Jinx wrote:

> >Thanks Jinx, but reading your page, came to me the idea I
> > said about the 24V relay connected directly to the 110V mains,

> With the opto-triac for on-off control not much to go wrong there.
> My other thought would have been to have a cap supply for just
> the relay so there are no glitches on the 5V supply. I can usually
> find large (1-2uF) ones that I need in old SMPS or TVs
>
> I'd like to know this though. Which has the lower MTBF - X2 cap
> dropper or high watt resistor dropper ? I suspect the hi-W R for
> heat reasons but that's just intuitive and probably has more to do
> with PCB layout


Really, you could design either type for NO
failure. Depends on the size and cost requirements.
:o)

I'd go for a good capacitor, with 10% of the
drop done by a good qual series resistor running
no more than 15'C temperature rise. Reasonably
efficient, but gentle on the cap. Also use a snubber
across the mains with a good mains cap and a smaller
resistor. I've got units like this running for
15 years and never failed.
-Roman

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