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01/21/12 13:06
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 		 #185600 - Have I done the sums wrong?
Responding to: ???'s previous message
You have 5 digits being multiplexed with a 20% duty cycle.
Each segment has a peak current of 3.7mA (average 0.74mA)

7 x 3.7mA is 26mA i.e. the maximum current for the whole 8-bit P0 port.

Ok. You will not always display 88888, but it will happen.
And of course you can spread the segments over the other ports.

It is simpler to choose a different 8051 variant.

David.



List of 44 messages in thread
TopicAuthorDate
switch interfacing            01/01/70 00:00      
   What?            01/01/70 00:00      
      switch interfacing            01/01/70 00:00      
         The 7-segment digits will not handle switches            01/01/70 00:00      
   Perhaps this may be useful to you            01/01/70 00:00      
      4 buttons - not full keypad            01/01/70 00:00      
         switch interfacing            01/01/70 00:00      
            That is called edit mode            01/01/70 00:00      
               switch interfacing            01/01/70 00:00      
                  You need to study some examples            01/01/70 00:00      
                     switch interfacing            01/01/70 00:00      
                  Details details - and where is debounce/repeat handling?            01/01/70 00:00      
                     switch interfacing            01/01/70 00:00      
            Why should this be a problem??            01/01/70 00:00      
            interfacing your switches has nothing to do with LED's            01/01/70 00:00      
   MUX LED AS O/P PIN            01/01/70 00:00      
      Switch interfacing            01/01/70 00:00      
         divide and conquer            01/01/70 00:00      
         simplified step-by-step way to post your schematic            01/01/70 00:00      
            remember            01/01/70 00:00      
               ? Not Muxing ?            01/01/70 00:00      
   switch interfacing            01/01/70 00:00      
      You need lots of resistors            01/01/70 00:00      
         (Back to) Basics            01/01/70 00:00      
            multiplex 5 digits            01/01/70 00:00      
               Don't think anyone would want 1:35 degenerate "multiplexing"            01/01/70 00:00      
                  Have I done the sums wrong?            01/01/70 00:00      
                     No but multiplexing requires few driver lines            01/01/70 00:00      
                        You MUST have digit drvers            01/01/70 00:00      
                           You missed '4094 OE+PWM for luminocity            01/01/70 00:00      
               No multiplexing needed...            01/01/70 00:00      
                  switch interfacing            01/01/70 00:00      
                     What help?            01/01/70 00:00      
                     how?            01/01/70 00:00      
                     Ah, a homework, right?            01/01/70 00:00      
                        switch interfacing            01/01/70 00:00      
                           language?            01/01/70 00:00      
                           i have no logical idea how i write code            01/01/70 00:00      
                           You need...            01/01/70 00:00      
                              Making a seven segment display blink            01/01/70 00:00      
                                 The 4094 chip has an OE pin            01/01/70 00:00      
                              switch interfacing            01/01/70 00:00      
   switch interfacing            01/01/70 00:00      
      would you provide some feedback ?            01/01/70 00:00      

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