why my shift register doesnt work?!

Discussion in 'General Electronics Chat' started by leonheard, Dec 31, 2014.

  1. leonheard

    Thread Starter Member

    Jan 8, 2013
    48
    0
    Hi!

    I bought an TC74HC595P (Toshiba) 8 BIT register... the datasheet:

    http://pdf1.alldatasheet.net/datasheet-pdf/view/31766/TOSHIBA/TC74HC595.html


    i want to use it without a microcontroller all with switch buttons ( for educational purposes only doesnt need to work 100%) since i am very interested in learning about serial to parallel data in "real time".


    like in this tutorial video:




    this is my schematic:

    http://s10.postimg.org/uscnqogw9/schematic123.jpg




    it doesnt work like it suppose to work, it gives me random outputs! :/

    is something wrong with:

    my schematic?
    IC ?
    debounce?

    i tried to fix this for 19 hours now and nothing :mad:
    i would appreciate your help...

    thanks! :D
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    You probably need to de-bounce the switches.
     
    leonheard likes this.
  3. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,226
    You mentioned debounce, why didn't you do that? As Blocco mentioned, that's quite likely what it needs.
    Here's a debounce circuit that should work for you.
    For your requirements connect R1 to GND with the PB connected to +5V.
    Leave diode polarity as shown.
    You could increase R1 to 47kΩ and reduce C1 to 1μF to reduce the inrush current through the PB.
     
    Last edited: Dec 31, 2014
    leonheard likes this.
  4. leonheard

    Thread Starter Member

    Jan 8, 2013
    48
    0
    thanks for your help! i made a simple monostable vibrator with an ic555... now my shift register WORKS 100%!:p i hope this helped someone else with same problem...
     
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