Lab # 4 Bank Alarm

Objective

In this experiment the student will design and implement an alarm system for a bank.

The alarm is controlled by the following inputs.

The front door

There is a Special-Switch, which the watchman turns off before opening the door in the morning. When the door is opened a Micro-Switch turns on and if the Special-Switch is not turned off before opening the door, the alarm will sound. When the bank is closed, the Special-Switch is turned on manually after the door is shut.

The time alarm

At 8 PM a Time-Switch is turned on automatically. If anyone opens the bank vault when the Time-Switch is on, the alarm will sound. The Time Switch is turned off automatically at 8 AM.

The vault

There are two keyed switches to the vault door (Vault-Switch 1 and Vault-Switch 2). Both switches must be turned on simultaneously to open the vault door. If one switch is activated alone, the alarm will sound. In other words, both of these switches must always be on or off together or the alarm will sound.

The janitor or watchman may enter the building between 8 PM and 8 AM without causing the alarm to sound if they have the key to open the front door and a special key to turn off the Special-Switch. However, if anyone tries to open the vault between 8 PM and 8 AM, the alarm will sound.

Inputs to the logic function are:

 

Switches

Assignments
Time-Switch

A
Front door Micro-Switch

B
Front door Special-Switch

C
Vault-Switch 1

D
Vault-Switch 2

E

Procedure:

  1. Develop a truth table for the five input variables using 1’s to activate the alarm.
  2. Obtain the minimum sum of products of your function using K-maps and verify your answer using EWB.
  3. Implement the function using all NAND gates on EWB
  4. Implement the function using all NAND gates on a breadboard. Connect inputs to switches and output to an LED.
  5. Verify your circuit against the truth table and have your lab signed off.
  6. Obtain the minimum product of sums of your function using K-maps and verify your answer using EWB.
  7. Implement the function using all NOR gates on EWB.
  8. Verify your circuit against the truth table.