John Donahue

Logic Gate Calculator


I made this device for my final project for an electronics course. It is a 3 bit x 3 bit multiplier, so it is capable of performing multiplication from 0x0 to 7x7. It does so purely with hardware using the various logic gates shown in the circuit diagram I made below. I chose this idea for my project because I was very interested in more complex logic operations and seeing how something like basic math can be done consistently with just these IC’s. I felt like after this course and working through this project I had a much better grasp of how exactly a computer thinks and operates, and how they can become so powerful. I also gained a lot more respect for the computer engineering that goes into a full blown calculator.

I had a lot of fun carrying out this project, and was able to greatly expand my basic knowledge and understanding of logic gates and circuits. I first had to develop a circuit diagram to plan out what I would be building. I was able to work it through logically and develop the above circuit simplified down to just basic gates. I then assembled all of my components and began to wire the breadboard.

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There were a ton of wires in this devicem, and I only had a certain number of colors for wires. I also knew that it would be very difficult to troubleshoot this and figure out where a mistake was made given it’s nature, so I developed my own system for carefully ensuring I wired it correctly. I worked through the diagram diagonally, and made sure every pair of wires matched colors. I then tried to have each gate only have one pair of a certain color going to it whenever possible. These measures kept me sane and made it easier to identify potential miswirings. With this strategy, I was able to get it all functioning on the first try. Below is a picture labeling my input and output sections, and showing a working calculation for .