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???
02/22/10 17:40
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#173434 - That won't help at all!
Responding to: ???'s previous message
Sandip Basu said:
I think I can do the same thing to one of the input pin of an op-amp and use its output through an optocoupler to annunciate the ZERO-CROSSING of the ac line. I think this method will sense ZERO-CROSS quicker than other methods at the same time will be less hazardous and less dangerous.

No, it won't!!

You are still connecting live mains direct to your low-voltage circuit - so that is still exactly as dangerous as before!

Please, for your own safety and the safety of others, do not connect direct to live mains!

Use a transformer.

Or, at least, use an opto-coupler; but that still requires you to take care of creepage & clearance distances - if you don't know what they are, then use a transformer!



List of 25 messages in thread
TopicAuthorDate
Zero crossing detector - technique adoption            01/01/70 00:00      
   Sounds like a bad idea to me!            01/01/70 00:00      
      relying on parasitic diodes            01/01/70 00:00      
         Confusing            01/01/70 00:00      
            I mean            01/01/70 00:00      
            Designing to typical values            01/01/70 00:00      
               what blather            01/01/70 00:00      
      " IDEA ? " - RIDICULOUS            01/01/70 00:00      
         at least for this one            01/01/70 00:00      
         Oh dear:            01/01/70 00:00      
            tough, but true            01/01/70 00:00      
            just caught this one            01/01/70 00:00      
         Idiom            01/01/70 00:00      
            It really is a *very* bad idea!            01/01/70 00:00      
         Don't blindly follow app note            01/01/70 00:00      
            It's not so much the parasitic diodes...            01/01/70 00:00      
               two reasons            01/01/70 00:00      
                  What should I do ...            01/01/70 00:00      
                     That won't help at all!            01/01/70 00:00      
                     two wrongs            01/01/70 00:00      
            Most app-notes don't work ... because they're wrong!            01/01/70 00:00      
         This is typical ...            01/01/70 00:00      
            I hate to tell this,...            01/01/70 00:00      
               App engineers not always the sharpest tools in the shed            01/01/70 00:00      
   Unbelievable!!            01/01/70 00:00      

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