Hi,

I'm working on a light controller for my yard lights.  My old power supply
is a nice 12VAC transformer with a timer and photocell that lets you
select several modes, including on all night, on for 1-12 hours after
dusk, always off, or always on.  The new lights came with a new xformer
but no fancy stuff, just an on/off mechanical timer.  Unfortunately it has
no indication of its current rating and it's running pretty hot - I'd like
to use the new transformer but don't want to lose all the cool features.
So of course I'm building a nice PIC-controlled add-on!  8-)  I plan to
add the same thing to the deck lights in back of the house once I get it
working.

My question relates to how to switch the 12VAC to the lights on and off.
I'm thinking a sensitive-gate (logic) TRIAC on each leg of the AC line to
the lights, with both gates controlled by the PIC.  From the looks of what
I have seen in various Web resources about TRIACs, it looks like I could
use one instead of two, but it just seems to me that for safety's sake
using two would be like using a DPST switch and completely remove any
potential from the lights when turned off.  Or should I even worry about
that?

Ebmarrassingly, I have never used a TRIAC before, but it looks from the
data sheet like I can turn the AC on and off with nothing more than a
logic HI to the gate(s).  Am I reading that right?  Is there a better way
to do this?  I guess I could use a SSR, but a couple of TRIACs will be a
lot cheaper and a LOT smaller.

Comments?  Suggestions?  Am I making this harder than it needs to be?

Dale
--
"Curiosity is the very basis of education and if you tell me that
curiosity killed the cat, I say only the cat died nobly."
          - Arnold Edinborough

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