Daisy,
Typical voltage range on a "12" volt LED is 9 to 15 volts. Not fragile, life
of an LED is hard to determine but most failure is due to over voltage
sudden death, and there exist very poor quality LED's that may not last.
Actual voltage of every LED is typically 1.5 to 3 volts, so resistors must
be chosen according to the input voltage. LED's are not able to be daisy
chained or multiple used on a single resistor. Each LED must have it's own
resistor. The only other way I know of to fire multiple LED's is by
transformer, which is simply stepping down the input with converted voltage.
LED's can and do work on ac voltage, stack bridged over resistors. The
bridging can be other LED's or just diodes. There is so much more such as
cathode polarity requirements. Some ac bulbs are cathode sensitive required,
but some are not. I just bought item BPC7/LED at Depot, a pair for $4.94
Feit Electric, 120v, candelabra base, cool white, 7 watt night light
equivalent. Not cathode sensitive. Each has three LED's.
-Eddie-
Houston, TX