Zero Crossing Triac

[Foaad]

Whats the difference between a regular normal optoisolator and zero
crossing optoisolator? Do ZC optoisolators automatically fire the
TRIAC on the crossing? If true, wouldnt that mean i shouldnt use them
if im willing to have dimming capabilities. In that case, what chips
are there that can detect zero crossing ?

 

[Fred Bloggs]

Foaad wrote:

Whats the difference between a regular normal optoisolator and zero
crossing optoisolator? Do ZC optoisolators automatically fire the
TRIAC on the crossing? If true, wouldnt that mean i shouldnt use them
if im willing to have dimming capabilities. In that case, what chips
are there that can detect zero crossing ?

Let me see- in the case that you shouldn't use the ZC opto, which ZC
opto's are there? Stay off the drugs.

 

[Rich Grise]

On Thu, 18 Nov 2004 13:23:12 -0800, Foaad wrote:

Whats the difference between a regular normal optoisolator and zero
crossing optoisolator? Do ZC optoisolators automatically fire the
TRIAC on the crossing? If true, wouldnt that mean i shouldnt use them
if im willing to have dimming capabilities. In that case, what chips
are there that can detect zero crossing ?

I did this once with just an opamp. I had a diode to ground on the
inverting input, with a res. to V+, and two diodes in series to ground
on the non-inverting input, with a res. to the 12 VAC winding. It worked
good enough for my regulator. (I used it for the timer capture input on
a 68HC11, so it was almost trivial to subtract out the slop.)

Don't use MOC3030 - they're zero-cross optos. I settled on some 4N series
straight opto SCRs - but I had a full-wave CT to work with.

In any case, it should indicate in the catalog whether the part is
zero-cross or not.

Hope This Helps!
Rich