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A while ago I was wiring a couple of sets of 3 white leds into observation cars, which seemed to be a cumbersome fiddley procedure. So I decided to whip up this little board just to make it easier. It's 31 x 55 mm overall size, with pads to solder in a rear led, and two alternate locations for side marker leds. Which ones to use will depend on what fits the particular car best. The board would mounted up inside the car roof, near the back end, using double sided foam adhesive tape, CA glue, or something similar.

The idea is to solder flat face white leds in with the leads full length, then use needle nose pliers to bend the leads as needed so that they shine directly on the red marker bezels when the car is assembled. The board includes a spot for a load resistor; I have found something in the range of 330-470 ohms seems to work nicely when connecting the board to an overhead strip of 3528 leds powered by a constant current regulator board such as that sold by grj through Hennings.

There is also a pad for a 1N4148 or similar GP diode, to rectify the track AC if no constant current board is used in the car. If using DC you would simply omit the diode and jumper the pads. You could use a standard 0.1" pitch 2 pin header and connector for wiring, but simply soldering 2 short lengths of #30 or so wiring would be an easy way to connect it to the led strip lighting.

To get a decent price point I went ahead and ordered 100 boards from an Asian board house, of which I only need about 15. So I can sell small lots of these to anyone else who may wish to use them. The price will be about 50 cents a piece, plus a nominal fee for shipping.  This is a small price to pay for the convenience they should provide. (OSHPark's price is about 13 bucks for three!)

Board PIC

Here is the dead simple circuit diagram.

LED Board Circuit jpg

Top Front 3D View

The 3D view above shows 5 leds installed, but normally you would use only one set of the side marker mount pads, whichever fits the car best.

Rod

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  • Board PIC
  • LED Board Circuit jpg
  • Top Front 3D View
Last edited by Rod Stewart
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Getting into this PCB stuff now, right Rod?

I wonder if maybe having a whole set of pads all along the side might make sense for a "universal" board, that way you could plop the LED anywhere it needed to be.  You also forgot the 22uh inductor for DCS...

Another interesting idea would be to have a constant current supply on the PCB with a capacitor so you don't have flickering markers/rear lighting.  That's one of the benefits of doing LED lighting, might as well take advantage of it.

I wonder if maybe having a whole set of pads all along the side might make sense for a "universal" board, that way you could plop the LED anywhere it needed to be.  You also forgot the 22uh inductor for DCS...

Another interesting idea would be to have a constant current supply on the PCB with a capacitor so you don't have flickering markers/rear lighting.  That's one of the benefits of doing LED lighting, might as well take advantage of it.

Good point grj; I might do a Mark 2 version with more location pads along the sides, after I experiment with the first ones a bit. They won't likely be here until about the end of the month, so we shall see.

Regarding the inductor, the idea was to couple these with led strips powered by my "roll-your-own" version of your constant current lighting boards, which already have the inductor built in; so no need I figured. Besides I didn't think there would be anything going on with this simple circuit that might create DCS interference anyway. And you already have the cap on the main board to mitigate flicker, bridge rectifier, adjustable current output, etc.

My thinking was to build up about 6 of these at a time, ready to install and hookup whenever converting a car to led lighting. I also plan to convert a few cabeese to led lighting and these may work for that purpose too. Thanks for the ideas!

Rod

Maybe replace the resistor with a 2K pot, that makes it universal.  With the pot you don't have to select a resistor, you can tune it for the proper light output.

Another good idea John, thanks! I will probably build one of the first boards up with a trim pot just to test things out. Once a value for R1 is settled on that will likely be all that I will use. Right now its looking like 330 ohm with the constant current board set at 30 ma, but that could change.

@bigboy25 posted:

@Rod Stewart This looks promising! I can't wait to see how this works out for you when the boards get here. I have had success using JLC PCB, but I don't know how their prices compare to other services.

JLCPCB is where I ordered the boards from. I have used them and ALLPCB for most board orders. Both are good. When playing with order quantities the base shipping cost was the same up to 100 boards, so that's what I went for. For quantities larger the shipping was going to be more. They said fab time was going to be 5-6 days, and shipping time another 5-6 days. This seems doubtful and I am betting on more like the end of August.

@Rod Stewart posted:

Another good idea John, thanks! I will probably build one of the first boards up with a trim pot just to test things out. Once a value for R1 is settled on that will likely be all that I will use. Right now its looking like 330 ohm with the constant current board set at 30 ma, but that could change.

Actually, you might find that you have cars with only side markers, and other cars with only rear facing lights.  Those require a different resistor value.  Also, sometimes the light fixtures require more or less intensity.  Also, if you use yellow or amber LED's in something like heavyweight coaches, they tend to require a bit more current, that would make the markers brighter, maybe too bright.

@Rod Stewart posted:

JLCPCB is where I ordered the boards from. I have used them and ALLPCB for most board orders. Both are good. When playing with order quantities the base shipping cost was the same up to 100 boards, so that's what I went for. For quantities larger the shipping was going to be more. They said fab time was going to be 5-6 days, and shipping time another 5-6 days. This seems doubtful and I am betting on more like the end of August.

You might be surprised.  I typically get boards in about two weeks including shipping from my China supplier.  Here's a recent order I made, from the time I put the order in with the two sets of Gerber files, until I actually had boards was just about two weeks.  Each of these were for 100 individual boards, and they panel them into larger panels for production.

___PCB

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  • ___PCB

UPDATE: So the board order arrived Aug 13; a couple of days under two weeks. Not bad at all.

Here is the first batch of boards built up and ready to drop in. I used cool white FF 3mm leds and 300 ohm load resistors, which looked right to my eye after some testing.

4 First Boards

The next car set on the led conversion list was MTH 60' N & W streamliners, so that's what is getting the test run. Here is the board glued in, strip leds in place and wired to the marker led board. The side marker leds have been aligned to the bezels (well, close anyway), all tested and ready to slip into the car.

8 Marker leds aligned, ready to close up

Here is the finished car on the layout and looking pretty good to me.

9 Finished

All in all I am quite happy with the way these boards turned out and how much easier they make the whole marker led installation business. As mentioned earlier I ordered a batch of 100 of these guys, so I can sell a few lots to those who might be interested. Price would be 50 cents a piece plus a nominal fee for standard mailing in a bubble envelope.

Alternatively I can post the gerbers for anyone who wants to have their own boards made, but I can tell you they are several times more costly from OSHPark. (Their price is $13 bucks for three boards I recall)

Rod

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  • 4 First Boards
  • 8 Marker leds aligned, ready to close up
  • 9 Finished

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