4020 14 stage binary counter

Discussion in 'The Projects Forum' started by Dave65, Nov 27, 2015.

  1. Dave65

    Thread Starter New Member

    Nov 1, 2015
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    I've just wired this chip up with, so far, 4 LEDS connected to the "first 4 outputs", expecting to be able to watch it counting in binary as I pulse its clock input.

    But..... I see that it only has 12 outputs, not 14. Q1 and Q2 are "missing". That seems to me to be completely bizarre. Why miss them out? What if I need them (I do need them)? Am I missing something?

    Many thanks,
    Dave
     
  2. paulktreg

    Distinguished Member

    Jun 2, 2008
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    That's how it was designed. You need the 4040.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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  4. ian field

    Distinguished Member

    Oct 27, 2012
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  5. Dave65

    Thread Starter New Member

    Nov 1, 2015
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    Many thanks for the replies and for pointing me at the 4040.

    I appreciate that the 4020 is designed like that... it just took me by surprise and seemed odd. No doubt there are plenty of applications that make use of it.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    It's not really odd. It's just that the package has a limited number of pins and the designers figured that most who used the chip would be more interested in the higher Q outputs then the lower.
    You're the exception. ;)
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Just add a dual flipflop and you can make the first two stages yourself. Either a dual D-type of JK flipflop are available in 4000 series.
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    If you look at the pinouts of the 4060 and 4521, you will see that other devices have a similar pinout pattern that favors the higher-order bits over the lower. The 4060 is particularly frustrating because the bits that are brought out are not contiguous.

    ak
     
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