Logic Gate & Comparator output

Thread Starter

miniElectronics

Joined Aug 4, 2009
20
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.
 

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Thread Starter

miniElectronics

Joined Aug 4, 2009
20
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.
 

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jj_alukkas

Joined Jan 8, 2009
753
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.
 

Ron H

Joined Apr 14, 2005
7,012
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.
 

Thread Starter

miniElectronics

Joined Aug 4, 2009
20
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?
 

Thread Starter

miniElectronics

Joined Aug 4, 2009
20
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?
 

Attachments

Ron H

Joined Apr 14, 2005
7,012
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?
As I said above,
Your power supply somehow needs to be referenced to ground.
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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