How to manually use a shift register.

Discussion in 'General Electronics Chat' started by utilityhacker, May 10, 2014.

  1. utilityhacker

    Thread Starter Member

    May 1, 2014
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    4
    So i have this shift register IC 74HC595 and I used it with Arduino many times.
    But i want to know if I can use it manually ie using push buttons for clock(pin 11),data(pin14),latch(pin12),clear(pin10) and blank(pin13).[​IMG]
    I tried to do it before using the IC 74HC595,8 LED's,5 tacticle push buttons for each pins mentioned above and a 9v battery.But as soon as I connect the 9v batterty the LED's starts blinking randomly even if i don't press any buttons.:confused:
    Can anyone help me out with this..........
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi,
    It can be controlled by switches, but its important the mechanical switches are 'debounced' in order to prevent misoperation

    E
     
  3. utilityhacker

    Thread Starter Member

    May 1, 2014
    40
    4
    so how can i prevent the switches from debouncing
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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  6. crutschow

    Expert

    Mar 14, 2008
    13,005
    3,232
    Did you have pull-up or pull-down resistors at the PB outputs? You cannot let CMOS inputs float or they will assume random values and cause the behavior you noted.

    You also need to add debounce circuits as mentioned to eliminate the effect of bouncing switch contacts.

    And as Bertus noted, 7V is the maximum voltage for that chip and it's designed to operate from 5V nominal.
     
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