Today, Dec. 29, I decided to build the ballast! The best idea I found yet is to build a simple choke with ~0.5mm wire. With a little search, I kinda figure out how to have the good voltage and current, I just don't know how to calculate it.

I know that more turns will give more inductance, and more inductance less current, but I can't find how many turns my choke should have if I want 6A - 7a Is there a way to calculate it? BTW I don't really mind for the voltage.