Project Overview:
The purpose of this project is to make a seven segment display that displays my birth date (05-01-2001) on a common cathode seven segment display. We were supposed to use the large breadboard to complete a tangible version of our project after modeling the circuit on Multisim.
Truth Table and Karnaugh Maps:
A truth table is used to find the unsimplified outputs of the circuit. With this truth table, Karnaugh Mapping can be completed quickly. I have xyz columbs to show the binary code (made by the combinations of the x, y, and z switches) that will represent each output of the display. To get this output, abcdefg represent the 7 segments in a seven segment display. In this case, A 1 means the segment is on and A 0 means the segment in the display is off. K-mapping (otherwise known as the only way I can solve Boolean Algebra) is taking a truth table and putting it into a Kavanaugh mapping table that you can then use to group the inputs and simplify the circuit easily. The groups need to be multiples of 2 (1,2,4,8, etc.). The table is labeled in this case by the first two inputs of X and Y on the left side of the table. The Z was on top of the table. To fill in the table each was filled in by the top 2 are the top row. Then the same for the second row. The third row is the last two inputs which were Xs in this map and then the last two numbers go in the last row. The resulting expressions are in Sum of Products form. Each Kavanaugh map represents each of the seven segments in the seven segment display.
Multisim Implementation:
My circuit is not in bus form. This is simply because I find it easier to trace the wires (thus making it easier to breadboard a small circuit like this) when its not in bus form. There are 10 NAND gates used to create the entire circuit. This meant that only 4 chips were needed. I used NAND gates to attempt to minimize the amount of gates I needed to create the circuit. We use NAND or NOR gates to do just the same. Unfortunately the NAND did not contain less gates than the AOI circuit. Thought it did contain one less chip than the AOI. This is important because the more chips that are used the more the cost goes up so you want to keep the cost of the project down. A seven segment display works by either grounding or adding power to the display. To get the display to light up segments the input of the seven pieces of the display needs to be opposite of what the display is hooked to. Common Cathode is hooked to a ground and Common Anode is hooked to power. The display we are using is the Common Cathode (CK) so when you turn an input on,it will light up. The resistor is used before the circuit so that the display will not burn out from the amount of power being put into it.
Date of Birth Circuit Bill of Materials:
In this bill of materials, all of the tools and components I needed to complete this project are listed, as well as the quantity of each I needed. Correction: there are supposed to be 3 "04" gates and 2 "32" gates. However, if the bill of materials is supposed to represent what the materials would be for breadboarding in real life, my list would remain the same.
Bread-boarding:
Conclusion:
Well, up until this project I have had a perfect record of no mistakes or having to troubleshoot the breadboard. Mrs. Zienty graciously stayed after school with me to help me troubleshoot the board. While all of my wires appeared to be in the correct locations, she thought that I had IC’s that were bad. After checking wires again and changing the faculty IC's no changes to the seven segment display were observed. Due to this I still got full credit but it left me wondering what could have went wrong if the wiring was spot on... With that being said, this project was challenging because I had chips that had inputs in a pin that was the output pin in another chip in the project. I was slowed way down because I had to constantly reference the green “cheat sheet” to make sure I was putting wires in the pin I wanted them to be in. As mentioned somewhere above, K mapping is useful because it is much faster and less likely for mistakes to be made when compared to the hateful Boolean Algebra. Next time, I will bring a breadboard home with me when I get behind on a project so the project wont make me behind in the classwork that follows.