> > From the FAQ: > > "What is the Flex run time? > > "Figure on 60 minutes at full continuous 500 lumens with degradation > > after. We do not have real world testing yet because the goal of this > > Kickstarter project is to build the real product." > > > > Eh? R&D comes after product build? =A0What did he really say? They probably have engineering based targets but know that the real world fights back as you head towards finality. The 500 lumen requires about 5 Watt LED input power. Or 5 Watt hours delivered capacity to give 1 hour operation. =3D more battery capacity than that. Am 18650 LiIon typically gives about 6 to 8 Watt hours. (If you buy cheap no name brands with higher capacity claims eg 2600 mAh you may expect more. YMWV.) If they can buck convert that to the LED at say 80% overall true efficiency overall that gives 4.8 - 6.4 Wh estimated from the above notional battery capacity range. That seems very doable. The main issue in using a buck converter with LiIon is that LED Vf at the high end of the power range tends to approach the Vout of a 1C+ loaded 2 Ah LiIon "rather closely". There may be some light drop off at the end or they may even need to go to buck boost to get the later portions of battery capacity, which would lower the mean efficiency. Overall the 1 hour target at 500 lumen seems reasonably conservative - which is encouraging. 500 lumen is a lot of light. In many applications such as camping, tyre changing, reading, illuminating a single multi person dinner table, over a kitchen bench and similar, less to far less than that would be fine. Rather than N modes I'd tend towards having a ramp-up ramp-down arrangement. This is just one of several options which can be programmed so you can switch between them. Push on - push off - push on ... -> operates at prior level. (Single push andrelease when on will turn off after a short delay - see push twice below) Push on and hold - ramps up. Release as desired. Push again -> ramps down. Push again-> ramps up. At top and bottom you can toggle or hold. I'd prefer hold as you then chase to and from to find max/min. Push twice fast when on-> change mode or go to menu or ... Push thrice fast when on ... Push twice / thrice fast when off ... > The way I read it, they have the 350 lumen version ready (not > rechargeable, not programmable, no USB), Yes. ie trivially easy. > and they have a concept (with > some design, possibly a proof-of-concept prototype, but not yet the > production design) for the 500 lumen version. Yes. ie conceptually trivially easy :-). I can think of some more features, but ... :-) Russell McMahon Applied Technology ltd. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .