Using a 3x5 keypad WITHOUT a microcontroller

Discussion in 'Homework Help' started by Masowai, Aug 24, 2006.

  1. Masowai

    Thread Starter New Member

    Aug 24, 2006
    2
    0
    I'm looking to build a counter circuit that will start at zero and increment by one up to 4096. The clock is a simple 555. I am using a 4 digit LED display driven by a BCD decoder/driver to display the numbers.

    I would like to use a 0-9 keypad to enter numbers to preset the count at any number I want. Since I am using 3 SN74193Ns (4-bit presettable counter), I could simply use 12 M.C. pushbutton switches to enter the number in binary form, but that's kinda goofy.

    So if I wanted to input "767", I would have to push 9 buttons (512+128+64+32+16+8+4+2+1)!!! At least I am using a latch so I won't have to hold them all down simultaneously!

    The problem is...I want to use a keypad, BUT I DON'T want to have to incorporate a microcontoller with the pad. Is there any other way I can input my numbers without using a microcontroller?

    I'm not worried about advancing the number to the next space or anything like that. I just want to push a "5" on the keypad and have a "5" appear on the LED readout!!

    What about a keypad with a common ground instead of a 3x5 matrix? Would that be easier to use?

    Arggh.
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Perhaps you could use a keypad encoder such as the 74C922.
     
  3. Masowai

    Thread Starter New Member

    Aug 24, 2006
    2
    0
    I talked to a fellow about that chip but he insisted that I had to use a microcontroller of some sort. I know see that I don't...at least for the purpose that I am using it for. THX!
     
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