Jim Weir wrote:
(Jay)
shared these priceless pearls of wisdom:

-I think someone may have already pointed this out, and maybe I didn't
-make it as clear as I should have... I stacked the forward drop of
-MULTIPLE LEDs up until I got somewhere near the bottom end of the
-supply voltage. So for the example I gave, I got to 4 LEDS in series.
- Why waste all that power as long IR (heat) off a big resistor when we
-want red and green light right?

And as somebody else has pointed out, running a series string close to the
bottom limit of Vcc and hoping that a single resistor will provide constant
current to these devices will cook them when Vcc rises to the charging voltage.

No designer in his right mind would use a circuit in this manner.

Jim



The criteria I had when laying out my circuit was that the lights would
operate down to 10V and still not exceed the max current limit at 15V.
I'm working from memory here, but I believe the SuperBright LEDs I used
had a forward voltage of 3.5V.

Putting 2 in series with a 220ohm, 1/4W resistor maximized the
efficiency while maintaining the range I wanted.

--
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"Ignorance is mankinds normal state,
alleviated by information and experience."
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