Hi John,
LED voltage is a function of the semiconductor material. Typical voltages
are as follows:
Red: 1.6 - 2.0
Yellow: 1.7 - 2.0
Green: 2.0 - 3.6
Blue/Violet: 3.6 - 5.0
White: 3.6 - 5.0
It takes a higher voltage to produce the shorter wavelengths - at least
until the next solid-state physics breakthrough... The array I built uses
two strings of 3 white LEDs in series, giving a nominal working voltage of
10.8 volts. Since LED brightness is a function of current, and LED longevity
is mostly a function of the current you push through them, the bottom
circuit board (that sits inside the lamp base) has two 30 mA current
regulator circuits on it. Without that, even increasing the voltage from
let's say 12 volts, to 13 volts, would cause an exponential increase in the
current flowing through the LEDs and they'd melt down in a hurry.
The current regulator is built out of two transistors and two resistors -
the component cost is under 25 cents for that portion of the circuit.
Theo
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