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???
02/08/08 06:10
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 		 #150438 - problems with edge triggering and noise
Hi,
I've made a hand soldered dev board for my atmel AT89c52.
I seem to be having problems with noise due to the microcontroller...

When i check the supply voltage on the oscilloscope (across vcc and ground) there is a lot of noise.shouldn't it be a straight 5v dc?
If i remove the microcontroller out of the socket, its fine-theres no noise.

i wrote a simple program to test the board-square wave of a certain frequency on P2. the output is quite noisy..its not a clean square wave.
i have only the crystal with 2 capacitors and a power on reset circuitry soldered onto the board. am i missing something here?



List of 58 messages in thread
TopicAuthorDate
problems with edge triggering and noise            01/01/70 00:00      
   5v regulator,capacitors - elko and creamic            01/01/70 00:00      
      not likely            01/01/70 00:00      
         not true!            01/01/70 00:00      
   How much noise?            01/01/70 00:00      
      using a 78L05 voltage regulator IC with 220 uF cap            01/01/70 00:00      
         be conservative ... for now ...            01/01/70 00:00      
   First things first - Begin at the beginning            01/01/70 00:00      
      yes i agree..            01/01/70 00:00      
         photo            01/01/70 00:00      
            Well done            01/01/70 00:00      
               the "backside" :)            01/01/70 00:00      
                  Use Solder Wick as Braid            01/01/70 00:00      
                     is this ok?            01/01/70 00:00      
                        i found this strange looking woven wire?            01/01/70 00:00      
                  Perf Board Types            01/01/70 00:00      
                  Pad-Per-Hole PTH            01/01/70 00:00      
                     How much ?            01/01/70 00:00      
                        This Much            01/01/70 00:00      
                           other boards            01/01/70 00:00      
                     Here\'s what I prefer.            01/01/70 00:00      
            it looks quite acceptable, with caveats ...            01/01/70 00:00      
      How much noise!            01/01/70 00:00      
   Regulator problems..            01/01/70 00:00      
      sorry wrong measurements            01/01/70 00:00      
         Actuall, you were right, in part ...            01/01/70 00:00      
            Different caps..            01/01/70 00:00      
      one more issue            01/01/70 00:00      
         7805            01/01/70 00:00      
            Swop the pins around !!            01/01/70 00:00      
            agreed            01/01/70 00:00      
               what about switching noise and ripple?            01/01/70 00:00      
                  to RE            01/01/70 00:00      
                     This is a real disappointment            01/01/70 00:00      
                        numbers            01/01/70 00:00      
                           that's not what was asked ...            01/01/70 00:00      
                              yes and no            01/01/70 00:00      
                                 I've got lots of those ...            01/01/70 00:00      
                                    not mostly - only and who cares            01/01/70 00:00      
                                       It's what's before the filter that matters!            01/01/70 00:00      
                                          enough            01/01/70 00:00      
                                             not exactly ...            01/01/70 00:00      
                                                as stated before            01/01/70 00:00      
                                                   Nonsense!            01/01/70 00:00      
                                                      you can't stop, can you            01/01/70 00:00      
                                                         I love to see Erik backpedal            01/01/70 00:00      
                                                            Better start giving a hoot            01/01/70 00:00      
                                                               as stated so often, I DO give a hoot ...            01/01/70 00:00      
                                                                  as stated so often, I DO give a hoot ...            01/01/70 00:00      
                                                                     I think you are right            01/01/70 00:00      
                                                                        I too favour looking inside black boxes            01/01/70 00:00      
                                                                           blindly?            01/01/70 00:00      
                                                                              Erik ... you\'re headed for a disappointment            01/01/70 00:00      
                                                                                 If you accept datasheet blindly I cant help            01/01/70 00:00      
                                                                                    you do not get the point, do you?            01/01/70 00:00      
                                                                     not exactly            01/01/70 00:00      
                                                                        I never made any such claim            01/01/70 00:00      
         gee ... that's a negative regulator ...            01/01/70 00:00      

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