Logic Gate & Comparator output

Discussion in 'The Projects Forum' started by miniElectronics, Aug 12, 2009.

  1. miniElectronics

    Thread Starter Member

    Aug 4, 2009
    20
    0
    Hi,

    I have connected this circuit such as you can see in picture. And output of this is

    A B C Led1 Led2
    1 0 1 0 1
    1 1 1 1 1

    A and C is connected together. I want a third output. Such as it will be
    Led1 Led2
    1 0

    So i am missing something. i dont understand what i have to put in this circuit. To get result like under. Without touching A and C. Because it is connected together.

    A B C Led1 Led2
    1 0 1 0 1
    1 1 1 1 1
    x x x 1 0

    Circuit have 2 input signals. And it will not be added a third input. Please see the attached file. It is to comparators.
     
  2. miniElectronics

    Thread Starter Member

    Aug 4, 2009
    20
    0
    I think i have got it to work. Just connected it on wrong way before. If someone other have a simulation software and just test it. Because when i create on MultiSim new project and test same circuit so it will not work.
     
  3. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    Since A and C are tied together, omit C.

    Then I see that B corresponds to Led1 and C corresponds to Led2. So you basically have output same as input.
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Your power supply somehow needs to be referenced to ground.
    Also, LM339 has open collector outputs. They need pullup resistors to a positive voltage in order to work.
     
  5. miniElectronics

    Thread Starter Member

    Aug 4, 2009
    20
    0
    Hi,

    I want to know how much ohm resistor do i need as a pullup? And someone know how much is maximum mV input a LM339 comparator can work with?

    In case is there any comparator where input voltages can be 0-6v?
     
  6. miniElectronics

    Thread Starter Member

    Aug 4, 2009
    20
    0
    Hi,

    I have connected the circuit exactly like this one on test board. And does not work on test board but it work in simulation software on computer. Can someone help me with what is wrong?
     
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    As I said above,
    Try connecting the negative terminals of all 3 of your voltage sources to ground. You should also do that in your simulation.
    Add 1kΩ pullup resistors from each output to +6V.
     
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