PROJECT OVERVIEW / INTRODUCTION
in this project we had to demonstrate our skills with k-maps, seven segment displays, multi-sim, and bread-boarding to create a circuit that displays my birth date based on the different chips needed to create it. some of the constraints I had to follow included:
- the seven segment display must be a common cathode
- current limiting resistors ( 150 ohms - 270 ohms) must be used
- the K-Mapping technique must be used to obtain the simplified logic expression for each of the seven segments
- at least one segment must be implemented with NAND only or NOR only logic.
truth table
this is the truth table I had to create in order to make the seven segment display show the numbers of my birth date. the purpose of creating the truth table was to find out exactly what different segments of the display needed to be turned on in order to create the number that is going to be displayed. A, B, C, D, E, F, and G represent the segments of the seven segment display. one example according to my chart, if A, C, D, E, F, G are turned on, then the number 6 will be displayed. these numbers would be displayed also depending on if the sequence of switches ( X, Y, Z) are flipped on or off.
k-maps and simplified logic expressions for each of the seven segments
K-mapping is a way of getting simplified logic expressions by filling out a table with 1's and 0's Depending on how a circuit is going to operate . the 1's in the k-maps are then grouped into 4's, 2's, and can be in its own group of 1. there are also different variations of grouping such as grouping in four corners , two corners, or on two sides. by "grouping" you can gain the min term expressions needed to build the unique circuit. using k-maps make it a much easier and faster process of obtaining these expressions than the boolean algebra alternative.
multi-sim implementation
this is the circuit that I created using the simplified logic expressions from the k-maps
- for this circuit, I put it into bus form to make the process go faster and to make the overall circuit neater. also added one common cathode seven-segment display, one NAND , and one NOR only circuit to follow the constraints that needed to be met. in my circuit, there were 3 inverters, 2 NAND gates, 2 NOR gates, and three OR gates. so with the number of gates given, there would be a total of 4 chips in my circuit. for segment D I Used NAND gates . the reason why we use NOR and NAND Gates is because they can make building a circuit easier and cost effective. Segment D contained 2 NAND gates, which in this case would be less simple than using combinational logic gates because if you used regular AND gates then there would be one less chip required including the inverters.
- the seven segment display used has of course, seven segments. each of these segments are represented by the letters A, B, C, D ,E ,F and G. Depending on which letters are turned on, the seven segment display will show a number. these numbers shown range from numbers 0 through 9. in this project we used a common cathode display which means that all of cathodes of the seven segments are connected directly together. he other type of seven segment display is a common anode which means that all the anodes of the seven segment are connected together and displays depending on which ones are grounded. we used resistors before the seven segment display to control the amount of current entering it.
bill of materials
below is a list of all the materials that were needed in order to breadboard the circuit
- wires
- breadboard
- 7400 chips
- 74LS32 chips
- 74LS04 chips
- 74LS02 chips
breadboarding
during the breadboarding section of this project, i ran into many difficulties trying recreate the circuit I made on multisim. one of the problems I ran into while bread boarding was with wiring the NOR chips. at first i didn't know that the NOR chip had to wired backwards compared to the other kinds of chips. another problem i ran into was that i lost track of what expression i was wiring and ended up restarting the whole breadboard.
conclusion
throughout this project i learned how i can implement different AOI chips to create something interesting and unique. some things i would do differently if I were to do this project again i would try to make the breadboarding a little neater and try to pay attention to each step I am doing because one little mistake can affect the whole circuit. K-mapping is important because it can make trying to find simplified expressions easier than using boolean algebra.