On Wed, 19 Apr 2006 08:03:06 -0400, "ALBERT C. GOOD JR."
wrote:

....

2. Both neon and LEDs require a ballast resister which with out they will
meet their demise before the intended time. Also since a LED is as its name
would imply, a diode and therefore conducts only on one half of a cycle
unless you wish to use a bridge rectifier with it.

---
Not necessary, just connect a diode across it in anti-parallel.
However, using a 20mA LED at 20mA would require the current limiting
resistor to dissipate about 2-1/2 watts, not a good idea. Using a
high-efficience 2mA LED would require the resitor to dissipate about
a quarter of a watt, so a 62,000 ohm half-watt resistor would do it.

--
John Fields
Professional Circuit Designer