what is the problem with this schematic

Discussion in 'General Electronics Chat' started by spidermanIIII, Dec 26, 2013.

  1. spidermanIIII

    Thread Starter Member

    Nov 22, 2013
    76
    0
    what is the problem with this schematic i need help please, in my college they asked for analog to digital converter using ADC0808 IC and potentiometer
    i built the schematic but it doesn't run in Proteus
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    What kind of buffers do you use?
    When they are open collector, there will never be any voltage on the leds.

    [​IMG]

    If they are not open collector types, you will need current limiting resistors for the leds.

    Bertus
     
  3. spidermanIIII

    Thread Starter Member

    Nov 22, 2013
    76
    0
    i tried not to use buffers and it stil don't work
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    You have pin 22 ( the adress latching pin ) floating.
    You need a high input to store the selected adress.

    See the timing diagram what is needed to convert an input signal:

    [​IMG]

    Bertus
     
  5. paulktreg

    Distinguished Member

    Jun 2, 2008
    611
    120
    Have put resistors (try 1K) in series with the LEDs?
     
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