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David Prentice
01/21/12 06:06
Read: 466 times
Wormshill
England


 
#185600 - Have I done the sums wrong?
Responding to: Per Westermark'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      Anil Kumar      01/11/12 00:38      
   What?      Per Westermark      01/11/12 00:58      
      switch interfacing      Anil Kumar      01/11/12 01:39      
         The 7-segment digits will not handle switches      Per Westermark      01/11/12 02:57      
   Perhaps this may be useful to you      Maunik Choksi      01/11/12 03:53      
      4 buttons - not full keypad      Per Westermark      01/11/12 04:39      
         switch interfacing      Anil Kumar      01/12/12 00:06      
            That is called edit mode      Maunik Choksi      01/12/12 01:55      
               switch interfacing      Anil Kumar      01/12/12 22:50      
                  You need to study some examples      Maunik Choksi      01/12/12 23:51      
                     switch interfacing      Anil Kumar      01/13/12 00:10      
                  Details details - and where is debounce/repeat handling?      Per Westermark      01/13/12 01:20      
                     switch interfacing      Anil Kumar      01/14/12 00:59      
            Why should this be a problem??      Kai Klaas      01/12/12 07:53      
            interfacing your switches has nothing to do with LED's      Richard Erlacher      01/12/12 22:02      
   MUX LED AS O/P PIN      Satish S Munot      01/14/12 19:47      
      Switch interfacing      Anil Kumar      01/19/12 23:19      
         divide and conquer      Mahmood Elnasser      01/20/12 01:35      
         simplified step-by-step way to post your schematic        KONSTANTINOS L. ANGELIS      01/20/12 02:12      
            remember      Erik Malund      01/20/12 07:31      
               ? Not Muxing ?      Michael Karas      01/20/12 08:17      
   switch interfacing      Anil Kumar      01/21/12 01:57      
      You need lots of resistors      David Prentice      01/21/12 04:34      
         (Back to) Basics      Andy Neil      01/21/12 05:17      
            multiplex 5 digits      David Prentice      01/21/12 05:43      
               Don't think anyone would want 1:35 degenerate "multiplexing"      Per Westermark      01/21/12 05:52      
                  Have I done the sums wrong?      David Prentice      01/21/12 06:06      
                     No but multiplexing requires few driver lines      Per Westermark      01/21/12 06:17      
                        You MUST have digit drvers      David Prentice      01/21/12 07:00      
                           You missed '4094 OE+PWM for luminocity      KONSTANTINOS L. ANGELIS      01/21/12 09:47      
               No multiplexing needed...      Kai Klaas      01/21/12 07:33      
                  switch interfacing      Anil Kumar      01/21/12 07:46      
                     What help?      Andy Neil      01/21/12 08:33      
                     how?      Erik Malund      01/21/12 08:34      
                     Ah, a homework, right?      Kai Klaas      01/21/12 09:21      
                        switch interfacing      Anil Kumar      01/21/12 09:55      
                           language?      Erik Malund      01/21/12 10:37      
                           i have no logical idea how i write code      Andy Neil      01/21/12 10:40      
                           You need...      Kai Klaas      01/22/12 07:07      
                              Making a seven segment display blink      Andy Neil      01/22/12 07:19      
                                 The 4094 chip has an OE pin      David Prentice      01/22/12 07:48      
                              switch interfacing      Anil Kumar      01/22/12 10:57      
   switch interfacing      Anil Kumar      01/31/12 22:07      
      would you provide some feedback ?      KONSTANTINOS L. ANGELIS      02/01/12 03:35      

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