Sorry for the long post, two replies to respond to:
Chagrin:
I'm not building the coils, using commercially available coil/tank combination to keep production costs down. So inserting a thermistor into the setup really isn't an option. As far as the coil cooling, probably won't be an issue. They're not designed to stay on, they heat up enough for a single drag when the user presses a button and then cool between drags. They only heat while the button is pressed. The cycle(from my own use) tops out at about 10 seconds on, 50 seconds off. Also, the way I'm planning the system, each user will have their own coil and tank. That way each can have their preferred flavor and nicotine content. This lowers the chance of overheating the coils as well.
Henry:
Thank you for the Ohm's law calculation. I'm sure there's somewhere on the "interwebs" I could have gotten that, but I'm terrible at math and a touch lazy. I'm assuming that's the "cold" resistance, as well.
I've considered wall power, but two things make me think batteries first:
1: I have no idea how I'd do that. If you happen to know and would like to throw that info my way when the time comes, I wouldn't scoff...
2: There is a good chance this will become a "display item" for taking to bars(pubs for my new English friend) and showing off. I can't see them being too keen on me running experimental electronics from their wall source. Ideally, being able to switch between battery and wall power would be totally brilliant.
As far as the "vapor condensing" issue, I'm running experiments now on how long the tube can be before that becomes an issue. Luckily, I have many friends who indulged in "less than legal" recreation in their youths(unlike me, who never even drinks), so there is some backroom expertise on that sort of thing close at hand. I'm hearing that if the tube is narrow enough, I should be able to get a comfortable length without condensation.
I will be experimenting with all of this as time goes on, and hope to pick up my Arduino Mega end of this week, beginning of next. That leads me to another question: If I get all of this to work well, I'm hoping to make it a permanent system, how hard would it be to replace the Mega in the circuit with a Mini or Nano? Would it be a total rewrite of the program, a simple upload, or somewhere in between?
P.S. for Henry,
I successfully fought the urge to use every last bit of rhyming slang I know in this post.