Re: Dimmers

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: dhmccauley-at-spacecatlighting-dot-com 

 > Hi Jim-
 > The rate doesn't change, the phase angle changes. If the dimmer is at 50%,
 > the output will be off for the first 90 degrees of the of the AC waveform,
 > on for the second quadrant, off for the 3rd, etc. As you vary one from
full
 > on to full off, the firing angle becomes later in the cycle.
 > db

Thats not entirely correct either.  The phase of the output of a dimmer
switch is identical to the phase of the input.  A dimmer switch merely
truncates a portion of the
original AC sinewave beginning at the first zero crossing.  And since the
TRIAC is a latching device, once the TRIAC is turned on and conducting, it
will remain on until
the next zero crossing at where this process will repeat.

Dan