Hello Mates,
Just adding my two cents,
In my some of my boats that have multiple LED lights (Mt Washington, Seguin) I use boards that step down the voltage. The reason being multiple lights can be powered from one source. if they are of the same voltage.
On my HO train layout, I use boards as I have multiple lights. some boards have three voltage outlets. Some of the boards are adjustable so I can control the output, as in my carnival rides.
The railroad passenger cars that I have installed LED lighting in, I have used resistors because of their cost and size.
I do admit that I have limited knowledge on the subject, although I do find it fascinating.
Trev

I wanted to add two more tips for those who intend to build a circuit themselves and use resistors.

MEASURING RESISTANCE

Resistance measurement (all multimeters, even low-cost ones, have this feature) should be performed on a de-energized circuit.
Be careful if the resistor is not isolated but connected to other components, the measurement may be distorted.
For example, if it is connected in parallel with other resistors, you will have the value in Ohms of the equivalent resistance of the resistors in parallel and not of the individual resistor.

DISPOSITION OF POWER INVOLVED

For small circuits with low currents, this information may be useless, but it's good to know.
When purchasing a resistor, only the resistance value in Ohms is considered.
In reality, we must also check its power, or rather, its ability to dissipate heat in Watts without breaking.

A small resistor, like those used in electronics, is typically 250 mW (1/4 Watt).
Well, to know if it's suitable for our use and won't get damaged, just do a little calculation.
In direct current, according to Ohm's third law, electrical power is given by the product of voltage and current.
P = V x I
For example, if a resistor is subjected to a voltage of 12 volts and a current of 40 mA, it must support a power of at least 0.48 W.
480 mW is greater than 250 mW, so one of the resistors mentioned above cannot be used. The resistor was 300 Ohms, of course.
So, in summary, the advice is: always calculate the power involved based on the voltage and current.

Hi EdW, as I was saying to Dave, everyone has their own needs, interests, and hobbies. I agree with you.
I agree with you about the difficulties of learning Arduino (which requires knowledge of computer science, not just electronics) and building a DC/DC yourself.
I agree that building electronic products, now sold cheaply on Aliexpress, is uneconomical.
Furthermore, people often want to save time. I could have made the anchors myself because I knew how to do it, but I chose to buy pre-made ones.
Some time ago, I started sourcing components to build an ESC myself, just for fun, certainly not to achieve better performance than ESCs sold online. I stopped because I couldn't find everything and didn't have time to finish a time-consuming project. I don't rule out picking it up again in the future, along with many other things.
Personally, I don't need to adjust the brightness of the lights on a boat. Once I've found the right brightness (combined with the right current, thus choosing the right resistor), I don't think it's necessary to change them, but that's my personal opinion.
In any case, I could place a variable resistor in series with a fixed resistor for fine adjustments.
As for me, I respect everyone's opinions and choices, so if anyone needs information on basic electronics, to the extent I can, I'm available and happy to share my limited knowledge.

As I have said before, I was an electronic engineer.
Resistors are ok for a single LED but to vary the brightness you have to change the value of the resistor, de-soldering and re soldering and probably replacing the sleeving. Arduino micro controllers are not for beginners unless you wish to go through a lengthy learning curve as you require electronic and coding knowledge. I see that some of you use Vero board, not the best idea in marine applications due to corrosion.
Designing and etching PC boards is another area requiring a lot of experience and best avoided for beginners.
I am able to design simple to complex electronic circuits, design and make their associated circuit boards as well as building them.
Then why, do you ask, do I use LED drivers and digital switches that I buy from Amazon. The answer is simple, they are cheaper than I can build them for and gives me more time to spend building and running model boats. After all my hobby is model boats, not electronics.
My two pence worth 🤔

Brinkman, you took the words right out of my mouth.
I’ve stayed on the sidelines on this topic since my knowledge is pretty limited, but from what I’ve read while researching out of curiosity, I came across someone online saying exactly what you mentioned—and I’m very inclined to do the same with my Juanita.

It’ll be interesting to see what kind of responses you get on this post.

Hi Dave, in electronics, there are many ways to achieve the same result.
I didn't say using resistors is the best solution.
The advantages of a small LED circuit with resistors are these:
You can understand what you're doing, and once you've learned it, you can repeat it over and over again, applying it to various situations.
It's fun to learn and apply the basics of electronics.
In fact, JSS4 is doing it very well with Ronald, congratulations to both of you.
Other systems, like DC-DC Buck Step Down or Arduino, are much more difficult to DIY. Impossible for a novice to learn easily.
There are those who want to learn more, and those who are content to buy what they need and assemble it.
Basically, with discrete components (resistors, capacitors, transistors, etc., etc.), it's simply fun.
This is obviously not a criticism; everyone is free to do as they prefer, and from your point of view, you've certainly made the best choice in achieving the result you wanted.
Furthermore, resistors are very cheap.

Sorry Ron, I'll reply to your PM as soon as possible.

Alesso,
Even someone like me—with zero knowledge about model lighting—can understand your diagram.
Well done!
😎

It is interesting that this conversation is happening right now.
At our local club's meeting last night, one of the members gave a presentation on LED lighting.
He talked about the different LED colors and voltages.
He is a strong proponent of using DC-DC Buck Step Down converters rather than resistors.
There are many types available online at very reasonable prices.
Most are adjustable, and they can be purchased with or without a digital voltage readout.
I myself have used Buck Step Down converters in a couple of boats.
I certainly don't claim to have the detailed knowledge that some of you have.
In fact, parts of this string have my head spinning!
Can somebody please explain why I would want to use resistors as opposed to what seems to me to be a much simpler solution using Buck Step Down converters?
I'm very open to learning the positives and negatives of both.
Dave B

JSS4, your model looks outstanding. The lighting is perfectly scaled — very realistic and beautifully done.
😎