Making a counter that counts to 12 and display it.

Discussion in 'The Projects Forum' started by skyshiro, Jul 8, 2010.

  1. skyshiro

    Thread Starter New Member

    Oct 2, 2009
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    0
    Over the summer my plan was to build a digital clock. I've gotten the counter for 60 minutes working, using 2 counters and used a 7447 to display it on a 7-segment LED. Now I needed to get the hours side working, I've got a 4bit counter, 74161 and a decade counter 4017.

    I know I can wire the leads of the decade counter to make it reset at 12, but I don't know what to do after that. The 7447 can display the digits till it gets to 10. I was wondering is there something I could do to make it work with 2 7-segment displays or do I need 2 7447s?

    My question is how can I display the binary 12 on 2 7-segment displays. Or how can I make a counter to 12 and have it display on 2 7-segments.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    [QUOTEI've got a 4bit counter, 74161 and a decade counter 4017.][/QUOTE]This will present a problem. TTL and CMOS have different requirements for logic inputs. You probably would find life easier using a '160, as it is a BCD counter. Let the carry output set a flip flop for the 10's digit. The value 12 is the set flip flop and the Q1 bit from the '160.

    You can look into multiplexing the displays, but using two drivers is easier by far.

    See the first part. Much easier to use a BCD counter.
     
  3. skyshiro

    Thread Starter New Member

    Oct 2, 2009
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    0
    I was looking for a 74160 but they didn't have any at Frys. And I forgot the 4017 isn't a BCD counter, woops.

    I was wondering if you could go into more detail about setting the CO to a flip flop and using the value 12 as the set flip flop and the Q1 bit. I've just recently read about flip flops, are you talking about an RS FF or a JK FF?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    282
    My background is in old Univac computers, so I am actually prone to use D flip flops - 7474's being the one in mind.

    If 74160's are hard to find, look for a 74162 or or a 74190.

    Use the chip number as a search term to find the data sheet. It helps to know what all the pins do. For all logic, unused inputs must be tied high or low to prevent strange behaviors. TTL can be tied right to ground, but using a 4.7K resistor to pull an input up is good practice.
     
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