Constructing a NAND Gate as Inverter: Troubleshooting Needed

In summary, the conversation discussed the construction of a NAND gate as an inverter. The circuit was provided and the output was always on, except when both inputs were zero. The conversation then delved into possible errors in the circuit, such as the upper wire of U1A not being properly connected and the lack of a pullup resistor at the switch. Suggestions were made to add a lead from U1 to the voltage source and to use a switch at the input to set logic 1 or 0. The conversation also mentioned the possibility of simplifying the circuit and using a resistor and LED at the output for the indicator. Finally, it was recommended to start over and use a different arrangement at the input.
  • #1

dwn

165
2

Homework Statement


Constructing a NAND gate as an inverter.

Homework Equations

The Attempt at a Solution


I've attached the image at my attempt to construct the circuit. The output is always on, which it should be except when both inputs are zero. Could someone explain what I am doing wrong?
Thank you.
 

Attachments

  • InvertedNAND.png
    InvertedNAND.png
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  • #2
Is U1A's upper wire connected properly?
 
  • #3
I'm afraid I don't understand what you mean. Shouldn't both ports be connected to the switch? In doing that, the gate will output whatever is opposite the input, or does it require an input from the voltage source? I'm really confused about all of this.
 
  • #4
I don't see a pullup resistor at the switch. How will you get a logic 1 for your inputs?
 
  • #5
Based off what you and Korisnik are saying, I need to run a lead from U1 to the voltage source in order to have a HIGH input value.

Tried that to see if it would work...no go.
 
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  • #6
dwn said:
Based off what you and Korisnik are saying, I need to run a lead from U1 to the voltage source in order to have a HIGH input value.

Tried that to see if it would work...no go.
No, I just asked if it was properly connected, as I can't see a junction there. I don't know about the pull up thingy, I've never worked with anything but logic (I don't know how "input", as in Vcc can be connected like this and pull-up to still work). Maybe if this is TTL logic you can't put Vcc on the output.. you need it on the input, also connect to ground and put some pull up resistors (~10k Ohms) before the gates (after switches) so it doesn't float. http://s22.postimg.org/ynlu13ech/DLr5_Bna.png
 
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  • #7
Thank Korisnik. I implemented the changes you suggested in your image, however, the circuit still doesn't function correctly. I found a couple example circuits online, to use NAND as an inverted logic gate, but I must not be making the connections correctly.
 
  • #8
dwn said:
Thank Korisnik. I implemented the changes you suggested in your image, however, the circuit still doesn't function correctly. I found a couple example circuits online, to use NAND as an inverted logic gate, but I must not be making the connections correctly.
Check all junctions, for example where U1A's upper wire connects to the wire coming from the switch. "Bigger" red dots should be junctions. Does your circuit work properly with any configuration of logic gates?
 
  • #9
Can I suggest you take a look at U4A. For example if you understand what U4A is doing you might see a way to simplify your circuit considerably.

PS: Inverters only have one input so why does your circuit have two switches?
 
  • #10
You could use a switch like this at the input, to provide the logic HIGH or logic LOW for your inverter.

03001x01.png


You won't need a complicated arrangement of gates if you use this to set logic 1 or 0 as input.

The indicator at the output isn't right. All you need from the gate's output is a resistor + LED to ground. The light will glow if the gate's output is HIGH, and it won't glow if output is LOW.

Start over afresh. You've got way off-course by using the wrong arrangement at the input.
 
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  • #11
If you don't have that type of switch use a pull-up resistor on the input and a single pole switch to pull it down.
 

1. How do I construct a NAND gate as an inverter?

To construct a NAND gate as an inverter, you will need two input signals and one output signal. Connect the inputs to the two inputs of the NAND gate and connect the output to the output of the inverter. Ensure that the NAND gate has a power supply and is properly grounded.

2. What could be causing my NAND gate inverter to not work?

There could be a few reasons why your NAND gate inverter is not working. Some common troubleshooting steps include checking the connections to make sure they are secure, ensuring that the NAND gate and inverter are receiving the correct power supply and are properly grounded, and checking for any damaged components.

3. How can I troubleshoot my NAND gate inverter?

To troubleshoot your NAND gate inverter, you can try using a multimeter to check the input and output signals. Also, check for any loose connections, damaged components, or incorrect power supply. You may also want to consult the datasheet for your specific NAND gate and inverter to ensure they are being used correctly.

4. Can I use any NAND gate and inverter for this construction?

Generally, any NAND gate and inverter can be used for this construction as long as they have compatible input and output voltages. However, it is always best to consult the datasheets for your specific components to ensure they are suitable for your intended use.

5. Can I use a NAND gate inverter for other logic functions?

Yes, a NAND gate inverter can be used for other logic functions such as AND, OR, and NOR gates. This is because a NAND gate is a universal gate, meaning it can be used to construct any other logic function. However, keep in mind that the input and output voltages may need to be adjusted for different functions.

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