John Payson wrote:
>
> > Tom Sgouros wrote:
> > > Does anyone know of an easy way to control the voltage on a 120VAC line? I

>
> While I acknowlege that your approach would probably work, its output would

> & more stuff..

Actually, no. There is a considerable amount of thermal inertia in even
small incandescents, and the practical lower illumination limits are at
high enough numbers that the flicker is not any more noticible than in
your monitor or conventionally dimmed lights. The trick is to evenly
distribute the half cycles while maintaining zero DC offset and also do
this smoothly in the presence of changing control values. In fact, we
designed this as a heater controller but ran light bulbs during debug
(old trick); the result was surprising to both of us. It ended up being
used elsewhere in a light controller.

Of course, higher frequency or DC control will do a better job, but at
the cost of complexity and (perhaps) noise. Our design did a really nice
job of controlling higher wattage floodlamps (for us higher wattage: 300
- 500) in a way that would have worked well on stage. In fact, I assumed
a similar scheme was being used commercially in some cases, because I
have seen a similar flicker signature in watching stage lights dimmed to
dark. You don't notice the flicker if you don't look at the lamps, and
you don't see it at all in high end controls.

-- Tom