I think a triac is about the most efficient way of handling the problem
(unless you want to go to an electromechanical relay).  The voltage drop
across the triac would be about 1.5 volts, so multiply that by the
current to get dissipation in watts.  Multiply the dissipation by your
heat sink's thermal resistance to ambient (degrees C/watt) to get
temperature rise above ambient.
        For typical drive circuits for the triac, see the datasheet on the
MOC3020 or similar opto couplers.  Also, for simplicity, you can just buy
an opto coupled solid state relay.  The manufacturer of the SSR has
solved all the drive and snubber problems for you.  You can drive the SSR
directly from a PIC.

Harold



On Fri, 14 May 1999 08:16:16 -0400 Jason Wolfson <jason@LIPIDEX.COM>
writes:
>Today I'm trying to control a 1800W electric heater with a PIC.
>About 16A @ 110VAC, I was thinking of using a 25A Triac and
>optocoupler/driver.
>My question is how hot will the Triac get? is there a better way?
>cheaper?
>thanks
>
>Jason
>P.S.
>I've archived all the PID discussions for the next step of this
>project.....
>

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