If you need white, then 3 semi complementary colours would be best. You can buy RGB LEDs or mix and match them yourself. Modern blue (and thus white ) LEDs have a very low peak to average permissible current ratio. Maybe only 1.2:1 or so. You can drive them well above this but the lifetime will drop drastcally. As you note, phosphor frequency response is not in most data sheets. .I'd guesstimate it to be far too slow for your purpose BUT there are web references suggesting 1 MHz + can be achieved. . On 29 April 2010 03:27, Michael Rigby-Jones wrote: > How well do white LEDs work in applications where you want a very short > pulse of? Intuition is suggesting that anything using phosphors is > going to significantly limit the minimum pulse width. The datasheets I > have found so far from CREE etc. don't have any data on this. > > > > I'd like to generate pulses of ~5us at a frequency of up to 300Hz for > use in a high speed strobe. Obviously I need quite a bit of light > output to compensate for such short pulse widths, but with such low duty > cycle I think I should be able to drive the LEDs quite hard. Extended > LED life is not required, e.g. life expectancy in the hundreds of hours > range would be OK. > > > > Is this going to be remotely possible with high power white LEDs, or > will I have to resort to RGB types? > > > > Regards > > > > Mike > > > ======================================================================= > This e-mail is intended for the person it is addressed to only. The > information contained in it may be confidential and/or protected by > law. If you are not the intended recipient of this message, you must > not make any use of this information, or copy or show it to any > person. Please contact us immediately to tell us that you have > received this e-mail, and return the original to us. Any use, > forwarding, printing or copying of this message is strictly prohibited. > No part of this message can be considered a request for goods or > services. > ======================================================================= > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist