By the way -ledguy (Wayne) is very good to deal with and has all kinds of goodies at his shoppe.
Cevulirn, have you seen that site of that guy in Israel that sells all those rings -I used to have the link saved but would have to look up the site now.
If you would be a little more specific about the info you want that would help.
Basically once you give an LED a current source that is above the vf or forward voltage of the led,it will draw as much current as it can.You have to match this closely or use a converter.You can also use a resistor to drop the voltage down to the vf of the led.This will waste energy as heat.