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???
12/05/05 12:42
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 		 #104701 - correct, but there has been umpteen post
Responding to: ???'s previous message
Very nice, Erik. But remember, we want to have galvanic isolation to mains, we want to detect zero crossings of both polarities and we want to make the job with a very low unipolar supply voltage (+3.0V). How looks your recommendation now?
just fine, thanks.

we want to have galvanic isolation to mains
easily attainable after the detector where you have a straight logic level.

Again, a hysteresis of 20mV is no problem, if you use proper ground routing and filtering.
correct, but there has been umpteen posts on "ground routing and filtering" problems. My suggestion is a way to do so without these problems.

Did I state that the low hyst was not doable?, if so, sorry, just it require a lot more than high hyst.

Erik

List of 35 messages in thread
TopicAuthorDate
LPC922 Comparator Interrupt Problems.            01/01/70 00:00      
   Vcc?            01/01/70 00:00      
      Vcc=3.0 to 3.3 Volts.            01/01/70 00:00      
         Possible causes            01/01/70 00:00      
            Noise could come from comparator itself            01/01/70 00:00      
               Re: Noise from Ground.            01/01/70 00:00      
                  Filter            01/01/70 00:00      
                     Exactly!            01/01/70 00:00      
                  R21 is contaminated            01/01/70 00:00      
                     Hystresis is 1.7 mV            01/01/70 00:00      
                        It's 20mV!            01/01/70 00:00      
                           oops calculation error            01/01/70 00:00      
                              waaaay too small a hysteresis..            01/01/70 00:00      
                                 Not at all !            01/01/70 00:00      
                                    there are (at least) 2 ways to skin this            01/01/70 00:00      
                                       Extreme care??            01/01/70 00:00      
                                          correct, but there has been umpteen post            01/01/70 00:00      
                     Please Suggest some filtering.            01/01/70 00:00      
                        100R plus 47µF            01/01/70 00:00      
                           Re: 100E + 47uF            01/01/70 00:00      
                              Like that...            01/01/70 00:00      
                                 Red LED.            01/01/70 00:00      
                                    Every red LED should work            01/01/70 00:00      
                                       also be aware            01/01/70 00:00      
                                          At 500µA...            01/01/70 00:00      
            Noisy ground?            01/01/70 00:00      
            Re: Possible Causes.            01/01/70 00:00      
               Mains Signalling?            01/01/70 00:00      
                  Mains filtering            01/01/70 00:00      
                     mains filtering            01/01/70 00:00      
                        Very informative!            01/01/70 00:00      
   Problem Frequency.            01/01/70 00:00      
      Filtering will help!            01/01/70 00:00      
         Problem Solved.            01/01/70 00:00      
            Nice to hear!            01/01/70 00:00      

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