On 25 January 2011 08:15, Josh Koffman wrote: > On Sat, Jan 22, 2011 at 5:24 PM, IVP wrote: >> Josh, this may or not be (very) relevant >> >> I'm currently reading up on LED lamps, and this is one of the Cree >> articles I looked at yesterday, dealing with failure mechanisms >> >> http://www.cree.com/products/pdf/XLamp-Pulsed-Current.pdf >> >> from this page >> >> http://www.cree.com/products/xlamp7090_xre.asp > > Interesting reading. Thanks Joe! > > Josh > -- > A common mistake that people make when trying to design something > completely foolproof is to underestimate the ingenuity of complete > fools. > =A0 =A0 =A0 =A0 -Douglas Adams > Josh, You should be able to work out the value of the series resistor by measuring the current at two (or more) different voltages. Assume constant voltage drop on the LEDs. Then R =3D (Vin-Vled) / I Vled will change slightly with current but this should get you reasonably close. Graphing over a voltage range would let you get closer by extroplation. RP --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .