How To Homebrew An Armor Class

Quote from Mairondil >>

I know. I saw the recent exchange and scrolled up and saw earlier comments weren't completely addressed.

I know it's a hack, but it's a specific hack.

 
Nono, by all means, inform and educate the masses. Your idea is rather clever and effective. I just wanted to make sure you were aware of how old that post was in this one particular instance in case you hadn’t previously.

Hi- sorry to ask- I'm looking for a way for the AC bonus to be automatically subtracted if heavy armor is put on?

Kinda like this- AC = 13 +  Dex + Armor (-3 if heavy armor)

I'm doing this for a species trait 

sorry to resurrect this thread. im trying to follow these instructions for a homebrew subclass that wants to replace dex with int for armored AC, but the steps are a little confusing, and i cant seem to get it to work correctly (or at all). i went to frequently asked questions and couldn't find an answer there either. if there is an answer to this can i get a link/path to that information please. thanks <3