Well, I can see I am going to have to do a LOT of work on the hardware side of this. From your link:
Like all math we can make the "proportion" bit into an equals if we put in a constant of proportionality, like this:-
V = k * I
The constant of proportionality is called "resistance" and so we write :-
V = R * I
In the first equation I am guessing 3.3V=(?)*40Ma? I have no idea what k stands for but the voltage should be the 3.3V the board runs at and the current is the 40Ma the pin puts out? If I thought I would have had any interest in electronics later in life I would have paid more attention in my high school electronics elective.
As for the second if it is 3.3V=220Ω*40Ma, and I am only guessing, how do you multiply ohms by Milliamps and come out with an answer that makes sense? Isn't that kind of like comparing apples to oranges or combining a tractor with a reading lamp?
This probably doesn't require a reply, what the link has illustrated for me is that I am going to have to take a class or something to figure out the electronics end.
Thanks for the reply.