>>If it's a triac device it will only work on AC, as the triac will stay
>>conducting until the current crosses zero.
>
>While this is correct there might be situations where you could use the
>behavior to advantage on DC. Shorting the output with a momentary
>switch (or interrupting the current) will turn it off ( assuming dv/dt isn't
>too high). So, for a security alarm powered from a 12VDC battery, it might
>be just what you want.
>Spehro Pefhany

The triac is two SCR's back-to-back.  An SCR is what you'd
use if you had DC, since you'd be wasting the other "half"
of the triac.  Of course it's now been revealed that
they don't switch themselves off unless you cut the power
briefly (Mr Gates take note :)

So I was really intrigued to find out these are the things
that drive your camera's strobe flash.  The smart ones
adjust for the distance (they actually read the light
coming back) and will vary the duration accordingly.  But
how do you switch that SCR off?  Turns out, you switch
a capacitor across the device which diverts the current
around it for just a few micro(?)seconds and that's
enough to turn it off.  Pretty impressive, I thought.

Barry

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