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    keypad project-3x4 keypad to 7 segment display

    I am working on a project that requires me to use a 3x4 keypad to put a number on a 7-segment display. I am trying to figure out what chips i need to use to be able to press a number on the keypad and have that number locked in and be able to press other numbers with out it changing the numbers until i reset the circuit. I believe i need an encoder, 4bit register, and decoder between the keypad and the 7-segment display but dont know which ones to use. Can anyone help me please?
    Last edited by bad92620; 27th October 2010 at 16:57. Reason: figured more info will help

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    Re: keypad project-3x4 keypad to 7 segment display

    There are many approaches here.

    If you are using a matrix keypad (such as found on a telephone), one is to use a 74HC922. It has a "data available" output that could be latched through an external gate/FF and reset circuitry, to implement the lockout feature you desire. A BCD to 7-segment decoder chip is necessary to provide your display.

    dj



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    Re: keypad project-3x4 keypad to 7 segment display

    thanks but what is the 4 bit register that is needed to lock the number on the 7-segment display.



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    Re: keypad project-3x4 keypad to 7 segment display

    Quote Originally Posted by djsfantasi View Post
    ... output that could be latched through an external gate/FF and reset circuitry, to implement the lockout feature you desire.
    dj
    I don't know? Where is it? You need some sort of latch?



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    Re: keypad project-3x4 keypad to 7 segment display

    There are display driver ICs that include key scanning capability. The ones in this chart are for LEDs: Maxim - Parametric Search - Product Table.



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