UpDown Counter In MultiSim and Breadboard Worked Differently.

Discussion in 'The Projects Forum' started by DennObi, Jul 11, 2015.

  1. DennObi

    Thread Starter New Member

    Jul 4, 2015
    Hi everyone! I am currently working with a 60-second UpDown counter for our project in traffic light system. I am using two 74LS190 as the counter, two 74ls47 as the decoder and one 74ls00 whose output is connected to the load of the second 190 ic.

    Everything worked properly when I simulated it in the MultiSim however, when I tried to construct the circuit on breadboard, it didn't. The working output only was the 7-segment display for the least significant digit(0-9) while the second 7-segment display for the most significant digit(0-5) did not even worked-totally blank(no output)!

    I already tried modifying the connection. Of course, ensuring that the the first display still works but my attempt was not successful.

    Can anyone please help me what's wrong? Any help will be greatly appreciated. Good day!

    Here is the result of my circuit construction. UpDown Counter.jpg
    RRITESH KAKKAR likes this.
  2. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    Hello and Welcome to AAC,

    In order to help we need more information like a schematic and possible some screen shot of the circuit on Multisim in order to help here..
    RRITESH KAKKAR likes this.
  3. DennObi

    Thread Starter New Member

    Jul 4, 2015

    Okay. So here's my simulated Schematic Diagram on MultiSim. UpDownCounter_190ic.png
  4. absf

    Senior Member

    Dec 29, 2010
    You cannot leave any of the ABCD inputs of U5 and U3 floating. At least it wouldn't work in my proteus sim. You also need current limiting resistors between the O/P of 7447 and 7-seg displays like 220-330Ω. It is OK for the simulator as there is no real components to burn. But in real hardware you're risking the life of 7-seg LED and the decoder chips.


    2 digit counter.PNG
    Last edited: Jul 13, 2015