[Elecraft] Re dimmable LED, Elecraft Digest, Vol 153, Issue 14

[Red]

If an AC voltage within the limits of the LED is applied, is another 
rectifier is needed, since the LED will rectify.  It's reverse voltage 
is limited so the AC probably must be a few volts.  See if any vendors 
of LEDs provide the reverse voltage limit.  Select a capacitor with 
impedance to limit the current to a desired value.  A  pot can be added 
for control.  I haven't tested this, but believe it will work fine.

I've used red LEDs, about 2 volts drop each, in strings of 5 from a 12 
VDC battery with a 5 or 10 K Ohm pot for control in my observatory for a 
few years with no problem and very good range of light intensity.

73, WO0W