Re: Controlling Holiday Lights

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

In article <slrneki5ra.a7n.ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxx>, ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxxxxxxxx (sylvan butler) writes:
| On 31 Oct 2006 23:14:34 GMT, Dan Lanciani <ddl@danlan.*com> wrote:
| > In article <slrnekfbic.bco.ZsdbUse1+noZs_0610@xxxxxxxxxxxxxxx>, ZsdbUse1+noZs_0610@xxxxxxxxxxxxxxxxxxxxx (sylvan butler) writes:
| >| synth a 50% on-time, and know that with a 4% error limit I would be
| >| close enough.  But again, that is power, not light.
| >
| > Power at 50% is fine, but can you describe the actual waveform that you
| > would synthesize to trigger the triac?
|
| For triac control I've been playing with small tables (a dozen or so
| entries) which I output to the port sequentially, repeating from the
| beginning every time the end is reached.  If alternating 1's and 0's in
| equal numbers, then it results in a fairly good square wave to the triac
| (a scope makes it pretty easy to see when task switches take away
| control when running under linux, or an interrupt (eg keyboard) under
| DOS).  Repeating a few 0's or a few 1's in unequal amounts just extends
| the off time or on time, respectively, destroying the symmetry of the
| square wave.

I understand how you synthesize the waveworm but I'm still not clear on
the specific triac trigger waveform you use for 50% power.  Could you
describe it in terms of frequency and duty cycle or such?

				Dan Lanciani
				ddl@danlan.*com