Its Christmas time in the McCurine house

Yeah, I tend to agree on the first points. All of my salvaged mini-bulbs so far are white incandescent bulbs (my LED strings are all still going strong), and in a lot of cases, I've opted for the low current draw and minimal heat of aftermarket LEDs, often pre-configured to accept the available supply voltage. Even free as salvage, such incandescent bulbs have enough inherent drawbacks to often make LEDs a better option. For instance, I'm currently rehabilitating a recently acquired used Menards burnt engine shed, and just replaced the weak (and in this case, non-functional) built-in LEDs with six flickering orange LEDs (each with resistor and flicker circuit pre-wired) that I bought at a fair price from Evan Design.

Sure, LEDs are a bit more finicky to use, but keeping a few points in mind will help:

--First, "LED" stands for "light emitting diode". The "light emitting" part is obvious enough, but the "diode" part is important -- it means current will flow in only one direction, so polarity (which side is positive, which negative) is important, in that it will work (emit light) when current flows in only one direction and will not work at all if the leads are reversed.

-- Like all diodes, LEDs are one way valves that will prevent any current flow if the polarity is wrong, but when the 'valve' is opened (wired in correct polarity), it can let too much current through if there's too much pressure (voltage). Each LED has its own specs, but most can only directly handle 2-3 volts -- apply more voltage, and the LED will have a very brief life before completely melting down/burning out! If the supply voltage is going to be more than 2-3 volts, a small resistor needs to be added in series with the LED to limit the current drawn. For instance, an arduino output voltage is something like five volts, so you need to add a resistor rated at something in the range of 330 to 470 ohms to prevent burn-out of any LED being powered by an arduino output circuit. Again, each LED has its own specs, but a little careful experimentation (or consulting someone who really knows this stuff!) will put you in the ballpark.

-- Finally, LEDs can be used either with DC of the correct polarity, *or* with AC. On AC, the LED (a diode, remember?) will block current flow in one direction, and allow it to pass (and light up!) in the other. There are some (to me!) complex concerns about peak and average voltage and power, and some report shorter lives on AC than on DC, but in general LEDs will work on either DC *or* AC, with some caveats.

Alright, on a roll. The tree's 95% decorated and the felt "snow" skirt is down:



Time to head to the attic and see what ceramic stuff I can lay my hands on.

Yeah, that'll do it! 

One other option is to buy a few cheap buck converters (less than two bucks from overseas sources), which accept AC or DC input up to typical track or accessory voltages, and converts it to DC at any level up to the input voltage. So, you could feed accessory AC voltage in, and set it to provide a regulated 3 VDC output, perfect for most 'naked' LEDs . . . without the fireworks!

Here's a pic of a buck converter (the one at the top left) feeding a delay relay module (the one at the bottom right) in a benchtop lashup of a trolley stop project:

 

Sure, here's a link to the kind I most recently bought:

www.aliexpress.us/item/2255800358604164.html?spm=a2g0o.order_list.order_list_main.66.182f1802Ros7hl&gatewayAdapt=glo2usa

There may be other, better suppliers or other options on AliExpress, but someone suggested this one and so far, they've worked well for me. There's a small screw on the top of the small blue box to adjust the output voltage. They're priced at less than a dollar each, and though shipping adds to that total, they were still under two bucks apiece, total.