BCD to Seven Segment Decoder: HND in Engineering, The London College

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Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Author Name
Engineering Design
The London College
Designing a Product that Meets Customer’s
Requirements
BCD to 7-segment decoder is being built,
designed, and tested using Karnaugh mapping
and SPICE simulation
BCD to 7-
SEGMENT
DECODER USING
LOGIC GATES
201
UCK

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Contents
Introduction......................................................................................................................................5
Design Planning Stating Specifications Under The Influence Of Stakeholder’s Brief...................5
Design Brief.................................................................................................................................5
Design Specs................................................................................................................................5
Influence Of Design Brief On Design Specs...............................................................................5
Project Schedule..........................................................................................................................6
Project Planning Techniques.......................................................................................................7
Critical Path Analysis Techniques In Project Scheduling...........................................................7
Prepared Design Specs Vs Relevant Industrial Standard Specs..................................................7
Possible Technical Solutions Addressing Design Specs.................................................................8
Industry Standard Evaluation And Analytical Tools For Conducting Preliminary Designs (PD)
.....................................................................................................................................................8
PD1..............................................................................................................................................9
PD2..............................................................................................................................................9
PD3............................................................................................................................................10
Problem Solving Software And Hardware............................................................................10
Evaluation Of PDs; Case For The Final Design Scheme (FDS); Improvements In FDS.........10
Industry Standard Final Design.....................................................................................................11
Final Design...............................................................................................................................11
Karnaugh Maps......................................................................................................................12
Limitations In Final Design.......................................................................................................14
Role Of Design Specifications In Final Designing....................................................................14
Compliance, Safety, And Risk Management Issues..................................................................15
Effectiveness Of Industry Standard Final Design.....................................................................15

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Communicating Design Solution...................................................................................................17
Design Presentation...................................................................................................................17
Effective Presentation Strategies...............................................................................................17
Evaluating Design Presentation Over Effective Presentation Strategies...................................18
Feedback Suggesting Potential Improvements In Design.........................................................18
Conclusion.....................................................................................................................................18
Appendix A: Simulation Diagram.................................................................................................19
Appendix B: Timing Diagram.......................................................................................................20
Appendix C: 3D Model.................................................................................................................21
List of Figures
Figure 1: Influence of Design Requirements...................................................................................6
Figure 2: Project Planning Gantt Chart...........................................................................................6
Figure 3: PERT Chart......................................................................................................................7
Figure 4: Industry Standard Analytical and Evaluation Tools........................................................8
Figure 5: PD1 design schematics.....................................................................................................9
Figure 6: PD2 Design Schematics...................................................................................................9
Figure 7: PD3 Design Schematics.................................................................................................10
Figure 8: Evaluating Preliminary Designs over Design Standards...............................................11
Figure 9: Block Diagram...............................................................................................................11
Figure 10: behavior of Seven Segment Display............................................................................12
Figure 11: K-map for ‘a’ segment K-map for ‘b’ segment................13
Figure 12: K-map for ‘c’ segment K-map for ‘d’ segment...........13
Figure 13: K-map for ‘e’ segment K-map for ‘f’ segment............13
Figure 14: K-map for ‘g’ segment.................................................................................................14
Figure 15: Role of Specifications in Design Process.....................................................................15
Figure 16: Simulation and Timing Diagram when Input A is Applied.........................................16
Figure 17: Simulation and Timing Diagram when Input B is Applied.........................................16
Figure 18: Simulation and Timing Diagram when Input C is Applied.........................................16

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Figure 19: Simulation and Timing Diagram when Input D is Applied.........................................16
Figure 20: Operating Diagram of BCD Decoder Wiring Diagram of BCD
Decoder..........................................................................................................................................17
Figure 21: Design Presentation......................................................................................................17
List of Tables
Table 1: State Table BCD to Seven-Segment Decoder.................................................................13

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Introduction
This assignment reflects the designing of BCD to 7-Segment Decoder using logic gates. 7-
segment display is an electronics device with seven LEDs placed in a manner of two boxes. Each
LED is called a segment, light up by mapping areas from a-g in different logical directions to
make certain outputs. The entire process is carried out by encoding and decoding of digits
through logic gates. Logic behind each step is also shown through K-maps, state tables and
timing diagrams.
Design Planning Stating Specifications Under The Influence Of
Stakeholder’s Brief
Design Brief
Stakeholder instructed us to design, build, and test a 7-segment decoder using logic gates. State
tables and K-maps are required in designing process to be simplified and understandable.
Multisim or SPICE based simulation must be chosen. Also make a physical distribution (Warter-
Perez, 2012).
Design Specs
Spec 1. 7 NAND Gates
Spec 2. 7 AND-OR-INVERT Gates
Spec 3. Input buffers
Spec 4. Input voltage VCC = 5V
Spec 5. Operating ambient temperature range = 0℃ ~ 80℃
Spec 6. Simulator = SPICE or Multisim
Spec 7. Mapping = K-maps
Influence Of Design Brief On Design Specs
Stakeholder’s brief always affect the design team’s preparation of design specifications
technically required for the project completion according to client’s satisfaction and industrial
standards. Influence can be shown on pie chart for better understanding (Poje, 2014).

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
44%
22%
10%
8%
16%
Influence of Client Requirements
Spec 1
Spec 2
Spec 3
Spec 4
spec5
Figure 1: Influence of Design Requirements
Project Schedule
Gantt chart is commonly used to plan projects from large scale networks to small system designs.
It keeps projects timeline in front of designers so they may remain on track. Gantt chart for this
project is being made on excel and contributes following features;
Shows the activities to be performed.
Highlights when each activity starts and ends.
Demonstrates actual duration as compare to planned duration.
Prevents tasks from getting late.
Shows the percentage completion of each task with in the specified duration.
Figure 2: Project Planning Gantt Chart

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Project Planning Techniques
There are more than eight planning techniques in project anagement field which can be used to
plan a project. But in order to show what are the possible planning techniques and the most
critical path among them, PERT chart is used. We have done the same by making a PERT chart
showing red path as a critical path to execute this project.
Figure 3: PERT Chart
Critical Path Analysis Techniques In Project Scheduling
Complex and large scale projects needs to be simplified while planning. There are a number of
activities that can be performed in parallel to other activities and many are dependent on other
activities in such a way that the completion of previous task results in the opening of next one. In
this context, critical path analysis is actually operational technique (Condrat, 2011). A small task
may have a high priority a compare to a major looking task; critical path highlights tasks as per
their importance.
Critical path analysis depicts three steps;
Timeline all the possible sub-projects.
Parallel happening tasks labelled separately.
Dependent tasks labelled separately.
Critical path is drawn between dependent tasks.
Prepared Design Specs Vs Relevant Industrial Standard Specs
In order to carry on this comparison, we have done a lot of research on different industrial
products and conclude some most common industrial standards (IS) on which our design specs
can be analyzed;
IS 1. Ripple-Blanking Input.

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
IS 2. Lamp Test Input.
IS 3. A B C D Inputs.
IS 4. Seven segment outputs.
IS 5. 1-15 digits can be displayed.
IS 6. Min Voltage 4.5V.
IS 7. Max. Voltage 5.5V.
IS 8. Ambient Temperature 0~70℃.
Comparing our design specs with these predicts great similarity between the two rather than
some ups and downs. Min and max voltage range is same. Lamp test and RBI/BI is the one not
included in our design specs. Ambient temperature almost approachable.
Possible Technical Solutions Addressing Design Specs
Industry Standard Evaluation And Analytical Tools For Conducting Preliminary
Designs (PD)
Theoretical design process includes both formal and informal methods to discover final results.
Formulation includes the problem definition extracted through the analysis of all the
alternatives available.
Analysis involves interpretation of results and prediction of threats.
Search includes gathering enough data for starting preliminary stage of design.
Decision means that each preliminary design solution is being evaluated until final
decision is made.
Specification means interpretation of design solution in a form of understanding diagram
or points.
Modification requires improvements to be done after re-evaluating final design.

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Figure 4: Industry Standard Analytical and Evaluation Tools
PD1
We have designed first model on Multisim simulator using only a seven segment display and a
power circuit to power it up using 5V input voltage. The following figure shows the mapping of
terminals of seven segment display. In the common cathode model on the right, all COM
terminals are common to the ground. For desired display, wire the specified COM terminal with
the high 1 logic and the other to ground. In this circuit, we made it to work manually but
according to design specifications, logic gates are must-to-use.
Figure 5: PD1 design schematics
PD2
In this design, we tried the same decoder using 4511 IC having LT, BI, and LE inputs according
to design standards. A B C D inputs are also present to assign certain digits to be displayed. It
can produce output from 0-15 digits. All the inputs are being attached through resistors for

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
excessive currents to flow towards ground. You can see the output displayed as 8 depicting
00000000 hexadecimal decoding.
Figure 6: PD2 Design Schematics
PD3
We have refined some design considerations and improved design accordingly. Now the input is
provided by one terminal through 10K resistor and 7 outputs lines through 220Ω resistors.
Resistors at output are used to limit excessive output current thus preventing LED’s of seven
segment display from burn-out.
Figure 7: PD3 Design Schematics
Problem Solving Software And Hardware
After analyzing all above designs, we came to conclude our hardware and software choices for
carrying out final design.

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
Software: SPICE simulator
Hardware: AutoCAD
Evaluation Of PDs; Case For The Final Design Scheme (FDS); Improvements In
FDS
Taking industrial standards and design specifications into account, we have evaluated all
preliminary designs and made assumptions for final design accordingly.
In the first preliminary design, Multisim simulator was tested making a very simple logic circuit
over it. But the main issue was with the simulator’s complexity and high computational time. In
the second design, we have shifted towards spice simulation of logic circuit. This time a circuit
consisting of 4 input lines and 7 output lines is used with the resistors at input line to provide
ground path for input high current. After implementation, we realized that output seven segment
display also need to be protected against excessive currents. That's where it leads towards third
preliminary design. Below is the graph showing evaluation of all three designs;
P D 1 P D 2 P D 3
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
E v a l u a tio n o f P r el i mi n a r y Desi g n s
Software
Output
Protection
Logic Gates
Preliminary designs
Percentage evaluation
Figure 8: Evaluating Preliminary Designs over Design Standards
Industry Standard Final Design
Final Design
There are two types of seven segment displays, common anode and common cathode. In
common cathode, cathodes of all LEDs common to the ground or negative Vcc, displays digits
when a high 1 value is communicated to them. The opposite is the case for common anode.
Seven segment displays output when a digits is encoded and then decoded from BCD to binary

Assignment of Engineering Design UCK Author Name Roll No
BCD to Seven Segment Decoder The London College HND in Engineering
counter. Decoder has a total 4 inputs and 7 outputs to light up seven segment display. Below is
the block diagram of BCD to seven segment display.
Figure 9: Block Diagram
The combination of all zero inputs results in seven segments as 0 making 0 as output. For
combinations where one of the inputs is high, outputs displayed according to the high input’s
logical position to the seven segment display. Below is the diagram depicting this behavior of
seven segment display.
Figure 10: behavior of Seven Segment Display
Now further proceeding our design, we made a state table depicting decoding behavior of binary
decoder from A B C D inputs towards a, b, c, d, e, f, g outputs in hexadecimal format. Below is
the state table shown;
Table 1: State Table BCD to Seven-Segment Decoder
Input Output
Digits A B C D a b c d e f g
0 0 0 0 0 1 1 1 1 1 1 0
1 0 0 0 1 0 1 1 0 0 0 0
2 0 0 1 0 1 1 0 1 1 0 1
3 0 0 1 1 1 1 1 1 0 0 1
4 0 1 0 0 0 1 1 0 0 1 1
5 0 1 0 1 1 0 1 1 0 1 1
6 0 1 1 0 1 1 0 1 1 1 1