Re: Making an X-10 lamp module immune to dimming

[ddl@danlan.*com (Dan Lanciani)]

In article <isw-3AB4BB.10494406062008@xxxxxxxxxxxxxxxxxxxxxx>, isw@xxxxxxxxxxx (isw) writes:
| In article <hpqdncmhFKn1b9XVnZ2dnUVZ_gWdnZ2d@xxxxxxx>,
|  "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

| > As I understand it now, the pulse to the triac has to occur twice every
| > cycle and has to be alternatingly negative and positive to allow each half
| > of the AC cycle to pass.
|
| The pulses do not have to alternate in polarity; that's one of the neat
| things about triacs.

Though it is possible that you might want them to alternate to stay in
the optimal triggering quadrants.

| > It sounds like the mod that uses the alternistor and the optoisolator does
| > just that.  It seems that the optoisolator extracts the ZC data and then the
| > additional circuitry creates its own full width pulse independent of
| > whatever length pulse comes out of the IC.
|
| It sounds like you're attributing too much functionality to the
| optoisolator; it doesn't *extract* anything. It's just a transistor that
| turns on when light shines on it. And the light is the LED that's inside
| it. The output of the opto just repeats whatever is on its input while
| isolating the possibly dangerous voltage levels on the input side.

The MOC3042 used in the modification is more than a simple optoisolator;
it includes its own zero-crossing detector.  The internal triac is fired
near the next zero crossing if the LED is on, i.e., if there is input drive.
This is convenient since the main triac will also fire near the zero crossing
independent of when the integrated drive signal reaches the activation
threshold.

				Dan Lanciani
				ddl@danlan.*com