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RE: Zero Crossing Strobe & possible kits?

Original poster: "Colin Dancer by way of Terry Fritz <twftesla-at-qwest-dot-net>" <CMD-at-dataconnection-dot-com>

Definitely worth a try :-)

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: 14 May 2002 00:29
To: tesla-at-pupman-dot-com
Subject: RE: Zero Crossing Strobe & possible kits?

Original poster: "Sean Taylor by way of Terry Fritz <twftesla-at-qwest-dot-net>"

Comments throughout . . .

> Original poster: "Colin Dancer by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <CMD-at-dataconnection-dot-com>
> The problem with the zero crossing detectors in these chips is that
> "test point" for the zero-crossing circuit is taken from the load

I was thinking about that, after all, the point of the zero crossing
is too ELIMINATE a transient . . .

> you tried to directly connect them to the gate of the triac in a
> trigger circuit you'd be disappointed because the triac in such a
circuit is
> holding off the ramped DC firing voltage rather than AC main.

However, if a load such as an inductor were used, the triac would shut
off at the peak of the AC waveform because the current would go to
zero, and you could get a nice voltage spike from it to either trigger
an SCR to fire a trigger transformer, or another triac, etc.

  The nice
> thing about the CA3059 and the T2117 is that the zero crossing
reference is
> separate from the output stage.
> I'd considered using a zero crossing isolator followed by a mains
> triac which in turn was being used to trigger the final triac, but
with the
> direct connection you still get into all sorts of trouble if you are
using a
> bridge rectifier as part of the PSU because the final triac isn't
> to neutral.
> I suspect if you put your mind to it you could get a MOC304? to
work, but
> with an Atmel T2117 at less than $1 each it seemed the easiest way
to go :-)

Exactly my thoughts :-)
But since I have 4 of the optoisolators sitting around, and about 10 8
amp, 600 volt triacs, I'm willing to give it a try.

> Colin.

Sean Taylor