Just wanted to report that I've adapted one of Colin's (colin55 here) Joule Thief circuits to drive multiple LEDs, and it continues to amaze me how well it works.
I'm using his "LED torch circuit C" from this page on his "Talking Electronics" site. I've built quite a few of these, driving either one or two "high-brightness" LEDs (28,000 mcd, 20mA bright white lights). But just for laughs, I hooked it up to a 3-volt supply and started loading on LEDs in series to see what it would do. It ended up driving 6 in series, no problem, nice and bright! (That's almost 20 volts from this primitive blocking oscillator boost converter.)
The only change I made from his design was to change the resistor to 1K.
My hat is off to Colin once again.
I'm using his "LED torch circuit C" from this page on his "Talking Electronics" site. I've built quite a few of these, driving either one or two "high-brightness" LEDs (28,000 mcd, 20mA bright white lights). But just for laughs, I hooked it up to a 3-volt supply and started loading on LEDs in series to see what it would do. It ended up driving 6 in series, no problem, nice and bright! (That's almost 20 volts from this primitive blocking oscillator boost converter.)
The only change I made from his design was to change the resistor to 1K.
My hat is off to Colin once again.