Re: Lambda\'s Fabulous Pill
Yep, the Pill cuts off at 1.4 to 1.6 volts (1.5V +-0.1V). I made it for use with NiMh in mind, that was one of the design objectives.
1 - Bright; with 2 hour+ runtime
2 - Cheap to operate; no special batteries required
3 - NiMh compatible
4 - Reliable; low parts count and solid assembly
On the question of how much current, that depends. First, remember the Illuminator circuit does not operate in steady state DC. It uses a pulse shaping circuit to drive the Luxeon; varying the pulse width to regulate. So, ma through the Luxeon is a relative comparison. My multimeter shows initially 500 to 450ma depending on batteries and Luxeon; most of the battery life is probably expended around 400ma. But that's on a multimeter set for measuring DC current, but is really measuring an unfiltered ~220kHz pulsed DC.
Because the Illuminator circuit has no adjustments, the Luxeon forward voltage drop will determine the current through the Luxeon. The Illuminator circuit will try to maitain 1.5 watts of overall power; supplying more current thru a lower voltage drop Luxeon, and less current thru a higher voltage drop Luxeon. This then has the effect of regulating overall heat production.
For example:
Luxeon with 3.1V forward voltage drop at 500ma
3.1*0.5=1.55 watts
Luxeon with 3.8V forward voltage drop at 400ma
3.8*0.4=1.52 watts
For the second example, the Illuminator circuit would be providing closer to 400ma to regulate the Luxeon power closer to 1.5W.
I hope I've not cunfused further.......
