Mains voltage zero crossing detector with optical isolated output

Seems awfully complex, even before you implement the clock and floating power supply.

Your link doesn't function. ...Jim Thompson

It is a reference to a news article. You should know other ways to hunt up said article on your news server.

The point lost here (apparently), is that he posted a circuit in Usenet at some time in the past and referenced it here.

And the JL twerp can't stop lying about him and others. This group is probably worse then the kook group after 12 years of "Larkin Gone Loony".

OK, say something about JF's circuit.

That's what I thought it was. For some reason Agent has lost it and can't re-find.

I did save it as a .asc ...Jim Thompson

I'd suspect it to have some logic hazards, too. There are a couple of race conditions associated with the asynchronous comparator output entering the clocked logic through multiple paths.

Can we see that circuit in ascii or the LTSpice listing or image shack somewhere?

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There are such things as master-slave comparator logic that completely eliminate race hazards.

the ltspice listing isn't very useful unless you get the libraries for counters,flipflop,nand and nor gates that came with it

anyways the OP intended to connect the zcd to an mcu, so anything more that something that can provide a trigger at a repeatable place in the sinewave, connected to a timer pin is really redundant

-Lasse

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How does that work?

The general rule about bringing an async signal into a clocked state machine is: synchronize the async signal to the clock in one place only, and bring that into the synchronous domain on one wire only. If you're really paranoid about metastability (which you should be with CD4000 stuff) use a dual-rank synchronizer.

If you violate that rule, it may work, but it becomes a huge effort to prove that it is safe.

no matter what point you define as ground you'll still need a supply for the logic and it needs to be floating with regards to the stuff on the other side of the isolator

-Lasse

Everyone! Please continue breathing. There will be no response from Larkin except denigration and platitudes. ...Jim Thompson

All this talk about zero crossing detection, when a simple monostable type transistor pair circuit floating on the load device coupled with a photo circuit will serve as a zero cross detector and trigger.

That will insure that the device gets switched on only at the base and not any other time, regardless of where the sine is when the control trigger comes on.. It just needs to be on at the time when it swings through the axes.

Jamie

I downloaded the whole deal when it first appeared. The only confusion was the call to a Message-ID that Agent croaked on. Still don't know why. It always worked in the past, even on stuff it has to search for on-line. ...Jim Thompson