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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>

The problem with the zero crossing detectors in these chips is that the
"test point" for the zero-crossing circuit is taken from the load side.  If
you tried to directly connect them to the gate of the triac in a strobe
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.  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 connected
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 referenced
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 :-)


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: 11 May 2002 06:25
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>"

> I may be mistaken, but, you want a controlled zero voltage crossing
> switching for inductive loads, right?
> Maybe the very-standard-stuff MOC3041 / 2 / 3 could be up to this
> application: it contains a triac drive via ZVC detector and optoisolator.

I was just working with this chip - actually the MOC3083, just differnent
isolation, trigger current . . .

Anyway, I have several left, and I could try hooking them up to an ignition
coil or firing coil for a xenon tube to see how reliably it could trigger
them.  I'll let everyone know the results . . .

Sean Taylor
The Geek Group
G-3 #1204J
Because the geek shall inherit the Earth! (c)