possible to not check the wiring under the seating area but I have seen some really bad soldering jobs under there so I like to check it to make sure. This case was not horrible but I did still clean things up a bit.

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Next I took a guess and sized the power wire for the board so it would sit on the roof near the edge and then soldered the power wires to the board on the AC side.

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Next I determine the number of LED sections I will need for this car by test fitting and then cutting the sections off. I have decided to use 6 sections for this car.

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Next I prepare the LED strip by soldering a lead to it and adding some heat shrink to protect the connection.

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Next I test fit the components and determine the final length of the LED leads. Trim them and then attach them to the board.

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At this point I recommend testing everything to make sure it works. It does :smokin:

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Finally we mount the board and the LED's and close everything up. Using the double sided tape I attach the board to the roof of the car on one side.

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Then expose the adhesive backing to the LED strip and place it on the roof of the car. I've found this diagonal works well. I also add several pieces of tape as I have found over time the adhesive back can give out and cause the strips to fall. The tape keeps it up there no matter what.

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Finally, close everything up and take some beauty shots. Once you have done one car the process goes pretty quick. These cars are some of the easier ones. I usually finish up the job by oiling the wheels and cleaning the rollers and ground straps. Then this baby is ready to go.

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I've been really happy with this setup. I know there are better designs out there but they are more expensive to put together. The goal here is cheap and quick and I think I've done that. I hope it helps someone else out there. It's been a fun project and I've learned a ton!
 

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Superb post--detailed instruction; product info; informative photos; and, all clearly stated. Essentially a PSA for passenger car lighting for that specific passenger car category.

WELL DONE, !!!
 

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Lost, fine presentation. I am a fan of the KISS principle as well. One clarification though, by using a single diode you don't actually cut the voltage in half. If you measure the voltage across the cap before you attach the LED strip I think you will find your voltmeter reading ~27 volts DC because the cap charges to the peak voltage of the 18 V ac wave even though its half wave. When you start drawing current then the voltage will be something lower depending on the size of the cap and amount of current you are drawing. I suspect it will still read more than 9 volts or 12 volts which is what the strip is rated for. The 470 ohm resistor is what keeps the current at safe level, hopefully.

Pete
 

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Nice step by step, excellent DIY project!

A couple of comments.

Pete is right, you're running right at the limits, and possibly a bit over, with a 25V rated cap. I'd up that to a 35V cap, you'll have a margin of safety on the voltage ratings. The MTBF of electrolytic caps is greatly reduced running at or near their maximum ratings.

You can actually get the LED strips for considerably less, and if you order now, you'll have them around the time you get the boards from OSH Park. I don't avoid eBay as I get better prices for a lot of commodity items. ;)

3528 LED Flexible Strip Light 300LEDS SMD Non Waterproof 12V, $4.78 Shipped
 

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Discussion Starter #8
Interesting. I've checked the voltage at the outputs and at 18.9v ac input (from a test transformer) the DC voltage going to the LED strip is 9.74. I couldn't hold the probes on the board and take a picture at the same time so just used the end of the led strip but the voltage is the same.

I'll put together another board and check the voltage on the CAP. I chose the 25v as it's quite a bit smaller than the 35v ones and I thought I was pretty safe. This is why I post it. Peer review is awesome :)

IMG_20161130_095059373_HDR.jpg

IMG_20161130_095228725.jpg
 

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Discussion Starter #9
I checked the voltage at the cap without the LED strip connected. It is 26.4V as you suspected. With the test LED strip connected which has 12 LED's the voltage dropped to 25V across the cap which is right at the edge of that one. Then my hand slipped and I shorted the board so that one won't work anymore lol.

Here is a 35v cap that is only $.03 more than the 25v one and 4mm longer.
https://www.digikey.com/product-detail/en/nichicon/UVR1V471MPD1TD/493-5931-1-ND/3438498

Since it is right at the edge I will update the original post with the change. Thanks for catching that. I guess I need to place a new order to digikey for the 35v caps. I have a bunch from before but they are significantly longer and I don't want to use those. I've already installed these in quite a few cars so I'll just watch and see how long they last. So far I have probably 80 hours+ on some of the cars as my ceiling train runs all day.

I'm learning so much. Thank you all for the suggestions and help!
 

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If you shorted the board the only thing to replace is the diode. The rest should be OK. You might want to check the temperature of 470 ohm resistor after leaving it on for 15 minutes or so. It is what is dissipating the excess power to the LED strip. You may have to replace it with one of higher wattage if it gets too hot to touch.

Pete
 

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Discussion Starter #12
Thanks. I'll try to replace that component and see if it works. My first board repair :)

I have handled the components while running to check temperature and nothing is getting excessively hot to the point where I can't touch the board. I can do a more formal test though to double check as I wasn't specifically looking at the resistor. Previously, when I was hand building these, the resistor wasn't even getting hot enough to effect the heat shrink around it.
 

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Well, if the resistor gets warm enough to affect heatshrink, it will likely fail soon after that, that would be way over it's operating temperature. :D With 9 volts dropping across the resistor, you are dissipating .17 watts, that's getting close to the resistor rating. If it gets too hot, consider a 1/2 watt resistor, however it'll probably be OK.

As far as the cars already done, I'd just leave them, they might last a long time since they have a load and the voltage isn't exceeding the 25 volts under load. It's just something to consider in the future.

Remember, we didn't learn this stuff overnight either, I have a few smoking ruins in my wake. :D
 

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Discussion Starter #15
Thanks GRJ, I fixed up that test board that I shorted and checked the resistor and it's not getting very hot at all. I do very much appreciate all of the comments and suggestions. I'm learning a TON and loving every minute of it :)
 

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Discussion Starter #16
If you shorted the board the only thing to replace is the diode. The rest should be OK.
It turned out that the short due to my shaky hands trying to probe the thing didn't take out the diode or any of the other components. It took out a trace on the board itself between the ground wire pads A- and L-. The trace from the A- to the CAP- was still good. I was able to repair it by soldering a wire on the back of the board between the the L- and A- ground wire pads. This is my test board anyway so it's always been throw away and certainly been abused. Kinda interesting tho.
 

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Discussion Starter #18
I've been using #24 stranded speaker wire for this stuff and is actually cheap to find locally here. It's been working pretty good. #30 would be easier to use though. Good to know I can go thinner :) Thanks for the tip.
 

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Interesting ... good post.

Now that I have revived two PS2 engines by swapping out the batteries, I'm ready to take on a bigger challenge :D
 
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