On Wed, Jul 21, 2010 at 5:46 PM, RussellMc wrote: > HID is nominally 3000-20000 hours either of which is fine for a tester > of this sort But their lifetime is heavily dependent on the number of starts - sounds like you'll be doing a lot of those relative to the actual running time. > FWIW, at 100 l/W you get about 25% of energy out s light, so a 32 Watt > LED array makes ~~ 8 Watts of light =A0:-). Rather more than that, depending on the spectrum of the output - isn't white light ~280lm/W? Of course the output spectrum of a white LED is far from smooth, at which point you surely have to also consider the freuquency reponse of your PV cell if that's what you're testing. HID should have a rather better CRI in general. Chris -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist