[TowerTalk] CFL vs. LED bulbs

[Bill Turner]

ORIGINAL MESSAGE:

On Wed, 31 Oct 2007 17:50:53 -0600, "Craig D. Smith"
<craig at powersmith.net> wrote:

>They require a ballast
>circuit in the form of a switched-mode constant current regulator either at
>each bulb base or at a more centralized location.  

------------ REPLY FOLLOWS ------------

Not necessarily. A string of LEDs can be fed by a capacitor directly
from the 120 volt line. Actually, there would be two strings, one
connected to charge the cap on one half cycle and the other to
discharge it on the other half. The value of the capacitor sets the
amount of current. You may also want a resistor to limit the surge
current when the switch is thrown at the exact moment of a voltage
peak on the line. As I recall, LEDs, like nearly all diodes, are
capable of absorbing single-cycle surges well in excess of their
working rating, so this resistor may not be really necessary,
depending on the individual diodes.

An inductor could also be used but capacitors are generally cheaper
for this kind of application.

73, Bill W6WRT