Let there be light! A beginners attempt at an MTH coach LED conversion.

Bell captain.....Since none of the more experienced members have responded I might be able to help. I use and recommend GRJ's passenger car board for this task. I built mine from his DIY posting giving the board design and parts listing. If your not yet ready to build the board, He has a complete kit on Hennings available for order. I think they come in a two pack.

https://hennings-trains.shopli...ed-lighting-kit.html

The board handles two of your points. Adjustable light level and flickering. The 12 volt strips run cool and there is no flicker. The cap on this board actually holds the lights on a second or  two after track power is cut off. I run a mix of TMCC and conventional both work great. If you still want to experiment you need a circuit with a resistor to get the current to the right level, a diode for half wave DC and capacitor for the flickering. You would need to change the resistor to get the light level you want. Hope this helps.

Richard

It can be done using a combinations of resistors, rectifiers and/or diodes, but not worth the effort IMHO, plus you will not have intensity adjustment unless you incorporate a pot in the mix.

My advice would be to just buy the full LED kit from GRJ or Hennings. Not cheap, but you get enough to do two cars and you're done in 15 minutes with no flickering and adjustable brightness.

I agree with Richard, just go th Hennings Trains and order the LED boards. For a little more money you can buy the complete LED lighting kit.

I'll third the suggestion to go with pre-built boards that have everything already built put together to mitigate flicker and yield the right amount of light.   I've heard only good things about GRJ's boards.   Another option is the boards from Royz Trains.   You can get them with the connector for MTH cars already installed, and customer service is great.   I have them in two sets of pax cars and am adding them to two more.

Well.  It always makes me smile to see guys taking the DIY-plunge buying a soldering iron, flux, etc. and giving it a go.  OGR is a very supportive community so whether you choose the pre-assembled Hennings LED modules or continue the DIY route, we've collectively got-your-back as they say.

Apparently you're running 18V AC on the track.  The 12V LED strips are meant to be operated with DC voltage.  It is true, and you've seen it with your own eyes, that 12V DC LED strips will light up if you apply 18V AC.  But the fact of the matter is AC and DC do NOT play well together and you are electrically "stressing" the LEDs by driving them with AC.  As previously noted, at minimum you really ought to insert a 10-cent diode into the circuit.  That will at least drive the LEDs with DC as was meant to be.  We can get into specifics of what part(s) to buy later if you continue the DIY route.

As for the flickering.  If you stay the DIY route, in addition to the diode, you at minimum need to add a 25-cent capacitor and 5-cent resistor.  The capacitor will demote the flickering.  OTOH, to eliminate (vs. demote) the flickering you need to additionally add some kind of 50-cent regulator IC chip.  Again, we can get into specifics of what exact part(s) to buy if you want to pursue the DIY route.

There have been many OGR threads on the nuts-and-bolts of this affair but each situation is really different.  That is, apparently your specific situation is 7 cars.  The logic, cost, analysis, or whatever you want to call it changes depending on if you're dealing with 1 car, 10 cars or 100 cars.  Then there's the issue of whether you are comfortable with soldering, how much time you have, thickness of your wallet, whether you want to learn more about electronics, etc.

Since you already have the LED strips, you could just use the regulator modules.  They'll give you flicker-free lighting, intensity adjustment, DCS compatibility, etc. 

LED Lighting Regulator Boards at Henning's Trains

Here's another option for the DIY fan.  This is somewhat buried in a thread in the Electrical forum.

This is pretty much the same functionality as my lighting module in the previous post, just a thru-hole DIY design.

DIY Constant Current Passenger Car Lighting Module - Circuit: gunrunnerjohn - Added: Rod Stewart - Level: Beginning - Estimated Cost: Less than $3 per Board

Easy to build module with only 6 components, and easy Through-Hole assembly. Very nice beginner level project. (Rod says: If I can build them, anyone can! ) Cost is less than $3 a board, and could be reduced to about $1.00 with all offshore parts. User notes are included for even more assistance with building this project.

Link to Thread: GRJ's Original DIY Constant Current PAX Car Lighting Module Files - DIY Project Files are in First Post of Thread  -  Gunrunnerjohn has posted this project on OSHPark, you can now order boards directly from this link: This Project on OSHPark - GRJ's post, including this link, is several posts down in the project thread.

Update!

A massive thank you to Gunrunnerjohn

Those regulator modules did the trick! It corrected all of the issues I had with the lights including the intense brightness inside the coaches.

It’s a bit difficult to pick up on camera but the lighting is far more natural now.

A huge thank you for everyone’s help!

I love success stories, glad it all worked out for you.