bad batch of zero crossing optos?

[Jamie]

Today, I debugged a little circuit that was put together for a commonly
used function at work, because I was told it wasn't behaving as it
should and they were correct in their assessments.

It seems the last tube of 3033 Opto couplers I got behave like random
triacs.

I removed one from a test unit and replaced it with one I had from
older stock and works as it should.

Has any experienced getting a bad batch of zero crossing opto couplers
that just acted like random types?


P.S.
The last tube I got is a "Everlight" brand, if that makes any
difference? I think i've used them before with no problems.

Jamie

 

[Jamie]

Was it EL3033? Should have identical performance to the MOC. Maybe you
got a counterfeit. http://www.everlight.com/index.php?option=com_k2&view=item&layout=item&id=348&Itemid=105&lang=en

Yes, it is a EL3033 and it's possible I got a badly marked units or
defective units in some why. We ordered another tube and will test one
of those when they come in. We'll see where this goes.

I do remember at one time having a strange problem with a very used
old coupler that was behaving much the same way. We replaced it with a
zero crossing type as was the original and the problem was solved.

Might have something to do with LED emissions level internally ?

Jamie

 

[Phil Allison]

"Dennis"

Could the design be marginal in someway?

** Do you know how a zero cross, mains voltage opto works??

Hint: LED drive has nothing to do with the zero cross trick.




..... Phil

 

[Jamie]

Could the design be marginal in someway?

That crossed my mind how ever, units in a test jig from that same lot
failed to operate as a zero crossing type and worked perfectly as a non
zero type.

'Place I worked for was making a very low power battery operated product.
Pullup resistors etc were very high values etc, switch on timings as short
as possible etc. Some brands of components would not work in these designs.

In many cases, the use of this lot may go on unnoticed because the
side effects of not using zero crossing type most likely will not show
up in many applications how ever, in this particular case, they are
being used to sequence beam shift with an irradiation unit. We shift
the beam between sweeps a little bit to have better coverage of the
product being
irradiated. Since we have 2 coils on the scan horn for this, its crucial
they both sync properly, other wise, you can cause heating on the
titanium window and start to generate a vacuum problem if the beam is
not properly synchronized.

we use zero crossing triggers to make sure both coils start at the
same time when scan is in the middle pass otherwise we get some
interesting angular sweep effects.


It's now a big issue, we'll just toss these and get more

Jamie