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Here's what I'd do for the drumhead.  This is a .4" board, it could be smaller if it didn't fit in the drumhead.  Three bare boards are 80 cents at OSHPark.  I used 0603 sized LED's, they could be the next size larger and still fit on this board.  The resistor is selected for the intensity you desire, probably a fairly high value for something as small as a drumhead.  The board is .03" thick.  The LED's are only a couple mm tall.  The board could also include a standard diode so it would run directly from track power.  You could also reverse the polarity of a couple of the LED's and eliminate a separate diode for AC operation.

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Last edited by gunrunnerjohn
@texgeekboy posted:

@TedW,

If you don’t mind, can you post links on where to buy the pcb and lights?  I’ve looked for them and am not sure about what I discovered.

For expediency, I get the pcbs from OshPark.  So download this attached Gerber file that GRJ designed into a location you remember.  Load the OshPark site, OSH Park ~, and the page will ask for your file, navigate to it, select and OshPark will automatically load the file and display your board.  set up your account to order, remember it will quote 3 boards at $2.30 shipped.  One board has six pcb on it.  So I ordered 6 boards per batch of three(2 batches) $4.60 shipped.  That's 36 pcbs.  select option "2 oz copper, 0.8mm thickness".  That's pretty much it.  Any problems send me an email(in profile)

For the leds, got those off the bay.  Can't give you a link cause of forum rules, but a screen shot and the item number.  Put that number in the bay search box and you should be good to go.  You might be able to do better in price with a search. Hope this helps.

ebay led

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@TedW posted:

Not sure how helpful this will be, but the measurements I could get readily were so different cause the designs were so different.  MTH heavyweight was 5mm thick, I installed a 3mm led there years ago.  The Lionel streamlined cars have a 3mm “gow” lighting an endcap design, indirectly.  Many weren’t lighted at all.  So I’m pretty sure one has to approach the task on a case by case basis.  But here are some photos if they help any.

...

093880EB-14F4-4F3F-A5BC-60AF271A1D45..

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49E5BB10-DBDA-4634-B492-C46F061F37CD.

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Thanks for the measurements.  I do not have any cars with drumhead lights so this was very instructive as to what the issue is in the first place!  I get it now!.

A multi-LED custom PCB may be one way to spread the light...but I'm thinking you would now just have multiple hot-spots..even with some kind of diffuser lens...though perhaps looking better than one glaring hot-spot in the middle.

I've been experimenting a variable filter to "equalize" the distribution of light.  I am mindful that there is only about 3mm of depth to work with.

high school science project

So, for example, I concocted the round filter shown in the inset that blocks more light in the center but then tapers off to the edges.  My cheesy drawing program can't draw smoothly decaying gray ring so as shown it's just 4 rings just to mess with.  The idea (open to suggestions) is to put a couple layers of diffusing material (plastic yogurt lid), then the filter, then another layer of yogurt lid.  So in the end it would be a round 3mm thick filter you plop over the LED to diffuse and equalize the light.

The key is to recognize we have more light than we need to start with.

Again, just a work in progress but I figure something anyone can do at home without special equipment, tools or what not...

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Last edited by stan2004

@gunrunnerjohn, suppose we should get a gerber file and order a few of the pcbs and start playing around.  That is if you haven’t ordered any already.  Obviously, I have too much time on my hands.    I have to get some of those tiny leds too.  Might be to much for me to handle…  BTW, what resistor value would you try?  Maybe 470ohm?  I have a resistor whachamacallit, to check different values, but no smt resistors, so I’ll have to get some of those too.  I do have some 200ohm ones.

Last edited by TedW

The LED's on my little board are this size.

SmartLED SMD Side 

Digikey has them: Osram LW L283-Q1R2-3K8L-1-Z, white.

The resistor in the board is an 0805 size resistor.  They come in power ratings up to 1/2 a watt.  I suspect that for this task, we'll light the LED's pretty dimly, so the standard 1/8 or 1/4 watt ones should do the trick.

The resistor value is totally dependent on the amount of light you want.  The Drumhead shouldn't be another headlight, so the resistor value is going to be at least 1K I would expect.  I'd probably pick up a few 470, 1K, 1.5K, and 2.2K values to start and see how it works out.  Also, the resistor value is TOTALLY dependent on the input voltage.  If you're going to try to run this on AC, swap the polarity of a pair of the LEDs, that will provide reverse voltage protection for the whole lot.  For DC, they have to be as shown, the little stripe is the cathode.

Here's the Gerber files.

Drumhead 6 LED Board Gerber.zip

Here is the complex schematic of the board.

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I pulled that "olympian" drumhead out of the end of the car.  Suppose you could say it's not mint anymore.  Tore out the 3mm led and put in one of the ground light pcb with a 3528 led.  Couple of layers of paper and see what you think.  This may be a solution looking for a problem 🤷‍♂️.  YMMV    Click for larger images:

143AD6EC-1F1E-40B6-A46D-51729591BC7C DCBFD524-DF18-4F2A-9666-33AA8B26BC26 6E4B0AB5-B621-420C-95B0-BBA458296509 82B1D098-3EE9-455B-A9F6-5B854E56A91F C46F36F0-1C34-48A5-A5D1-FF26C700AC16 979AD172-4B76-47F9-9991-DAD2825D9357 C68F69E7-9A12-4A59-8045-808180C5B84E

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Since I was the OP, I figure I need to let y'all know the outcome from my original post.  I've attached 3 pics to help with my explanation.

The first, 'Original Roof' shows the back of the observation car with the factory lenses.  My question was should I cut off the large part of the lens sticking out before adding LED lighting.  After a lot of discussion, I proceeded with drilling holes in the lenses to insert 3 mm LEDs.  Since my drilling of tiny holes was significantly impacted by my large banana fingers, that was a failure.  I bought another observation roof on the bay with similar lenses, and painted it so it looked pretty good.

Looking at all the posts, I thought about simply gluing the leds from a light strip to the lenses, and connecting that small strip to the end of the long LED strip on the ceiling.  I first glued the LEDs to the unaltered lenses.  I think there were 9 LEDs in that strip to get around all the big lenses.  The resulting light output wasn't that good.  I even glued 2 LEDs , one to the front and one to the back, of the large lenses.  I still didn't think it was good.  Sorry, no pics of that effort.

I then cut off the large end part of the red lenses, making a flat surface, and glued one led to each lens.  I used a small strip of 6 LEDs for this, and you can see it in the 'Modified Lenses with Lights' picture.  I was originally going to put liquid tape over the extra lights, but I thought the end of the observation car could use the extra light.

The 'End Result' picture shows what it looks like.  The lenses are very bright IMO.  I also replaced the factory installed GOW bulb for the drumhead with a 5 mm warm white LED.

My work will not win any accolades from the electrical techs out there, but it works okay

Update:  I didn't have the pic of the original roof, so I just copied it and then reposted it.  The image is pretty small.  If you want to see it bigger, look at the first post in this thread.

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Last edited by texgeekboy

Well boys and girls, this is me tapping out.  I'm sure a "I coulda told you so" smile is starting across your faces as I look over the drumhead pcbs I just got in the mail.  They are too small for me to tackle with the soldering of 0603 leds.  Then a resistor and hookup wire on top of that, above my pay grade.  And I have a whopping $3.20 in a dozen boards.  Anybody want some shoot me an email and they are yours.  Probably will mail in a standard first class envelope.  I wish you well with this little project.  🤷‍♂️

12264255-4BDA-4ECE-9FC3-261231803BC7 6A536BBE-15E4-44AF-9A9D-CFCFFA876110

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@TedW,

Kudos for the attempt!  I wouldn’t have even tried it since that level of detailed work is way above my pay grade as you say.  Since your drumhead was separated from the car, I was luckier with mine being attached to it and already being lit with a GoW bulb.  I replaced that with a LED and from my pic above I think it came out pretty good, I’m happy with it anyway.

@TedW.  I received my boards last Thursday, didn’t open the envelope until Saturday.  Thought pretty much the same thing as you, doubt that I will successfully get the LED’s soldered on the board.  I might attempt it at some point but since one LED costs more than three of the boards, maybe not.  I bought six boards because buying only three seemed like I was being “cheap.”

I also bought six of the single LED boards, I already have LEDs for them.

Last edited by GregM

So of course this little drumhead light got to working on me as we all know can happen in this hobby.  So, I got the leds, weaponized the hakko with a new tiny tip and some .020 solder and went to work.  Went together better than I thought it would.  But, no joy.  It won't light.  Powered at 3vdc, individually, each led lights, but of course that doesn't test the circuit.  I get no continuity.  Should I?  What else should I check?  I think I have the led polarity correct throughout.  Any help out there on troubleshooting this pcb lighting module?  Here's some photos, but not sure how much help they'll be.  Thx in advance.

B93520C2-3B25-4A57-98F0-F36A70A8D3630667306C-D43F-4AD1-83B0-B2BEEE6B094B1F7220E7-B480-4A1E-9CE1-D083059F9707

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what value resistor are you using?  It will take at least six volts to light it if it's the circuit I posted.  There are three sets of two LED's each in series, and the three sets are in parallel.  If you put at least 5.5-6.0 volts on it, it'll light.  That presumes that all the LED cathodes face the proper direction, see arrows in the graphic below.

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Well, that was easy.  Shoulda tried more voltage, but afraid to blow something up as they are 3vdc led.  Didn't know how the circuit worked.  Presumed it they were in series?  This is 5vdc with a jumper across the resistor pads.  Is pretty good that way, but using your thumbnail resistor calculator, from 12 to 6vdc would take around 300 ohms , so use a 330ohm resistor, and we're golden.  18vac would be a diode and around 660ohm.

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Last edited by TedW

At 12 volts DC, any resistor from 150 ohms or larger would be suitable.  Obviously, the 150 ohm resistor would probably result in REALLY bright lighting, so I'd be guessing more along the lines of a 1K or so resistor to tone the amount of light down.  The whole idea of the multiple LED's is to spread the light evenly, so each one shouldn't be like a miniature sun.

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