Spehro Pefhany wrote...

>Very nice, Dave! A couple of IRLZ544's maybe. They would have
>a total drop of about 1.1V at 20A, so about as good as a triac.
>At 10A, they'd beat it by a mile.

I've got some old NSC NDP706's in my junk drawer.  TO-220, rated at 75A,
Rds(on) something like 0.05 ohms.  They'd be great...

>You should be able to get half-wave power using a diode from the
>top transformer wire to a PIC-GND referenced supply.

Dang, why didn't I think of that...

OK, here's Rev. 2.0, with a half-wave rectifier & filter for supplying
power to a 7805 regulator:

            0-----------+--------------0
                        |=20
         FROM 12V       |          TO LAMP
         XFORMER        |           STRING
                        |
            0------+    |      +-------0
                   |    |      |
                   |    |      |    D1
                   |    +----------->|-----+-----0 +17V to
                   |           |  1N4003   |       7805 Reg.
                   D           D           |=20
               Q1    G---+---G    Q2       |+
              Nch  S     |     S  Nch      C1 470 uF
                   |     |     |           |-  35 WV
  GATE DRV  0------------+     |           |
                   |           |           |
                   |           |           |
  PIC GND   0------+-----------+-----------+


Cheers,

Dave

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