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View Full Version : [Computer Engineering ] Need help understanding logic gates and how to make them?


Chin19
Oct 24, 2013, 03:50 PM
I have a logic gate assignment due on Friday and I really have trouble understanding designing the logic circuit, drawing the logic diagram of the gate design, drawing the circuit diagram, boolean expressions, truth tables, and building the logic gate circuit. I have no clue on how to do logic gates and I need urgent help before I fail. I would like to know exactly how to exactly read and wire the actual breadboard. Pictures would be nice.

NOTE: I am only in grade 10 and this is very simple logic gate experiments, so nothing too fancy or hard.

Equipment that I have: Switch, AND gate, OR gate, NOT gate, wires, small breadboard, LEDs and brown and green resistors.

Questions:

1) Design a 5 gate circuit using each of the AND, OR, NOT at least once and with at least 3 different inputs.
2) Draw a Logic diagram of the gate design (eg. A, B, C, D, W, X, Y, Z )
3) Draw a circuit diagram including the gates, power, switch, resistors, LED’s etc. (colour code each new connection) using the proper symbols
4) Create a Boolean Expression
5) Make detailed truth table (eg. A, B, C, D, W, X, Y, Z ).
6) Produce your designed logic circuit using all the wiring and circuit rules discussed in class

This is how he will mark us:
Marking
1) Design a 5 gate circuit using each of the AND, OR, NOT at least once /1
2) Logic diagram is neat, clear, and accurate /1
3) Circuit diagram includes proper symbols and all components /2
4) Boolean Expression is correct /1
5) Detailed and correct truth table (eg. A, B, C, D, W, X, Y, Z ) /2
6) Produced logic circuit using all the wiring and circuit rules discussed in class
a. Colour coded wiring /2
b. Neat, clean wiring /2
c. Correct wiring (no cross overs) /2
d. Placement of LED to indicate key inputs/outputs /2
e. Works correctly on first try at test /2
Total /17

Once again, nothing too hard as I am only in grade 10. Pictures would be extremely helpful. Also, I need help reading logic diagrams and actually putting on a legit breadboard.

Please simplify on how to do logic gate circuits please. I am really, really lost in class and I have no clue how to do logic gates. Please help :(

ma0641
Oct 24, 2013, 05:26 PM
How long have you had this? You want US to do all this for you tonight? If you need "colour" it's already Friday there.

Chin19
Oct 24, 2013, 05:31 PM
I just got this project yesterday, but I posted my questions on some other site. It would be really appreciated if you would. I don't know how much I could thank you because this is one assignment that I am so stumped on. It's 8:30 PM here so there is still a lot of time left.

Just please respond to this message if you see this as I would like to stay informed with you.

Thank you, thank you, thanks you much if you do it. Much appreciated.

Chin19
Oct 24, 2013, 06:03 PM
How long have you had this? You want US to do all this for you tonight? If you need "colour" it's already Friday there.

Sorry to bother you, but I just want to check if you are there because I am really starting to panic now as time is slipping by.

Thanks

Chin19
Oct 24, 2013, 07:12 PM
How long have you had this? You want US to do all this for you tonight? If you need "colour" it's already Friday there.

Hello? I am really starting to panic now. Please respond as you are my only hope.

Chin19
Oct 24, 2013, 07:53 PM
How long have you had this? You want US to do all this for you tonight? If you need "colour" it's already Friday there.

I just got this project yesterday, but I posted my questions on some other site. It would be really appreciated if you would. I don't know how much I could thank you because this is one assignment that I am so stumped on. It's 8:30 PM here so there is still a lot of time left.

Just please respond to this message if you see this as I would like to stay informed with you.

Thank you, thank you, thanks you much if you do it. Much appreciated.

ScottGem
Oct 25, 2013, 01:23 PM
We do not do your homework for you. We may critique your work but we aren't going to do it for you.

Chin19
Oct 25, 2013, 01:26 PM
We do not do your homework for you. We may critique your work but we aren't going to do it for you.

I have created my logic diagram, but I need someone to check if it is all right.
imgur: the simple image sharer (http://imgur.com/hdIZEsY)

I just need some help on how to read and actually wire the breadboard. Any website/programs would be helpful.

Chin19
Oct 25, 2013, 07:09 PM
Hello,

For my assignment I must create a custom designed electronic logic circuit. I also need help on how to wire it on a breadboard. I do not understand how to put your diagram onto the breadboard.

Note: I am only in grade 10, so nothing to fancy.

The questions are:

1) Design a 5 gate circuit using each of the AND, OR, NOT at least once and with at least 3 different inputs.
2) Draw a Logic diagram of the gate design (eg. A, B, C, D, W, X, Y, Z )
3) Draw a circuit diagram including the gates, power, switch, resistors, LED’s etc. (colour code each new connection) using the proper symbols
4) Create a Boolean Expression
5) Make detailed truth table (eg. A, B, C, D, W, X, Y, Z ).
6) Produce your designed logic circuit using all the wiring and circuit rules discussed in class

So I have completed my logic diagram:
imgur: the simple image sharer (http://imgur.com/hdIZEsY)

My truth table:
imgur: the simple image sharer (http://imgur.com/AQR4VPH)

Now I have trouble determining the boolean expression, making the circuit diagram and physically making the logic gate. Wiring/building it is what I have trouble on the most. I don't know where to place the wires, resistors, LEDs, etc.

Is the truth table correct? If so, how would you wire it? Pictures would be extremely appreciated. Or if there is any website/program that can teach me exactly how to wire logic diagrams onto a breadboard.

Items: Wires, LEDs, breadboard, Switch, AND gate, OR gate, NOT gate, green and brown resistors.

I also need help on the

Thanks

Celine91
Oct 26, 2013, 07:39 AM
-logic diagram is your choice, its correct as long as you satisfy the conditions (use AND, OR, NOR at least once, and at least three different inputs). so yes its correct according to the specifications (but you could have made a much simpler one!)
- I did not check every column of your truth table, you're not supposed to have mistakes there, except that the final expression is not correct! (NOR is not applied to each bracket but to the whole expression), you're supposed to get:
_________________
[(A+B).(C+D)].(C+D), if you want to rewrite this it becomes, (A.B) + (C.D) + (C.D) . The Boolean expression: AB + CD (check with karnaugh map if covered in the course)

NOTE: you can do the truth table on the simplified expression (not the complicated one!)

- Wiring and building the circuit diagram using the items you specified refer to this: Electronic Circuits For Beginners: Logic Gates (http://electroniccircuitsforbeginners.blogspot.com/2009/04/logic-gates.html)

Chin19
Oct 26, 2013, 11:45 AM
-logic diagram is your choice, its correct as long as you satisfy the conditions (use AND, OR, NOR at least once, and at least three different inputs). so yes its correct according to the specifications (but you could have made a much simpler one!)
- I did not check every column of your truth table, you're not supposed to have mistakes there, except that the final expression is not correct! (NOR is not applied to each bracket but to the whole expression), you're supposed to get:
_________________
[(A+B).(C+D)].(C+D), if you want to rewrite this it becomes, (A.B) + (C.D) + (C.D) . The Boolean expression: AB + CD (check with karnaugh map if covered in the course)

NOTE: you can do the truth table on the simplified expression (not the complicated one!)

- Wiring and building the circuit diagram using the items you specified refer to this: Electronic Circuits For Beginners: Logic Gates (http://electroniccircuitsforbeginners.blogspot.com/2009/04/logic-gates.html)

Ok, so I've changed the last part of my truth table

Truth Table: imgur: the simple image sharer (http://imgur.com/shwxj4i)

Boolean Expression: AB + CD

Looking at the website you sent me, I still do not understand how to do the circuit diagram because we do not use transistors. I do not know where to put LEDs, resistors, etc.

I am still lost on how to physically make the logic gate on a breadboard with wires, LEDs, resistors, switch, etc.

Celine91
Oct 26, 2013, 01:03 PM
You use transistors to design logic gates, given the gates, what is it that you don't understand?

if you don't know where to place the components:
LEDs and current limiting resistors should be placed at the output of each logic gate. (LEDs to indicate the behavior of the Boolean expression, output resistors for LEDs not to break) also input resistor should be used for digital circuit not to break.
The switch between voltage source and ground, when switch open the input voltage is low (0 Volts) and when switch closed input is high. (switches will be applied to input of logic gates)

This pdf should help you understand: [http://www.ittc.ku.edu/~siddharth/EECS318/labs/EECS318_Lab6_LogicGates.pdf]

if you still don't get it, then ask your teacher, you should not be the only one with questions about the homework! Good luck

Chin19
Oct 26, 2013, 01:20 PM
You use transistors to design logic gates, given the gates, what is it that you don't understand?

if you don't know where to place the components:
LEDs and current limiting resistors should be placed at the output of each logic gate. (LEDs to indicate the behavior of the Boolean expression, output resistors for LEDs not to break) also input resistor should be used for digital circuit not to break.
The switch between voltage source and ground, when switch open the input voltage is low (0 Volts) and when switch closed input is high. (switches will be applied to input of logic gates)

This pdf should help you understand: [http://www.ittc.ku.edu/~siddharth/EECS318/labs/EECS318_Lab6_LogicGates.pdf]

if you still don't get it, then ask your teacher, you should not be the only one with questions about the homework! Good luck

I don't know why I have such hard time. My teacher never showed us how to physically make it on a breadboard. I guess I'm just confused about putting all 3 gates on 1 breadboard.

Here's what I got so far.

Breadboard: imgur: the simple image sharer (http://imgur.com/iDppS5U)

First chip is AND, then NOT, then OR. (Left to right)

What would you suggest I do next?

Celine91
Oct 26, 2013, 01:56 PM
[http://www.youtube.com/watch?v=Ynxg19lEkvg]
Breadboards and Logic

this should be detailed now! anything else ask your teacher :)

good luck again.

Chin19
Oct 26, 2013, 04:26 PM
[http://www.youtube.com/watch?v=Ynxg19lEkvg]
Breadboards and Logic

this should be detailed now! anything else ask your teacher :)

good luck again.

Oh OK this helps a lot.

Ill check back with you later when I am finished.

This is what I have so far: imgur: the simple image sharer (http://imgur.com/eqyknEj)

Gates from left to right: OR, AND, NOT

Is this OK? I am not sure where to go next.