First off, bison is mighty tasty. I used to live in Wyoming and Colorado and that was the last time I had it but it was good.
Now that thats out of the way, I won't post up exact schematics until I get everything on the breadboard, but I will go ahead and give you guys the general idea of what I have going on. The rest of this post will be kinda tech-ish so go ahead and skip it if you start to get sleepy.
I am putting all of this in the 2AA/AAA NiMh charger madvapes sells. I got one on my last order and it is super ergonomic and screams to be a PV. It is a little smaller than a pack of 100's and holds two 14500s perfectly.
I am basing the VV electronics around the Ti 4050 buck/boost converter. Breaktru has listed a few mods using this chip, if you search you will find several threads he made that explain how it works, schematics and data for it, ect. In his design where he uses different resistors of different values to change the output voltage range, I will be using a pot so I can adjust this whenever I want. The pot will be inside the battery door so it can't get "accidently" messed with.
For the actual control of the VV, I will be using the ds1869-100 digital potentiometer chip, but I will have it set up with an "up" button and a "down" button instead of the slightly confusing setup Breaktru used in his copper mod design. There will also be a dual color LED attached in a way that it will light green when you press one button and red when you press the other, the LED will get brighter or dimmer based on how high you crank the voltage. This way you always have a visual indicator of what is going on when you adjust.
There will be a "master on/off button" on the top, and my favorite blue 3A pushbutton will serve as the "hit" button. It will also have a usb charging port built in to the bottom, I have a special way of hooking this up so no current can go either way through it unless a usb cord is plugged in. "Just in case" the charging circuit doesn't play well with the VV or something. I am swiping the charging circuit from a 400mah kr808d charger that I pretty much can't use for anything else.
I should have the rest of the electronics in this week, then it's just a matter of breadboard testing, hole drillin' and some JB weld to get the good times rollin'. I will post up schematics and some pics at that point.