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Powering x-opto white leds
Hi,
I'm making some LED lights for illumination as part of some costumes, in fact I have to put these things together tomorrow! In my prototype I used some ultra-bright reds I had lying around, and my series resistance calculations were fine. The device is simply a D-type flip-flop, reed switch and npn transistor, enabling the light to be switched on and off by waving it near a magnet. For the real things I ordered these: http://www.rapidelectronics.co.uk/rk...1376&XPAGENO=2 Made by X-opto. Who they?? I cannot find any online presence. Lens Material V F max V R max Chromaticity Int.mcd@20mA View angle water clear GaN 4.2V 5V X=0.31, Y=0.32 3000 15° As the intensity is quoted for 20mA, I factored in the forward drop of 0.7V per LED and calculated the resistance. Nothing. I Checked all my cables, measured voltages. Eventually I tried upping the current, and finally with 5V connected directly across them they are putting out what looks like 3000mcd to me! Am I right in thinking that I can do this because VFmax is 4.2V, and 4.2 + 0.7 = about 5? Am I wrong to assume a forward drop of 0.7V? Does anyone know anything about these LEDs? Thanks for any help, Alex |
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