Lab 4: A REAL PROBLEM

Introduction

In this laboratory the student is introduced to a real life hardware application. The student will use circuit wiring techniques to construct a prototype digital circuit and verify its correct operation. This application should be complete and recorded in the student's design notebook. Also, the student’s general method of solving digital electronics problems from start to finish should be thoroughly documented.

Equipment needed

Microprocessor power supply

Digital voltmeter

Logic probe

Solderless breadboard

TTL IC's (7400, 7404, 7410)

The problem

Suppose a loading dock for large trucks is shaped as shown in figure 1. The dock is obviously blind; that is, the trucks entering cannot see into the dock area. We want a signal to warn trucks when not to enter the dock area. Also, due to the tight fit we require that only three trucks are allowed in the dock area at one time. If slots 1 and 2 are filled in the dock are, other trucks can not enter.

When a truck is in one of the parking slots, a sensor in that slot produces a low output signal, A "no parking" light at the entrance to the lot should light when the dock area is full. A high output signal is required to light the "no parking" light.

Figure 1

(The loading dock)

Procedure

A general method for solving problems should include (at least):

1) A definition of the problem in words

2) Identification of constraints to the problem

3) Formulation of the problem as a logic function (create a truth table)

4) A schematic of the logic circuit that evaluates the logic function

5) A computer simulation and analysis of the problem

6) The breadboarded prototype design

7) A hardwire of the proven circuit.

8) Documentation (hardware requirements, cost etc.)

Part 1

1. Follow the above steps in solving the loading dock problem (refer to lecture notes for steps 1-4). Make sure all this information goes into your lab notebook (situation drawing, truth table, Karnaugh map-solved with LW-3.01, circuit diagram draw with LW-3.01)

2. Use the SOP design using NAND/NAND technology and breadboard the following circuit. Pay attention to the input/output assertion levels.

3. Verify that is circuit design agrees with the proposed truth table for the loading dock problem.

4. Use LogicWorks to create a timing diagram of the problem. Be sure to include the timing diagram in your design notebook.

Questions

1. What would the circuit of SOP in NOR/NOR technology look like?

2. What would the circuit of SOP in NAND/NOR technology look like?

3. Which circuit is best? How many discrete gates are used? How many IC chips are needed for each design? Which circuit is most expensive (consider labor as well as parts)?