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02/22/10 11:38
Modified:
  02/22/10 11:59

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#173409 - Zero crossing detector - technique adoption
So many articles are written on this topic, - new techniques are developing to detect the zero crossing as early as it occours.
As in PIC 12C508 and in AVR182 the high voltage live line can be connected through some megaohm resistor directly to the port pin of the micro. Some clamping diodes are there in-built. In AT89C51 or C52 there is no such clamping diode. Can I use such diodes externally if I want to connect high voltage live line through some megaohm resistor directly to the port pin and detect zero-crossing in the firmware. If it is possible then what type of diode should I use and what should be the maximum rating of the diode.

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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