At 03:31 PM 12/26/2003 -0800, you wrote:


>You're not wanting to turn the triac on when the voltage is 240V, you
>want
>to turn it on when the voltage is near zero.  The fairchild data sheets
>have MUCH smaller resistors in their "sample schematics" (360 ohm for
>240V)
>I didn't look carefully enough to see to what extent you MUST limit the
>isolator output current, and I don't have any relevant experience.  But
>I'll bet 5.6k is way too big...  (This implies that triac circuits
>normally
>waste quite a bit of gate current.  Interesting.)

No current is wasted. All gate current goes through the load, and
it only flows for a few tens of microseconds at the beginning of each
AC 1/2-cycle until the triac turns on. After that point, the load current
flows through MT1 (instead of the gate in series with the resistor and
the opto-triac).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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