4017,s

Discussion in 'The Projects Forum' started by jack mcleod, Dec 9, 2008.

  1. jack mcleod

    Thread Starter Member

    Sep 4, 2007
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    How are three 4017s connected to give 24 consecutive outputs and then recycle?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    A CD4017 is a decade counter. Two of them can count to 24. Possibly you mean something else by "24 consecutive outputs"?
     
  3. jack mcleod

    Thread Starter Member

    Sep 4, 2007
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    What is required is 24 outputs that go high one after the other then recycle.
    My limited knowledge has my first 4017 counting units but my second 4017 is counting 10,s and the first 4017 recycles rather than stopping. Help!
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    That won't work with 4017's. Each only has 4 outputs, and they are BDC coded. It sounds more like a shift register is more the thing than a counter.

    Can you post a schematic?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Ahhh, 4017's are 5-stage Johnson counters; they have 10 outputs, only one of which is high at any given time.

    When cascading 4017's, you need to use a couple of AND gates. The first 4017 will have 9 outputs, subsequent 4017's will have 8 outputs, for a total of 25 unique states.

    See the attached schematic.

    If you want it to recycle at 24 counts, on the rightmost 4017 move the Q9 output's connection to the Q8 output.

    You could use 4011's for the AND gates. Make sure to tie any unused inputs to GND or VDD.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Neat! I'd been thinking in terms of one "master" mux/demux chip controlling others through the enable pin. This is much neater. Here is the datasheet for a 4017.
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    You're right. I peeked in my logic manual and saw "Decade Counter" and concluded another BCD counter like a 4029.
     
  8. jack mcleod

    Thread Starter Member

    Sep 4, 2007
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    Thanks to all especially Sgt Wookie. The second part of this project will be posted under 4017's Part Two.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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