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Hex to Seven-Segment Decoder

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by synckewl, Jul 25, 2006.

  1. synckewl

    synckewl New Member

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    Dear guys,

    I would like to design a HEX to Seven Segment Decoder using K-maps for seven 4-input functions.

    eg 0000 produces 0 while 1111 produces F

    I use kMap to derive the logic function for a,b,c,d,e,f,g segment

    This is what I get
    a = BC + A'C + AD' + B'D' + A'BD
    b = B'D' + B'C' + A'CD + AC'D + A' C' D'
    c = C'D + A'D + AB' + A'B + B'C'
    ....
    g = AC + B'C + AB' + BC'D + A'BD'

    As you can notice, if I draw out the logic diagram, it will be complex. eg: Just a alone, I will need 5 AND gates and 5 inputs OR gates.

    Are there any ways I can minimize the use of my logic gates?

    Thank you
     
  2. Overclocked

    Overclocked Member

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    Im guessing you have to convert the Hex to Bin and then To BCD. Or since Hex is just another way of expressing Binary in Microprocessors, just convert Binary to BCD. Once you have it in BCD, you can then use any ordinary BCD to 7 Segment Chip.

    Atleast thats my guess on it..
     
  3. synckewl

    synckewl New Member

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    sorry, I think I did not make clear in my first post

    For eg: If I have input ABCD in Binary, I will get hex as an output

    Input - Output
    0000 - 0
    0001 - 1
    0010 - 2
    0011 - 3
    ...
    ...
    1110 - E
    1111 - F

    the truth table I got is this

    A B C D a b c d e f g
    0 0 0 0 1 1 1 1 1 1 0
    0 0 0 1 0 1 1 0 0 0 0
    0 0 1 0 1 1 0 1 1 0 1
    0 0 1 1 1 1 1 1 0 0 1
    0 1 0 0 0 1 1 0 0 1 1
    0 1 0 1 1 0 1 1 0 1 1
    0 1 1 0 1 0 1 1 1 1 1
    0 1 1 1 1 1 1 0 0 0 0
    1 0 0 0 1 1 1 1 1 1 1
    1 0 0 1 1 1 1 1 0 1 1
    1 0 1 0 1 1 1 0 1 1 1
    1 0 1 1 0 0 1 1 1 1 1
    1 1 0 0 1 0 0 1 1 1 1
    1 1 0 1 0 1 1 1 1 0 1
    1 1 1 0 1 0 0 1 1 1 1
    1 1 1 1 1 0 0 0 1 1 1

    [​IMG]
     
    Last edited: Jul 25, 2006
  4. dave

    Dave New Member

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  5. philba

    philba New Member

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    use an EPROM/EEPROM/...
     
  6. survivingbrain

    survivingbrain New Member

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    Microcontrollers.. use the ones with lower IO pin count.. in your case you need 4 bits for input and 7/8(if u want to control dot) bits for output. So go for a controller with 12 I/Olines. If you want to have 2 seven segments, u'll need the ones with 24 I/Olines. But, a single chip + crystal+two or three resistors will do. But u'll have to program it.....

    here are some of the chips...

    PIC 16F628 - 16 I/O lines
    PIC 16F54 - 12 I/O lines
    PIC 16F84 - 13 I/O lines - try this one!! outdated, but good for ur project

    try 89C2051 if you dont want microchip..
    there are a lot of other Chips available..

    Other options are a PLA, or a PAL.
     
  7. synckewl

    synckewl New Member

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    I need to build up my 7 segment decoder gates by gates using basic gates.

    Should I form the following logic using NAND?
    My aim is to minimize the propagation delay and gates required.
    a = BC + A'C + AD' + B'D' + A'BD
    b = B'D' + B'C' + A'CD + AC'D + A' C' D'
    c = C'D + A'D + AB' + A'B + B'C'
    ....
    g = AC + B'C + AB' + BC'D + A'BD'
     
  8. philba

    philba New Member

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    what are you doing this for? it's starting to smell like a course assignment.

    you've gotten several good suggestions but seem to be ignoring them.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It looks EXACTLY! like a course assignment!.
     
  10. survivingbrain

    survivingbrain New Member

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    If you really want to do it with gates...

    Do it with GATES !!!!
    :mad:

    However you can always use XOR gates - you can reduce some of your expressions in terms of XOR..

    That way you can reduce your number of gates. Also look for common expressions. U need not use separate gates for them...
    :eek:
     
  11. Ghasemzadeh

    Ghasemzadeh New Member

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    Hex to Seven-Segment

    Hello,
    I want to make hex to 7-segment with Digital gates (Look like and-or-xor and ... )
    and know I want to make I know how can make output is there any program that give me output?
    This is my truth table:

    A B C D a b c d e f g
    0 0 0 0 1 1 1 1 1 1 0
    0 0 0 1 0 1 1 0 0 0 0
    0 0 1 0 1 1 0 1 1 0 1
    0 0 1 1 1 1 1 1 0 0 1
    0 1 0 0 0 1 1 0 0 1 1
    0 1 0 1 1 0 1 1 0 1 1
    0 1 1 0 1 0 1 1 1 1 1
    0 1 1 1 1 1 1 0 0 0 0
    1 0 0 0 1 1 1 1 1 1 1
    1 0 0 1 1 1 1 1 0 1 1
    1 0 1 0 1 1 1 0 1 1 1
    1 0 1 1 0 0 1 1 1 1 1
    1 1 0 0 1 0 0 1 1 1 1
    1 1 0 1 0 1 1 1 1 0 1
    1 1 1 0 1 0 0 1 1 1 1
    1 1 1 1 1 0 0 0 1 1 1

    How can I find output with out drawing karnaugh maps?
    if anyone give me gates of this system I will become pleased.
     
  12. shokjok

    shokjok Member

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    You have many suggestions posted here. We are assisting you with ideas, not work practices.
     
  13. Ghasemzadeh

    Ghasemzadeh New Member

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    a = BC + A'C + AD' + B'D' + A'BD
    b = B'D' + B'C' + A'CD + AC'D + A' C' D'
    c = C'D + A'D + AB' + A'B + B'C'
    ....
    g = AC + B'C + AB' + BC'D + A'BD'

    This is what I need can anyone make d,e,f for me?
    Where can I download KMap?
     
  14. Hurra Tux

    Hurra Tux New Member

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    I can do d :
    [​IMG]
    Can you tell what '+' mean and what " ' " mean in your equation ?
     
  15. Ghasemzadeh

    Ghasemzadeh New Member

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    I did it thanks
     
  16. Hurra Tux

    Hurra Tux New Member

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    I've got an idea to do it whith less gates :
    You can draw the karnaugh map, and make a circuit to do make a 1 when there should be a 0, and then put a NOT gate at the end (Or change the OR/AND gate to make a NOR/NAND).
    So :

    a = BC + A'C + AD' + B'D' + A'BD = A'B''C''D'' + A''B''C'
    So you reduce to two AND gate (and two Or inputs)
     
  17. jhadeA9

    jhadeA9 New Member

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    How to make a hex to octal converter circuit?
    our teacher ask to do this. can some one help me?

    Hexadecimal-to-Octal Converter with Display

    Input: 1-digit Hexadecimal Number represented by 16 input points
    Output: 2-digit Octal Number represented by 8 output points

    Logic Function

    The circuit will convert the hexadecimal input into its octal equivalent. Both the input and output must be displayed using a seven-segment display. Note: For the number 6 the 'a' LED with light and for the number 9 the 'd' LED will light.
    12 hours ago - 3 days left to answer.
    Additional Details
    can you please provide me the circuits diagram? we are required to do it in a breadboard. and i'm really bad at it.
    1 hour ago
     
  18. abell118

    abell118 New Member

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    I believe the code for "C" should be 1 1 0 0 1 0 0 1 1 1 0 for the 7 segments ...
     
  19. abell118

    abell118 New Member

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    I think "9" also has the "d" segment on as well ...
     
  20. kubeek

    kubeek Well-Known Member

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    And I think you are almost four years too late ;)
     
  21. JimB

    JimB Super Moderator Most Helpful Member

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    Welcome to ETO.

    You realise that you are picking over a 9 year old thread.

    I think that "9" can be drawn with the "d" segment on or off.
    It all depends on personal preference.

    The table in post #9 is confusing in several ways.
    1, the input bits A,B,C,D are run together with the output bits as though it were all one big word.
    2, the input bits A,B,C,D conventionally have weightings of 1, 2, 4, 8 respectively.
    The way that the table is written shows the weighting as 8, 4, 2, 1.

    JimB
     

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