On Fri, 29 Apr 2005 02:43:31 -0700, Roy Lewallen
wrote:

I haven't kept up well with LED technology,
but I haven't heard of any LEDs that have a built-in regulator,
switching or otherwise.

Hi Roy,

Constant current LEDs have been around since the late 70s. They were
marginally common then, but I rarely see them now.

As for the spectrum of LEDs, the all require different battery
voltages to bring them to full output. Light power is always
expressed as a function of current, not voltage however. The voltage
is somewhat likened to the forward conduction knee.

IR LEDs have the lowest knee voltage, roughly at the same potential as
common diodes: 0.6V. Blue LEDs have the highest knee voltage, roughly
3V to 3.5V. The colors Red, Orange, Yellow, Green, Aquamarine, Blue,
UV exhibit the order of ascending voltage (and in the conventional
order of wavelength for a rainbow). The White LED is simply a Blue or
UV LED coated with phosphor (a solid state fluorescent light).

73's
Richard Clark, KB7QHC