Just a quick update...  I have my yard light timer running right now with
a very light load (no pun intended).  If you will recall from this
thread's earlier life, Dave Dilatush. came up with an idea (subsequently
debated at length) I had not seen before to switch low voltage AC with a
pair of N MOSFETs.  I have built the circuit and use the PIC to soft-start
the lights with about a 2 second or so gentle PWM ramp-up to full on.
The visual effect is exactly what I wanted.  I ended up using a pair of
IRLZ34's because of price and availability.

Never realized how tough it is to find something around the workshop that
will put a good load on a 12VAC power supply!  I did run the output to the
secondary of another yard light transformer - 2A load there, then I
conected a 40W bulb across the primary, which gave me 3.4A.  MOSFETs were
cool to the touch.  Tried a 150W bulb for half a minute or so - dim light,
9A+ load, the MOSFETs started to warm up but nothing spectacular.  Way
more than I expect to put on the main transformer, though, and nothing was
conected well so I didn't leave that on long.  Now I just have a pilot
light connected to test the on/off schedule timing and stuff.  This may
make it to the PICLIST contest...  simple stuff, but lots nicer than the
mechanical on/off timer commonly found on yard lights.

-PWM soft turn-on/off
-Daylight sensor (CdS cell)
-One-button setting of mode & delay time
-10-minute anti-false delay to ignore headlights etc.
-Multi-mode: On at dusk/Off at dawn
             On always
             Off always
             On at dusk, off after 1-23 hour delay
-LED readout with auto-off
-Daylight indicator for adjusting sensor

Sorry for the public celebration, but it's been a while since I had time
and bench space to work on my own projects!  8-)

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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