Logic Circuit Teaching Board Team 3 David Lee, Younas Abdul Salam, Andrzej Borzecki ECE 445 Senior Design TA: Ankit Jain Date: April 27, 2015

Purpose and Objective Promote STEM for students in grammar school Introduce students to gate level logic design Provide a simple user interface for learning Assist educators in explaining logic design

How It Works

How It Works (Continued)

Initial Board Layout

Initial Board Dimensions Top View Side View

Final Board Specifications Powered Logic Inputs – 3 Rows and 5 Columns Board Size – Initial Size (Length 44cm, Width 30cm, Height 16cm) – Final Dimensions (Length 60cm, Width 100cm, Height 16cm) Board Material – PVC(Polyvinyl Chloride) Logic Input Polarity with Banana Plugs

Board Functions Compare truth table inputs to the logic design circuit Identify errors in the logic circuit using LEDs Optimize the number of each logic gate required for the truth table Open source design with USB connection

Board Circuit Design

Testing Procedures Voltage output on the board with all components powered to ensure 5Vdc +/-0.5V Open and close power supply switch and test voltage and current output for safety Test strength of banana plug connections Test maximum current with the maximum amount of inputs connected

Actual Design

Microcontroller

Purpose Implement different functions that assist teaching and learning Examples include logic tester, number of gates calculator Assist with debugging any problems with the board, without having to open the board

Connections Structure

Power Circuit Microcontroller needs >6V power. DC-DC voltage booster used, voltage ~6.2 V. Higher capacitance, more voltage. 4.7uF = ~5.7V. 22uF = ~6.2V

NOT gate LED buffers Booster utilizes capacitors Higher current drain, lower voltage Buffer LEDs for indirect power

Start and Inputs Switch Floating voltage issue Solved using NOT gates Floating outputs LOW. Ground outputs HIGH.

Logic for Truth Table Switches Microcontroller cycles through selection logic, picks up individual values through a MUX. Same logic sent to logic board for gate values, and computation LED logic to turn on specific LEDs. Saves microcontroller ports

Microcontroller Code Code to test correctness of designed circuit. Accounts for number of inputs Guides student to which values are causing issues Communicates with hardware to implement functions

Microcontroller Code Green LED indicates correct logic Red LED indicates error, and computation LEDs point to error values

Additional Features Hardware debug

Additional Features Number of Gates Code for this feature reads truth table and compares it to a database

Logic Design Pieces

Initial Design

Circuit Schematic

2D Schematics NOT GATE Initial sketches Preparation for 3D printing Visual sizing representation

2D Schematic AND GATEOR GATE

3D Renderings

Modifications

3D Printed Logic Pieces

Logic Unit Assembly

Testing Procedures Continued AND GATE A BC OR GATE A BC NOT GATE AC Voltage output for logic pieces: Logic Low V Logic High 2-5.6V Plug in inputs as represented by truth tables and test the output Plug the pieces to the board and ensure stability

Output Testing in Volts

Conclusion Board performed and satisfied all requirements and verifications for the different components Voltage and current values are within range and correctly propagate logic forward Microcontroller performs checks correctly and does not interfere with design process unless logic check requested

Future Development Larger variety of gates for more complex implementation Additional control features, such as password protected logic verification and “test mode” Integrated timers and buzzers for logic design competitions

IEEE Code of Ethics To accept responsibility in making decisions consistent with the safety, health, and welfare of the public, and to disclose promptly factors that might endanger the public or the environment; To be honest and realistic in stating claims or estimates based on available data; To improve the understanding of technology; its appropriate application, and potential consequences;

Special Thanks To Professor Carney Professor Oelze Ankit Jain (TA) Greggory Bennett (ECE Machine Shop) David Switzer (ECE Machine Shop)

Questions?

Thank You!