Excellent tutorial!
But one thing, some of these little boards might not be suitable at all.
For me to explain this I need you to fully understand how the electronics work, so here we go:
How it works (most of you probably knows this):
Mechanically there are two kinds of switches, latching and momentary. Latching switches mechanically "closes" the circuit and thus feeding power to the electronics continually. The work a bit like a door, the are either opened or closed ("off" or "on")
Momentary switches does as the name suggests only momentarily close the electric circuit. Imagine a simple flashlight with a momentary switch, for it to work you would have to press down the button all the time. As soon as you released the button, you would break the circuit and the light would go out.
Mechanically momentary switches are a lot easier to make and can be made smaller.
You can however make a momentary switch act like a latching one with a simple electronic processor of some kind. Those are a bit tricky to make yourself, but are easy-peasy for factories. The processor is the little black dot. You can see them on the FX boards as well.
However, since you want that little black dot and its board to be really small, you would find them in little keychains lights and the likes. And in bike lamps. There is one problem with this. A lot of them probably has another little function that you don't see.
The blink the LED (the electricity) in short pulses, like 100 times a second or so. This will make the runtime longer. If the LED is off for half a second every sec, splitted into 100 fragments it would double the lifetime of the battery. The LED is off half the time right?
The funny thing with this is that our eyes and brain ain't fast enough to see it, it looks just as bright.
If the processor (small black dot-thingy) does that, its NOT sutaible for lightsabers.
There is however an easy way to test this: put a string ('bout 0,5m) on the keychain light you plan on using and spin it!
If the circle you can see is dotted, you know the processor is pulsing the electricity. And if the processor is pulsing the electricity
the board is NOT suitable.
MTFBWY and sorry for the long post.