On Saturday 06 August 2005 04:46 pm, Olin Lathrop scribbled:
> The inductor would be rather small physically and also inexpensive.  Since
> more LEDs would be in series, the current would be low and easily
> manageable with a cheap transistor.  I wasn't talking about "high" voltages
> that would be dangerous.  The voltage just needs to be enough above the 15V
> or so top end normal operating voltage that the LED string doesn't come on
> without a boost pulse.  20V sounds like a nice target, and there's no
> safety issue with that.  The cap can be similarly small and cheap, maybe
> something around 220uF 50V (I haven't worked it out).

I had thought of the higher voltages to reduce the number of resistors.  But 
there is perhaps the advantage of using more strings, that if one LED blows, 
less go out overall.  (Not sure if LEDs go open or shorted when dead).

Relatively, the cap (and inductor) would still be taller than the 
multiple-LM317 options.  Both solutions would work, but the latter is simpler 
and lower cost.

Cheers,
-Neil



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