Interfacing of Hex Keypad and Seven Segment Display Using 8051 Microcontroller

Discussion in 'Homework Help' started by Ralf123, Aug 17, 2014.

  1. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Hey Guys!
    Here is a situation.... I have been assigned a task to make a full adder connected to seven segment displays...........problem here is that I have to show both the Inputs and outputs on the ssds (its not restricted to show them at a time).... I have found a few circuits related to it.......but I am stuck at the beginning...I am working on proteus 8 professional....here is my circuit Its giving no error...but its not working!

    [​IMG]

    [​IMG]
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Your resistors R1, R2 and R3 are much to large.
    Try values between 1K and 10K for them.
    Also I see no current limiting resistors on the segments of the displays.
    Put resistors of 100 to 220 Ohms between the P1.X and the display segments.

    Bertus
     
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  3. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Thanks for your response :)
    I have done the changes you said....now the display is on but the numbers donot change even after pressing the buttons of keypad!! have a look

    [​IMG]
     
  4. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    I think the problem is with the crystal oscillator i used the one named as X1 its value is 12MHz have a look maybe you get some hint!
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    It could be that the capacitors C1 and C2 are to large.
    You could try some values between 12 and 22 pF.

    Bertus
     
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  6. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    I have made the values 18pf but no effect!
     
  7. bertus

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  8. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Yes firstly when I ran the simulation in the software there were a number of errors like "could not load the program code" than i inserted the .asm file in the assembly source code of 89V51RD2..... After that there was no error with everything working smooth but the display on the ssds remained same they are not changing even after pressing the keys of the keypad!!!
     
  9. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Bertus
    Is it possible to connect the two circuits??
    Otherwise all of my efforts will be of no use....because basically what I am trying to do here is to make a Full adder and the display to be shown on ssds, also adding the keypad to enter input?
    Thanks In advance!
     
  10. bertus

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    Apr 5, 2008
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  11. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Yes Its a kind of homework (more specifically a Project assigned).......I have to make it work practically but I will do that easily once the circuit starts working in proteus!

    No there is no condition of using this micro controller... I am free to use anything.....
    here is what is demanded....but the use of hex-pad is compulsory!

    'Design and Implement a simple ALU (Arithmetic Logic Unit) with only ADDITION function. You have to display the digits and their results on a seven segment display".
     
  12. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Thanks for your help bertus I will let you know if I get somewhere!
     
  13. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The matrixed keypad won't work properly unless you have pullup (or pulldown) resistors on 4 pins.

    Do you understand how a matrixed keypad works in hardware and in the code?
     
  14. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Thanks for your Response :)
    Sir can you be more specific where should I place the pullup resistors.....Is it on each of the 8 output terminals of the hex-pad?


    No Sir I dont have any concepts related to the phenomenon of its working!
     
  15. shteii01

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    Feb 19, 2010
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  16. Ralf123

    Thread Starter New Member

    Aug 16, 2014
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    Lol...nice one...
    I meant to say that I dont know about the deep concepts of working.....I know the basics that are need to make connections in the circuit.......
    I know there is a minute point that I am ignoring is creating the fault...thats why asked the help of you guys.....
     
  17. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    This gives you an idea;

    [​IMG]

    The resistors pull the column lines up to 5v when no buttons are pressed.

    Then you take a row low to 0v, and check all 4 columns. This has to be repeated 4 times to read all 4 rows.

    You need to understand the basic operation of the circuit AND the code operation, if you want to be successful making a project.
     
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