>>6927926I'm just an amateur at this but I will try to pass off what I know:
LED circuit is one of the most basic electronic circuits you can build, just remember Ohm's law ( I =V/R) and calculate necessary resistors needed for your circuit. Most LEDs will require 2 - 3.3 v depending on the color.
When building them into gunpla note that most small form factor batteries (like the CR2032 I'm using) will only provide 3v and watch batteries provide as little as 1.5v. This may require you to use multiple watch batteries (wired in sequence) to even power a single LED.
LEDs will require wiring from a positive power source to the positive end (usually the longer prong) and negative to the shorter prong, with resistance to the positive end of your LED. Do note these small cell batteries have pretty good internal resistance so you don't really need a resistor but it's probably still a good idea not to burn out your LEDs with too much power. Also consider wiring in a switch before that so you have a mechanism to turn them on and off. I like to go a step further and try to integrate them into the theme of the gunpla, like the GN Cone of the GN-X housing the battery.
Past all of that you need to consider how to hide the circuit (LED / wires / components ) within the gunpla itself, without sacrificing integrity of the gunpla itself, and to not restrict any movement. The greatest problem with my build was fitting a LED into a 1/144's head without drilling away too much at what holds the pieces of the head together.
