Automatic Filament Change. NOT MULTI-MATERIAL.

I've searched and searched, but I've only found Two things that somewhat do what I'm looking for. The Infinityflow S1, which is bigger, more expensive than I'd like, and only works with two spools at a time, and the AMS Mech, which, I believe is unpowered and uses spring power and I'm unsure of how long a ptfe tube that one can load. My question is, Does anyone know of a diy version of the infinityflow S1, or what parts and logic I'd have to use to make my own version? I'm not interested in multimaterial for this machine, just not running out of filament for it on big prints. It's a Centauri Carbon, so it's not firmware hackable at the time of this writing...